Hendra virus

Template:Short description Template:Virusbox Hendra virus (Henipavirus hendraense) is a zoonotic virus found solely in Australia. First isolated in 1994, the virus has since been connected to numerous outbreaks of disease in domestic horses and seven human cases. Hendra virus belongs to the genus Henipavirus, which also contains the zoonotic Nipah virus. The reservoir species of Hendra virus are four species of bat within the genus Pteropus native to Australia.

Pathology

The Pteropus fruit-eating bats, commonly known as flying foxes, experimentally infected with the Hendra virus develop a viraemia and shed the virus in their urine, faeces and saliva for approximately one week. There is no other indication of an illness in them.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Symptoms of Hendra virus infection of humans may be respiratory, including hemorrhage and edema of the lungs, or in some cases viral meningitis. In horses, infection usually causes one or more of pulmonary oedema, congestion and neurological signs.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Ephrin B2 has been identified as the main receptor for the henipaviruses.<ref name=Lee2011>Template:Cite journal</ref>

Transmission

Flying foxes have been identified as the reservoir host of Hendra virus. A seroprevalence of 47% is found in the flying foxes, suggesting an endemic infection of the bat population throughout Australia.<ref name=":1">Quammen, David. Spillover: Animal Infections and the Next Human Pandemic. New York: W.W. Norton, 2012. Print.</ref> Horses become infected with Hendra after exposure to bodily fluid from an infected flying fox. This often happens in the form of urine, feces, or masticated fruit covered in the flying fox's saliva when horses graze below roosting sites.<ref name=":1" />

In 2021 a new variant of Hendra virus named "Hendra virus genotype 2" (HeV-g2) was identified in two flying fox species in Australia.<ref name=":0">Template:Cite journal</ref> It shares 84% sequence homology to other published Hendra virus genomes.<ref name=":0" /> This variant has been identified in at least two horses that showed signs of Hendra virus infection.<ref>Template:Cite journal</ref>

Prevention, detection and treatment

Three main approaches are currently followed to reduce the risk to humans.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

• Vaccine for horses.

In November 2012, a vaccine became available for horses. The vaccine is to be used in horses only, since, according to CSIRO veterinary pathologist Deborah Middleton, breaking the transmission cycle from flying foxes to horses prevents it from passing to humans, as well as, "a vaccine for people would take many more years."<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref><ref>Template:Cite news</ref>

The vaccine is a subunit vaccine that neutralises Hendra virus and is composed of a soluble version of the G surface antigen on Hendra virus and has been successful in ferret models.<ref name=pallister>Template:Cite journal</ref><ref>Template:Cite news</ref><ref>Template:Cite news</ref>

By December 2014, about Template:Val doses had been administered to more than Template:Val horses. About 3 in 1000 had reported incidents; the majority being localised swelling at the injection site. There had been no reported deaths.<ref>Template:Cite news</ref>

In August 2015, the Australian Pesticides and Veterinary Medicines Authority (APVMA) registered the vaccine. In its statement the Australian government agency released all its data on reported side effects.<ref>Template:Cite news</ref> In January 2016, APVMA approved its use in pregnant mares.<ref>Template:Cite news</ref>

• Stall-side test to assist in diagnosing the disease in horses rapidly.

Although the research on the Hendra virus detection is ongoing, a promising result has found using antibody-conjugated magnetic particles and quantum dots.<ref>Template:Cite news</ref><ref name=lisi>Template:Cite journal</ref>

• Post-exposure treatment for humans.

Nipah virus and Hendra virus are closely related paramyxoviruses that emerged from bats during the 1990s to cause deadly outbreaks in humans and domesticated animals. National Institute of Allergy and Infectious Diseases (NIAID)-supported investigators developed vaccines for Nipah and Hendra virus based on the soluble G-glycoproteins of the viruses formulated with adjuvants. Both vaccines have been shown to induce strong neutralizing antibodies in different laboratory animals.

Trials began in 2015 to evaluate a monoclonal antibody to be used as a possible complementary treatment for humans exposed to Hendra virus infected horses.<ref>Template:Cite news</ref>

• Deforestation Impact.

When considering any zoonosis, one must understand the social, ecological, and biological contributions that may be facilitating this spillover. Hendra virus is believed to be partially seasonally related, and there is a suggested correlation between breeding time and an increase in the incidence of Hendra virus in flying fox bats.<ref>Plowright, R. K. et al. (15 January 2008). Reproduction and nutritional stress are risk factors for Hendra virus infection in little red flying foxes (Pteropus scapulatus).http://rspb.royalsocietypublishing.org/content/royprsb/275/1636/861.full.pdf</ref><ref name="dx.doi.org">Template:Cite journal</ref>

Additionally, recent research suggests that the upsurge in deforestation within Australia may be leading to an increase in the incidence of Hendra virus. Flying fox bats tend to feed in trees during a large part of the year. However, due to the lack of specific fruit trees within the area, these bats are having to relocate and thereby are coming into contact with horses more often. The two most recent outbreaks of Hendra virus in 2011 and 2013 appear to be related to an increased level of nutritional stress among the bats as well as relocation of bat populations. Work is currently being done to increase vaccination among horses as well as replant these important forests as feeding grounds for the flying fox bats. Through these measures, the goal is to decrease the incidences of the highly fatal Hendra virus.<ref name="dx.doi.org"/>

History

File:Flying fox distribution.png

Locations of henipavirus outbreaks (red stars–Hendra virus; blue stars–Nipah virus) and distribution of henipavirus flying fox reservoirs (red shading–Hendra virus; blue shading–Nipah virus)

Emergence

Hendra virus (originally called "Equine morbillivirus") was discovered in September 1994 when it caused the deaths of thirteen horses, and a trainer at a training complex at 10 Williams Avenue, Hendra, a suburb of Brisbane in Queensland, Australia.<ref name=Selvey>Template:Cite journal</ref><ref>Template:Cite AV media</ref>

The index case, a mare called Drama Series, brought in from a paddock in Cannon Hill, was housed with 19 other horses after falling ill, and died two days later. Subsequently, all of the horses became ill, with 13 dying. The remaining six animals were subsequently euthanised as a way of preventing relapsing infection and possible further transmission.<ref name="DPI-Hendra virus: the initial research"/> The trainer, Victory ('Vic') Rail, and the stable foreman, Ray Unwin, were involved in nursing the index case, and both fell ill with an influenza-like illness within one week of the first horse's death. The stable hand recovered but Rail died of respiratory and kidney failure. The source of the virus was most likely frothy nasal discharge from the index case.<ref>Template:Cite news</ref>

A second outbreak occurred in August 1994 (chronologically preceding the first outbreak) in Mackay Template:Convert north of Brisbane resulting in the deaths of two horses and their owner.<ref name=field>Template:Cite journal</ref> The owner assisted in necropsies of the horses, and within three weeks was admitted to hospital suffering from meningitis. He recovered, but 14 months later developed neurologic signs and died. This outbreak was diagnosed retrospectively by the presence of Hendra virus in the brain of the patient.<ref>Template:Cite news</ref>

Outbreak in Australia

As of June 2014, a total of fifty outbreaks of Hendra virus have occurred in Australia, all involving infection of horses. Since 1994, Hendra virus has been the cause of death in over 100 horses. Most cases have been the result of spillover infection from flying-foxes. Others have been the result of direct transmission from infected horses.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Case fatality rate in humans is 60% and in horses 75%.<ref name=Field2011>Template:Cite journal</ref>

Four of these outbreaks have spread to humans as a result of direct contact with infected horses. On 26 July 2011 a dog living on the Mt Alford property was reported to have HeV antibodies, the first time an animal other than a flying fox, horse, or human has tested positive outside an experimental situation.<ref>Template:Cite news</ref>

These events have all been on the east coast of Australia, with the most northern event at Cairns, Queensland and the event furthest south at Kempsey, New South Wales. Until the event at Chinchilla, Queensland in July 2011, all outbreak sites had been within the distribution of at least two of the four mainland flying foxes (fruit bats); Little red flying fox, (Pteropus scapulatus), black flying fox, (Pteropus alecto), grey-headed flying fox, (Pteropus poliocephalus) and spectacled flying fox, (Pteropus conspicillatus). Chinchilla is considered to be only within the range of little red flying fox and is west of the Great Dividing Range. This is the furthest west the infection has ever been identified in horses.Template:Cn

The timing of incidents indicates a seasonal pattern of outbreaks. Initially this was thought to possibly be related to the breeding cycle of the little red flying foxes. These species typically give birth between April and May.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>Template:Cite journal</ref> Subsequently, however, the Spectacled flying fox and the Black flying fox have been identified as the species more likely to be involved in infection spillovers.<ref>Template:Cite journal</ref>

Timing of outbreaks also appears more likely during the cooler months when it is possible the temperature and humidity are more favourable to the longer term survival of the virus in the environment.<ref name="auto">Template:Cite journal</ref>

There is no evidence of transmission to humans directly from bats, and, as such it appears that human infection only occurs via an intermediate host, a horse.<ref>Template:Cite journal</ref> Despite this in 2014 the NSW Government approved the destruction of flying fox colonies.<ref>Template:Cite journal</ref>

List of Australian Hendra outbreaks

List of Australian Hendra outbreaks
Date	Location	Details	Deaths (Human)	Deaths (Horse)
August 1994	Mackay, Queensland	Death of two horses and one person, Mark Preston.<ref name=field/>	1	2
September 1994	Hendra, Queensland	20 horses died or were euthanised. Two people infected. One of them, Victory ("Vic") Rail, a nationally prominent trainer of racehorses, died.<ref name=Selvey/>	1	20
January 1999	Trinity Beach, Cairns, Queensland	Death of one horse.<ref>Template:Cite journal</ref>		1
October 2004	Gordonvale, Cairns, Queensland	Death of one horse. A veterinarian involved in autopsy of the horse was infected with Hendra virus, and suffered a mild illness.<ref name=Hanna06>Template:Cite journal</ref>	0	1
December 2004	Townsville, Queensland	Death of one horse.<ref name=Hanna06/>		1
June 2006	Peachester, Sunshine Coast, Queensland	Death of one horse.<ref name=Hanna06/>		1
October 2006	Murwillumbah, New South Wales	Death of one horse.<ref>Template:Cite journal</ref>		1
July 2007	Peachester, Sunshine Coast, Queensland	Infection of one horse (euthanised)
July 2007	Clifton Beach, Cairns, Queensland	Infection of one horse (euthanised).<ref>ProMED-mail. Hendra virus, human, equine – Australia (Queensland) (03): correction. ProMED-mail 2007; 3 September: 20070903.2896.</ref>
July 2008	Redlands, Queensland	Death of five horses; four died from the Henda virus, the remaining animal recovered but was euthanised because of a government policy that requires all animals with antibodies to be euthanised due to a potential threat to health. Two veterinary workers from the affected property were infected leading to the death of one, veterinary surgeon Ben Cuneen, on 20 August 2008.<ref>Template:Cite news</ref> The second veterinarian was hospitalized after pricking herself with a needle she had used to euthanize the horse that had recovered. A nurse exposed to the disease while assisting Cuneen in caring for the infected horses was also hospitalized.<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> The Biosecurity Queensland website indicates that 8 horses died during this event,<ref name="DPI-Hendra virus: the initial research">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> however a review of the event indicates that five horses are confirmed to have died from HeV and three of the horses "are regarded as improbable cases of Hendra virus infection...".<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>||1||4
July 2008	Proserpine, Queensland	Death of four horses.<ref name="DPI-Hendra virus: the initial research"/>		4
July 2009	Cawarral, Queensland	Death of four horses.<ref name="DPI-Hendra virus: the initial research"/> Queensland veterinary surgeon Alister Rodgers tested positive after treating the horses.<ref>Template:Cite news</ref> On 1 September 2009 after two weeks in a coma, he became the fourth person to die from exposure to the virus.<ref>Template:Cite news</ref>	1	4
September 2009	Bowen, Queensland	Death of two horses.<ref name="DPI-Hendra virus: the initial research"/>		2
May 2010	Tewantin, Queensland	Death of one horse.<ref>Template:Cite news</ref>		1
20 June 2011 – 31 July 2011	Mount Alford, Queensland	citation	CitationClass=web }}Template:Cbignore</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref> On 26 July 2011 a dog from this property was reported to have tested positive for HeV antibodies. Reports indicate that this Australian Kelpie, a family companion, will be euthanised in line with government policy. Biosecurity Queensland suggest the dog most likely was exposed to HeV though one of the sick horses.<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref><ref>Template:Cite news</ref> Dusty was euthanised on 31 July 2011 following a second positive antibody test.<ref>Template:Cite news</ref>||||3
26 June 2011	Kerry, Queensland	The horse was moved after it became sick to another property at Beaudesert, Queensland. Death of one horse.<ref>Template:Cite news</ref>		1
28 June 2011	Loganlea, Logan City, Queensland	citation	CitationClass=web }}</ref><ref>Template:Cite news</ref>||||1
29 June 2011	Mcleans Ridges, Wollongbar, New South Wales	Death of one horse.<ref>Template:Cite news</ref><ref>Template:Cite news</ref> The second horse on the property tested positive to Hendra and was euthanised on 12 July 2011.<ref>Template:Cite press release</ref>		1
3 July 2011	Macksville, New South Wales	citation	CitationClass=web }}</ref><ref>Template:Cite news</ref>||||2
4 July 2011	Park Ridge, Logan City, Queensland	Death of one horse.<ref>Template:Cite press release</ref>		1
11 July 2011	Kuranda, Queensland	Death of one horse.<ref>Template:Cite news</ref>		1
13 July 2011	Hervey Bay, Queensland	Death of one horse.<ref>Template:Cite press release</ref>		1
14 July 2011	Lismore, New South Wales	Death of one horse.<ref>Template:Cite news</ref>		1
15 July 2011	Boondall, Queensland	Death of one horse.<ref>Template:Cite press release</ref>		1
22 July 2011	Chinchilla, Queensland	citation	CitationClass=web }}</ref>||||1
24 July 2011	Mullumbimby, New South Wales	Death of one horse.<ref>Template:Cite press release</ref>		1
13 August 2011	Mullumbimby, New South Wales	Death of one horse. A horse was found dead after being unwell the day before. HeV infection was confirmed on 17 August 2011.<ref name="dpi.nsw.gov.au">Template:Cite press release</ref>		1
15 August 2011	Ballina, New South Wales	Death of one horse.<ref>Template:Cite press release</ref>		1
17 August 2011	South Ballina, New South Wales	Death of two horses. The horses were found dead in a field. Both tested positive to HeV. The exact date of death is not known, but HeV infection was confirmed on 17 August 2011.<ref name="dpi.nsw.gov.au"/>		2
23 August 2011	Currumbin Valley, Gold Coast, Queensland	Death of one horse.<ref>Template:Cite news</ref>		1
28 August 2011	North of Ballina, New South Wales	Death of one horse.<ref>Template:Cite press release</ref>		1
11 October 2011	Beachmere, Caboolture Queensland	citation	CitationClass=web }}</ref> On 15 October 2011 another horse on the property was euthanised following a positive HeV antibody test.<ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>||||1
3 January 2012	Townsville, Queensland	citation	CitationClass=web }}</ref>||||1
26 May 2012	Rockhampton, Queensland	citation	CitationClass=web }}</ref><ref name=ABCHVJLY12>Template:Cite news</ref>||||1
28 May 2012	Ingham, Queensland	citation	CitationClass=web }}</ref>||||1
19 July 2012	Rockhampton, Queensland	One horse died. On 27 July it was announced that two other horses on the property, showing clinical signs of the disease, had been euthanised. Two dogs were assessed, and the property was quarantined.<ref>Template:Cite news</ref><ref>Template:Cite news</ref><ref>{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>||||1
27 June 2012	Mackay, Queensland	citation	CitationClass=web }}</ref>||||1
27 July 2012	Cairns, Queensland	citation	CitationClass=web }}</ref>||||1
5 September 2012	Port Douglas, Queensland	One horse died. The property with 13 other horses is quarantined.<ref>Template:Cite news</ref><ref>Template:Cite news</ref>		1
1 November 2012	Ingham, Queensland	One symptomatic horse euthanised. A test for HeV the following day proved positive. The property, with seven other horses, quarantined.<ref>Template:Cite news</ref><ref>Template:Cite news</ref>		1
20 January 2013	Mackay, Queensland	One horse died.<ref>Template:Cite news</ref>		1
19 February 2013	Atherton Tablelands, North Queensland	One horse died. Four horses and four people from the property were assessed.<ref>Template:Cite news</ref>		1
3 June 2013	Macksville, New South Wales	Death of one horse, a second horse vaccinated, five cats and a dog were monitored.<ref>Template:Cite news</ref>		1
1 July 2013	Tarampa, Queensland	One horse died. HeV virus confirmed.<ref>Template:Cite news</ref>		1
4 July 2013	Macksville, New South Wales	Six year old gelding died. Several other horses, dogs and cats were tested.<ref>Template:Cite news</ref><ref>Template:Cite press release</ref> A dog from the property tested positive for HeV and was euthanised around 19 July 2013<ref>Template:Cite news</ref>		1
5 July 2013	Gold Coast, Queensland	citation	CitationClass=web }}</ref>||||1
6 July 2013	Kempsey, New South Wales	Eighteen-year-old unvaccinated mare died, other animals on property under observation.<ref>Template:Cite press release</ref>		1
9 July 2013	Kempsey, New South Wales	Thirteen-year-old unvaccinated quarterhorse died, other animals on property were put under observation.<ref>Template:Cite press release</ref><ref>Template:Cite news</ref>		1
18 March 2014	Bundaberg, Queensland	Unvaccinated horse euthanized. Tested positive for Hendra and was euthanized<ref name="Jo Skinner">Template:Cite news</ref>		1
1 June 2014	Beenleigh, Queensland	citation	CitationClass=web }}</ref>||||
20 Jun 2014	Murwillumbah, New South Wales	citation	CitationClass=web }}</ref>||||1
20 July 2014	Calliope, Queensland	citation	CitationClass=web }}</ref>||||1
20 Jun 2015	Murwillumbah, New South Wales	Horse found dead after several days of illness. HeV confirmed as the cause of death.<ref name="ReferenceA">Template:Cite news</ref>		1
About 20 July 2015	Atherton Tableland, Queensland	citation	CitationClass=web }}</ref>||||1
About 4 September 2015	Lismore, New South Wales	Infected horse euthanised and property quarantined.<ref>Template:Cite news</ref>		1
About 15 December 2016	Casino, New South Wales	citation	CitationClass=web }}</ref>||||1
About 24 May 2017	Gold Coast, Queensland	citation	CitationClass=web }}</ref>||||
About 8 July 2017	Lismore, New South Wales	citation	CitationClass=web }}</ref>|| ||
About 1 August 2017	Murwillumbah, New South Wales	citation	CitationClass=web }}</ref> NSW Department of Primary Industries identified this as the second Hendra case in NSW for the year 2017.|| ||
About 5 August 2017	Lismore, New South Wales	citation	CitationClass=web }}</ref> Property was placed under inspection. Third confirmed case in NSW in the span of four weeks.|| ||
7 June 2019	Scone, New South Wales	An unvaccinated mare contracted Hendra and had to be euthanized.<ref>Template:Cite news</ref> Quarantine protocols and assessments were completed on the property. Represents the Southernmost documented case of Hendra in horses.		1
3 June 2020	Murwillumbah, New South Wales	An unvaccinated horse contracted Hendra and had to be euthanized.<ref>Template:Cite news</ref> Represents the first documented case of 2020.		1
18 July 2023	Newcastle, New South Wales	citation	CitationClass=web }}</ref>		1

Events of June–August 2011

Template:Update In the years 1994–2010, fourteen events were recorded. Between 20 June 2011 and 28 August 2011, a further seventeen events were identified, during which twenty-one horses died.Template:Cn

It is not clear why there was a sudden increase in the number of spillover events between June and August 2011. Typically HeV spillover events are more common between May and October. This time is sometimes called "Hendra Season",<ref>Epidemiological methodology of communicating higher contagion periods for better common, non-scientific individual understanding</ref> which is a time when there are large numbers of fruit bats of all species congregated in SE Queensland's valuable winter foraging habitat. The weather (warm and humid) is favourable to the survival of henipavirus in the environment.<ref name="auto"/>

It is possible flooding in SE Queensland and Northern NSW in December 2010 and January 2011 may have affected the health of the fruit bats. Urine sampling in flying fox camps indicate that a larger proportion of flying foxes than usual are shedding live virus. Biosecurity Queensland's ongoing surveillance usually shows 7% of the animals are shedding live virus. In June and July nearly 30% animals have been reported to be shedding live virus.<ref>Template:Cite news</ref> Present advice is that these events are not being driven by any mutation in HeV itself.<ref>Template:Cite news</ref>

Other suggestions include that an increase in testing has led to an increase in detection. As the actual mode of transmission between bats and horses has not been determined, it is not clear what, if any, factors can increase the chance of infection in horses.<ref>Template:Cite news</ref>

Following the confirmation of a dog with HeV antibodies, on 27 July 2011, the Queensland and NSW governments will boost research funding into the Hendra virus by $6 million to be spent by 2014–2015. This money will be used for research into ecological drivers of infection in the bats and the mechanism of virus transmission between bats and other species.<ref>Template:Cite news</ref><ref>Template:Cite news</ref> A further 6 million dollars was allocated by the federal government with the funds being split, half for human health investigations and half for animal health and biodiversity research.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

External links

• 'hendrafacts' Template:Webarchive
• Biosecurity Queensland Hendra virus
• The Australian Pesticides and Veterinary Medicines Authority - Hendra vaccine registration and data release - August 2015
• Hendra virus factsheet – CSIRO
• The science and mystery of hendra virus – by Renee du Preez (ABC Rural) – Australian Broadcasting Corporation.
• Vic Rail and Hendra Virus Films 1994-2011, State Library of Queensland. Unfinished documentary footage relating to the outbreak of Hendra virus and the death of horse trainer Vic Rail.