Hypomyelination Associated With Bovine Viral Diarrhea Virus Type 2 Infection in a Longhorn Calf

Abstract

A newborn Longhorn heifer calf presented with generalized tremors, muscle fasciculations, ataxia, and nystagmus. At necropsy, no gross central nervous system lesions were observed. Histologically, the brain and spinal cord had mild to moderate diffuse microgliosis and astrocytosis, minimal nonsuppurative encephalitis, and decreased myelin staining. Ultrastructural examination revealed thinning and absence of myelin sheaths. Various cell types were immunohistochemically positive for bovine viral diarrhea virus (BVDV). Noncytopathogenic BVDV was isolated from the brain and identified as BVDV type 2 by phylogenetic analysis. BVDV-induced hypomyelination is rare and analogous to lesions in neonates infected with border disease and classical swine fever viruses. This is the first documented case of hypomyelination in a calf specifically attributed to BVDV type 2 and the first description of the ultrastructural appearance of BVDV-induced hypomyelination.

Congenital infection with atypical porcine pestivirus (APPV) is associated with disease and viral persistence

“…Furthermore, ultrastructural examination of cerebellar white matter showed not only hypomyelination but myelin disruption and breakdown in affected animals. This is in contrast to ultrastructural lesions reported in piglets with classical swine fever [3] and a calf infected with BVDV [24]. We therefore conclude that in utero infection with APPV has a deleterious effect on fetal oligodendrocytes, which are present in sufficient numbers.…”

“…The discrete histologic lesions present in the spinal cord of infected animals were consistent with hypomyelination. These alterations were quite similar to lesions reported in piglets infected with CSFV [3] and a calf infected with BVDV [24]. The mild vacuolization of the cerebellar white matter of affected animals is in accordance with lesions reported in piglets with CT due to suspected BVDV-related pestivirus infection [25].…”

An emerging novel virus: Atypical porcine pestivirus (APPV)

“…Further ultrastructural examination found that not only hypomyelination was present in the spinal cord but also myelin breakdown in the cerebellar white matter of CT type A‐II‐affected pigs. These alterations differ somewhat from the lesions identified in CSFV‐infected piglets and BVDV‐infected calves . The immunohistochemical analysis indicated that the numbers of oligodendrocytes in the spinal cord were not changed, but the oligodendrocyte transcription factor 2 (Olig 2) was found to express increasingly in the CT type A‐II‐affected piglets .…”

“…These alterations differ somewhat from the lesions identified in CSFV-infected piglets and BVDV-infected calves. 29,30 The immunohistochemical analysis indicated that the numbers of oligodendrocytes in the spinal cord were not changed, but the oligodendrocyte transcription factor 2 (Olig 2) was found to express increasingly in the CT type A-IIaffected piglets. 12 The results indicate that APPV infection may affect myelin development and result in disruption of the myelin, which sheds light on understanding pathogenesis of the disease.…”

Infectious Agents

“…150,176,177 Less commonly, congenital BVDV infection can cause CNS hypomyelination, which has been reported with both species of BVDV. 178,179 In addition to CNS abnormalities, congenital BVDV infections can result in brachygnathism, osteopetrosis, thymic aplasia, hypotrichosis, hair coat abnormalities, pulmonary hypoplasia, and growth retardation. 150,175,176,180 While abortions are still possible in later stages of gestation, congenital infections following the completion of organogenesis and immunocompetence result in effective immune responses and clearance of the virus.…”