Neurological disease in horses

An increased number of horses showing muscle and joint soreness, and neurological signs have been reported in southern states since February 2011. Reported cases peaked from mid March to early April and numbers have been steadily declining since.

Many cases have been diagnosed as due to an arbovirus infection. Arboviruses are a large group of viruses spread mainly by blood sucking insects, and include alphaviruses and flaviviruses.

The arbovirus infections have been attributed to the alphavirus Ross River virus (RRv) in many musculoskeletal cases, and to flavivirus infection with Murray Valley Encephalitis virus (MVEv) and Kunjin virus in the majority of neurological cases.

There are indications that cooler weather in south-eastern Australia has led to a reduction in mosquito numbers and a consequent reduction in the number of new cases being reported in horses since early April.

Most cases have recovered gradually over 1-3 weeks. Current reports indicate that 10-15 per cent of affected horses have died or have been euthanased for welfare reasons.

National situation

The following table shows equine cases as at 24 May 2011. Cases are horses with suspect arboviral disease showing neurological or musculoskeletal disease, with samples taken for lab testing.

StateTotal casesTotal deathsPercentage
of cases with
neuro. signs (%)

*NSW has been investigating only cases showing neurological signs.

Further information

  • Flavivirus nervous disease in horses in New South Wales
    (NSW Department of Primary Industries website)
  • Murray Valley encephalitis virus alert for veterinary practitioners in Victoria
    (Victorian Department of Primary Industries website)
  • Horse 'wobbles' being investigated in South Australia
    (South Australian Department of Primary Industries and Resources website)
  • Mosquito borne neurological disease in horses - South Australia
    (Biosecurity SA website)
  • Disease in horses due to insect borne viruses - National information
    (National Pests & Disease Outbreak website)
  • Mosquito-borne infections implicated in severe neurologic disease in horses -WA
    (Western Australian Department of Agriculture and Food website)
  • Biosecurity Queensland