Hendra virus
[edit]Emergence
Hendra virus (originally Equine morbillivirus) was discovered in September 1994 when it caused the deaths of thirteen horses, and a trainer at a training complex in Hendra, a suburb of Brisbane in Queensland, Australia.[9]
The index case, a mare, was housed with 19 other horses after falling ill, and died two days later. Subsequently, 19 of the remaining horses became ill, with 13 dying. The remaining 7 animals were subsequently euthanised as a way of preventing relapsing infection and possible further transmission[10]. Both the trainer and a stable hand were involved in nursing the index case and both fell ill within one week of the horse’s death with an influenza-like illness. The stable hand recovered while the trainer died of respiratory and renal 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 1000 km north of Brisbane resulting in the deaths of two horses and their owner.[11] 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.
A survey of wildlife in the outbreak areas was conducted, and identified pteropid fruit bats as the most likely source of Hendra virus, with a seroprevalence of 47%. All of the other 46 species sampled were negative. Virus isolations from the reproductive tract and urine of wild bats indicated that transmission to horses may have occurred via exposure to bat urine or birthing fluids.[12]
[edit]Outbreaks
As at 17 July 2011, a total of twenty-three events of Hendra virus have occurred, all involving infection of horses. Four of these outbreaks have spread to humans as a result of direct contact with infected horses.
These events have all been on the East coast of Australia, with the most northern event at Cairns, Queensland and the furthest south at Macksville, NSW. All outbreak sites are with in 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). The timing of incidents indicates a seasonal pattern of outbreaks, possibly related to the seasonality of grey-headed flying-fox, and black flying-fox and spectacled flying-fox birthing. As there is no evidence of transmission to humans directly from bats, it is thought that human infection only occurs via an intermediate host (horse).
In the years 1994 - 2010 14 events were recorded. Between 20 June 2011 and today (17 July 2011) a further nine events were identified. It's not clear why there has been a sudden increase in the number of spillover events in June/July 2011 although there are suggestions that the flooding that affected SE Queensland and Northern NSW in December 2010 and January 2011 may be having an impact. 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. [13]
August 1994, Mackay, Queensland: Death of two horses and one person.[11]
September 1994, Brisbane, Queensland: 20 horses died or were euthanised. Two people infected, with one death.[9]
January 1999, Cairns, Queensland: Death of one horse.[14]
October 2004, Cairns, Queensland: Death of one horse. A veterinarian involved in autopsy of the horse was infected with Hendra virus, and suffered a mild illness.[15]
December 2004, Townsville, Queensland: Death of one horse.[15]
June 2006, Sunshine Coast, Queensland: Death of one horse.[15]
October 2006, Murwillumbah, New South Wales: Death of one horse.[16]
July 2007, Clifton Beach, Queensland: Infection of one horse (euthanized).[17]
July 2008, Redlands, Brisbane, Queensland: Death of five horses; four died from the Henda virus, the remaining animal recovered but was euthanized because of the threat to health. Two veterinary workers from the affected property were infected leading to the death of one, veterinary surgeon Ben Cuneen, on the 20th of 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.[18]
July 2008, Cannonvale, Queensland: Death of two horses.
August 2009, Cawarral, Queensland: Death of one horse; the death of three other horses is being investigated. Queensland veterinary surgeon Alister Rodgers tested positive after treating the horses.[19] On September 1, 2009 after two weeks in a coma, he became the fourth person to die from exposure to the virus.[20]
May 2010, Tewantin, Queensland: Death of one horse.[21]
June 2011, Kerry (subsequently Beaudesert), Queensland: Death of one horse. Eight people tested for infection. [22]
June 2011 Wollongbar, New South Wales: Death of one horse, nine people potentially exposed [23] The second horse on the property tested positive to Hendra and was euthanised on 12 July 2011[24] .
June - July 2011 Mt Alford, (near Boonah) Queensland: Death of three horses (all confirmed to have died of Hendra). Six people and eight other horses exposed. The first horse death on this property occurred on 20 June 2011, although it was not until after the second death on 30 June 2011 that samples taken from the first animal were tested [25] [26] [27]
July 2011 Park Ridge, Logan City, Queensland: Death of one horse, 2 people potentially exposed [28]
July 2011 Macksville, New South Wales: Death of one horse, 6 people potentially exposed [29]
July 2011 Kuranda, west of Cairns, Queensland: Death of one horse, 4 people potentially exposed, 37 horses potentially exposed [30]
July 2011 Hervey Bay, Queensland: Death of one horse, one horse being monitored and [31]
July 2011 Boondall, Queensland: Death of one horse, 6 other horses being monitored. [32]
July 2011 Lismore, NSW: Death of one horse, 1 other horse being monitored. [33
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