Bovine besnoitiosis: transfer of colostral antibodies with observations possibly relating to natural transmission of the infection.

Colostral antibodies to B. besnoiti were detected by immunofluorescence in four calves born to two Besnoitia-infected dams, with titres ranging from 1:64 to 1:1024. A specific antibody titre of 1:1024 was found in colostrum collected from one of the dams. Two of the newborn calves, when sampled immediately after birth, were serologically negative to B. besnoiti, but became positive on the next day. In all the calves, antibodies were detectable up to the age of 4 months. Observations concerning passive transfer of antibodies from Besnoitia-infected dams to offspring, and transmission of the infection among infected and non-infected closely kept cows, are discussed.