THE HISTOLOGY OF EQUINE ENCEPHALOMYELITIS

Area of Science:

• Veterinary Neurology
• Virology
• Pathology

Background:

• Equine encephalomyelitis viruses (eastern and western strains) are significant neurotropic pathogens.
• These viruses cause severe neurological disease in various animal species.

Purpose of the Study:

• To describe and compare the neuropathological effects of eastern and western equine encephalomyelitis viruses.
• To detail the characteristic lesions and cellular changes induced by these viruses in different animal models.

Main Methods:

• Histopathological examination of nervous tissues from infected animals.
• Comparative analysis of lesion severity and distribution between eastern and western strains.
• Observation of clinical and pathological manifestations in horses, dogs, sheep, calves, guinea pigs, rabbits, and mice.

Main Results:

• Eastern strain caused intense encephalomyelitis in horses, characterized by neuronal degeneration, nuclear inclusions, glial proliferation, and perivascular cuffing, with grey matter more affected than white.
• Lesion distribution varied, with cerebral cortex, thalamus, and hypothalamus more severely affected than the cerebellum.
• Small mammals infected with the eastern strain showed a predilection for olfactory centers, with additional nuclear inclusions and potential bronchopneumonia.
• Western strain induced less intense and extensive lesions in horses compared to the eastern strain.
• In guinea pigs, western strain infection could be indistinguishable from eastern strain infection.

Conclusions:

• Both eastern and western equine encephalomyelitis viruses induce distinct neuropathological changes.
• Species-specific differences in lesion severity and distribution are evident.
• The study highlights the significant impact of these viruses on the central nervous system across various animal species.