Neospora caninum infection in a clinically healthy calf: parasitological study and serological follow-up.

In this study a case of congenital infection in a clinically healthy calf is reported. The mother showed high antibody levels (IFAT) at 230 days of gestation (IgG titres greater than or equal to 1:1600, IgM titres greater than or equal to 1: 320) and the parasite was isolated from placental cotyledonary villi at calving. The IgM values are indicative of a recent infection in the third trimester of gestation. The calf was monitored serologically for IgM and Ige from birth until slaughtering, at 8 months of age. IgM titre showed a peak at birth, while IgG peak was observed at 40-60 days of age. Parasitic isolation was obtained by biological tests using Swiss mice or VERO cell cultures inoculated with brain and spinal cord tissues. The parasitic presence in the calf was also evidenced in the myocardium with immunohistochemical method. The results are very important because they demonstrate that the period of gestation in which the cow becomes infected is an important factor in the pathogenesis of N. caninum induced abortion: in fact, the acquisition of infection in the third trimester of gestation allowed the foetus to develop a sufficient grade of immunocompetency to limit parasite multiplication with the result of a calf born clinically healthy.