Protozoan disease

1. WELCOME

2. Seminar
on
Protozoan Disease in
Fishes
Presented by
Balwant Singh
M.Sc. (AAS)

3. Protozoan Disease in Fishes
• Protozoan disease in fishes are divided in to
following categories-
1)Flagellated Protozoans
2)Ciliated Protozoans
3)Myxozoans

4. (1) Flagellated Protozoans
• Flagellates are protozoans: simple, single-celled
animals (over 50,000 recognized species)
• Very small (15-30 µM), body elongate, leaf-like
appearance, up to 975,000/mL of blood
• Flagellum arises posteriorly and can be connected
to other parts of body, pulls animal through the
blood
• Most famous are Trypanasoma, Trypanoplasma,
Ichthyobodo necatur

5. Ichthyobodo necatur
• A Mastigophoran, but a member of Class
Diplomonadea
• Also small, but flat and ovoid when swimming
• It has 2-4 flagella arising from a basal body
(kinetosome) at anterior end
• Obligate parasite, poor swimmer, attaches to gills,
but not good at attaching
• Uses a sucking organelle to penetrate host
• Tissue penetrated becomes necrotic

6. Icthyobodo necatur
• Largely affects young, undernourished carp
and trout
• It can also parasitize frogs/tadpoles
• Wild fish/frogs serve as reservoirs, found
everywhere
• Seasonality affect resulting from salmonid
hatchery stocking seasons (April - May)
• Affects smolts by attaching to gills and not
allowing them to adapt to seawater

7. Ichthyobodo necatur
• Pathogenicity: dull spots on body (blue
slime), pale gills, hemorrhaging, fin
necrosis, loss of appetite, flashing,
moribund fish
• Control: salmonids need prophylaxis with
formalin (1:4000 for 1 hr); carp need 1%
salt bath 30 minutes repeated 3-4 times

8. Ichthyobodo necatur

9. (2)Ciliates: Ichthyophthirius
multifilis (ICH)
• Another single-celled protozoan type
• Adult is round in shape, up to 1 mm in diameter,
known as “trophont” (rem? Same as Amylodinium)
• Short cilia in rows over entire cell, obvious as free-
living stages “tumble” through the water
• Life Cycle: the trophont attaches to gills or skin, after
7-10 days, the trophont drops off and is called a
“tomont” (same, also), tomont attaches to substrate
and encysts, cyst ruptures releasing swarmers known
as “theronts”
• Throats are the parasites (have perferatorium), also
use hyaluronidase, only for less than 20 hrs, displace
normal tissue as they grow

10. Ichthyophthirius multifilis (ICH)
• Signs: white pustules in advanced cases,
sometimes called white spot disease; if found on
gills, not found on body
• Behavioral changes: fish scratch against bottom
(flash), hide in corners, twitching fins
• Death in 20-26 days, thought to be due to
osmoregulatory failure in most cases
• Host/parasite range: broad, mainly in
catfish/salmonids

11. Ichthyophthirius multifilis (ICH)
• Control: prevention (once in, difficult to
treat)
• Chemotherapy requires treating water, not
the fish (cysts, stages in fish unaffected)
• Formalin: around 250 ppm, goes up as
temp goes up
• Malachite green: 1.25 ppm daily for 30 min
(Nox-Ich, Ich-out)
• Remove fish, raise temp to 90o
F

12. Ichthyophthirius multifilis (ICH)
Cell embedded in tissue

13. Ichthyophthirius multifilis (ICH)
Theronts (swarmers)

14. Ichthyophthirius multifilis (ICH)

15. Ichthyophthirius multifilis (ICH)

16. Cryptocaryon irritans
• Similar to ICH
• primarily marine
• trophozoite similar to
ICH
• life cycle similar to
ICH
• primarily problem for
mariculture facilities
and marine aquaria

17. Epistylus sp.
• Colonial, stalked
ciliate
• possess ciliary spiral
around cytostome
• usually on skin
• causes flashing, which
can lead to harm
• really just a bother,
little apparent harm

18. Trichodina sp.
• Body shaped like hockey
puck
• also spiral cilia around
cytostome
• makes them fly through
the water like a flying
saucer
• lives on gills, skin mainly
• have rings of chitinous
teeth

19. (3) Myxozoans:
Myxobolus cerebralis
• Rather odd, exclusively endoparasites
• Cnidarians? (Phylum Cnidaria)
• Multicellular during adult life
• Cause: “whirling disease”
(specifically: Salmonid Whirling Disease)

20. Salmonid Whirling Disease
• Important characteristic: can produce spore that is highly
resistant (15 yrs dessication), associated with dispersal
• Life Cycle: infective stage (amoebula; “trophozoite”)
penetrates skin, most visible stage is the spore, spore
released to environment, oligochaete vector.
• Fish eats oligochaete or encounters free spores

21. Salmonid Whirling Disease
• Found in salmonids, not contagious.
• Pathology: development in cartilage, usually
young fish, carriers asymptomatic, fish exhibits
whirling (tail chasing) when feeding or alarmed,
whirling caused by destruction of inner ear by
spores (loss of equilibrium)
• Can cause “blacktail” by controlling production of
chromatophores in spinal column, also “pugnose”,
skeletal deformities

22. Salmonid Whirling Disease
• Diagnosis: remove gill arch, grind and
allow to settle, check supernatant for spores
• other methods: cook head/plankton centri-
fuge, pepsin-trypsin digestion/centrifuge
• Fluorescent Antibody Test (FAT) w/rabbit
• Transmission: direct during first year,
indirect via annelid, contamination (cyst)
• Hosts: trout, salmon, char, grayling

23. Salmonid Whirling Disease
• How did it get here? Came from Europe
via Danish frozen trout in the 50’s
• Control: Non-treatable, avoidance critical,
UV of water, filtration to less than 10 µM
• Accomodation: incubate eggs and rear fry
separately in UV trt’d water, check new
ponds with sentinels (poor fish)

24. Salmonid Whirling Disease
sporoblast
mature spores

25. Salmonid Whirling Disease

26. Thank You