Pathological Patterns of the Central Nervous System Lesions in Stillbirths and Newborns Small Ruminants with Neurological Signs in Semnan Province

BACKGROUND: The defects of the central nervous system caused by viruses are associated with tissue changes in certain areas of this system. OBJECTIVES: We conducted the current work to determine and categorize the pathologic pattern of central nervous system lesions in stillbirths and newborns small ruminants with neurological symptoms in Semnan province. METHODS: Primarily, we selected the affected animals and carried out systematic post mortem examination of lambs and kids. Subsequently, brain and spinal cords were completely removed. Processing, sectioning, and staining from different regions of the central nervous system was performed and 15 different regions of the brain and 10 different levels of the spinal cord were prepared. Subsequently, the histopathological study was performed and the observed lesions were arranged. RESULTS: This study was performed on 20 lambs and kids with nonsuppurative inflammatory lesions in the brain and spinal cord. In the gross examination of the brain and spinal cord, we observed 4 cases of arthrogryposis, 1 case of spinal cord hypoplasia, 2 cases of hydranencephaly, 2 cases of porencephaly, and 1 case of cerebellar hypoplasia. According to the presence of nonsuppurative inflammation in the brain and spinal cord, 20 positive cases were categorized into 4 groups. In the first 3 groups, the main lesion was nonsuppurative encephalomyelitis and the main lesion of the fourth group was nonsuppurative encephalitis. Accordingly, 6 cases in the first group had extensive and inclusive nonsuppurative inflammation in over 75%  of the brain and spinal cord sections; in the second group, five cases had multiple scattered nonsuppurative inflammation in 50% - 75% of the brain and spinal cord sections; in the third group, five cases had non-inclusive and focal nonsuppurative inflammation in less than 50% of the brain and spinal cord sections, and in the fourth group, 4 cases had nonsuppurative inflammation in the brain without lesion in the spinal cord. CONCLUSIONS: It seemed as though in each of the four pathological patterns, certain viral agents were responsible for the pathological changes.