Neurological disorders, virus persistence and hypomyelination in calves due to intra‐uterine infections with bovine virus diarrhoea virus

Abstract

The clinical and pathological findings after a natural intra-uterine infection with BVD-virus in a Friesian dairy herd are described. The virological and serological aspects will be discussed in a separate paper (30). In a period of 4 years, 11 calves were born with the following nervous symptoms: more or less serious incoordination, tremor, oscillating nystagmus, and a negative blinking reflex. The pupillary and sucking reflexes were normal. No ocular defects, such as lenticular opacity or retinal atrophy were observed. The first calf was born in 1979. Within 6 months the symptoms disappeared. After a normal conception and pregnancy this animal gave birth to 2 clinically normal calves in 1981 and 1982. The second calf died at the age of 2 months, due to an ulcerating enteritis. In 1980, again 8 calves with the same nervous symptoms were born within a period of 3 months. Two calves died at the age of 3 days and 5 weeks respectively; 2 calves were sold when 10 days and 3 weeks old; one calf did not improve and was necropsied at the age of 17 days. The remaining 3 calves showed only a slight hypermetria when examined after 6 months. At that time nystagmus was only visible with ophthalmoscopy. Two calves were slaughtered when 10 months old. The last one, a bull, proved to be sterile and was necropsied at the age of 1 1/2 year. A calf, born in 1981, recovered within a week and was necropsied at the age of 15 days. The last calf, born in 1982, did not improve at all and was necropsied at the age of 14 days. During these 4 years none of the other animals in the herd showed any symptoms due to an acute or chronic BVD-virus infection. At post mortem examination of 6 animals no macroscopically visible malformations were found. Hypomyelination and abnormal glial cells were evident in 5 cases, especially in the two youngest calves which did not show any improvement. One of them had had an obvious thymic hypoplasia. The calf which recovered within a week showed only very slight changes. In one of the calves slaughtered at 10 months, inflammatory lesions were found in the brain. The diagnosis was confirmed by virological investigations. Clinically as well as pathologically there was a close resemblance to Border disease in lambs and congenital tremor in piglets after prenatal exposure to Hog cholera virus.

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

“…In a dairy farm in the Netherlands, an outbreak of BVD resulted in multiple calves being born with neurologic signs similar to those described here, and histologic findings included widespread loss of myelin staining, an increased number of microglia and astrocytes with enlarged vesicular nuclei, and mild mononuclear cell cuffing of blood vessels. 5 Another report describes a single case of BVDV in a newborn Holstein calf that resulted in ataxia, hypermetria, and intention tremors of the head. 23 Hypomyelination was reported in that case but not accompanied by gliosis or inflammation.…”

“…Most fetal infections with BVDV result in persistent subclinical infection, fetal death, or defects such as cerebellar hypoplasia, hydranencephaly, internal hydrocephalus, microencephaly, and porencephaly. 5,10,14 Neuropathologic descriptions of natural in utero BVDV infection resulting in hypomyelination are limited. In a dairy farm in the Netherlands, an outbreak of BVD resulted in multiple calves being born with neurologic signs similar to those described here, and histologic findings included widespread loss of myelin staining, an increased number of microglia and astrocytes with enlarged vesicular nuclei, and mild mononuclear cell cuffing of blood vessels.…”

“…Types of BVDV-induced central nervous system (CNS) defects include cerebellar hypoplasia, spinal cord hypoplasia, microencephaly, porencephaly, hydranencephaly, internal hydrocephalus, and a variety of ocular changes. 2,10,14 Hypomyelination has been reported in calves congenitally infected with BVDV; 5,10,20,23 however, hypomyelination is a relatively uncommon outcome compared with intrauterine infections with BDV and CSFV strains in sheep and pigs, respectively. Here we describe the histologic, immunohistochemical, and ultrastructural findings in a calf with severe hypomyelination presumably induced by naturally acquired intrauterine infection with a virus specifically genotyped as BVDV type 2.…”

Non-Cytopathic Bovine Viral Diarrhea Virus Infection Inhibits Differentiation of Bovine Neural Stem/progenitor Cells into Astrocytes in Vitro

“…Retardation of myelin production resulting from interference of oligodendrocyte differentiation has been suggested as a mechanism in the pathogenesis of congenital hypomyelination [2]. Astrocytes have long been considered as structural-and metabolic-supporting cells for neurons, but recent evidences have shown that they have versatile roles in the development and function of the CNS [10,14,15].…”

Prevalence and Characterization of Bovine Viral Diarrhea Virus in the White-Tailed Deer Population in Indiana

“…The effect of BVDV on the wild white-tailed deer population is not clear, but it is suspected that these animals may develop mild clinical disease such as that described for cattle. 3,22 Since prevalence of BVDV in deer is low, it is likely that cattle serve as the potential reservoir for infection in deer. 25 Pasture fence contact and ''other animal traffic'' were also identified as risk factors.…”