Tritrichomonas foetus is a flagellated protozoan parasite of domestic cats that resides in the lumen of the colon and causes colitis and chronic, foulsmelling diarrhea.1,2 The infection is prevalent among cattery cats,3 in which transmission via the fecal-oral route is suspected. Infected cats may have persistent diarrhea for up to 2 years and can remain infected for life.4 The susceptibility of trichomonads to 5-nitroimidazole antiprotozoan drugs is caused by reductive pathways that convert these drugs into autotoxic free-radical metabolites.5,6 Treatment of feline T foetus infection with metronidazole, a 5-nitroimidazole drug, has not been successful. Cats treated with metronidazole have transient improvement in diarrhea but remain infected with the organism.4,7 A related nitroimidazole, ronidazole, is effective in eradicating infection from experimentally infected cats on the basis of PCR assay results.8 Unfortunately, ronidazole is not approved by the FDA or commercially available in the United States. The pharmacokinetics of ronidazole are not known for cats, and in our experience, cats may be at more risk for ronidazole neurotoxicosis than metronidazole neurotoxicosis.
Tinidazole is a second-generation 5-nitroimidazole that is FDA approved for use in treating metronidazole-resistant Trichomonas vaginalis, Giardia spp, and Entamoeba histolytica infections in humans.9 Susceptibility of feline T foetus to tinidazole has been detected in vitro,8 and pharmacokinetic studies in cats reveal a long elimination half-life that would be consistent with once-per-day administration.10 The purpose of the study reported here was to determine the ability of tinidazole to eradicate T foetus on the basis of PCR assay results when given orally once per day to cats with experimentally induced infection.
Modified Diamond medium, Remel, Lenexa, Kan.
Tinidazole [1-(2(ethylsulfonyl)ethyl)-2-methyl-5 nitroimid-azole] T3021, Sigma Chemical Co, St Louis, Mo.
Liberty Research Inc, Waverly, NY.
Hills' Science Diet Feline Growth, Hills' Nutrition Inc, Topeka, Kan.
IDEXX Giardia antigen test kit, IDEXX Laboratories, Westbrook, Me.
Tindamax, Mission Pharmacal, San Antonio, Tex.
In Pouch TF, Biomed Diagnostics Inc, White City, Ore.
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