Bluetongue virus-induced hydranencephaly in cattle

Area of Science:

• Veterinary Pathology
• Virology
• Neuroscience

Background:

• Bluetongue virus (BTV) is a significant arbovirus affecting livestock globally.
• Congenital defects in cattle can result from various infectious agents.
• The neuropathogenesis of BTV in bovine fetuses is not fully understood.

Purpose of the Study:

• To investigate the pathological effects of direct bluetongue virus inoculation into bovine fetuses.
• To characterize the resulting brain lesions and their temporal development.
• To assess the potential viability and role of infected calves as virus reservoirs.

Main Methods:

• Direct inoculation of bluetongue virus into 125-day bovine fetuses.
• Necropsy and histopathological examination of fetal brains at various time points post-inoculation.
• Gross and microscopic evaluation of brain lesions, including encephalitis, meningitis, and vascular damage.

Main Results:

• Inoculation led to hydranencephaly, characterized by thin-walled cerebral hemispheres, dilated ventricles, and cerebral cysts.
• Earliest lesions included severe necrotizing encephalitis and nonsuppurative meningitis, predominantly in the cerebrum.
• Hemorrhagic cerebral necrosis resembling infarcts and widespread microcavitations were observed.
• Vascular damage was evident in fetal brains 12 and 20 days post-inoculation.
• No gross lesions were found in the brain stem or cerebellum.

Conclusions:

• Direct BTV inoculation in bovine fetuses causes severe, characteristic brain malformations.
• The observed lesions suggest a primary vascular component contributing to neuropathogenesis.
• Calves with BTV-induced hydranencephaly exhibit poor viability and are unlikely to serve as significant virus reservoirs.