In a media release circulated by the AVA on the 8th March, the veterinary profession and the public were made aware of the discovery of a variant of the deadly Hendra virus (HeV) - a discovery made by the Australian veterinarian-led research project, ‘Horses as Sentinels’. For an update on what’s been happening since the initial discovery, I speak with Dr Peter Reid, one of the research group founders and the attending veterinarian at the HeV outbreak in Hendra, Queensland in 1994 when 20 horses died and horse trainer Vic Rail also died as a result of being infected.
The initial discovery
The research group has confirmed the newly discovered variant of the virus as the cause of the previously unexplained death of a horse in south-east QLD in September 2015.
Undetectable by previously available biosecurity testing procedures, the initial discovery of the variant of the virus was achieved through the research group’s batched molecular testing pathway that combines next generation sequencing with the use of PCR screening of samples from disease cases which are prioritised using the group’s custom Structured Query Language database.
Following the initial discovery of genomic evidence of the probable new variant in late January, the variant was fully sequenced by Dr John-Sebastian Eden from the University of Sydney Medical School and Westmead Institute of Medical Research.
The currently available vaccine
The research group then set about the vital next step which involved determining whether potent neutralising antibodies, mounted in response to the currently available horse vaccine, would provide protection against the variant and also whether the currently available human monoclonal antibody m102.4 would be effective as an early post-exposure prophylaxis for human infection with the new variant. The good news is that evidence for both the efficacy of the current horse vaccine and of the human monoclonal antibody m102.4 has been established.
New assay developed for detecting the variant
“The newly developed M gene assay to detect the variant HeV has now been shared with Queensland’s Biosecurity Sciences Laboratory (BSL), the New South Wales Elizabeth Macarthur Agricultural Institute(EMAI) Laboratory, the Queensland Health Forensic and Scientific Services (QHFSS) Laboratory , and CSIRO’s Australian Centre for Disease Preparedness (ACDP, formerly AAHL). Suspect samples collected in Victoria, Tasmania and South Australia for HeV exclusion testing are normally forwarded directly to ACDP without testing in State run laboratories.”, says Dr Peter Reid.
Detection in grey-headed flying foxes
Another critical finding has been the detection of the HeV variant in grey-headed flying foxes from Adelaide in samples collected in January 2013. “The variant detected in these samples shares approximately 99% sequence identity with the 2015 horse case variant. Importantly, partial sequences of the variant have also been detected in flying foxes in other states”, says Dr Reid.
Of concern, is the fact that grey-headed flying foxes migrate. Their range includes parts of southern Australia, which previous advice had classed as low risk – with some interpreting this to mean negligible risk of Hendra virus spill-over. Up until this point, the original strain of Hendra virus has only been known to occur within the range of black flying foxes and spectacled flying foxes.
In light of these findings, HeV should be considered as a differential diagnosis in sick, unvaccinated horses in any region of Australia where flying foxes are found, and that suspect horses which return an initial negative Hendra virus test should continue to be treated with the same caution as a Hendra virus positive case, until testing for the new variant is performed.
A time for vigilance
Now is the time for Veterinarians, horse owners and handlers to review their Hendra virus management plans”, says Dr Peter Reid. Measures to reduce the risk of infection, including vaccination, use of PPE and good hygiene and biosecurity should be employed
by those who work closely with horses. More information on these protocols can be found on State Government and AVA websites.
Future work
Dr Peter Reid says that “The full genome sequence of the HeV variant will be placed with GenBank and publication of the new findings will be submitted for publication in the US Centres for Disease Control Emerging Infectious Diseases Journal. Further syndromic surveillance and genomic analysis of archived horse samples is continuing, and additional announcements will be forthcoming.
Dr Ed Annand will be presenting details of the group’s findings and new research at the Equine Veterinarians Australia Bain Fallon Conference in July. Workshops are also being planned over the next few months with State Government testing laboratories, the Animal Health Policy Branch, Biosecurity Animal Division, Australian Government Department of Agriculture, Water and the Environment, where discussions will centre around the Biosecurity Innovations Project, and with Griffith University’s Wildlife Disease Ecology Group.”