Vertical transmission of Neospora caninum in dogs

Herein we report the development of a canine model to examine transplacental and/or transmammary transmission of Neospora caninum. Six pregnant bitches were experimentally infected with N. caninum on day 21 of gestation. One bitch successfully delivered a litter of 3 live pups. These pups showed slight proprioception deficits, increased muscle tone, and spasticity in both pelvic limbs; however, N. caninum was neither demonstrated by bioassay in cell culture nor seen in histological sections of tissues from these pups. The remaining 5 bitches aborted. Neospora caninum was isolated from tissues of 4 of the experimentally infected bitches and pups from 2 of the miscarried litters. Experimental infections of 2 litters of 5-day-old nursing pups produced variable results. Neospora caninum was isolated from 2 of 2 inoculated pups in 1 litter and 3 of 6 inoculated pups in the second litter.