Toltrazuril treatment of cystoisosporosis in dogs under experimental and field conditions

Coccidia of the genus Cystoisospora cause mild to severe diarrhoea in dogs. The effects of toltrazuril treatment on cystoisosporosis were studied unde r experimental and field conditions. Twenty-four puppies were experimentall y infected each with 4 x 10(4) oocysts of the Cystoisospora ohioensis group . Three groups of six puppies were treated 3 dpi with 10, 20 or 30 mg/kg bo dy weight of toltrazuril suspension (5%); the remaining six puppies served as non-treated controls. Toltrazuril suspension or microgranulate were give n once in a dose of 10 or 20 mg/kg body weight, respectively, to naturally infected puppies in conventional dog breeding facilities, depending on the coproscopical evidence of infection. Oocyst excretion and clinical data wer e recorded. Under experimental conditions, the non-treated puppies excreted oocysts beginning at 6 dpi and suffered from catarrhalic to haemorrhagic d iarrhoea. On 12 dpi, four of six non-treated puppies died. Irrespective of the dose, toltrazuril treatment totally suppressed oocyst excretion and no diarrhoea or other signs of disease were observed in the treated groups. Na tural Cystoisospora infections were regularly found during the 3rd or 4th w eek of age in dog breeding facilities although not always associated with d iarrhoea. A single oral application of toltrazuril abrogated oocyst sheddin g and the treated puppies remained generally coproscopically negative durin g the following 2-4 weeks. Cystoisospora is pathogenic for puppies and can induce severe disease. Natural infections are common in conventional dog br eeding facilities. Toltrazuril treatment is suitable for controlling cystoi sosporosis under experimental and field conditions. A single oral treatment for puppies in the 3rd or 4th week of age is recommended.