An update on three important protozoan parasitic infections in cats: cryptosporidiosis, giardiasis, and tritrichomoniasis - Veterinary Medicine
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An update on three important protozoan parasitic infections in cats: cryptosporidiosis, giardiasis, and tritrichomoniasis
Our knowledge of these protozoan parasites in cats continues to expand. Here's what you need to know about diagnosing these infections and treating affected patients.


VETERINARY MEDICINE SUPPLEMENT


Giardia species

Giardia species cysts excyst in the duodenum after exposure to gastric acid and pancreatic enzymes and release two trophozoites that then separate, mature, and attach to the brush border of the villous epithelium throughout the intestinal tract in cats. The pathogenesis of diarrhea may be related to secretory-excretory products of the parasite. As with Cryptosporidium species, clinical signs may be related to immunodeficiency, coinfections, other gastrointestinal diseases, host susceptibility, or infection with more-pathogenic strains.

Tritrichomonas foetus

Several elements, such as adhesion, secretion of proteases, and release of lytic factors, are involved in the mechanism of tissue damage of T. foetus.31 In a study of naturally infected cats, mild-to-moderate lymphocytic-plasmacytic and neutrophilic colitis and crypt epithelial cell hypertrophy were common.32 Coinfection with other organisms occurs and influences the pathogenesis of disease. For example, cats with preexisting Cryptosporidium species infection had more severe signs of disease when experimentally inoculated with T. foetus than did cats inoculated with T. foetus alone.12 However, coinfections with Cryptosporidium species and T. foetus are rare in naturally exposed cats. Other predisposing factors as described for Cryptosporidium and Giardia species may also play a role in the pathogenesis of this disease.

CLINICAL SIGNS

Cryptosporidium species

Most cats with Cryptosporidium species infection have subclinical disease.15,33,34 Some infected cats develop small bowel diarrhea, weight loss, and anorexia. Clinical signs associated with infection can occur in immunocompetent or immunodeficient cats.28,35,36 Coinfection with other protozoans including Giardia species and T. foetus may aggravate clinical signs of cryptosporidiosis in cats.13,37,38

Giardia species

Although most of the cats shedding Giardia species do not show clinical signs of disease, some develop acute or chronic diarrhea and weight loss. The diarrhea is usually mucoid, pale, and soft and has a strong odor; steatorrhea may be present.9,11,39,40 Most infected cats are afebrile, do not vomit, and have normal total protein and hemogram values.9

Tritrichomonas foetus

Kittens with T. foetus-associated illness usually present for evaluation of chronic large bowel diarrhea. The diarrhea is often semiformed and malodorous and contains blood or mucus. The anal area frequently becomes edematous, and feces can fall from the anus. Clinical signs of disease are often intermittent and usually resolve with antimicrobial therapy, only to recur after therapy is discontinued.


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