Congenital defects of the bovine central nervous system

Anencephaly and Severe Myelodysplasia in a Stillborn Brown Bear (Ursus arctos arctos)

Simple Summary

A captive twenty-four-year-old female Eurasian brown bear (Ursus arctos arctos) gave birth to a stillborn cub at the end of gestation. Several malformations resulting from the anomalous development of the neural tube, not previously reported in bears, were observed in the cub. These included anencephaly, hypoplasia, micromyelia, severe myelodysplasia, syringomyelia, and spina bifida. The aetiology remains unidentified.

Abstract

Malformations in the development of the neural tube have been described to be associated with different aetiologies, such as genetic factors, toxic plants, chemical products, viral agents, or hyperthermia. A twenty-four-year-old female Eurasian brown bear (Ursus arctos arctos), permanently in captivity and kept under food and management control, gave birth to a stillborn cub at the end of gestation. Several malformations resulting from the anomalous development of the neural tube, not previously reported in bears, were observed, such as anencephaly, hypoplasia, micromyelia, severe myelodysplasia, syringomyelia, and spina bifida. Multiple canal defects (e.g., absence) were also observed in the spinal cord. In some regions, the intradural nerve roots surrounded the spinal cord in a diffuse and continuous way. The aetiology remains unidentified, although the advanced age of the mother and/or folic acid deficit might have been the possible causes of this disorder. Supplements of folate given to the mother before and during early pregnancy may have reduced the incidence of neural tube defects. That supplementation should be considered when the reproduction of bears is to occur in captivity, in order to prevent the loss of future generations of this endangered species.

Case Report: Complex Congenital Brain Anomaly in a BBxHF Calf-Clinical Signs, Magnetic Resonance Imaging, and Pathological Findings

This case report describes the clinical signs, magnetic resonance imaging (MRI) findings and associated (histo)pathological findings in a crossbred Belgian Blue calf with congenital complex brain anomaly. The calf was presented with non-progressive signs (including cerebellar ataxia) since it was born, suggestive of a multifocal intracranial lesion. A congenital anomaly was suspected and after hematology, biochemistry, serology, and cerebrospinal fluid analysis, a magnetic resonance imaging study was performed. The following suspected abnormalities were the principal changes identified: severe hydrocephalus, porencephaly, suspected partial corpus callosum agenesis (CCA), and increased fluid signal between the folia of the cerebellum. Post-mortem examination predominately reflected the MRI findings. The origin for these malformations could not be identified and there was no evidence of a causative infectious agent. Corpus callosum abnormalities have been reported in bovids before and have been linked to bovine viral diarrhea virus (BVDV) infections, as have several other central nervous system anomalies in this species. In this case, BVDV was deemed an unlikely causative agent based on serology test results and lack of typical histopathological signs. The etiology of the congenital anomaly present in this bovine calf remains unknown.

Multiple Cephalic Malformations in a Calf

Congenital malformations of the central nervous system (CNS) can affect the CNS alone or the CNS and craniofacial structures. Here, we report an unusual and complex congenital cephalic malformation observed in a 3-day-old male crossbreed calf. Clinical examination disclosed a dome-shaped cranial vault, a flat face with a short snout, a median cleft lip, and increased intraorbital distance. The frontal region of the head was remarkable for a fluctuant, sac-like protrusion covered with haired skin. Neurologic findings suggested a multifocal intracranial lesion affecting the prosencephalon and the central vestibular system. While pathological and histopathological findings posited for a presumptive diagnosis of either hydranencephaly or holoprosencephaly associated with multiple congenital facial abnormalities, not all the findings could be definitely attributed to either of the two encephalic malformations alone. To our knowledge, a similar combination of severe congenital abnormalities affecting both the CNS and the craniofacial structures has not been reported in calves to date.

Recurrent outbreaks of myelodysplasia in newborn calves

The present study records recurrent outbreaks of myelodysplasia of unknown origin occurring in a specific geographical location in the north of Spain, and involving up to 30% of the calves born in affected herds. The affected calves were of different breeds and displayed non-progressive signs of spinal cord dysfunction. The disease has occurred annually in February-March over a period of at least 15 years. Only calves born to cattle grazed on mountainside pastures and under high grazing pressure were affected. Seven calves were subjected to necropsy examination. Myelodysplasia was not associated with vertebral defects or arthrogryposis and involved the entire length of the spinal cord. Microscopically, there was abnormal distribution of the grey matter, aberrations of the central canal and failure of formation of the ventral median fissure. Infectious, nutritional and physical disorders were ruled out as possible aetiologies. A critical period of embryonic susceptibility to the causal agent was identified. This was during the time of secondary neurulation when cows in the early stages of gestation were grazed on mountainside pastures. Consequently, the presence of neuroteratogenic plants in these pastures is proposed as a likely cause. Two plants, Carex brevicollis and Erythronium dens-canis, which contain alkaloids, were identified on the mountainsides where affected cattle were grazed and not in other pastures, and are proposed as the possible aetiology of the disease.

Segmental hypoplasia of the spinal cord in a Japanese black calf

Segmental hypoplasia not associated with vertebral abnormalities was found in a Japanese Black calf that was unable to stand. Constriction occurred between the third and 5th segments of the lumbar spinal cord, and was most severe in the 4th segment. Myelodysplasia, such as hydromyelia and syringomyelia, absence or interruption of the central canal, dysplasia of the gray matter, and absence or divergence of the septal connective tissue at the dorsal median septum or the ventral median fissure, were confirmed histologically. These changes indicate hypoplasia of the segments affected following neural tube closure. Therefore, this case was suspected to be a closed neural tube defect.

Congenital defects in the llama

When faced with the question of what you should do as a veterinary practitioner, when presented with a congenital defect in a llama, one answer is to seek qualified help from your state veterinary diagnostic laboratory. But most importantly, encourage the owners of such animals to report the defect to their llama association, including pedigree information. The better we understand the pathogenesis of such defects, the better we will be able to control their incidence.

Investigating perinatal calf mortality in beef herds

This article summarizes the information presented in this issue to identify the reasons for a perinatal calf mortality (PCM) problem through a risk-factor-evaluation approach. The benefits of necropsies in PCM investigations are discussed, and the gross lesions of the major causes of PCM are described. The use of 2 x 2 tables to calculate odds ratios and the Chi-square method to test the validity of the odds ratios are presented as methods to determine suspected risk factors. The article concludes with a discussion of the management plan used to solve a PCM problem.