hendra virus hendra virus hendra virus (hev), scientific name hendra henipavirus, is a bat-borne virus that is associated with a highly fatal infection in horses and humans. numerous disease outbreaks in australia among horses have been caused by hendra virus. the hendra virus belongs to the genus henipavirus, which also contains the nipah virus, which has also caused disease outbreaks. hendra henipavirus colored transmission electron micrograph of a hendra henipavirus virion (ca. 300 nm length) virus classification (unranked): virus realm: riboviria kingdom: orthornavirae phylum: negarnaviricota class: monjiviricetes order: mononegavirales family: paramyxoviridae genus: henipavirus species: hendra henipavirus pathology 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. 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. ephrin b2 has been identified as the main receptor for the henipaviruses. 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. 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 are allowed to graze below roosting sites. in 2021 a new variant of hendra virus named "hendra virus genotype 2" (hev-g2) was identified in two flying fox species in australia. it shares 84% sequence homology to other published hendra virus genomes. prevention, detection and treatment three main approaches are currently followed to reduce the risk to humans. 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 dr 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." 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. by december 2014, about 300 000 doses had been administered to more than 100 000 horses. about 3 in 1000 had reported incidents; the majority being localised swelling at the injection site. there had been no reported deaths. 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. in january 2016, apvma approved its use in pregnant mares. 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. 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. 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. 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. history 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. 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. 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. a second outbreak occurred in august 1994 (chronologically preceding the first outbreak) in mackay 1,000 km north of brisbane resulting in the deaths of two horses and their owner. 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. outbreak in australia hendramackaytownsvillebowenhervey baychinchillarockhamptoninghamcairnsred dots show outbreaks in queensland ballina macksvillemullumbimbylismorekempseysconesydneyred dots show outbreaks in new south wales as of june 2014, a total of fifty outbreaks of hendra virus have occurred in australia, all involving infection of horses. as a result of these events, eighty-three horses have died or been euthanized. a further four died or were euthanized as a result of possible hendra infection. case fatality rate in humans is 60% and in horses 75%. 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. 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. 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. 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. 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. 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. despite this in 2014 the nsw government approved the destruction of flying fox colonies. list of australian hendra outbreaks list of australian hendra outbreaks date location details deaths (human) deaths (horse) august 1994mackay, queenslanddeath of two horses and one person, mark preston.12 september 1994hendra, queensland20 horses died or were euthanised. two people infected. one of them, victory ("vic") rail, a nationally prominent trainer of racehorses, died.120 january 1999trinity beach, cairns, queenslanddeath of one horse.1 october 2004gordonvale, cairns, queenslanddeath of one horse. a veterinarian involved in autopsy of the horse was infected with hendra virus, and suffered a mild illness.01 december 2004townsville, queenslanddeath of one horse.1 june 2006peachester, sunshine coast, queenslanddeath of one horse.1 october 2006murwillumbah, new south walesdeath of one horse.1 july 2007peachester, sunshine coast, queenslandinfection of one horse (euthanised) july 2007clifton beach, cairns, queenslandinfection of one horse (euthanised). july 2008redlands, queenslanddeath 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. 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. the biosecurity queensland website indicates that 8 horses died during this event, 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...".14 july 2008proserpine, queenslanddeath of four horses.4 july 2009cawarral, queenslanddeath of four horses. queensland veterinary surgeon alister rodgers tested positive after treating the horses. on 1 september 2009 after two weeks in a coma, he became the fourth person to die from exposure to the virus.14 september 2009bowen, queenslanddeath of two horses.2 may 2010tewantin, queenslanddeath of one horse.1 20 june 2011 – 31 july 2011mount alford, queenslanddeath of three horses (all confirmed to have died of hendra) and sero-conversion of a dog. the first horse death on this property occurred on 20 june 2011, although it was not until after the second death on 1 july 2011 that samples taken from the first animal were tested. the third horse was euthanised on 4 july 2011. 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. dusty was euthanised on 31 july 2011 following a second positive antibody test.3 26 june 2011kerry, queenslandthe horse was moved after it became sick to another property at beaudesert, queensland. death of one horse.1 28 june 2011loganlea, logan city, queenslanddeath of one horse. unusually this horse had hev antibodies present in its blood at the time of death. how this immune response should be interpreted is a matter of debate.1 29 june 2011mcleans ridges, wollongbar, new south walesdeath of one horse. the second horse on the property tested positive to hendra and was euthanised on 12 july 2011.1 3 july 2011macksville, new south walesdeath of one horse.2 4 july 2011park ridge, logan city, queenslanddeath of one horse.1 11 july 2011kuranda, queenslanddeath of one horse.1 13 july 2011hervey bay, queenslanddeath of one horse.1 14 july 2011lismore, new south walesdeath of one horse.1 15 july 2011boondall, queenslanddeath of one horse.1 22 july 2011chinchilla, queenslanddeath of one horse.1 24 july 2011mullumbimby, new south walesdeath of one horse.1 13 august 2011mullumbimby,