parasitology lab notes
TRANSCRIPT
Lab 6: Protozoans & Equine Nematodes
Intestinal Coccidians - Isospora
• Isospora spp. – intestinal parasites of cats & dogs
• One of the most common protozoan diseases of kittens & puppies
• Rarely cause issues in mature animals
• Oocysts can be found on fecal floatation, are unsporulated in fresh feces & are very small
• Prepatent period usually 7-10 days
Isospora canis
Isospora spp. – Life Cycle
• Unsporulated oocyst in feces, sporulates in environment – infective stage contains 2 sporozoites
• Ingestion – invades intestinal epithelial cells, becomes meront
• Undergoes asexual reproductionto become merozoites, which then become microgametocytes or macrogametes which then undergo sexual reproduction to produce oocysts which are shed in feces
Isospora spp. – Signs & Predisposing factors
• Clinical signs associated with heavy infections only
• Chronic diarrhea, straining – especially in puppies & kittens
• Some animals may become asymptomatic carriers
• Predisposing factors include humid summer months, exercise pens, indoor boarding kennels/vet hospitals, stress
Intestinal Coccidians –Eimeria spp.
• Intestinal coccidian of ruminants & horses, rabbits, rats, mice & guinea pigs
• Have cap on one end & up to 4 nucleii depending on species
• Life cycle, clinical signs & predisposing factors similar to Isospora
• Avians can have both Isospora and/or Eimeria
Intestinal Coccidians – Toxoplasma gondii
• Toxoplasma gondii – intestinal coccidian of cats
• Usually diagnosed on standard fecal flotation, unsporulated in fresh feces
• Immunodiagnostic tests also available using whole blood or serum
• Prepated period varies depending on infection route (5-24 days)
• Very important zoonotic parasite! Can cause severe damage/death to developing fetus in pregnant women
Intestinal Flagellates – Giardia spp.
• Several different species infects people, domestic animals & birds
• Intermediate hosts are beavers, cows & dogs
• To diagnose: will see oocysts in formed stool (using zinc sulfate only) or will see trophozoites in direct smear (using iodine to highlight internal structures)
• Trophozoites are very fragile, stomach acid will kill
Giardia trophozoite
Intestinal Flagellates – Giardia spp.
• Clinical signs can range from asymptomatic carriers to severe watery diarrhea
• If severe can see severe dehydration, poor hair coat, weight loss, emaciation
• Zoonotic potential!!! Drinking or swimming in contaminated water
Giardia oocysts: stained
Equine Nematodes – Parascaris equorum
• Largest nematode (roundworm) of horses
• Affects foals <6 months most – can get from contaminated food sources (plus foals LICK everything!!!!)
• Can cause stasis, intestinal rupture due to size of worms & large burden – can cause death by impaction
Parascaris ova
Parascaris equorum: Life cycle & predisposing factors• Undergoes hepatotracheal migration• Prediliction site – small intestine• Clinical signs: unthriftiness, depression, pot-
bellied, anorexia, colic & cough w/ nasal discharge
• Predisposing factors: contaminated food/water troughs, contaminated pastures, very environmentally resistant
• Control – worming & rotating pastures especially where foals & weanlings graze
Equine Nematodes: Strongyles
• Divided into large & small strongyles – eggs are virtually identical
• Large strongyles more pathogenic
• Eggs found on fecal flotation – identification of species through fecal culture (allows identification of larvae)
• Eggs contain 8-16 cell morula
3 common types of strongyles
Strongyles: Life cycle & clinical signs
• Clinical signs: colic, weight loss, lethargy, fever & poor appetite
• Prevention: worming, pasture rotation & routine fecal exams
Strongylus westeri:Intestinal Threadworm
• Unique equine nematode – only females are parasites (parasitic males do not exist)
• Produces larvated eggs• Mare can transmit to foal
through colostrum• Prepatent period 5-7 days• Signs: diarrhea, weight loss,
anemia & poor appetite• Good worming for mare &
foal needed to prevent infection
Equine Nematodes:Oxyuris equi - Pinworm
• Adult worms found in cecum, colon & rectum
• Adult females attach eggs to exterior anus with a gelatinous, sticky material that produces anal pruritis
• Eggs may be larvated, have an operculum, are smooth & thick shelled, very tapered on one end
• Common in foals, not zoonotic• Diagnosed by scotch-tape test!• Can see eggs on fecal flotation,
occasionally see adults in stool
Oxyuris equi: Life cycle
• Gravid female migrates to rectum/anal area – lays eggs on perianal area (sticky!) – eggs hatch, horse rubs against food/water troughs, eggs/larvae fall into trough – eggs ingested by host – adults develop in cecum, colon & rectum