Lecture 36 & 37: Parasitic Protozoa of Phylum Apicomplexa

What is the difference between monoxenous and heteroxenous?

M: 1 host life cycle

H: 2 host lifecycles

What are there three classifications of coccidia?

intestinal, tissues, blood

coccidia

What are cryptosporidium spp. associated with?

waterborne outbreaks

What is unique about cryptosporidium spp. metabolism?

• pathways are more similar to bacteria than other apicomplexa

• lack Krebs cycle → cannot synthesize fatty acids

• lack plastid bodies for manufacturing food

• unresponsive to anti-coccidal drugs

Oocysts of all cryptosporidium spp. are passed in feces, immediately _________, and morphologically indistinguishable.

infective

True or false: cryptosporidium spp. are able to survive in the environment and water treatment by chlorination.

true

Describe the life cycle of cryptosporidium spp.

• Direct lifecycle

• sexual and asexual replication in small intestinal epithelium

• oocysts passed in feces following 3-5 day incubation

• immediately infection

• host infection via fecal-oral route and ingestion of oocysts

• asymptomatic or symptomatic

What are the clinical signs of cryptospordidium spp. infections?

• voluminous watery diarrhea

• mucous present, rarely blood/leukocytes

• abdominal discomfort, anorexia, nausea, vomiting, weight loss, fatigue, fever

• self-limiting if immunocompetent

What species is cryptosporidium most associated with?

dairy calves

How does cryptosporidium cause malnutrition and reduced growth?

blunting of brush border, loss of microvilli, villous atrophy in SI

What is an important part of supportive care for cryptosporidium infections since there are no consistently effective pharmaceutical products?

restoring electrolyte balance from diarrhea

What species of intestinal coccidia infects domestic livestock through ingestion of sporulated oocysts?

eimeria sp.

Where do eimeria sp. replicate?

asexual replication in small intestine

sexual replication in large intestine

What is the diarrhea caused by eimeria sp. associated with?

destruction of enterocytes by developing oocysts

What is disease of coccidiosis associated with?

onset of sexual replication in host tissues, mechanical disruption of mucosal cell by gametes

Eimeria oocysts

Coccidiosis is a function of:

age, nutrition, stress, sex, season, gestational status, inherent pathogenicity

How is coccidia treated?

environmental hygiene and chemoprophylaxis

What stage of replication do chemoprophylactic drugs target?

asexual

What is the function of coccidiostatic drugs?

arrest development of specific stages of the lifecycle (parasites remain alive in the tissues)

What type of drugs used to treat coccidia allow the parasite to resume development and completion of lifecycle if withdrawn?

coccidiostatic drugs

True or false: anticoccidial drugs may have static and cidal properties depending on the dose of the drug and length of parasite exposure to the drug.

true

How does coccidiostatic drug decoquinate function?

• feed additive

• acts on the sporozoite stage

• parasite penetrates host cell, further development is arrested

• no activity against adult parasites

How does coccidiostatic drug amprolium function?

• drinking water additive

• ats on 1st generation schziont in the intestinal cell wall

• prevents differentiation into metrozoites

• suppress sexual stages and sporulation of oocysts

What are drugs with coccidiocidal activity and what do they act on?

diclazuril, ponazuril, totazuril; act on apicoplast organelle involved in biosynthesis of fatty acids and AA metabolism

What class of drugs have coccidiocidal activity and coccidiostatic and what do they act on?

sulfonamides (ex. Albon); active against folic acid pathway and interfere with folate biosynthesis

What is a clinical drawback from using sulfonamides?

significant negative effects on gut microbiota

cystiosospora (intestinal coccidia)

What cystoisospora sp. infect dogs vs cats?

Dogs: C. canis and C. ohioensis

Cats: C. felis and C. rivolta