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