Use of cerebellar brain smears in the diagnosis of babesiosis (Babesia bovis) in cattle.

Cerebral and cerebellar smears were made from 4 animals acutely reacting to Babesia bovis and 94 animals free from clinical babesiosis. The brain smears were stained by the Giemsa method and examined for the presence of B. bovis parasites. In animals showing clinical babesiosis capillaries congested with parasitised erythrocytes were abundant in cerebral and cerebellar smears. Results obtained from both types of brain smears in animals free from clinical babesiosis agreed closely (83% conformity) as to the presence or absence of parasites. A third group of 39 animals from which cerebral and cerebellar smears were taken was also examined serologically by the indirect immunofluorescent antibody test (IFAT); about 69% of the IFAT positive and doubtful animals showed parasites in the cerebellar brain smears. The existence of false negatives in the IFAT test has been shown and discussed. It has been concluded that cerebellar samples obtained through the foramen occipitale can be used for the microscopic detection of B. bovis parasites in latently infected bovines. This method can also be used in field cases suspected of cerebral babesiosis permitting brain sampling without resorting to the opening of the skull. Such an approach might prove particularly useful in areas where rabies occurs and the animal's head has to be sent to a diagnostic centre.