Ronidazole

Tritrichomonas foetus has recently been recognized as a cause of chronic large bowel diarrhea in young cats. Different antibiotics have been used to treat T. foetus infection, but ronidazole remains the most effective agent at eradicating the organism and preventing relapse of infection.⁹ Ronidazole is a nitroimidazole antimicrobial similar to metronidazole. It is not FDA-approved for use in companion animals and must be acquired from a compounding pharmacy.

It is important that the dose be calculated for each cat since neurotoxicosis has been reported and seems to be more likely if the recommended dose is exceeded (Table 1).¹⁰ Signs of toxicosis include incoordination, anorexia, ataxia, and seizures. These signs usually resolve once the drug is discontinued but can last up to four weeks. Because of the risk of neurotoxicosis, treatment with ronidazole should not be considered without confirmation of T. foetus infection.

Treatment of protozoal diarrhea is greatly enhanced by environmental control because this minimizes the chance of reinfection. Prompt removal of feces from the litter box is essential since protozoal cysts may otherwise become scattered in the home. Disinfection with quaternary ammonium compounds (e.g. Roccal D—Pfizer Animal Health) or steam cleaning eliminates Giardia species cysts and Cystoisospora species oocysts as long as adequate drying time is allowed for desiccation. Bathing affected animals during and after therapy is also helpful because it removes cysts and oocysts carried on the fur.

ANTIBACTERIAL AGENTS

Antimicrobials can be used to treat cats with Clostridium or Campylobacter species-associated diarrhea, chronic idiopathic diarrhea, or inflammatory bowel disease (IBD).

Metronidazole

Metronidazole is a nitroimidazole antimicrobial with activity against anaerobic bacteria and some protozoal species. It may also exert some immunomodulatory effects and anti-inflammatory properties. Metronidazole can be used to treat Clostridium difficile-associated diarrhea, chronic idiopathic diarrhea, and IBD¹¹ (Table 2).¹²