Feline Dermatology

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Eric GUAGUERE
Pascal PRELAUD
A PRACTICAL GUIDE T O
Feline
Dermatology
Preface by D. W. SCOTT
Translation by M . CRAIG

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T Janine,
o
Anne, Adeline, Flore,
To Francoise,
Hadrien, Clara, Leo
We love you.

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In memory of Charles Leblois,
Clinical director of the National Veterinary School, Alfort,
who in the 1920s, was the first to propose a diagnostic approach in animal dermatology,
that was based on history taking, clinical examination, differential diagnosis and
performing suitable diagnostic tests.
"Diagnosis is an art I pursue with passion
Treatment is a chore"
Area of initial presentation of notoedric
mange: base of the anterior concha1
cartilage. It is from here that samples
should be taken.
Distribution m a s of notoedric mange
Distribution areas of notoedric mange
Documents pour servir d l'~d@cation
d'une Dermatologie Animale.
~ d i t i o n Vigot, 1926
s

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To Didier Noel Carlotti,
Pierre Fourrier.
to whom French and European dermatology owes its dynamism and international
recognition
To Zeineb Alhaidari,
Blaise Hubert,
Dominique H&ripret,
Thierry Olivry,
old friends and companions in veterinary dermatology
To Jean-Pierre Magnol,
for teaching us our first steps in dermatohistopathology
To Peter Ihrke,
Danny Scott,
Ton Willemse,
Stephen White,
for instilling in us a thorough approach, both clinical and scientific
To all the members of the Groupe d ~ t u d en Dermatologie des Animaux de Compagnie (GEDAC),
e
for keeping us motivated

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Our thanks go particularly to :
- Merial, who has enabled this ambitious project to take place
- Doctors Alhaidari, Atlee, Bensignor, Bourdeau, Bourdoiseau, Burton, Carlotti, Cozette, Declercq,
Degorce, Dehasse, Delabre, Delisle, Denerolle, Devauchelle, Dryden, Ferrer, Fondati, Fontaine, Fritz,
Gaultier, Groux, Habran, Hkripret, Hubert, Hugnet, Ihrke, Laubis, Leclercq, Legrand, Lopez, Magnol,
Mason, Mege, Mialot, Mueller, (G) Muller, (G.H.) Muller, Noli, Olivry, Paghs, Poirson, Power, Prost,
Rivierre, Rzeznik, Saenz de Santa Maria, Scott, Smal, Thomas, Verde, Vroom, White, Wilkinson,
Willemse, for contributing their outstanding photographs.
- Doctor Mark Craig for his outstanding translation skills
- Doctors Emmanuel Bensignor, William Bordeau and Cathy Curtis for checking the manuscript.
%
.
- Professor Gilles Bourdoiseau for his generous encouragement and advice.
- Gabrielle McGarvey, Mary Craig, Aiden Foster, Sarah Heath and Maggie Fisher for assisting in the
translation of certain chapters.
- Blackwell Science, PMCAC, Le Recueil de Mkdecine Vktkrinaire, Harcourt Publishers, Saunders for
permission to reprint certain illustrations.

10. a aGuide to k h DamatoIogy
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I Preface
I have to share a little something with you..,
When my friends, Eric Guagdre and Pascal Prflaud, contacted me and told me that this great work on feline
dermatology was being developed... and that they wanted me to write the preface ... I chuckled to myself. You know that
you are getting old when folks start asking you topresent overviews and historical perspectives, and to write prefaces !
Eric also told me that I was considered to be the "father " offeline dermatology.Now ... I must say... I never considered
myselfto be father of anything but Travis (my son) and Tracy (my daughter). However, as Ipondered the invitation and
the acclamation, it certainly gave me a warm,fuzzy (or is thatfurry ?/feeling inside.
It is certainly true that dermatology has been my professional life, and that feline dermatology, in particular, has
always been my "professional hobby", my little " subspecialty ". But I suppose it was my "fatherly " monograph'
and the three addendumsZ4 that followed that publicised and validated my " felinophilic " nature. I want to
acknowledge the inspirational writings of three of my predecessors in thefeline dermatology arena :Kenneth P. Baker,
Jean Holzworth, and Joan 0.Joshua.
Feline dermatology began to " boom " in 1980, with over 3,000 publications being devoted to the subject over the
course of the subsequent decade. " Feline endocrine alopecia " evolved from a common to a vanishing cause of
bilaterally symetric hypotrichosis, and hypersensitivity (allergy) disorders (atopy, food hypersensitivity, flea-bite
hypersensitivity) took its place. The " eosinophilic granuloma complex " vacated the veil of idiopathy and became
increasingly recognised as a manifestation of hypersensitivity disorders. " Idiopathic milliary dermatitis " became an
endangered species, vanishing before the onslaught of numerous spec$c diseases. " Psychogenic alopecia " retreated
to the realm of the rarely diagnosed when we realised that most cats were perfectly sane, they just itched !
In this new millennium, the possibilities are enormous, with more folks interested in, working in, and contributing to
the field of feline dermatology than ever before. The knowledge and discoveries in this area can only continue to
skyrocket. Continued specialisation in veterinary medicine... look at all the practices andpractitioners now exclusively
devoted to cats... will demand increasing expertise and sophistication, be it in the clinic, in the research laboratory, or
in the continuing education arena.
In this practical guide to feline dermatology, a host of international experts and " stars " have been assembled. You
will find, tucked in between the covers of this guide, the absolute most current and useful information in feline
dermatology... all thoughtfully, lovingly, and analytically packaged for you. This guide has been expressly designed to
be practical, concise, and user-friendly. Use it frequently and use it in good health (yours and that of your feline
patients !).
Feline dermatology is the best !
Danny W. Scott, DVM, Dip. ACVD
Ithaca, New York
March 1999
REFERENCES
1 Scott, D.W. J. Amer Anim. Hosp. Assn. 16,331-459 (1980).
2 Scott, D.W. J. Amer. Anim. Hosp. Assn. 23,255-274 (1987).
3 Scott, D.W. J. Amer Anim. Hosp. Assn. 26,515-537 (1990).
4 Norman, P.S. Currenr Opinion in Immunology 5,968-973 (1993).

11. A Practical Guide to Feline Dermatology 1 www.vet4arab.co.cc
Blaise HUBERT PIN Didier
Clinique VCtCrinaire Foch Cabinet de Dermatologie VCt6rinaire
38, avenue du MarCchal Foch HCliopolis B3 -Avenue de Magudas
34500 BCziers - France 33700 Bordeaux-MCrignac - France
Chapter :24 Chapter :2
Ken MASON Pascal PRELAUD
Albert Animal Hospital 2, me Gay Lussac
333 1 Pacific Highway 44300 Nantes - France
Springwood 4127 -Australia Chapters :1 0 , 1 1 , 2 3 , 2 4 , 2 6
Chapter :12
Maite VERDE
Catherine MEGE Servicio Dermatologia - Facultad de Veterinaria
Clinique V6t6rinaire des Grands Cms C/Miguel Servet, 177
60, avenue du 14 juilllet Zaragosa - Espana
21300 Chenove - France Chapter :25
Chapter :17
Margreet VROOM
Karen A. MORIELLO Veterinaire Specialisten Oisterwijk
Department of Medical Sciences Boxtelsebaan 6
School of Veterinaxy Medicine 5061 VD - Oisterwijk - The Netherlands
University of Wisconsin-Madison Chapter :9
2015 Linden Drive West
Madison-Wisconsin - W 53706 - USA Ton WILLEMSE
Chapter :4 Utrecht University
Faculty of Veterinary Medicine
Ralf S. MUELLER Department of Clinical Sciences
Department of Clinical Sciences of Companion Animals
Colorado State University VTH Yalelaan 8
Fort Collins - CO 80523 - USA 3584 CM - Utrecht - The Netherlands
Chapter :6 Chapter :13
Chiara NOLI
Via Sismondi 62,
20133 - Milano - Italy
Chapter :1
Translator
Mark CRAIG
Re-Fur-All Referrals
3 1 Porchester Rd
Newbury, Berks
RG14 7QH
England

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SUMMARY OP CONTENTS
IStructure and functions of skin and coat
1
Chiara Noli
The skin and cutaneous adnexae make up the most important anatomical and physiological barrier
between the external environment and the internal organism. Knowledge of the anatomy and
histology of the various cutaneous structures, some of which are specific to cats, allows better
understanding of all the functions of the skin in the cat (e.g. mechanical protection against water
and light, thermoregulation, biochemical homoeostasis, metabolic regulation, immunoregulation,
sensory perception and social functions). Genetic determination of coat type and colour, and
specific aspects of felime skin and its ecosystem are discussed in detail.
12 Diagnostic approach
Didier Noel Carlotfi - Didier Pin
The diagnostic approach in feline dermatology must be methodical and include the various steps
of a conventional medical consultation as well as additional ones relevant to felime dermatology.
Information gleaned from the history and clinical examination, both general and dermatological,
allow the practitioner to construct a differential diagnosis. Appropriate diagnostic tests are then
chosen to narrow down this list and produce a definitive diagnosis.
01 3 Ectoparasitic skin diseases
Eric Guaguere
Skin diseases caused by mites and insects are of prime importance in feline dermatology and enter
into the differential diagnosis of many diierent conditions. Although some are often suspected,
others are less so because the signs associated with them are non-specific. Some ectoparasitic
conditions may be the source of human infestations, unrecognised by either the vet or the
dermatologist. This chapter deals with notoedric mange, sarcoptic mange, otodectic mange,
cheyletiellosis, trombiculiasis, dernodicosis, pediculosis and flea infestation. Methods of flea
control, both mechanical and chemical, are described.
14 Dermatophytosis
Karen A. Moriello - Douglas J. DeBoer
Dermatophytosis is a superficial fungal infection of the skin. Microsporum canis, the most
common cause of feline dermatophytosis, is not p m of the normal fungal flora of cats and its
isolation warrants special attention. As dermatophytosis is an important zoonosis, it is very
important for veterinary surgeons to be familiar with the condition. Dermatophytosis is
transmitted by direct contact involving an infected cat or indirectly via a contaminated
environment. Clinical signs are very pleomorphic and dermatophytosis should be considered in
the differential diagnosis of all feline skin conditions. Fungal culture is still considered the gold
standard for diagnosing feline'dermatophytosis as it allows genus and species identification of the
causal organism. Although the disease will resolve spontaneously, treatment is required to speed
up resolution, limit the risk of spread to other animals and man, and prevent contamination of the
- -.
environment. Svstemic antifungal treatment is the treatment of choice. Cliooing oromotes faster
.&
healmg and is recommended for long-haired cats and cats with severe infections. Topical therapy
limits transmission and the spread of spores in the environment. It needs to be continued until
fungal cultures are negative on two or three successive occasions in all animals examined. A
contaminated environment is often an important reservoir of spores. Environmental
decontamination requires repeated cleaning to eliminate organic debris and frequent application
of an antifungal disimfectant. Vaccination is not currently an effective means of preventing
dermatophytosis.

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5 ~ e mycoses
e ~
Lluis Ferrer - Alessandra Fondati
Deep mycoses are rare in the cat and may affect only the skin (subcutaneous mycoses) or internal
organs and the skin (systemic mycoses). They are caused by saprophytic fungi that normally live
in the soil, vegetation and decomposing organic matter. Most are considered opportunistic
pathogens. Dermatological signs are characterised by nodules, fistulae and ulcers on the ventrum,
distal limbs and/or the face. In systemic mycoses, various systemic signs (respiratory,
neurological, ocular, bony) are observed. Diagnosis is based on cytology or histopathology to
demonstrate fungi in affected tissues. Fungal culture is necessary to identify the causal organism.
Immunological techniques can sometimes be used in the diagnosis of systemic mycoses.
Treatment of deep mycoses is difficult and definitive cure is rarely possible.
1 6 R. Mueller dermatoses
Bacterial
Bacterial dermatoses, also called pyodermas, are rare in the cat despite being so common in the
dog. The main reasons for this are perhaps the small number of bacteria on the skin and coat of
the cat and also the importance of grooming in this species. Bacterial skin infections are usually
secondary to trauma, bites or scratches and resolve easiiy with suitable antimicrobial treatment.
However, some specific bacterial infections, possibly secondary to a systemic illness (e.g.
retrovirus infection), can be difficult both to diagnose and to treat.
Viral dermatoses
1 7 E. Guaguere
Vial dermatoses are a developing field in felime dermatology. They are underdiagnosed because
of difficulties in identifying the causal virus, but new investigative procedures (e.g. electron
microscopy, immunohistochemistry and molecular biology) now enable these new dermatoses to
-
be characterised. An understanding of them is imoortant as thev enter into the differential
diagnosis of many different conditions. Some of these conditions also represent a major zoonotic
risk for man. Poxvirus infection, feline infectious peritonitis, papillomavirus infection, retrovirus
infections and herpesvirus infection are considered in this chapter.
8 The cat flea: applied biology
M . Dryden
The cat flea Ctenocephalides felis felis is the cause of recurrent infestations in cats, dogs and their
environment. Flea control can be difficult without a good understanding of how the flea interacts
with its hosts and environment. This chapter deals with the biology, ecology and epidemiology of
the cat flea. Practical, effective methods of flea control are presented.
9 Flea allergy dermatitis
Margreet W. Vroom
Flea allergy dermatitis (FAD) is the most common pruritic dermatosis in the cat. A diagnosis of
FAD cannot be e l i i a t e d by the absence of fleas or flea faeces because allergic cats can remove
fleas from their coat by grooming. FAD should be suspected when self-induced, principally
dorsolumbar, alopecia, miliary dermatitis or, more rarely, eosiiophiiic plaques or limear
granulomas are present. Allergy testing has little diagnostic value. Treatment initially involves
rigorous flea control for the affected cat, in-contact animals and the environment. When
antipruritic treatment is necessary, the use of corticosteroids produces immediate improvement.
Immunotherapy is, currently, of no benefit.

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10 Atopic dermatitis
Pascal Prdlaud - Sophie Gilbert
Atopy is the cause of many pruritic dermatoses (e.g. miliary dermatitis, eosinophilic plaques, self-
induced alopecia and cemicofacial pruritus). Lesions can sometimes even resemble those seen in
human and canine atopic dermatitis. Diagnosis of atopy is complicated by the unreliability of
intradermal testing, poor specificity of serological tests, many normal cats having comparable
serum allergen-specific IgE levels, and relatively non-specific clinical signs. Treatment is usually
based on avoidance of the allergens involved (e.g. using elimination diets and flea control), anti-
inflammatory medication, either steroidal or non-steroidal, and as a last resort specific
immunotherapy, although the efficacy of this is difficult to assess.
I l Food intolerance
l
E. Guagu2re
Food intolerance should be considered a possible cause of non-seasonal pmritus in the cat,
especially for self-induced lesions of the face and neck, and when lesions are accompanied by
gastrointestinalproblems. Diagnosis is based on response to an elimination diet fed over at least
10 weeks. The diet must contain novel sources of protein and should only be formulated after
looking very carefully at the cat's previous diet. Either a commercial or home-prepared diet may
be given, depending on what suits the animal and its owners. Challenging the cat with its previous
diet is the only way to conf~rm diagnosis and to select foods for inclusion in the maintenance
the
diet.
12 Eosinophilic granuloma complex
K . Mason - G . Burton
The eosinophilic granuloma complex is a group of diverse clinical entities. Typical forms
(indolent ulcer, eosinophilic plaque and eosinophilic granuloma) and atypical forms (mosquito
bite hypersensitivityand familial forms) are described. These entities are, in fact, reaction patterns
with many diierent causes. A thorough diagnostic approach is, therefore, required to investigate
allergic and infectious causes. For refractory or prolonged cases, an inverse allergy work-up can
be implemented. This consists of eliminating all the possible causes, associated with symptomatic
treatment, then challenging the cat with one thing at a time, once lesions are under control.
Therapy should, primarily, be based on treating the cause. Symptomatic therapy is often required
and involves mainly corticosteroids, antibiotics and cyclosporin.
1 1 3 Auto-immune dermatoses
Auto-immune dermatoses are rare. They are characterised immunologically by the deposition of
auto-antibodies at various levels of the epidermis (pemphigus) and basement membrane (bullous
pemphigoid), or immune complexes within the basement membrane (lupus erythematosus).
Knowledge of these diseases is important as they enter into the differential diagnosis of many
diierent conditions. The pemphigus complex consists of several forms: pemphigus vulgaris (PV),
pemphigus foliaceus (PF) and pemphigus erythematosus (PE). Bullous pemphigoid (BP) has just
recently been identified in the cat. Discoid lupus erythematosus (DLE) and systemic lupus
erythematosus (SLE) are encountered only exceptionally. Diagnosis is based on the history,
clinical examination, and histopathology. For SLE, other procedures such as haematology and
antinuclear antibody tesimg, must be canied out. The prognosis for auto-immune disorders is
variable; relatively good for PF, PE and DLE, guarded for PV, BP and SLE. Treatment involves
mainly oral corticosteroids at immunosuppressive doses and possibly certain alkylating agents
(chlorambucyl) and gold salts (aurothioglucose).

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14 ~ermatolo~ical
manifestations of systemic diseases
D. Hkripizt
Dermatological manifestations of systemic diseases are starting to be documented in the cat,
although their pathogenesis is not always understood. They are very diverse, clinically, and relate
to various systemic illnesses. Their diagnosis is important as these skin lesions enter into the
differential diagnosis of many different conditions and may appear before the underlying illness.
Unlike in the dog, endocrinopathies very rarely cause skin lesions in the cat. Spontaneous and
iatrogenic Cushing's syndrome are very rare, spontaneous hypothyroidism is exceptionally rare,
hyperthyroidism produces a few non-specific changes in the skin, and dermatological signs
associated with sex hormone imbalances are now hotly disputed. However, the cat has a whole
range of systemic disease-associated dermatological lesions, of its own.
15 Skin tumours
Delisle - Pahick Devauchelle
Fran~oise
Tumours of the skin and its adnexae are some of the most diverse and common tumours seen in
the cat. Such a large variety is possible because the skin is made up of lots of different
components, each of which can potentially form a tumour. We, therefore, see epithelial tumours
which involve the malpighian layer, the adnexal sebaceous or sweat glands and hair follicles,
tumours of the melanogenesis system, mesenchymal tumours developing in the dermis or
subcutaneous connective tissue, tumours derived from lymphoid tissue and finally, nerve and
vascular tumours. The majority of skin tumours in the cat are primary. Tumours secondary to, for
example, a pulmonary adenocarcinoma (which is usually asymptomatic) or a mammary
adenocarcinoma are much less frequent.
1 1 6 Genodermatoses
Eric Guagusre - Zeineb Alhaidari -Jacques Fontaine
Genodermatoses are rare, although they constitute a developing field in feline dermatology. In
- .
recent vears. investieative orocedures such as electron microscopv and immunohistochemis@y
have lei to the identification of new genodermatoses. It is imp;&t to be familiar with these
conditions as they enter into the differential diagnosis of many different dermatoses.
Genodermatoses affect the epidermis and its adnexae, the melanogenesis system, the dermo-
epidermal junction and the dermis. In this chapter, the following conditions are reviewed:
hereditary greasy seborrhoea of the Persian, congenital hypotrichosis, follicular dysplasia, hair
dysplasia, pili torti, genetic abnormalities of melanin pigmentation, hereditary cutaneous
asthenia, and urticaria pigmentosa of the Sphinx.
17 Skin conditions associated with behavioural disorders
Catherine Mege
Sldn conditions associated with behavioural disorders are probably rare hut remain under-
diagnosed in the cat. They are characterised by self-induced lesions (e.g. alopecia, nail chewing
and various mutilations). Advances in the study of animal behaviour have enabled these
conditions to be placed in the context of behavioural disorders (e.g. anxiety, depression and
dysthymia). Thanks to a better understanding of the behaviour of the domestic cat and the
availability of new psychotropic drugs, pheromones and behavioural therapies, specific diagnosis
and effective treatment are now possible.

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1 1 8 ~ i a ~ n o s tapproach to pruritic dermatoses
ic
2.Alhaidari
The diagnostic approach to fel'me pruritic dermatoses must be methodical and should include
certain fundamental diagnostic steps: a detailed history, thorough clinical examination, and
carefully chosen diagnostic tests, selected according to the differential diagnosis. An initial range
of tests (e.g. skin scrapings, tape strips, mycological investigations and skin smears) should be
performed routmely, given the incidence of ectoparasitic infestation and dermatophytosis in the
cat. Differential allergy diagnosis is based on avoidance measures (e.g. flea control and restricted
diet) as allergy tesimg remains unreliable in this species. Skin biopsies are indicated when the
history and clinical examination suggest a dermatosis that requires histological diagnosis.
1 1 9 Diagnostic approach to alopecia
2.Alhaidari
The diagnostic approach to alopecia must be methodical, and should involve certain fundamental
steps: a detailed history, thorough clinical examination, and carefully chosen diagnostic tests,
selected according to the differential diagnosis. An initial range of tests (e.g. skin scrapings, tape
strips, and mycological investigations) should he performed routinely, given the incidence of
ectoparasitic infestation and dermatophytosis in the cat. Differential allergy diagnosis is based on
avoidance measures (e.g. flea control and restricted diet) as allergy testing remains unreliable in
this species. Skin biopsies are indicated when the history and clinical examination suggest a
dermatosis that requires histological diagnosis.
1 2 0 Diagnostic approach to crusting dermatoses
E. Bensignor
Crusting dermatoses are a common reason for consultation in feline dermatology. Crusts can be
defined as a mixture of blood. serum. exudate. andlor us which has dried on the surface of the
skin and to which scale and hairs have become stuck. t o make a specific diagnosis and institute
effective treatment requires a good knowledge of the clinical aspects and causes of crusting
dermatoses. The diagnostic approach rests on the history, clinical examination and appropriate
diagnostic tests. It is important to distinguish 1) crusts secondary to excoriation, for which the
diagnostic approach is the same as that of the pruritic dermatoses, 2) large, spontaneously-
appearing crusts associated with erosions and their dried-up exudate, and 3) punctate crusts seen
in miliary dermatitis, a cutaneous reaction pattern usually associated with ectoparasitic infestation
or flea allergy dermatitis, and occasionally with dermatophytosis, bacterial folliculitis or atopic
dermatitis.
21 Diagnostic approach to erosive and ulcerative dermatoses
E. Bensignor
In the cat, erosive and ulcerative dermatoses are a common reason for consultation, probably
because of the thinness of the epidermis. Erosions and ulcers K&ed to self-excoriation should be
distinguished from those which appear spontaneously. They are usually secondary lesions with
little diagnostic significance. The diagnostic approach should involve taking the history,
conducting a thorough clinical examination (general and dermatological), and performing
appropriate diagnostic tests, especially cytology and skin biopsies.

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1 2 2 '~ia~nostic
approach to otitis externa
E. Bensignor
Long thought of as a local phenomenon, otitis externa should be reclassified in a broader
dermatological context, as it is usually one local manifestation of an underlying dermatosis. The
diagnostic approach should be rigorous, including a history, thorough clinical examination
(general and dermatological), and simple, appropriate diagnostic tests, especially auroscopic
examination, direct microscopical examination of cerumen, cytology and bacteriology.
Occasionally, radiography, CT scanning of the tympanic bullae, paracentesis and biopsies are
indicated.
1 2 3 Diagnostic approach to facial dermatoses
Pascal Prilaud - Eric Guag3re
Facial dermatoses are a very important and diverse group of diseases. In some cases, the face is
affected directly whereas in others, facial involvement is a consequence of systemic disease. One
reason why the face is frequently involved is that it is a very exposed part of the body, not easy to
groom, and with sparse hair cover offering scant protection. Mucocutaneous junctions (e.g. lips,
nose and eyelids) are predisposed to infectious, parasitic and immune-mediated dermatoses.
W e is such a plethora of potential causes of facial dermatoses that a very rigorous and
methodical diagnostic approach is essential. The history and clinical examination (general and
dermatological) are used to formulate a differential diagnosis, which can be narrowed down by
performing weU-chosen diagnostic tests. The main facial dermatoses (excluding those of the
external ear) are dermatophytosis, allergic dermatoses, superficial pemphigus conditions and
squamous cell carcinoma.
Diagnostic approach to feline pododermatoses
124
Eric GlcaguPre - Pascal Prdlaud - Blaise Hubert
Pododepnatoses are a very important and diverse group of diseases. In some cases, feet are
affected directly whereas in others, pedal involvement is a consequence of systemic disease.
Although pododermatoses are a less frequent reason for consultation than in the dog, the foot can
be targeted directly in various specific conditions: bacterial paronychia, plasma cell
pododermatitis and cutaneous metastasis of a pulmonary adenocarcinoma. Pedal involvement
may also be part of a more generalised dermatological condition. There is such a plethora of
potential causes of pododermatoses that a very rigorous and methodical diagnostic approach is
essential. The history and clinical examination (general and dermatological) are used to formulate
a differential diagnosis, which can be narrowed down by performing weU-chosen diagnostic tests.
Used alongside routine diagnostic tests (e.g. Wood's lamp examination, direct examination of
hairs and scale, skin scrapings, fungal culture and cytology), the skin biopsy is often the key to
diagnosis.
1 2 5 Zoonotic dermatoses
Maire Verde
The term 'zoonotic dermatoses' refers to those zoonoses in which the causal agent causes sldn
lesions. The most important feline zoonotic dermatoses are dermatophytosis, flea infestations -
involving possible transmission of cat scratch disease and the plague - cheyletiellosis and
notoedric mange. Other zoonotic dermatoses are less common: sporotrichosis, blastomycosis,
histoplasmosis, otodectic mange, tuberculosis and poxvirus infection. A detailed knowledge of
these diseases in man is essential for clinicians involved in feline dermatology.

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1 2 6 Therapeutic tables
Pascal Prdlaud - Eric Guaguere
This chapter lists the principal medications used in feline dermatology. Dose, route of
administration, indications and whether a product licence exists are outlined for each
drug.
1 2 7 General index
1 2 8 Index of illustrations

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-l Foreword
The cat has long been neglected, even ignored, by veterinary medicine,for reasons that are partly cultural andpartly
economic.
It was only with the development of companion anlmal medicine, in the 1960s, that the cat was seen as an animal
species worthy of veterlnary interest. Back in 1964, E.J. Catcott's Felme Medicine and Surgery, thefirst veterinary text
book devoted exclusively to the cat, was already predicting the huge increase in impiXZce of the cat as a companion
animal. Yet,for a long time, the cat was treated merely as ifit were a small dog. Furthermore, thefact that cats tolerate
high doses of corticosteroids so well meant that there was little incentive to research and develop alternative therapies
in this species.
The 1980s saw the birth of a more spec@ feline medicine, triggeredprobably by the discovery of the retroviruses and
diseases that were unique to the cat. Pharmaceutical companies began to show a growing interest in researching new
treatments for cats. At the same time, academic bodies like the American Association of Feline Practitioners and the
European Society of Feline Medicine and journals - such as Feline Practice, and more recently Journal of Feline
Medicine and Surgery - dedicated entirely to the cat, appeared on the scene.
Today,feline dermatology is a thriving discipline in its own right, no longer confined to a few paragraphs at the end
of a chapter in a small animal dermatology book or severalpages in afeline general medicine text. To our knowledge,
the first atlas dedicated entirely to feline dermatology was G.H. Muller's Feline Skin Lesions, in 1974, which
contained 35pages on the principal dermatoses. Then came the celebrated monographs by D.W. Scott which appeared
in 1980, 1987 and 1990 in the Journal of American Animal Hospital Association. These were to provide the real
foundation of modern feline dermatology. In 1981, J.M. Keep, in Australia, produced a series of three dermatology
books, each on a different species, one of which was the cat. Finally, in 1995, Veterinary Clinics of North America
(Small Animal Practice) asked Gail Kunkle to produce a special Feline Dermatology issue, still seen today as a
milestone. We have deliberately excludedfrom our list all the dermatology text books which include chapters on feline
dermatology.
Our aim, here, has been to provide a guide which is both instructive and easy to read, but without any claim to being
an encyclopaedia. We have tried toproduce a book that will allow each vet to develop his or her own expertise infehne
dermatology. Such an ambitious project could come to fruitlon only within the framework of internatlonal
collaboration between expertsfrom various backgrounds. Veterinary dermatology belng a large family that embraces
enthusiasts everywhere, irrespective of nationality or university status, it was easy for us, as scient$c editors, to
assemble a team of authorsfrom all corners of the globe. We have been overwhelmed by the enthusiasm shown by the
twenty-six authors recruitedfrom eight different countries. We would like to thank them for the excellence of their
contributions, as well as for their kindness, encouragement andfriendship.
A Practical Guide to Feline Dermatology is divided into two main sections. The first is a detailed study of the main
topics in feline dermatology, presenting the most up-to-date information alongside high quality colour plates. The
second section, which outlines diagnostic approaches to all the pr~ncipaldermatoses, isreadily accessible to the vet
in practice, struggling to make the correct diagnosis.

21. www.vet4arab.co.cc
We would like to extend our very sincere thanks to one of our mentors, Professor D.W. Scott for doing us the honour
of writing the preface. He can be assured of our deepest respect and admiration for his outstanding contribution to
feline dermatology, which he refers to as his own 'professional hobby'.
Lastly, A Practical Guide to Feline Dermatology would not have been possible without the interest and enthusiasm of
Merial, under the direction of Doctors Daniel Gouffd and Ronan Gillard who have had the foresight to see that, in the
21st century, the cat will be the animal species with the greatestpotential for medical development. We hope that this
book will instill in you, as it has in us, a new passion for feline dermatology and dispel forever the notion that it is
about nothing more than reaching for the bottle of long-acting corticosteroid!
2 September, 1999
Restaurant le Pamphlet, Paris.
Eric GuaguPre Pascal Prdlaud
Docteur Vdtdrinaire Docteur Vdtdrinaire
CertGed in Veterinary Dermatology Cert$ed in Veterinary Dermatology
Diplomate of the European Diplomate of the European
College of Veterinary Dermatology College of Veterinary Dermatology

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1 Structure and functions of skin
and coat
The skin and its adnexae make up the most important organ of the body and form an essential
anatomical and physiological harrier between the external environment and the internal organism. Knowledge of
the anatomy and histology of the various cutaneous structures, some of which are specitic to cats, allows better
understanding of all the functions of the skin in the cat. The skin also acts as a mirror which reflects the health and
comct functioning of the organism.
Structure of the skin and its adnexae
The skin of cats is thinner than that of dogs, 0.4 to 2 mm thick on average. It is thicker on the dorsal regions
and proximal limbs, and thinner on the ventrum and distal limbs '.
Epidermis
The epidermis is a squamous keratinised epithelium made up of 3 to 5 cellular layers (excluding the horny
layer), 25 pm thick ' (Diagram 1 : 1) (Fig. 1 : 1). In the non-hairy areas (nasal planurn, footpads), it is
thicker (up to 900 p) lined by a more developed horny layer (Fig. 1 : 2). The thickness of the horny
and
layer is between 3 and 20 p in the hairy areas and between 15 and 35 pm on the footpads '. The
epidermis does not contain any blood vessels, its nutrients being provided by diffusion fmm the dermal
hlocd supply.
Keratinocytes make up the majority (85-90%) of the epidermal cells. Other epidermal cells, such as
Langerhans' cells (3-8%), melanocytes (2-5%) and Merkel cells, appear as clear cells under the light
microscope. Lymphocytes and occasionally mast cells can also be found ' (Fig. 1 : 3).
Keratinocytes undergo keratinisation or comification, a differentiation and maturation process which
progressively transforms the small, round, basal layer cells into large, flat, anuclear, polyhedral
corneocytes (Diagram 1 : 1). The corneocytes are shed by desquamation. The replacement rate of
keratinocytes has not yet been determined in cats. In dogs (Beagles), it takes 22 days for a basal cell to
reach the horny layer '.
Diagram 1 : 1 : Schematic diagmm of the epidermis
Horny layer
Granular layel
Spinous (Malpighian) layer
Basal layer
Basement membrane

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Melanocytes are dendritic cells which synthesise melanin pigments in specific structures called
melanosomes, situated in the epidermal basal layer or in the hair follicle matrix. They generally appear
as clear cells, without specific colouration, under the light microscope. In black or grey cats, these
melanocytes are easily recognisahle due to their intracytoplasmic black p u l e s . The melanocytes, via
their dendrites, are in contact with several keratinocytes to which they transfer their pigment granules.
There are up to 25 keratinocytes per melanocyte in the epidermis.
Langerhans' cells are antigen-presenting cells which phagocytose antigens at the skin surface, and
migrate into the drainmg lymph node where they present the captured antigen to T lymphocytes. They are
responsible for triggering specific immune reactions. Langerhans' cells contain specific intracytoplasmic
organelles, shaped like rackets, called Birbeck p u l e s 4. Their immunophenotypes are CDlat, M H C P
and C D ~ +In cats, the density of Langerhans' cells in the skin is higher on the p m a e and middle of the
.
back, and lower on the abdomen I.
Merkel cells are mechanoreceptor cells situated in the basal layer, in contact with nerve fibres.
Basement membrane
The keratinocytes of the basal layer sit on the basement membrane which separates the epidermis from
the dermis. They are attached to it by hemidesmosomes and other adhesion molecules. The basement
membrane acts as mechanical supporl for the epidermis and regulates metabolic transfer between the
dermis and epidermis. It is around 40 nm thick. It can be seen under the light microscope usimg special
stains such as Periodic Acid-Schiff (PAS). Ultrastructural studies have enabled three zones to be
disimguished: the lamina lucida, in contact with cells of the basal layer, the lamina densa and the
sublamina densa which permits adhesion to dermal collagen.
Dermis
The dermis is a rich network of fibres, intercellular ground substance, blood and lymphatic vessels,
nerves, muscles and cells.
Collagenfibres produced by fibroblasts are made up of 90% collagen, a filamentous protein with great
tensile strength.
Elastinfibres make up around 4% of dermal fibres and form a network in the dermis beneath the pilo-
sebaceous units.
Reticulinfibres are very h e fibres which form a loose network around collagen fibres and other dermal
structures.
Dermal ground substance is made up of proteoglycans, glycoproteins and large quantities of water. It
appears as an amorphous gel, produced by fibroblasts, and has an important barrier function with regard
to micro-organisms and large molecules passing between the epidermis and subcutaneous tissue.
Three interconnected vascularplen'are found in the dermis. The uppermost sub-epidermal plexus brings
nutrients to the epidermis and hair follicle infundibula. The middle plexus, situated at the level of the
sebaceous glands, provides a blood supply to the glands, muscles and follicular isthmus. The deep plexus
below the hair follicles, supplies the dermal papilla, apocrine glands and the two other plexi.
Arteriovenous shunts, situated mainly in the distal limbs, are associated with thermoregulation.
Lymph vessels in the deep dermis enable drainage of cutaneous fluids and maintain homeostasis.
Nervefibres follow the blood capillaries and are organised in three plexi. Free nerve endings reach the
epidermis or form more complex structures such as Pacinian corpuscles..
Dermal cells are numerous. Fibroblasts responsible for collagen synthesis and production of dermal
ground substance also produce enzymes, notably a collagenase and a gelatinase, capable of catabolising
ground substance and fibres. The fibroblasts are therefore responsible for maintaining the dynamic
homeostasis of the dermis. They also play an important role in inflammation and healing. The numerous
mast cells in cat skin are situated mainly in the perivascular region and synthesise a range of enzymes
(chymase, tryptase) (Fig. 1 : 3). Other cells found in the dermis include macrophages, lymphocytes,
neutrophils, eosinophils and plasma cells.

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1 : Strucw and functions of sldn and coat
Figure I :I : Normal cot epidermis: note thinness of the epidermis Figure 1 :2: Normalfoofpadepidermis: note thickness of the horny layer
(HE,x 402) (HE,x l w
Figure I :3 :Intraepidermal mast cells, (+) (Tolu~dlne x 100)
blue, Figure 1 :4 : I n ~ u l w of a normal hairfoNicle (HE,x 460)
n
Pigave 1 :5 :Hairfoll~clebulb in nnagenphose(HE,x400) Fkure I : 6 : Tr~ctwgmmof central pnmmy, lateral primnry and
secondary h r s (x 100)

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Subcutaneous connective tissue
Subcutaneous tissue is composed of a layer of connective tissue, rich in adipose cells. It has many roles,
the most important of which are storage of lipids and fat-soluble substances, thermal insulation and
protection from physical trauma.
Hair follicles
Hair follicles are epidermal invagimations into the dermis, which synthesise and provide support for the
hair. Hair follicles are divided into three regions (Diagram 1 :2): the infundibulum (Fig. 1 :4), the isthmus
and the bulb (Fig. 1 : 5).
In the adult cat, each follicle has its own bulb and isthmus but several follicles share the same
infundibulum. These are called compound hair follicles. Ten to twenty hairs are present per infundibulum.
The density of the coat is around 250 hairs/cmi. The coat is denser on the abdomen than on the back.
Newly-born kittens up to the age of 3-4 months have simple hair follicles.
Types of hair
Hair follicles generally contain one central primary hair, up to five lateral primary hairs and up to twenty
secondaq hairs. The clusters of follicles on the back have larger primary hairs and fewer secondaq hairs
than those on the abdomen.
Central primary hairs (40 to 80 p in diameter) have a large medulla and thin cortex ' (Fig. 1 : 6). They
are rigid, cover the whole skin surface, provide protection against the rain and are responsible for coat
colour. The primary hair follicles are the largest and longest in the follicular cluster, extending into the
deep dermis. They are associated with sebaceous glands, apocrine sweat glands and an m c t o r pili
muscle.
Lateralprimary hairs (25 to 40 pm in diameter) are moderately supple '. They have a different orientation
to the undercoat, therefore providing better thermal insulation. They are characterised by a sub-apical
bulge at the base of the hair.
Secondary hairs (10 to 20 pm in diameter) are fine and supple with a relatively thin medulla and a thick
cortex (Fig, 1 : 6). They form the undercoat responsible for maintaining temperature. Secondary
follicles can sometimes have a single sebaceous gland, but never apocrine sweat glands nor m c t o r
muscles.
Hair shrcture
The hair consists of a colunm of comified, vety adherent, stratified cells, arranged in a cuticle, a cortex
and a medulla (Diagram 1 : 2).
The cuticle is made up of a single layer of cuboidal epithelial cells which dierentiate into anuclear, flat
and adherent comeocytes. These comeocytes line and protect the hair, like tiles on a roof, and are
orientated towards the isthmus. The cuticle cells are oriented in the opposite direction to those of the inner
follicular root sheath and are therefore overlapping. This protects the hair follicle and ensures support for
the hair during its growth phase in the deep p a s of the hair follicle. In cats, the cuticle cells are thin and
arranged in a very smooth flattened manner, which is why cat hair feels softer to the touch than dog hair.
The cortex consists of elongated comified cells arranged parallel to the axis of the hair. In primary hairs,
the cortex makes up a sixth of the diameter of the hair 3. Secondaq hairs have a relatively thicker cortex
than the primary hairs which have a much larger medulla.
The medulla is the internal part of the hair. It is produced by the hair matrix and generally contains air,
glycogen vacuoles or pigments. The medullary cells of cats are flatter than those of dogs and arranged at
a 90" angle to the axis of the hair 9.
Structure of the hair follicle
The base of the hair follicle is made up of a bulb matrix, a dermal papilla and a hair bulb. Above the bulb
are the inner and outer epithelial root sheaths which are surrounded and supported by a layer of dense
connective tissue (Diagram 1 : 2).
The bulb matrix is formed from small, round, basophilic epithelial cells which divide actively at the centre
to create the hair, and at the outside to create the inner root sheath. Melanocytes ate responsible for
pigmentation by transfer of melanosomes to the cells of the hair's cortex and medulla. The bulb matrix is
nourished by the dermal papilla, made up of connective tissue rich in blood vessels and nemes within a
mucopolysaccharide matrix.

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1:Smcture and functlons of skin a d coat
n
F w e I :7 : fdllirle In anugen p b e (HE,&Oil]
Xar Pigm 1 : :
8 Holrfollicie inmagenirelogenphme (HE,x 400)
F i g m I :9 : Sebaewur $ I d s ( H E , 4WJ
corpuscle (PAS, x IW)
Fipre 1 :11 :Pac~nran Figure I :12 :Whrsker note the blood slnur a m m i the h l r (HE,x 100)

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Diagram 1:2 : Schematic diagram of a hair follicle
Hair
Cuticle
Medulla
Isthmus
Inner root sheath
Outer root sheath
Apocrine sweat gland
Dermal papilla
At the base of the follicle above the bulb matrix, the hair is surrounded by two concentric sheaths. The
outer root sheath represents an invagimation of the superficial epidermis into the dermis. In the deeper part
of the isthmus and in the bulbal zone, the outer root sheath is not cornifid. In the isthmus and upper
bulbal zone, the cells of the outer root sheath appear larger and clearer due to high levels of glycogen. In
the deeper parts of the bulb, they appear small and basophilic, like the mahix cells. The inner root sheath
swounds and supports the hair, from the matrix where it is produced, up to the isthmus where it is
destroyed.
Follicular cycle
Hair growth consists of diierent phases: a growth (anagen) phase (Fig. 1 : 7), an intermediate (catagen)
phase (Fig. 1.8) and a resting (telogen) phase. Duration of the anagen phase depends on breed and region
of skin. Long-haired cats have a longer anagen phase than short-haired cats. Dorsal hair has a longer
anagen phase than nasal hair. Hairs grow from 0.04 to 1 mm each day and long hairs grow faster than
short hairs.
The genetics of different coat types
Hair length is influenced by various genes, a dominant, L "short hair" gene (average 4.5 cm) and a
recessive, I "long hair" gene (up to 13 cm). Other lengths (very long as in the Persian, mid-length as in
the Norwegian or the Maine Coon) are produced by polygenes or modifier genes.
Genes of the series "I", "h" and " W engender important modifications to the texture and structure of
hairs. The "I" series is seen in "Rex" cats which do not have central primary hairs, and whose lateral
primary and secondary hairs and whiskers are abnormal. There are different types of Rex cats (Cornish,
Devon, Oregon, Dutch and Sekirk) depending on recessive or dominant mutations of this gene. The "h"
series is expressed in the Sphinx, (no relation to the Rex), which has no primary hairs. However,
secondary hairs are present on the extremities (nose, pinnae, limbs, tail). The dominant "Wh" gene is
responsible for the development of very curly hair. In this case, the three types of hair are entwined.

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1 : Structure and functions of skin and coat
Genetics of hairpigmentation
The colour of the skin and coat depends on the quantity, type and location of melanin pigments in the
skin. There are two types of melanin, eumelanin @lack/brown)and phaeomelanin (red/yellow). The large
number of colours seen in the various breeds of cats depends on the prevalence, combination and
distribution of these two types of melanin in the skin. White colouration occurs through an absence of
pigmentation resulting from lack of melanisation of melanocytes. This is called albinism when complete
( i s is very light blue or red).
The most important gene involved in feline hair pigmentation is the dominantA "agouti" gene responsible
for the o r i g ' i , wild, banded pigmentation of primary hairs. Cats carrying this gene have dark-tipped
hairs with one or more bands of colour. Those which express the recessive a, "non-agouti" gene, have
uniformly pigmented hair. Wid cats also carry the T "tabby" gene, responsible for dark markings on a
lighter, generally yellow or grey, base. There are different variants of the "tabby" gene which produce
variable distribution of stripes or spots on the body.
Colours seen in domestic cats are divided into phaeomelanic colours (orange / g'mger (red) and cream
(diluted red)) and eumelanic colom (black, grey (generally called blue, diluted black), chocolate
(chestnut), lilac (diluted brown), cinnamon (light chestnut) and fawn (diluted cinnamon). As the genes
responsible for hair colour are situated on the X chromosome, cats with concurrent red and black/brown
colours are generally females which can carry the two red and black/brown genes on each of the two X
chromosomes.
Colour dilution is caused by the recessive d gene. In colour-dilute breeds, l i e the C h W u x , hairs contain
irregularly distributed melanosomes grouped in melanin clusters in the melanocytes and hair cortex. A
foUicular dysplasia of colour-dilute cats has been described in the Cornish Rex.
Silver coats are coded by the I "colour inhibitionn gene. Colour is lost in the proximal hair which grows
out white. There are different types of silver coat, depending on the extent of hair depigmentation.
The recessive variants of one pdcular gene, the C gene, are responsible for "colour point" coats, typical
of the Siamese. Tnis gene codes for an enzyme whose activity is temperature-dependent. This causes
excessive colouration in colder regions such as the extremities. The ca gene is responsible for blue eye
albinism, the c gene for red eye albinism.
White spots are due to the expression of a different gene, the S "white spotting" gene, whereas generalised
white colouration of the coat is encoded by the dominant W gene. This latter gene is often associated with
deafness because it causes degeneration df the cochlea and atrophy of the organ of Corti.
3utaneous glands
Sebaceous glands
Sebaceous glands are simple alveolar holocrine glands, associated with hair follicles in groups of two or
thee (Fig. 1 : 9). Their excretorv ducts open into the follicular isthmus. Sebum is the product of sebaceous
gland cell destruction in the Addle of the gland. It combines with sweat, produied by the apocrine
glands, to form a lipid emulsion (the surface hydrolipid film) which protects the skin surface. The
sebaceous glands are large and numerous in the skin around the lips and on the chin, and play a role in
territorial marking when the cat rubs its face against objects and human beings. The perianal glands and
supracaudal organ are modified sebaceous glands which are larger than the other glands. As development
is hornonally dependant, they may be particularly large in entire male cats. Excessive accumulation of
glandular secretion in this region is known as stud tail.
Sweat glands
Apocrine sweat glands are present over the whole surface of hairy skin and their ducts open above the
sebaceous gland ducts into the follicular isthmus. Apocrine glands are simple tubular glands with a
straight duct and a convolutedsecretory part surrounded by myoepithelial cells (Fig. 1 : 10).Tney produce
an aqueous secretion which forms an emulsion with sebum at the skin surface (the surface hydrolipid
film).
Eccrine sweat glands have the same structure as apocrine sweat glands but are only found in non-hairy
areas of skin l i e footpads. Their ducts open directly at the skin surface. These sweat glands are situated
close to blood vessels and are controlled by blood adrenaline and noradrenaline. Hence, frightened cats
sweat excessively from their footpads.

29. 1~;
~.4hctical
~~ ~
GuidetoFehe Dermatology
I www.vet4arab.co.cc
Modified sweat glands make up the mammary glands, ceruminal glands and the glands of the anal sacs
There are no sweat glands on the nasal planum '.
Functions of the skin and coat
The skin and coat have many important functions including protection from the external environment,
thermoregulation and maintenance of biochemical homeostasis. They also have metabolic, sensory, immunological
and social functions.
Mechanical protection
The coat is the first barrier to mechanical trauma. It is often thick because of an undercoat covering the
whole skin surface. Dermal collagen fibres impart a high tensile strength and prevent skin tearing.
Protection against water
Thanks to this thick coat and the surface hydrolipid film,water does not readily reach the skin surface.
The orientation of primary hairs ensures that water droplets are quickly shed. Constant grooming keeps
primary hairs clean and ensures optimal protection from water. Certain breeds, such as the Norwegian
Forest, exhibit a very hydrophobic coat. This characteristic is often tested by show judges who let several
drops of water fall on the hairs to see if the drops slide off the coat without wetting the animal. I water
f
does reach the skin surface, it cannot pass through it because intercellular spaces in the horny layer
contain lipids impermeable to water and water-soluble substances.
Protection from light
The coat is an excellent barrier to visible light and ultra-violet (UV) rays. In the areas where the coat is
sparse or absent, pigments (mainly melanins), keratin, proteins and blood absorb the UV rays and prevent
certain skin lesions. Nevertheless, in white or light-coated cats with little pigment, solar keratotic lesions
and epidermal carcinomas can appear in sparsely-haired areas such as the pinnae, nose, eyelids and the
a m behind the ears, following prolonged or frequent exposure to the sun.
Thermoregnlation
Temperature regulation is also an important function of the coat and skin. The thick coat and the layer of
subcutaneous connective tissue, rich in adipose cells, protect the cat when the temperature is cold. An
insulating air cushion exists between the hairs. The size of the air cushion can be increased or decreased
by the action of arrector muscles. The undercoat is shed in the spring and re-grows in the autumn in breeds
which experience large seasonal temperature variations. This is_particularlytrue in the k k i s h Van breed,
origimating in central Anatolia, where the temperature variation between summer and winter can be as
much as 50°C. The highly developed dermal vascular system plays an important role in thermoregulation.
Vasodilatation produces heat loss and vasoconstriction causes closure of arteriovenous shunts, which
prevents excessiveheat loss from the circulation. The cutaneous vascular system stores large quantities of
blood and peripheral vasoddatation or vasoconstriction can also have an effect on central blood pressure.
Cats have a particular way of reducing their body temperature as, unlike in humans, sweat glands are not
involved in thermoregulation. Cats constantly wet their coats by licking. This produces a cooling effect
as saliva evaporates from the skin surface.
Biochemical homeostasis
Many substances are stored in the dermis and subcutaneous comective tissue. Large quantities of water
and electrolytes are associated with proteoglycans and other molecules in the ground substance, while
lipids and fat-soluble molecules are stored in subcutaneous adipose tissue.
Metabolic and immunological functions
For a long One, the skin was considered to be an organ with only a passive protective role, not one that
involved the individual's general metabolism or immunological defence mechanisms, with the exception
of vitamin D synthesis. Various metabolic pathways prodicing systemic effects (for example, effect of
androgens and oestrogens on smell) have recently been demonstrated in the skin. In addition, an

30. www.vet4arab.co.cc
1 : Structure and functions of skin and coat
immunological system has been identified, capable of specitic reactions against micro-organisms,
parasites or foreign antigens present on skin.
Sensory functions
Various different sensations such as pain, pruritus, heat, cold, pressure and touch are felt at the cutaneous
level. Free nerve endimgs in the epidermis are responsible for sensations of pruritus, pain, heat and cold.
Specialised structures, l i e Pacinian corpuscles (Fig. 1 : 1l), tylohich pads, whiskers " (Fig. 1 : 12), hair
follicles, type C mechanoreceptors and Merkel cells all have mechanoreceptor functions 12.
Social functions
The colour of wild cats l i e the Lynx, enables the animal to hide easily in woods and forests (mimicry).
Domesticated breeds have lost this characteristic, perhaps with the exception of black cats used in the
Middle Ages, to chase mice and rats from the holds of ships. Specialised glands, like the hepatoid
circumanal glands, the anal sacs, the supracaudal organ and the sebaceous glands of the lips and chin,
produce pheromones. Pheromones are used in territorial marking, facilitate recognition between
individuals and influence sexual attraction. Various fractions (F3, F4) have been isolated recently. Cats in
dangerous situations raise the hairs on their back and tail and present themselves sideways-on to their
adversary in order to appear larger.
Cutaneous microbi9logy and barrier functions
--
Horny layer
' The compact horny layer represents the f hmolecules and micro-organismsand parasitic infestations. In
normal conditions, water, water-soluble
t physical banier to infections
cannot cross it. Constant
shedding of the most supeficial cells reduces excessive bacterial colonisation which could otherwise
predispose to infection.
Dermis
I a micro-organism or parasite enters the dennis, it must pass through a very dense network of collagen
f
fibres and intercellular ground substance molecules, before fmdiig itself in contact with a very active
immune system.
Hydrolipid surface film
The sebum and sweat form an emulsion on the skin surface which acts both as a physical banier,
preventing the passage of water and water-soluble substances, and a chemical banier, made possible by
the presence of certain substances involved in skin defence mechanisms. These include Ransferrin which
l i i t s bacterial proliferation, and free fatty acids such as linoleic acid, produced from surface higlycerides
by bacterial lipases, which prevent skin colonisation by pathogenic micro-organisms. Other lipids such as
glycosphingolipids arising from the decomposition of the horny layer might play an even greater
antibacterial role. Specific factors, such as complement and immunoglobulins, can attach themselves to
the skin surface and prevent microbial adherence and proliferation. Skin pH in cats varies between 5.73
and 6.01, with the exception of the nose and footpads (areas of eccrine secretion) where it is less acidic,
between 6.81 and 7.97". A low pH has bacteriostatic and bactericidal effects.
Resident microbial flora
The resident surface flora, which occupies micro-ecological niches, prevents colonisation by pathogenic
micro-organisms by producing antibiotics, enzymes or other toxic substances. They utilise available
nutrients. Resident bacteria on cat skin include Micrococcus spp., coagulase-negative staphylococci
(especially Staphylococcus simulans), a-haemolytic streptococci and Acinetobacter spp. 12. It is possible
to isolate more bacteria from cats in close contact with humans than froiii cats living in catteries, which
suggests that humans may be involved in transmitting bacteria to cats ". Transient bacteria, isolated from
cat skin, include R-haemolyhc streptococci, Escherischia coli, Proteus mirabilis, Pseudomonas spp.,
Alcaligenes spp., Bacillus spp., and staphylococci 12. These hacteria can occasionally become pathogenic
if conditions are favourable for multiplication.
Yeasts of the genus Malassezia are commensal micro-organisms found on the skin of cats, especially in

31. www.vet4arab.co.cc
humid regions such as ears, penanal and inguinal regions Id. Malassezia pachydermatis, Malassezia
sympodialis and Malassezia globosa have been isolated from cat skin 14.
Van'ous saprophytic fungi can be isolated from the skin and coat of normal cats. These include Alternaria
spp., Aspergillus spp., Cladosporium spp., Mucor spp., Penicillium spp. and Rhodotorula spp. ",''.
Microsporum canis isolated from normal cats must always be considered a pathogen 16.
REFERENCES
1. Strickland, J. H. & Lois Calhoun, M. Amer J Vet. Res. 24, 1018-1029 (1963).
2. Scott, D. W Vet.Dermatol. 1,6569 (1990).
3. Baker, B. B. Amer. J. Vet. Res. 3,93 (1973).
4. TsagaraIds, C., Marchd, T., Magnol, J. P., Fournel, C., Dezutter-Dambuyant, C. & Schmitt, D. Research in Virology 145,245-249 (1994).
I 5. Saint-Andr6 Marchal, I., Dezutter-Dambuyant. C. & Mutin, I. P and others Br. J. Dermarol. 136,961-965 (1997).
.
6. Badleston, D. L., Roosje, P. & Goldschmidt, M. H. J. Vet. Allergy Clin. Immunol. 5,54-58 (1997).
7. Blazej, A. Galatik, A. Galatik, I. Krul, Z. & Mladek, M. Atlas of Microscopic Structures of Fur Skins (Elsevier, Amsterdam, 1989).
8. Lochte, m.Atlas der Menschlichen und TierischenHaare (Paul Schps Verlag, Leipzig, 1938).
9. Creed, R. E S. Vet.Rec. 70, 171-175 (1958).
10. Kumamoto, K., Takei, M., Kinoshita, M., Ebara, S. & Matsuura, T. J. Anat. 182,23-28 (1993).
11. Ikeda, M. & Okada, S. Okajimas Folia Anaromia Japanensis 67,365-369 (1990).
12. Scott, D. W Miller Jr, W. H. & Griffin, C. E. Muller & Kirk's Small Animal Dermatology,5th edih'on (Saunders, W.B., Philadelphia, 1995).
13. Meyer, W. & Neurand, K. Arch. Dermatol. Res. 283.16-18 (1991).
14. Bond, R., Howell, S.A.,Haywood, P. I. & Lloyd, D. H. Vet. Rec. 141,200-201 (1997).
15. Moriello, K. A. & DeBoer, D. J. Amer J. Vet. Res. 52,602-606 (1991).
16. Moriello, K. A,, Kunkle, G. A. & DeBoer, D. J. Vet. Dermatol. 5,57-62 (1994).
AKNOWLEDGEMENTS
Diagrams 1 : 1 and 1 : 2 have been reprinted with kind permission fmm Peters S.: "Haut und Haarkleid k m Hund", Ferdinand EnkeVerlag, 1997,Pages 4 and 21.
i

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I
F
'
D. N. Carlotti - D. Pin
Diagnostic approach
The diagnostic approach in feline dermatology must be methodical and include the various steps of a
conventional medical consultation as well as additional ones relevant t o feline dermatology. Information
gleaned from the history and clinical examination, both general and dermatological, allow the practitioner to
construct a differential diagnosis. Appropriate diagnostic tests are then chosen to narrow down this list and
produce a definitive diagnosis 14.
History
The history is an essential part of the diagnostic approach, and 10-15 mlnutes should be allocated to taking the
htstory before examming the ammal. Sometimes, the history alone will suggest the diagnosis. The best method
is to use a printed sheet which details most of the questions to ask the owner. This ensures that nothing is
forgotten. It also allows the time scale of events to be appreciated, enables the climlcian to gain some time, and
demonstrates to the owner that interest 1s being taken in the case 14.
Signalment
Breed :Breed predispositions should be known but are less important than in the dog 35-" (Table 2 :
1). However, be careful, knowing the breed alone is not enough to make a diagnosis!
Sex :Entire male cats are often aggressive. They are prone to subcutaneous abscesses arising from
bites and scratches, certain specific bacteria infections (e.g. nocardiosis and actinomycosis), and
indirectly to opportunistic dermatoses associated with retroviral infection.
Age :Some dermatoses are more common in certain age groups. For example, parasitic dermatoses
(e.g. otitis caused by Otodectes cynotis, cheyletiellosis, demodicosis) and dermatophytosis are more
common in kittens. Genodermatoses (e.g. junctional and dystrophic epidermolysis bullosa, follicular
dysplasias and cutaneous asthenia) are more likely to be seen in the young cat (aged under a year).
Allergic dermatoses tend to appear between 6 months and 3 years. Cats of 10 years and over are more
susceptible to auto-immune dermatoses, tumours or systemic diseases with dermatological
manifestations. It should be appreciated that age of onset of clinical signs is not always the same as
age at diagnosis. Age at diagnosis of an allergic dermatitis varies from 1to 10 years!
Colour : White cats, or cats with white ears, are prone to solar dermatitis and squamous cell
carcinoma, whereas gimger cats are prone to lentigo simplex. Persian cats with a mutation for the beige
gene are predisposed to Chediak-Higashi Syndrome.
Weight : Weigh'mg the cat helps determine if the patient is in the correct weight range. It also allows
correct dosing of medications and accurate interpretation of water intake over 24 hours (e.g, if
hyperadrenocorticism is suspected).
Diet:Knowledge of the diet is essential in order to institute an appropriate elimmation diet.
Origin :Some colonies or pet stores may be known for their poor hygiene and incidence of contagious
dermatoses (e.g. dermatophytosis, Otodectes otitis, cheyletiellosis, etc ...). Stray cats should be
examined meticulously and checked thoroughly for retroviruses.
Some dematoses have been reported to affect cats of the same line: urticaria pigmentosa in the
Sphinx, dystrophic epidermolyis bullosa in the Persian, eosinophilic granuloma complex in a lime of
Specific Pathogen Free cats 13.

33. 1 A h r i c a l Gude to F h e Dermatology
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Persian Dematophytosis
Cheyletiellosis
Histoplasmosis
Lupus erythematosus
Idiopathic facial dermatitis '
Facial interhigo
Hereditary greasy seborrhoea
Congenital hypotrichosis
Chediak-Higashi syndrome '
Dystrophic epidemolysis bullosa '
Exotic Short Hair Hereditary greasy seborrhoea6
Siamese Demodicosis
Self-induced alopecia of behavioural origin
Food intolerance?
Sporotrichosis
Cryptococcosis
Lupus erythematosus
Vitiligo '
Junctional epidetmolysls bullosa
Periocular leucohichia
Histiocytic mastocytoma
Abysinnian Self-induced alopecia of behavioural origin
Blastomycosis
Cryptococcosis
Follicular dysplasia
Havana Blastomycosis
Sphinx Urticaria pigmentosa
Alopecia universalis
Birman Congenital hyponichosis 'I
Burmese Demodicosis
Self-induced alopecia of behavioural origin
Congenital hypotrichosis
Devon Rex Urticaria pigmentosa "
Himalayan Lupus erythematosus
Ehlers-Danlos syndrome
Hereditary greasy seborrhoea "
The environment
Meticulous details of internal and external surroundings must he documented: being confmed to
inside the house, and the presence of rngs and carpets, expose the cat to a high level of house dust
mite allergens. Old houses and frequent visits to the cellar and attic favour the multiplication of fleas
and consequently flea allergy dermatitis. An outdoor country life predisposes to certain parasitic
dermatoses (e.g. Otodectes otitis and tromhiculiasis), allergies (e.g. mosquito bite hypersensitivity),
fungal infections (dermatophytosis) and viral infections (e.g. poxvuus infection reported in cats that
hunt small rodents). If dermatological signs are worse when the cat is in certain locations, this may
suggest atopic dermatitis.
Any tips abroad or to different regions should be documented. Notoedric mange is prevalent in the
French overseas territories, and parts of Italy, Switzerland, Spain, Slovenia and Croatia. Some
systemic mycoses occur in particular geographical regions.
The presence of other animals in the house and evidence of transmission to other animals or
people: the presence of in-contact animals favours the development of certain dermatoses such as flea
allergy dermatitis or contagious dermatoses like dermatophytosis, Otodectes otitis and cheyletiellosis.
Evidence of transmission to man suggests dermatophytosis or a parasitic dermatosis like notoedric
mange or cheyletiellosis.
Changes in the environment: changes in the family situation (moving house, new furniture, new
arrival or death of an animal or person) may cause behavioural disorders that can have dermatological
manifestations.

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2 : Diagnostic approach
Development of the dermatosis
Date of initial onset: knowing the date of onset allows the age of onset to be determined along with
the duration of the condition.
Acute or chronic development: Acute-onset dermatoses include cutaneous drug reactions and viral
dermatoses whereas more gradually developing dermatoses include allergic dermatoses and turnours.
Seasonality: conditions occurring more in autumn or summer include flea allergy dermatitis, atopic
dermatitis, trombiculiasis, mosquito bite hypersensitivity or more rarely poxvirus infection.
Initial nature and distribution of lesions: this information will help establish the extent to which the
dermatosis has progressed. The owner should be asked precise questions: where were lesions first
seen? What did initial lesions look like?
The presence of pruritus, initially, or later in the development of the dermatosis: the distinction
between a pruritic and non-pruritic dermatosis is arbitrary and oversimplified because a condition that
is initially non-pruritic ma; later become pnuitic. here are five imp&ant aspects to be determined
from the history:
Did pnuitus develop before, at the same time as, or after the lesions appeared?
How severe is the pruritus and how frequent is it? It is often described by the owner in a whole range
of ways such as frantic, severe, constant, intermittent or occasional.
How does pruritus manifest itself?
Which parts of the body are affected?
How does pruritus respond to corticosteroid therapy?
Prior and current therapy
Establishing every minute detail of prior and current treatments is essential. This must include the
name of the drug, dose, frequency and duration of administration, any side-effects, whether given as
instructed, and clinical response obtained. If a cutaneous drug reaction is suspected, all treatments
should immediately be stopped and the cause investigated.
Clinical examination ~~~~~~~~ ~ ~ -
General examination
A systematic general examination should he conducted. Methodical examination of the different
organ systems should allow detection of general signs that might be associated with dermatological
signs: for example, respiratory signs associated with atopic dermatitis, herpesvirus infection,
herpesvirus-associated erythema multiforme or digital metastasis of a pulmonary adenocarcinoma;
gastrointestinal signs associated with food intolerance; joint or renal signs associated with systemic
lupus erythematosus; diabetes mellitus seen frequently with hyperadrenocorticism or the whole
gamut of signs linked to cutaneous paraneoplastic syndromes (e.g. pancreatic paraneoplastic alopecia
and paraneoplastic exfoliative dermatitis). In some cases, testing should be carried out for
retroviruses.
uermatological examination
Identification of lesions
Dermatological diagnosis depends on the morphological identification of lesions '"". The
dermatologist must identify and investigate primary and secondary lesions. Primary lesions
make up the early lesions, representative of the dermatosis. They are sometimes transient and
rapidly altered. Secondary lesions may develop spontaneously fro^ primary lesions. They may
also arise as a consequence of scratching and licking, especially common in the cat, or
following treatment. The identification and interpretation of these lesions is more difficult than
in the dog. This is due to the dense coat of the cat and also because cats lick themselves a lot,
both as normal grooming behaviour and as a sign of pruritus. There is no clear association
between dermatosis and lesion: one particular lesion may suggest various different derinatoses
and, conversely, one particular dermatosis may present in lots of different ways.

35. cal Guide
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Primary lesions
Erythema refers to redness of the skin, diffuse or localised, which disappears when a piece of
glass is pressed over it. Erythema results from vasodilatation in the superficial dermis '.1,'4,'i. This
common lesion has little diagnostic significance: Generalised erythema may suggest atopic
dermatitis, food intolerance (Fig. 2 : I), cutaneous drug reaction or epitheliotropic T cell
lymphoma. Localised erythema should lead to suspicion of an infection or infestation (e.g.
dermatophytosis (Fig. 2 : 2) or demodicosis), or, depending on its location, actinic or contact
dermatitis.
Purpura refers to a dark red, non-palpable spot which does not disappear when a piece of glass
is pressed over it. It results from extravasation of red blood cells from dermal vessels 2,3.14,'5.
Purpuric macules are called petechiae, when punctate or lenticular, and ecchymoses when more
extensive (Fig. 2 : 3). Purpura is rare in the cat and should be considered a sign of disordered
blood clotting (e.g. peripheral or central thrombocytopaenia) or other systemic illness. Platelet
purpura occurs in thrombocytopaenia and vascular purpura in necrotising vasculitis that
accompanies infectious illnesses (e.g. feline infectious peritonitis).
A macule is a flat spot, with no infiltration, associated with a change in skin colour 2.'.'4.'s.
Hyperpigmented macules arise from an increase in melanin pigmentation. Circumscribed areas
of hypermelanosis may he congenital (e.g. lentigo) and caused by an increase in the number of
melanocytes in the epidermal basal layer. They may also be acquired as in post-inflammatory
melanin pigmentation (e.g. in pemphigus foliaceus or pancreatic paraneoplastic alopecia
(Fig. 2 : 4)), and associated with melanocytic hyperactivity. Hypopigmented macules relate to a
reduction (hypomelanosis) or absence of (amelanosis) melanin pigments. In the cat, the
congenital, circumscribed hypo- or amelanoses (vitiligo) are classified separately from the
generalised conditions (piebaldism, Waardenburg Syndrome and albinism).
A vesicle is a small (1-3 mm in diameter), translucent elevation containing clear fluid ','.'4.'5. Due
to the extreme thinness of the epidermis, the vesicle is a fragile, transient lesion and therefore,
rarely identified. Theoretically, epidermal vesicles are seen in for example, pemphigus vulgaris
and poxvirus infection, whereas subepidermal vesicles are seen in epidermolysis bullosa and
bullous pemphigoid.
A bulla is a large vesicle, greater than 3 mm in diameter2.3.'4.'3.
A pustule is a raised, purulent spot, associated with an accumulation of neutrophils and modified
keratinocytes i.'~'4.1*. Unlike in the dog, pustules are hard to identify, macroscopically, in the cat,
as they are fragile and short-lived. Follicular pustules are centred around a hair and usually
indicate bacterial infection (e.g. bacterial folliculitis (rare in the cat) and acne) (Figs 2 : 5,6),
dermatophytosis or, very rarely, intra-follicular demodicosis. Non-follicular pustules are flat and
independent of hair follicles. Also very fleeting, they are seen mostly in superficial pemphigus
conditions (foliaceus and erythematosus). Both follicular and non-follicular pustules containing
eosinophils are sometimes seen in allergic dermatoses, eosinophilic granuloma complex and
notoedric mange.
A papule is a small, raised circumscribed swelling associated with thickening of the epidermis or
superficial dermis '~'~"~''. are classified according to their location: epidermal, follicular,
Papules
dermal. Epidermal papules are found in squamous cell carcinoma in situ (Fig. 2 : 7). Follicular
papules are common in cats with miliary dermatitis and allergic dermatitis, in which case the
infiltrate is made up mainly of eosinophils. In dermatophytosis and bacterial folliculitis,
follicular papules often develop into intra-follicular pustules, progressing towards fumculosis
and a granulomatous reaction. Dermal papules arise from localised infiltration in the dermis by
inflammatory cells: eosinophils and mast cells in allergic dermatitis (Fig. 2 : 6), eosinophils in
eosinophilic granuloma complex, and mast cells in urticaria pigmentosa. Papules sometimes join
together to form plaques (eosinophilic plaques) (Fig. 2 : 8). Some dermal papules called
dysmetabolic papules (Fig. 2 : 9) are associated with an intradermal excess of amorphous
material which accumulates secondary to a systemic metabolic disorder. These papules are rare.
They may be due to dermal accumulation of lipid (xanthoma), secondary to diabetes mellitus, or
a primary lipid disorder (e.g. familial hypertriglyceridaemia).

36. www.vet4arab.co.cc
2 : Diagnostic approach
,.:..: Figure 2 :2 :Localisedpinnal eryihema in a cat with dermarophytosis
Figure 2 : I :Generalisedfacial erythema in a cat withfood intolerance
:t
caused by Microspomm canis
Figure 2 :4 :Multiple hypermelanotic macu. ...
. - .. ..h pancr~
paraneoplastic alopecia
Figure3 :6 ;Pal~~~~(Iarpurtoles
und papules in a ,=,,.,,,
L,. ,.!ergy
dermantb
Figure2 :8 :Dermalp~pu.,,,., ,.u.iations in a cat withfoodiiitolerance