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Enteric fever
1. Enteric Fever
Dr. Priyamadhaba Behera
References
WHO Document, 5th edition OTPH, 18th edition Harrison
principle of medicine, Articles however applicable
1
2. Epidemiology
• Etiologic agents of enteric fever
– S. typhi and S. paratyphi serotypes A, B, and C
– No known hosts other than humans
• Estimated 22 million cases, with 200,000 deaths annually
• Incidence
Rate
Location
Cases per 1 Lakh opulation per Yr.
Highest
South central and Southeast Asia
>100
Medium
Rest of Asia, Africa, Latin America
and Oceania (excluding Australia
and New Zealand)
10–100
Low
Other parts of the world
<10
4. Epidemiology
• Multidrug-resistant (MDR) strains of S. Typhi emerged
in 1989 in China and southeast Asia
• Resistance to chloramphenicol, ampicillin and
trimethoprim antibiotics long used to treat enteric
fever
• Increased use of fluoroquinolones to treat MDR
enteric fever in 1990s, reduced susceptibility to
ciprofloxacin [MIC, 0.125–1 g/ml] have emerged in
the Indian subcontinent, southern Asia
• Resistance - first-generation Quinolone nalidixic acid
detects most but not all strains with reduced
susceptibility to ciprofloxacin
5. Disease Outbreak Reported
• 17 June 2003 (Haiti)
– As of 30 May, 200 cases and 40 deaths, reported by WHO regional
office for the Americas (PAHO) and the MoH, Haiti
– Epidemic started in April in villages in the Grand Bois area, bordering
the Dominican Republic
• 15 December 2004 (Kinshasa)
– Total of 13400 cases were reported
– Between 1st October and 10th December 2004, 615 severe cases with
peritonitis, with or without perforation, including 134 deaths (case
fatality rate, 21.8%) have occurred
• 19 January 2005
– From 27 September 2004 - 11 January 2005, WHO reported total of
42564 cases and 214 deaths (case fatality ratio, 0.5%), and 696 severe
cases of intestinal perforation in Kinshasa
• Very poor sanitary conditions and a lack of drinking water
have been reported in all these areas
6. Mode of transmission
• Most commonly, food-borne or waterborne
• Faecal contamination by ill or asymptomatic chronic
carriers
• Health care workers -exposure to infected patients or
during
processing of clinical specimens and cultures
• Sexual transmission between male partners has been
described
8. Risk factors
•
•
•
•
Contaminated water or ice
Flooding
Contaminated food and drinks
Raw fruits and vegetables grown in fields fertilized
with sewage
• Lack of hand washing and toilet access
• Evidence of prior helicobacter pylori infection
9. Risk factors
Severe disease ( 10–15% of patients)
• Host factors (immunosuppression, antacid therapy,
previous exposure, and vaccination)
• Strain virulence and inoculums
• Choice of antibiotic therapy
Incubation period
• 3 - 21 days (average 10-14 days)
10. Symptoms
•Enteric fever is a misnomer
•Hallmark features of this
disease—fever and abdominal
pain—are variable
•Fever >75% of cases,
abdominal pain is reported in
only 30–40%
13. Signs
•Relative bradycardia
•Coated tongue (51–56%)
•Splenomegaly (5–6%)
•Abdominal tenderness (4–5%)
• Rose spots (30%)
End of the first week and resolves
without a trace after 2–5 days
Two or three crops of lesions
Salmonella can be cultured from punch
biopsies of these lesions
Faintness of rash makes difficult to
detect in highly pigmented patients
14. Investigations
• Definitive diagnosis of enteric fever by isolation of S.
Typhi or S. Paratyphi from blood, bone marrow,
other sterile sites, rose spots, stool, or intestinal
secretions
• Serologic tests- widal test
ƒTiming of test is important
ƒSingle test is usually of not much value
ƒBaseline titre of the population must be known
before attaching significance to the titres (≥100 for O
and ≥200 for H)
Treated with antibiotics may not show any rise
False positive reactions
Anamnestic response ƒƒ
15. Investigations
• None of these tests is sufficiently sensitive or specific
to replace culture-based methods for the diagnosis
• PCR and DNA probe assays to detect S. typhi in blood
have been identified but have not yet been
developed for clinical use
17. Control
• Health education about personal hygiene, especially
regarding hand-washing after toilet use and before
food preparation
• Provision of a safe water supply
• Proper sanitation systems
• Excluding disease carriers from food handling
18. Control
• Possible to eliminate enteric fever since they
survive only in human hosts and spread by
contaminated food and water
• High prevalence of the disease in developing
countries that lack adequate sewage disposal and
water treatment, goal is currently unrealistic
• Travelers to developing countries should be
advised to monitor their food and water intake
carefully and to consider vaccination
19. Typhoid vaccines
Two typhoid vaccines are commercially available .
Currently, there is no licensed vaccine for paratyphoid
fever
Ty21a
– Oral live attenuated S. Typhi vaccine
– Days 1, 3, 5, and 7, with a booster every 5 years
– Minimal age for vaccination is 6 years
20. Typhoid vaccines
Vi CPS
• Parenteral vaccine consisting of purified vi
polysaccharide from the bacterial capsule
• Given in 1 dose, with a booster every 2 years
• Minimal age for vaccination is 2 years
Meta-analysis of vaccine trials comparing whole-cell
vaccine, ty21a, and vi CPS in populations in endemic
areas indicates
• All three vaccines are similarly effective for the first year
• 3-year cumulative efficacy of the whole-cell vaccine
(73%) exceeds both ty21a (51%) and vi CPS (55%)
21. Typhoid vaccines
• Typhoid vaccine is not required for international travel,
but recommended for travellers to moderate to high
risk areas (Asia, Africa, the Caribbean, and Central and
South America)
• Typhoid vaccine should be considered even for persons
planning <2 weeks of travel to high-risk areas
• laboratory workers who deal with S. typhi and
household contacts of known S. typhi carriers
• Immunization is not recommended for adults residing
in typhoid-endemic areas or for the management of
persons who may have been exposed in a commonsource outbreak
Notes de l'éditeur
as antibodies begin to arise during end of first week. The titres increase during second, third and fourth week after which it gradually declines. The test may be negative in early part of first week. .
2-A rise in titre between two sera specimens is more meaningful than a single test. If the first sample is taken late in the disease, a rise in titre may not be demonstrable. Instead, there may be a fall in titre
3-The antibody levels of individuals in a population of a given area give the baseline titre. A titre of 100 or more for O
antigen is considered significant and a titre in excess of 200 for H antigens is considered significant.
Patients already treated with antibiotics may not show any rise in titre, instead there may be fall in titre. Patients treated with antibiotics in the early stages may not give positive results.
Patients who have received vaccines against Salmonella may give false positive reactions. This can be differentiated from true infection by repeating the test after a week. True untreated infection results in rise in titre whereas vaccinated individuals don’t demonstrate any rise in titre
Those individuals, who had suffered from enteric fever in the past, sometimes develop anti-Salmonella antibodies during an unrelated or closely related infection. This is termed anamnestic response and can be differentiated from true infection by lack of any rise in titre on repetition after a week.
