Nipah/Hendra Virus & Fruit Bat Home Range – WHO
Although long known to carry rabies, over the past two decades bats have increasingly been linked to emerging infectious diseases.
The SARS-CoV (coronavirus) outbreak of 2002-2003 – which infected roughly 8,000 people and killed nearly 800 – is undoubtedly the best known of these diseases, but is by no means the only one to emerge.
Genetic analysis of two recent novel coronavirus infections in the Middle East suggest (but fall short of proving) that bats may be the primary host for this virus as well (see Coronavirus `Closely Related’ To HK Bat Strains).
And the natural reservoir for the Ebola viruses (including Marburg) are believed to be fruit bats of the Pteropodidae family.
Prior to the SARS outbreak - during the 1990s – two new bat-borne viruses made headlines; Nipah and Hendra, both henipaviruses of the family Paramyxoviridae.
Of the two, Nipah has been the deadliest, causing outbreaks primarily in India and Bangladesh. But the virus was first discovered in April of 1999 when an outbreak occurred at a pig farm in Malaysia.
During this initial outbreak, the virus jumped to local swine herds from bats, and infected more than 250 people, killing more than 100. The virus was then exported via live pigs to Singapore, where 11 more people died (see MMWR Update: Outbreak of Nipah Virus -- Malaysia and Singapore, 1999)
Over the past decade, Nipah has sparked a hand full of smaller outbreaks across Southern Asia with the greatest activity centered around Northern India and Bangladesh. Fruit bats (Pteropodidae) are considered the natural host of Nipah virus.
Perhaps most concerning has been evidence of limited nosocomial, or human-to-human transmission, of the Nipah virus (see Bangladesh: Updating The Nipah Outbreak).
The Nipah virus, like it’s close cousin the Hendra virus, is classified as a biosecurity level 4 (BSL-4) agent.
While not associated with as many human fatalities, the Hendra virus was first identified after the deaths of 13 horses and a trainer in Hendra, a suburb of Brisbane, Australia in 1994. A stable hand, who also cared for the horses, was hospitalized, but survived.
Another outbreak was later identified as having taken place in MacKay, 1000 km to the north of Brisbane, the previous month. Two horses died, and the owner was hospitalized several weeks later with meningitis. He recovered, but developed neurological symptoms and died 14 months later.
Over the past 18 years 40 outbreaks of Hendra virus – all involving horses – have been reported in Australia. Four human fatalities have been linked to the virus as well.
Subsequent studies have showed a high prevalence of the newly identified Hendra virus in Pteropid fruit bats (flying foxes) in the region.
Unlike Nipah, to date no human-to-human transmission of Hendra has been documented.
All of which brings us to the latest outbreak news, and hope for a new vaccine for horses that just became available. First stop, an update from the QLD Department of Agriculture, Fisheries, and Forestry.
Hendra virus incident Ingham
Biosecurity Queensland is managing a Hendra virus incident in Ingham after a positive test result was received on Friday 2 November 2012.
A mare was first noticed unwell on Wednesday 31 October 2012 by her owner. She was not interested in food, had a slight nasal discharge, rapid, laboured breathing, elevated heart rate, lowered head and was unsteady on her feet.
A private veterinarian visited the horse and collected samples for Hendra virus testing. The horse deteriorated and went down and was euthanased on Thursday 1 November 2012.
Biosecurity Queensland has quarantined the property and undertaken tracing and risk assessments to determine susceptible animals that may have had exposure to the virus.
There are eight horses remaining on the property as well as dogs and cats. Several rounds of testing will be conducted on animals assessed to be at risk of being exposed to Hendra virus before the quarantine can be lifted.
Restrictions will apply to moving horses and horse materials on and off the infected property, and the property will be quarantined for at least one month. There are no other movement restrictions for the general Queensland horse population because of Hendra virus.
Hendra virus vaccine
A commercial pharmaceutical company has released a Hendra virus vaccine for use in horses under a Minor Use Permit. Under permit conditions, only accredited veterinarians can administer the vaccine.
The vaccine provides another option for the horse industry to reduce the risk of Hendra virus infection; however it is important to remember no vaccine is 100% effective and people in contact with horses need to continue to practice good biosecurity and hygiene measures even if horses are vaccinated.
Horse owners should discuss with their veterinarian whether vaccinating their horse is appropriate.
From CSIRO (Commonwealth Scientific and Industrial Research Organisation) we get more details on this newly available vaccine, via a 9 minute audio podcast & transcript.
Australian horse owners and the equine industry have received an important boost in their fight against the deadly Hendra virus with the introduction of Equivac® HeV vaccine. (9:02)
- 1 November 2012
A final note, in the QLD notice above, it mentions that dogs and cats are quarantined, as well as horses. This comes about primarily because in 2011, we saw the first evidence of canine infection with the virus (see Australia: Dog Tests Positive For Hendra Virus).
The Queensland DAFF maintains a FAQ file on Hendra and dogs, where they write:
What animals have been shown to get Hendra virus?
Naturally occurring infection is limited to horses, flying foxes, humans and dogs. In animals, naturally occurring clinical disease is limited to horses.
Hendra virus is present in wild flying fox populations but does not appear to cause disease in them.
Laboratory studies have shown that other species including cats, guinea pigs, ferrets and pigs can develop disease when inoculated with Hendra virus in an experimental setting. Other species, including rabbits and dogs, have developed antibodies to Hendra virus in an experimental setting, but did not develop any signs of illness.
Although transmission from animals other than horses to humans has not been demonstrated, it is always a concern whenever a virus adapts to or jumps to a new host.
It not only gives the pathogen fresh opportunities to mutate and evolve, it provides another potential vector to spread the disease.
And when that host is a dog or a cat – animals with whom humans closely interact – it naturally serves to increases those concerns.