Random Analytics: Hendra! (to 1 Aug 2013)

by Shane Granger

Recently I wrote and completed some analytics about the Ebola Haemorrhagic Fever (EHF) which lives in the rain forests of Africa. The natural host of that disease are the fruit bats of the Pteropodidae family.

Queensland is also host to a range of fruit bats. It has also become the host of a new and highly dangerous virus. Originally coined the equine morbillivirus it was later named the Hendra Virus (HeV) after the suburb which hosted the index cluster. It is closely related to another deadly variant, the Nipah virus which emerged from Malaysia in 1999.

HeV is a rare, emerging zoonotic virus (a virus transmitted to humans from animals), that can cause respiratory and neurological disease and death in people. It can also cause severe disease and death in animals, namely horses, resulting in considerable economic losses for horse breeders.

Key Facts (last updated July 2012 via the CSIRO):

  • In 1994, CSIRO and Queensland researchers discovered a completely new virus now called Hendra virus;
  • Scientists believe fruit bats are the natural ‘host’ of Hendra virus, meaning the virus is carried by bats but has little effect on them;
  • Hendra virus is not highly contagious but if transmitted to horses and humans it can be lethal
  • CSIRO has shown that a prototype vaccine can protect horses against Hendra virus;
  • Pfizer Animal Health has made the Equivac HeV vaccine available, under permit, for accredited veterinarians to administer to horses.

Since August 1994 to the 28th July 2013 there have been 48-clusters of the disease in Australia which have resulted in four human deaths. The confirmed human cases stand at seven giving it a very high Case Fatality Rate of 57%, fortunately in in a very low sample size.

It has also caused the deaths of 90-horses. From that number I have been able to verify, with a reasonable amount of certainty, that at least 54-horses died of HeV (60%) and that 36 (40%) were euthanized. Since 2011 two dogs have also become infected; one recently and both were subsequently euthanized. The practice of euthanasia has occurred prior to death due to humane reasons or as part of the AUSVETPLAN (2013) directive which prescribes euthanasia in all animals that test positive for HeV.

Most primary source subject matter experts on the subject state that the horse CFR is approximately 75%. If you interested in the research then I’d suggest the 2011 FAO Report Investigating the role of bats in emerging zoonosis.

A Quick History of HeV

01 - Hendra_CasesbyLocation_130728

Aug 1994 – Oct 1995: Mark P, a 35-year old Mackay canefarmer and horse breeder assists his wife, a veterinarian, undertake necropsies on their property after two horses die of mysterious circumstances. Mark would become ill and be admitted to hospital with suspected aseptic meningitis. 13-months later he relapses and dies 21 October 1995 thus becoming Hendra’s only victim to die of HeV linked late-onset encephalitis. Further testing reveals the presence of HeV in his brain and samples taken from the two horses also confirm HeV making this the retrospective index case.

Sep 1994: The first known outbreak of the disease occurs in the northern Brisbane suburb of Hendra which is a hub of horse racing and the location of two race-tracks. After tending to a sick horse Vic R, a 49-year old local trainer and his 40-year old stable-hand become sick. Vic would die within the fortnight while the stable-hand slowly recovered and was released in October 1994. 20 horses would die during this index outbreak with the necropsies undertaken onsite. From Queensland Department of Primary Industry (now QDAFF) it would lead to the discovery of a new disease by the CSIRO Australian Animal Health Laboratory.

02 - HendraSite_1994

Photo: Queensland Department of Primary Industry officer’s onsite at the Hendra (1994).

Oct 1994 – May 2008: During the next 13-years and 8-months there are only 7 HeV virus clusters recorded, each involving a single horse and all but one are located within Queensland. In the Gordonvale cluster (Oct 2004) a young female veterinarian assisting on a necropsy is infected, she becomes ill but does not die. In October 2006 the first case of HeV is recorded in Mullumbimby, New South Wales.

Jun – Aug 2008: While treating a sick horse both Ben C (34 year-old veterinarian) and a Natalie B (20-year old vet nurse) became infected after taking nasal swaps. They both had flu-type symptoms and were given a five-day intravenous drug course of Ribavirin when found to have HeV before going into intensive care. Ben C survives in intensive care before dying 20 Aug 2008 (about 37-days after admission). Natalie B was discharged the day before his death. Eight horses are infected; three die of HeV and five are euthanized. The ABC Australia Story covered this case in some detail including an emotional interview with Natalie B and The Weekend Australian Magazine did a comprehensive piece in Mar 2013.

Jul – Aug 2009: Alister R, a 55-year old Rockhampton veterinarian became the seventh person ever to contract the virus. After a long day he endoscopes an additional sick horse without first returning to his car to don his PPE (Personal Protective Equipment) such as a surgical mask or gloves. Although he is one of four people to be given an experimental anti-viral treatment he becomes ill approximately 20-days later and dies on the first day of September. Prior to his own infection he stated that the next person to die of Hendra would be another veterinarian.

2011: With 18 recorded clusters in a calendar year (eight in NSW and 10 in Queensland) HeV spikes to record levels. 2011 is also the first year a case is confirmed in a dog which is subsequently euthanized.

2012: On November 1 2012 the CSIRO announced a vaccine against Hendra Virus: Equivac® HeV, the world’s first commercially available Hendra vaccine for horses. CSIRO senior pathologist Deborah Middleton discussed the vaccine via The Conversation.

2013 – Vaccination uptake low – Cases of HeV Continue

There already have been eight clusters of HeV already recorded in 2013, all in unvaccinated horses and equal to the cluster total for 2012. While a horse vaccine has been made available uptake has been low. A recent report by Rural Weekly covered the subject.

In July the NSW DPI confirmed that a dog on the mid north coast had tested positive to HeV. Currently there is no vaccine for domestic animals (cats and dogs) or humans.

The following infographic shows cluster events since the vaccine became available in November 2012.

03 - Hendra_CasesbyUVLocation_130728

Temporal Pattern

As shown in the following graph the season of winter is the peak period for HeV. Winter outbreaks account for 27 (56.3%) of the cluster onsets.

04 - TemporalPattern(CalYr)_130728

Information Underload

One of the biggest discoveries I made during my research into HeV was that there are a large number of web-sites which purport to be knowledgeable about the subject yet contain incorrect, misleading or untruthful information.

One prominent site which has been active for many years states “There is currently no cure and no vaccine”. Not only is this untrue but after discussing Hendra with a number of specialists I found that there was also a significant amount of disinformation which was impeding the uptake of the Equivac HeV vaccine program.

Another issue I found was that some primary source outlets had horribly out-dated information regarding both HeV and the Nipah virus. The World Health Organisation is especially at fault here having last updated these pages in July 2009. As an example the WHO still incorrectly states in its HeV Key Facts that there is no vaccine for horses.

When primary source health agencies, especially those with global health responsibilities don’t update their sites with the most recent and updated information (and data) they allow the cranks and the quacks space to operate in this asymmetric digital world.

If you want to know about HeV on the internet then stick to primary source materials (i.e. BioSecurity Queenland and the New South Wales DPI are both recommended).

If you NEED to know about HeV then seek professional advice, preferably with someone face-to-face.

Final Thoughts

One of the fondest memories of my early childhood (lived in the late 1970’s) is that of my brother and myself lying on our backs on the 18th-hole of the Bellingen Golf Club looking up at the sky at sunset. The fading blues would be cut in half, as if by a black knife, as tens of thousands of fruit bats would evacuate their caves in the Dorrigo Hills and venture down to the banana plantations that surrounded Coffs Harbour.

Some three decades later I find myself living in regional Queensland, in a region that has experienced a Hendra outbreak and next to a horse paddock with agisted horses. Often we will interact, feed or pat the horses.

It’s not unusual for my family to sit outside in the early evening during winter, next to a fire and watch the horses graze in the next door paddock.

Occasionally, much to the delight of my youngest son we will see a flying fox.

Out of interest I’ll continue to track HeV, a very rare zoonotic disease.

Using the evidence I know that the risks to my family are negligible.

Note: If you found this interesting you might also like to see my analytics of Ebola or H7N9.

Acknowledgements: My fellow Queensland blogger, Dr Ian Mackay has commenced a Virology Down Under page for Hendra. His H7N9 & MERS-COV material is excellent so looking forward to see how this page develops. Many thanks to Trish Roderick (Heritage Collection Coordinator, Mackay Regional Council) who was able to confirm and send through scanned details of the Mark P (35M) case from local reporting.

Update (1/08/2013)

  • Updated ‘A Quick History of HeV’ section with confirmed Mark P details.