What Are Feline Coccidia, Tritrichomonas, and Giardia?

1 Overview

Feline coccidia

Common canine/feline coccidia are Cystoisospora; infection from oocysts or sporozoites. Most common symptom: chronic diarrhea—profuse watery diarrhea for weeks, little treatment effect.

Diagnosis by oocysts in feces, history, symptoms; severe or fatal coccidiosis can occur before oocysts form, so absence doesn’t rule it out. In successive regular diarrhea in young animals, consider coccidiosis first.

Coccidiosis is usually self-limiting, improves with host immunity, but oocysts still shed. Treatment and prevention are troublesome—routine dewormers don’t work, no reliable disinfectant. Late-stage: supportive care; sulfonamides control numbers; vets may use triazine drugs.

Also, Cryptosporidium, Toxoplasma, Hepatozoon, Haemobartonella, Plasmodium can infect dogs and cats.

Feline tritrichomonas

The infective trichomonad is Tritrichomonas foetus, a major worldwide cause of cat diarrhea. It parasitizes vagina, uterus, placenta, prepuce, penis, epididymis, vas deferens. It has 3–5 long flagella and a wavy membrane; hard to identify morphologically.

Infection links to chronic or recurrent large-intestine diarrhea: mucus, foul pasty or semi-formed stool with mucus and blood; may constipate, occasional blood, increased frequency. Median diarrhea duration 135 days (1 day to 7.9 years). Anus often red, swollen, painful; incontinence not rare. Most cats are alert, normal appetite. Can be isolated from asymptomatic cats. Infected are young, age 3 months–13 years (median 9 months).

Diagnosis by PCR; treat with ronidazole—the drug of choice. Dose accurately by weight; overdose risks neurotoxicity (lethargy, anorexia, ataxia, seizures), which resolves after stopping but can last 1–2 weeks. Stop ronidazole immediately if neurotoxicity appears.

T. foetus environmental control is fragile—no cysts. Dryness, refrigeration, above 40.6°C, and prolonged oxygen exposure kill it. During treatment, change litter and disinfect the box to prevent reinfection.

Feline giardia

Giardia infection comes from water contaminated by human or animal feces. Seven assemblages: A and B mainly humans, C and D dogs, E hoofed animals, F cats, G rodents. Cats can also get D, A, C besides F; cat infection with A means zoonotic risk, but cat-to-human spread is rare.

Adult cat giardia is usually subclinical; early infection temporarily softens stool. Kittens get acute diarrhea—pale, foul, mucoid.

Diagnosis mainly by ELISA or zinc sulfate float; distinguish from T. foetus (concave ventral disk, two nuclei, leaf-rolling motion) versus tritrichomonas (spindle, single nucleus, wavy membrane, irregular jerky motion).

Treatment: metronidazole, albendazole, fenbendazole all work. Besides drugs, control infection and minimize reinfection:

1. Clean environment: remove cysts; clear feces often, rinse box with water, cover with disinfectant 10–20 min, rinse and dry.

2. Bathe to remove cysts from fur.

3. Prevent reinfection: clean drinking water, no contaminated sources.

Note:

For persistent diarrhea, first determine cause and rule out one by one; exclude underlying disease or inflammation; if coccidia, giardia, or T. foetus found, treat specifically.