Efficacy of Ronidazole for Treatment of FelineTritrichomonas foetusInfection

Abstract

Objectives: To determine the efficacy of ronidazole (RDZ), tinidazole (TDZ), and metronidazole (MDZ) againstTritrichomonas foetusin vitro and of RDZ for treatment of feline naturally occurring or experimentally inducedT foetusinfection.Animals: A cat naturally infected withT foetusinfection and diarrhea. Ten specific‐pathogen‐free (SPF) kittens.Procedure: RDZ, TDZ, and MDZ were tested for activity against 3 different feline isolates ofT foetusin vitro. RDZ then was administered to a naturally infected cat at 10 mg/kg PO q24h for 10 days. SPF kittens were infected orogastrically with felineT foetusand treated with either placebo or RDZ (10 mg/kg PO q12h for 14 days). Cats with relapsing infection or those receiving placebo were treated subsequently with RDZ (either 30 or 50 mg/kg PO q12h for 14 days). Feces were examined forT foetusby direct microscopy, culture, and polymerase chain reaction (PCR) testing weekly.Results: Both RDZ and TDZ killedT foetusat concentrations >0.1 μg/mL in vitro. In the naturally infected cat, RDZ abolished diarrhea andT foetusinfection for 85 days after treatment, at which time infection and diarrhea relapsed. Retreatment with RDZ eradicated diarrhea andT foetusinfection for over 407 days. In experimentally induced infection, RDZ at 10 mg/kg caused initial improvement, but infection relapsed in all 5 cats 2 to 20 weeks after treatment. At 30 or 50 mg/kg, 10/10 cats were negative forT foetusinfection for follow‐up durations of 21 to 30 weeks after treatment.Conclusions and Clinical Relevance: Oral administration of RDZ at 30 to 50 mg/kg q12h for 14 days resolved diarrhea and eradicated infection (on the basis of polymerase chain reaction [PCR] testing) in 1 naturally infected cat and 10 experimentally inoculated cats receiving a different isolate ofT foetus.