Use of ponazuril paste to treat coccidiosis in shelter-housed cats and dogs.

Cystoisospora (synonym Isospora) spp. infections are common in dogs and cats worldwide, especially in crowded or unsanitary environments. Ponazuril (toltrazuril sulfone) is a widely used oral treatment, but protocols that will produce oocyst excretion below the detection limit in shelter-housed animals have not been determined. The aim of this study was to determine the efficacy of ponazuril paste at each of three dosages (dosage 1, 50mg/kg q24 h for 3 days, dogs n=14, cats n=16; dosage 2, 50mg/kg as a single dose, dogs n=13, cats n=25; or dosage 3, 20mg/kg as a single dose, dogs n=16, cats n=23) in shelter-housed dogs (n=43) and cats (n=64) with confirmed coccidiosis. Fecal oocyst counts and identification and fecal consistency scoring was performed pre-treatment (Day 1) and again at Day 3-4 and Day 8. There were higher proportions of animals with oocyst excretion below the detection limit at both Day 3-4 and Day 8 in the dosage 1 group (dogs 92.9%, cats 87.5%) than in the other two groups (dosage 2, dogs 76.9%, cats 80.0%; dosage 3, dogs 68.8%, cats 47.8%). Animals with high fecal oocyst counts at Day 1 were significantly more likely to be infected at Day 3-4 (dogs, P<0.001; cats, P=0.013). Fecal consistency score at Day 3-4 was not significantly related to infection status (dogs, P=0.898; cats, P=0.136). Further studies are warranted to investigate a ponazuril protocol that can safely reduce fecal oocyst burdens in infected dogs and cats to levels below the detection limit. Environmental decontamination is also important to reduce the likelihood of re-infection.