Horses grazing poor pastures may be at greater risk of contracting Hendra virus (HeV) according to recent research in Australia.
In a joint study, DL Anderson of Bahrinna Thoroughbred Services, Beaudesert, Queensland and Wayne Bryden, Professor of Animal Science at the University of Queensland's School of Agriculture and Food Sciences, investigated the relationship between outbreaks of HeV and grazing conditions in 2011.
They identified sites where cases of HeV infection had occurred, and interviewed veterinarians that had dealt with them. They also collected data on local climatic conditions at the time the infections developed and assessed likely forage availability and pasture dynamics.
Professor Bryden presented the results of the study at the Australasian Equine Science Symposium, held June 2012 at Queenland's Gold Coast.
Preliminary data suggested a strong association between pasture availability and infection of horses with HeV.
Bryden reported that during 2011 climatic factors that influenced forage growth and quality had been severe. Long periods of frost at three sites where infection had occurred, and prolonged rain at two sites, had limited the availability of pasture for grazing.
“Hendra virus infections in 2011 coincided with periods of poor pasture growth caused by extended periods of frost and rain and so horses were likely to have been hungry at the time of infection,” he said.
“A hungry horse is more likely to consume bat-related material found on pastures.
As well as increasing the risk of horses coming in contact with contaminated material, poor grazing may have deleterious effects on the horse's immune response.
“And because a horse's nutrient intake is significantly reduced due to poor pasture quality and availability,” he added, “its immune system is possibly also compromised, thereby setting the scene for an infection.”
Professor Bryden said further work was required to understand the risk factors involved with Hendra virus infections. However, he advised that owners should provide horses with supplementary feeding when pasture quality is low as this might help reduce the risk of of them contracting the infection.
For more details see:
Does pasture availability influence Hendra virus infection of grazing horses?
DL Anderson and WL Bryden
Proc. Australasian Equine Sc. Symp., Vol 4, 2012 , p33-34
The symposium Proceedings are available on line