Experimental oral inoculations in birds to evaluate potential definitive hosts of Neospora caninum.

Experimental oral inoculations to evaluate potential definitive hosts of Neospora caninum were conducted by feeding infected rodent tissues to 9 carnivorous birds of 4 species. Birds included 2 red-tailed hawks (Buteo jamaicensis), 2 turkey vultures (Cathartes aura), 2 barn owls (Tyto alba), and 3 American crows (Corvus brachyrhynchus). The rodents (mice or rats) had been inoculated with 100,000 culture-derived tachyzoites of N. caninum 1-6 mo before feeding to the birds. Fecal samples were collected from each bird daily for 1 mo after feeding rodents and examined for oocysts by fecal flotation. In addition, processed aliquots from all avian fecal samples were fed to BALB/c mice. Five weeks after feeding, mice were bled and sera were tested for antibodies against N. caninum. One to two months later, mice were killed and brain tissue was examined microscopically for protozoal cysts. While occasional oocysts were found in avian fecal samples, these were likely not N. caninum because they were not infective to BALB/c mice. It was concluded that the bird species tested are not likely to be definitive hosts of N. caninum.