Chapter 275

Neospora caninum is a protozoal agent in the phylum Apicomplexa. The domestic dog and coyotes are definitive hosts, and herbivores, including deer and cattle, are considered intermediate hosts. Encephalomyelitis and myositis develop in experimentally infected kittens, and seropositive, naturally exposed cats have been detected, but clinical disease in naturally infected cats has not been reported (Bresciani et al, 2007). After the sexual phase is completed in the dog’s gastrointestinal tract, infected dogs pass unsporulated oocysts in feces. After sporulation, the oocysts are infectious to definitive and intermediate hosts. However, in one study, dogs fed sporulated oocysts became infected and seroconverted but did not shed oocysts (Bandini et al, 2011). Dogs also become infected by ingesting bradyzoites in tissue cysts from intermediate hosts, including bovine placentas, or any meat from deer or cattle. The organism also has been detected in the tissues of free-ranging chickens. Transplacental infection also is common in dogs and can occur repeatedly once a bitch is infected.

Neospora caninum seroprevalence rates have varied from 0% to 100% depending on the country and lifestyle of the dog. Infections are found throughout the world, with prevalence rates higher in feral dogs than in domestic dogs. Furthermore, dogs that eat raw meat also have higher seroprevalence rates than do dogs fed commercial diets. However, because of the short duration of the shedding period, oocysts rarely are reported in fecal surveys. In one study of 24,677 dog samples, oocysts consistent with N. caninum were detected in only 0.3% of the samples (Barutzki and Schaper, 2011).