Neurotoxicosis in 4 Cats Receiving Ronidazole

Abstract

T ritrichomonas foetus is a protozoan that can cause chronic large-bowel diarrhea in cats. Ronidazole, a nitroimidazole, has been shown to effectively treat T foetus in cats at doses of 30 to 50 mg/kg body weight twice daily for 14 days. To our knowledge, adverse effects in cats have not been reported. This case series describes neurologic abnormalities suspected to be secondary to ronidazole administration in 4 cats. Case 1 is a 2.5-year-old male castrated Domestic Shorthair that was presented with a chief complaint of chronic, intermittent, mucohemorrhagic diarrhea of 1.5 years’ duration. The owner was unable to comment about the frequency or the urgency of defecation. The cat, when 6 weeks of age, was adopted by the owner from a rescue organization and had been housed strictly indoors since then. He resided with 5 other cats, all of whom tested negative for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) and had no history of diarrhea. The only medical problems among the cats were occasional upper respiratory tract infections. Serum biochemistry panel, CBC, and T4; a blood smear to scan for Mycoplasma hemofelis; and (ELISA) for FeLV antigen and FIV antibody (FeLV/FIV test), performed by the referring veterinarian (rDVM) were unremarkable. Coronavirus 7B antibody titers were 1 : 80, 1 : 160, and 1 : 80 on 3 sequential serum samples in an 8-week period. Initial physical examination (PE) revealed a bright, alert, responsive, and well-hydrated cat. He weighed 4.7 kg, with a body condition score (BCS) of 7 of 9. Rectal temperature was 102.9uF, and a small amount of frank blood was observed on the thermometer. The patient had a mild serous ocular and nasal discharge, as well as gingivitis, faucitis, and halitosis. The remainder of his PE was unremarkable. Serum chemistry profile, CBC, urinalysis, abdominal ultrasound, and FeLV/FIV test were all unremarkable. Fecal flotation and direct wet preparation were negative for intestinal parasite ova and motile protozoa; Giardia ELISA was negative; stained direct preparations were unremarkable; and fecal cultures for Salmonella, Yersinia, and Campylobacter were negative. A rectal scrape revealed neutrophilic inflammation, with occasional cocci, diplococci, and a few sporulating bacteria consistent with Clostridium sp. A second fecal wet smear was positive for flagellated protozoa. Culture for Tritrichomonas foetus was positive, and the patient was prescribed ronidazole at a dose of 54 mg/kg PO q12h for 14 days. Five days after starting ronidazole, the owner reported that the cat had normal stools, lethargy, a blank stare, and appeared to be in ‘‘slow motion.’’ Neurologic evaluation of the cat was declined, and the ronidazole was continued for an additional 3 days. These clinical signs progressed, and the cat also developed an unsteady gait, pelvic-limb weakness, and trembling. Ronidazole therapy was discontinued, and the cat remained stable over several days, with gradual improvement. The patient was presented 7 days after discontinuation of ronidazole, and physical examination revealed a crouching, wide-based stance and mild ataxia in the pelvic limbs. The rest of the physical examination was unremarkable. The cat had complete resolution of its neurologic signs 1 month after discontinuation of ronidazole, and physical examination was unremarkable. The hematochezia recurred several days after discontinuing the ronidazole. Direct wet preparation of feces for motile protozoa and culture for T foetus were negative; however, the owner elected to re-treat with ronidazole at a lower dose (30 mg/kg PO q12h). The hematochezia resolved quickly, but, 12 days later, the owner reported that the cat had been unsteady, stumbling, and ‘‘spacey’’ for several days and that she had been giving him only 1 dose daily during this period. Neurologic signs resolved over a period of weeks after discontinuation of ronidazole. The patient was returned for reevaluation approximately 6 weeks after discontinuing the second course of ronidazole, and the PE was unremarkable. Culture of fresh feces was negative for T foetus. Case 2 is a 5-year-old female spayed Persian who was examined because of chronic mucohemorrhagic diarrhea since the cat was acquired from a breeder at 4 months of age. The diarrhea episodes initially occurred 6 to 8 times daily, and the cat was fecally incontinent. Routine deworming by the rDVM with pyrantel pamoate and empiric antimicrobial administration with metronidazole had no effect on the diarrhea. Dietary trials with Royal Canin Innovative Veterinary Diet Green Peas and Venison, Hill’s Prescription diet w/d, and Nestle Purina OM also had no effect on the diarrhea. The rDVM obtained multiple full-thickness biopsy specimens from the small and large intestines, which were characterized by mild lymphoplasmacytic inflammation. The cat was From the Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL (Rosado, Specht); and Department of Medicine and Epidemiology, University of California at Davis School of Veterinary Medicine, Davis, CA (Marks). Reprint requests: Dr. Andrew Specht, P.O. Box 100126, Gainesville, FL, 32610; e-mail: SpechtA@mail.vetmed.ufl.edu.