Parasitology Chapter 11 P1 - Protozoans of Domestic Animals

Study material for part 1 of Chapter 11 of Diagnostic Parasitology for Veterinary Technicians. For class BIO225 at MWCC.

Protozoans are referred to what instead of species?

Assemblages

Assemblages & their hosts

A: Humans, dogs, & cats

B: Humans

C: Dogs

D: Dogs

E: Ruminants, horses, pigs, etc.

F: Cats

G: Rodents

Giardia

• Flagellate

• Hosts: Dogs, cats, ruminants, exotic species​

• Intestinal mucosa​

• Cause of infection: Ingestion of cysts​

• Main symptom is diarrhea within 5 days of exposure​

• Rare to find trophozoite, common to find cysts in feces​

• Trophozoite: Pear shaped, four pair of flagella, two nuclei, adhesive disk​

• Immature cysts: oval, refractile wall, two nuclei​

• Mature cysts: four nuclei

Entamoeba histolytica

• Amoeba

• Hosts: Dogs, cats, primates, humans​

• Found: Worldwide but rare in U.S.​

• Large intestine ​

• Cause of infection: Ingestion of cysts​

• Causes amebic dysentery in humans: severe diarrhea​

• Can infect dogs associated with humans, rare in cats

Other Entamoeba histolytic characteristics

• Trophozoite has single round nucleus with tiny pinpoint endosome in center​

• Cysts are round, thin refractile wall, up to four nuclei in mature (one in immature)​

• Diagnosed by fecal float​

• Formed stool only cysts are found, in diarrhea, cyst and trophozoites can be seen​

• Should refer to human path lab if suspected in human client​

• Significant problem in monkeys and chimpanzees and can be public health issue in zoos, research facilities, etc.

Balantidium coli

• Cilitate

• Hosts: Dogs and pigs (more common)​

• Cecum and colon​

• Found: Worldwide​

• Cause of infection: Ingestion of cysts​

• Zoonotic

Cistoisospora

• Apicomplexan

• Host: Dogs, cats, pigs​

• Small intestine​

• Found: Worldwide​

• Cause of infection: Ingestion of cysts​

• Common name: coccidian — cause “coccidiosis” caused by inflammation of intestine​

• Most common in puppies and kittens, causes diarrhea​

• Unsporulated cysts found in fresh feces, can sporulate in older fecal samples​

• Prepatent period: 7-14 days

Toxoplasma gondii

• Apicomplexan

• Hosts: Definitive host is only cat, can occur in other species, humans are incidental hosts​

• Found: Worldwide​

• Zoonotic​

• Intestines​

• Cause of infection: Ingestion of sporulated cysts from cat feces or meat of other encysted animals​

• Prepatent period: 5-24 days​

• Can cause significant disease in humans, particularly fetus infected in utero​

• Cats only shed cysts for up to two weeks

Crpytosporidium

• Apicomplexan

• Hosts: Dogs, cats, cows, sheep, pigs, birds, guinea pigs, snakes, mice​

• Small intestine​

• Standard fecal float​

• 4-6um cysts see on cover slip, Acid Fast stain can be used to see them better​

• Antibody based ELISA assays also used​

• Zoonotic​

• C. parvum most common, but also C. canis, C. felis, C. meleagridis (birds), C. muris (mice), C. suis (pigs) have been seen in humans

Sarcocystis

“Flesh cyst”

• Apicomplexan

• Host: Dogs and cats​

• Intestine​

• Worldwide​

• Each oocyst contains two sporocysts,​

each with four sporozoites​

• Fecal float​

• Ingestion of cysts by ruminants, horse or pig allow cysts to go through multiple asexual stages and finally encyst in muscle tissue. ​

• Dogs and cats ingest infected muscle of intermediate host

Trypanosoma cruzi

• Flagellate

• Hosts: Humans and sometimes dogs​

• Found in: Central and South American, occasionally southern U.S.​

• Cause of infection: Ingestion of intermediate host, transmission by reduviid “kissing” bug or feces of reduviid​

• Zoonotic​

• Hemoprotozoan found in blood​

• Extracellular banana-shaped trypomastigote swims in blood​

• Non-motile cyst stage is called amastigote – can be found in cardiac muscle, esophagus, etc.​

• Diagnosed by blood smear

Leishmania sp.

• Flagellate

• Host: Dogs​

• Endothelial cells of capillaries, spleen, other organs, WBCs​

• Cause of infection: Bite of intermediate host, the phlebotomine sand fly​

• Zoonotic​

• Intracellular blood parasite​

• Amastigote diagnosed in infected tissues

Babesia canis

“Piroplasm”

• Apicomplexan

• Host: Dog​

• Inside RBCs​

• Found in: Europe, Africa, Asia, N. and S. America​

• Cause of infection: Bite of intermediate host, the tick​

• Zoonotic​

• Pear shaped inside RBC​

• Symptoms: pale mucous membranes, jaundice, depression, weakness, splenomegaly, fever, anorexia, anemia, hemoglobinemia

Hepatozoon canis and H. americanum

• Apicomplexan

• Host: Dogs​

• Found in: U.S., Africa, Asia, S. Europe​

• Cause of infection: Ingestion of intermediate tick host​

• Malaria-like intracellular parasites​

• Blood form: gamonts found inside WBCs​

• Tissue form: schizonts found in endothelium of spleen, bone marrow, liver​

• Cysts of H. americanum can be found in muscle of dog