The ‘Horses as sentinels for emerging infectious viral disease research’ program research team recently communicated to the EVA and its members regarding their recent detection of a variant Hendra virus strain in a retrospective horse sample from 2015. This update from NSW DPI is in response to that communication.

Hendra is rare zoonotic disease in humans which sporadically affects horses and causes severe illness with high case fatality rate in horses and humans who work closely with infected horses. Hendra virus infection can be passed to horses through the virus’s normal wildlife host, the flying fox (fruit bat)

The ‘Horses as sentinels for emerging infectious viral disease research’ program undertaken by the University of Sydney and CSIRO, aim to identify emerging and novel pathogens in horses.  The research into the discovery of new pathogens will help increase Australia’s preparedness for emerging infectious diseases, and in doing so improve horse and human health and Australia’s biosecurity.  

This research group has identified a variant Hendra virus in a single horse from a 2015 case of fatal equine disease in south-east Queensland that was found negative to Hendra virus by routine PCR testing in a State laboratory¹. The horse was euthanased at the time of sampling and no autopsy undertaken. 

An almost identical variant has also been detected in grey headed flying foxes by CSIRO scientists on a number of occasions. Further research to determine the prevalence of this variant in various flying fox species in Australia is ongoing. The initial findings of the research have been reviewed by all Chief Veterinary Officers (CVO’s) and expert scientists nationally with consideration given to national surveillance (including diagnostic testing) and additional research. Diagnostic tests to recognise the new variant virus have been in use at ACDP for many years and the research assay will be adopted by NSW state laboratories.  

The finding is a timely reminder of measures that horse owners and people that work closely with horses can put in place to reduce the risk of infection with Hendra virus and other henipaviruses, including: 

• Vaccination of horses is the most effective way to help manage Hendra virus disease and provides a public health and workplace health and safety benefit by reducing the risk of Hendra virus transmission to humans and other susceptible animals. Expert opinion suggest that the current vaccine is likely to provide immunity against the variant strain as well as the normal Hendra virus strain. 
• Feeding and stabling horses overnight 
• Reduce flying fox and horse interaction by removing feed and water containers from under or near trees and removing horses or restricting their access to paddocks where flowering/fruiting trees may be attracting flying foxes.  
• Adopt sound hygiene and biosecurity measures as a routine practice for all horse contact including: 

• washing hands regularly and cover any cut/wound with a water-resistant dressing 
• using appropriate personal protective equipment (PPE) when working with horses  
• cleaning and disinfecting equipment that has been in contact with horses' body fluids. 

It is also a reminder that flying foxes can carry a number of diseases transmissible to humans and animals. People handling flying foxes should be vaccinated against Australian bat lyssavirus, trained in their safe handling and always wear personal protective equipment. 

Flying foxes are protected species. They are critical to our environment because they pollinate our native trees and spread seeds. Without flying foxes, we wouldn't have our eucalypt forests, rainforests and melaleucas. 

Flying foxes are a natural host of Hendra virus, although they do not show any signs of illness when infected. There are four species of flying-fox on mainland Australia – the black flying-fox, spectacled flying-fox, little red flying-fox and grey-headed flying-fox and serologic evidence of Hendra virus infection has been found in all four species.

Direct infection from flying foxes has only been observed in horses, with human and dog infection associated with infected horses.  

Hendra virus causes vague symptoms early in infection such as restlessness, depression and fever. The virus can be spread by infected horses for up to three days before they show any clinical signs of infection. 

If you are uncertain, but suspect your horse may be infected with Hendra virus, it is very important to: 

• Seek veterinary advice early. If your vet is unavailable, you can call a District Veterinarian with the Local Land Services or the Emergency Animal Disease Watch Hotline on 1800 675 888 
• Minimize contact with horses that are not vaccinated until the infected horse can be examined by a veterinarian 
• Avoid physical contact with the horse unless using full, correctly fitted PPE. 

Hendra virus is a notifiable disease and the vet will notify Local Lands Services or NSW Department of Primary Industries if they suspect Hendra virus immediately. 

Research on Hendra virus is ongoing and continues to help us learn more about the disease and allows activities to reduce the risk of infection to be applied.  

For more information, visit NSW DPI Hendra virus webpage. 

Dr Sarah Britton

NSW Chief Veterinary Officer