Seroepidemiological evidence for a relationship between Neospora caninum infections in dogs and cattle

Dogs from dairy farms with a known prevalence of Neospora caninum antibodie s in the cattle were examined for the presence of N. caninum antibodies usi ng an ELISA. Data of farm dogs were compared with those of dogs examined at a university clinic, which originated mainly in urban areas. Of the 152 fa rm dogs, 36 (23.6%) were seropositive to N, caninum, which was significantl y higher than the proportion of seropositives in the clinic dog population (19 of 344, 5.5%). Seroprevalence was significantly higher (P = 0.01) in fe male dogs than in male dogs. Seroprevalence in dogs increased with age, ind icating postnatal infection. Seropositivity to N. caninum in farm dogs was strongly correlated with a high prevalence of N. caninum antibodies in the cattle. At farms where no dogs were present, the seroprevalence to N. canin um in the cattle was significantly lower (P = 0.0002) than in farms where d ogs were present. These findings suggest that there is a relationship betwe en N. caninum infection of farm dogs and cattle. Since dogs have been shown to be definitive hosts of N. caninum, cattle may be infected by exposure t o canine oocysts. Further research is needed to find out whether and how do gs may acquire the infection from cattle. (C) 1999 Australian Society for P arasitology Inc. Published by Elsevier Science Ltd. All rights reserved.