An increased incidence of neurological disease in horses has been reported across a number of Australian states in 2011. Heavy summer rainfall and flooding across Queensland, New South Wales, Victoria and South Australia have increased mosquito activity and the neurological signs in horses have been linked to mosquito-borne diseases known as ‘arboviruses’.
Affected horses have shown varying signs, such as muscle and joint soreness, stiff gait, depression, incoordination and tremors. Most horses have recovered with supportive care. Some of the more severely affected horses have been euthanized on animal welfare grounds.
Viruses implicated in the disease outbreak in eastern Australia include Ross River virus, Murray Valley encephalitis (MVE) and Kunjin virus. MVE and Kunjin virus have been responsible for the more severe nervous signs. Hendra virus and Japanese encephalitis have been ruled out as possible causes.
DAFWA’s Animal Health Laboratories investigated four cases of horses with neurological signs in April in the South West Land Division of Western Australia, which were found to be infected by the flavivirus group of viruses (which includes MVE and Kunjin). Further testing is continuing. Affected horses are not contagious. They cannot infect other horses, people or any other animal.
However, in a small percentage of cases bites from mosquitoes carrying these viruses may cause serious infection in people. Appropriate protection against mosquito bites is highly recommended for both people and horses. Registered repellents, rugs, fly veils, reduced exposure at dawn and dusk are recommended for horses.
Diseases such as Hendra should be considered when handling horses with nervous signs. For veterinarians and animal handlers, correct personal protective equipment (PPE) is recommended. Visit www.biosecurity.qld.gov.au for the most up-to-date recommendations on PPE in suspect Hendra cases.
Report any suspicious or unusual signs in your horse immediately to your private veterinarian, the local district veterinary officer or the Emergency Disease Watch hotline on 1800 675 888.