Hendra Virus: A Deadly Disease of Horses and Humans

Presentation Description / Summary: Hendra virus (HeV) is a low incidence high consequence pathogen with high case fatality rates of 80% in horses and 57% humans. Horses are infected from body fluids of large Pteroid fruit bats (flying foxes). Infected horses predominately demonstrate respiratory and neurological signs, although non-specific early signs such as fever, depression, inappetence and restlessness are very common. Neurological manifestations include ataxia, disorientation, head tilt, facial nerve paralysis, circling, and seizures. Laboured breathing, tachypnoea, frothy or blood-tinged nasal or oral discharge are not uncommon terminal signs with respiratory involvement. Sudden death and colic have also been reported. Infected horses amplify the virus and can spread the disease via aerosol or fluid transmission to other horses and humans. Disease prevention is by vaccination of horses using a recombinant HeV soluble G glycoprotein vaccine. This was the first vaccine commercialised against a BSL-4 agent. Vaccine administration by veterinarians of microchipped horses is logged in a publicly accessible registry. Only 10% of horses in endemic areas are vaccinated due to cost and fear of vaccine reactions perpetuated in social media. Veterinarians are advised not to treat any unvaccinated sick horse prior to a negative HeV exclusion test, unless full personal protective equipment is utilised. Our research has focused on maternal antibody acquisition and duration in foals, and response of foals to vaccination. Sixty percent of foals from well vaccinated mares have antibody titres ≥1:32 at the time of vaccination (6 months), however, these foals respond poorly to vaccination due to interference of maternal antibody.