Neosporal abortion in Oklahoma cattle with emphasis on the distribution of brain lesions in aborted fetuses.

Abstract

a preliminary placentitis from which the organism is distributed through the blood to fetal tissues. In field cases of neosporal abortion, the organism has been identified in brain, spinal cord, striated muscle, liver, kidney, lung, adrenal gland, and adipose tissue, and it is associated with either granulomatous or nonsuppurative inflammation. Since late 1995, a small number of cases of neosporal abortion have been positively identified in Oklahoma cattle. In cases in which the entire fetus was submitted to the Oklahoma Animal Disease Diagnostic Laboratory for examination, microscopic lesions were similar to those reported by others, with the brain being the most commonly affected organ. However, all areas of the brain were not uniformly affected, and the current literature does not detail the specific distribution of brain lesions. 5 The purpose of this report is to document the occurrence of neosporosis in Oklahoma cattle and to describe the distribution of brain lesions in these diseased bovine fetuses. Six cases of bovine neosporal abortion in which the complete fetus was submitted for diagnostic examination were reviewed from medical records at the Oklahoma Animal Disease Diagnostic Laboratory. Diagnosis of neosporal abortion was based on the presence of typical histological lesions for fetal neosporosis and the identification of tachyzoites and tissue cysts in lesions by immunohistochemistry with antiNeospora antiserum. Moreover, bacteriologic and viral isolation procedures failed to identify any significant agents that may produce similar histological lesions, and serological profiles for infectious bovine rhinotracheitis virus, Brucella abortus, bovine virus diarrhea virus, and 6 serovars of Leptospira spp. were negative. Representative samples of lung, heart, liver, kidney, spleen, and abomasum from each fetus were fixed in 10% buffered formalin. The entire brain was placed in either 10% or 30% buffered formalin. In this series of cases, spinal