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Hendra Virus Update – in Humans, Cats, Bats, Dogs..& Horses

5th Dec 2013

New virus types, Virus in Dogs & Cats, Flying Fox input & managing vaccination in Hendra areas mean that if you or your clients have an interest in Hendra virus in horses you MUST keep up with all the news.

 The Qld Department of Agriculture & Fisheries Biosecurity Queensland division has produced a completely updated resource update for veterinarians on Hendra virus, but it is also useful for those with an interest in horses, those competing with horses & those interested in potential virus transmission to dogs & cats.  You can see the full report by CLICKING HERE.

You can access information from the Qld Horse Council HERE

 Here’s a summary for those who want high level information as a summary…..

GENERAL INFORMATION…

HeV was first isolated during 1994 when it occurred in a stable in the suburb of Hendra, Brisbane. Early names included acute equine respiratory syndrome and equine morbillivirus. It is now termed Hendra virus.

 Flying foxes are a host reservoir of HeV1. Sporadic ‘spillover’ of HeV from flying foxes to horses occurs; however the factors associated with spillover events are not yet fully understood and research is ongoing.

 HeV has the potential to be a serious human disease for which stringent biosecurity and safety measures are necessary. Careful risk management of the situation, safe work practices and PPE are required to manage potential exposure.

 While much is now known about HeV, the scientific information available for HeV is not complete and there may be insufficient scientific knowledge to answer some questions that are posed. The consequences of HeV infection for both horses and humans can be potentially catastrophic. As a result, a conservative ‘precautionary principle’ approach should be taken whenever uncertainty exists—that is, procedures should be put in place to limit possible harm in all cases where HeV is considered as a possible diagnosis.

 Given the potential for death from HeV, it is vital that possible cases be notified and investigated. It may not be clear at the beginning that HeV is involved.

Note: Hendra virus is not related to equine influenza or Australian bat lyssavirus.

INCIDENCE…

Until 2011, there had been 14 incidents of HeV over 17 years from 1994 to 2010. In 2011, there were 10 HeV incidents in Queensland and eight in New South Wales. A case of HeV was confirmed in a horse at Chinchilla, Queensland, in 2011, which was the first  detection west of the Great Dividing Range. Another case was confirmed in a horse at Macksville, New South Wales, which is the southern most case detected to date. Prior to 2011, the known detections had occurred on or east of the Great Dividing Range from Cairns to northern New South Wales. There were eight incidents in 2012 and HeV infection in horses continues to be identified in 2013.

 THE ROLE OF FLYING FOXES….

Flying foxes are a natural reservoir of HeV. HeV is present in flying fox populations in Australia & Papua New Guinea. Surveillance of Australian flying foxes has found antibodies to HeV in all four mainland Flying Fox species.There is no evidence that other animals are  a natural reservoir for HeV.

HeV is possible wherever horses and flying foxes are close to each other. Horses transported long distances & could be moved within the incubation period from an area where they may have been in contact with flying foxes or a horse infected with or incubating HeV, to an area where flying foxes do not exist.  HeV is not present continuously in flying fox colonies, and the level of excretion in any particular colony fluctuates over time

 Flying foxes can be infected and excrete virus at any time of the year and that spill-over of virus to horses requires factors other than just the presence of virus. There is currently no reliable method to predict the high risk periods, but the  majority of incidents roughly coincide with the period from mid/late pregnancy to early birthing of three of the four Australian flying fox species.

 All properties with HeV cases have had some level of flying fox activity identified in the vicinity but not necessarilya roosting colony.

 The exact route of transmission of HeV between flying foxes and from flying foxes to horses is not known but is thought to be via contact or droplet transmission. HeV has been isolated from the urine, saliva, faeces and uterine fluids of flying foxes and it is possible that pasture or discarded fruit contaminated with flying fox body fluids and/or excreta are probable routes of viral transmission to horses. Transmission to horses via the nasal route is also ;possible.

IN HORSES….  DeadHorse

HeV infection of horses generally causes an acute illness that is rapidly fatal. HeV has been found in horse blood, oral & nasal secretions. HeV genetic material has been found in urine, faeces & a wide range of body tissues of infected horses. It is possible HeV could be present in any body fluids. Research has also shown evidence of the virus widespread in the body from as early as two days post exposure, which was three to five days before the onset of clinical signs

 Early clinical signs are depression, an increase in body temperature and heart rate and a discomfort or restlessness expressed by weight shifting between legs (both fore and hind limbs). HeV should be considered as a possible diagnosis even at this early stage.

 Duration & type of exposure also contributes to infection risk. Longer contact time & invasive procedures may increase the potential for acquisition of an infectious dose of virus. Certain types of contact or procedures may contribute to human infection, such as nasal intubation (eg for drenching)  or dental procedures, where operator risk is increased even before symptoms appear. 

The feverish & then symptomatic horse, particularly those late in the disease process are likely to shed more virus from a variety of excretions & pose a higher risk of disease transmission. Conducting autopsies poses a higher risk of infection transmission because of the potential for contamination & the handling of sharp instruments.

 It appears that the virus attacks the base of the blood vessels, so clinical symptoms will vary according to which blood vessels are attacked worst, but lung tissue & nerve tissue is well served with blood vessels, which may explain respiratory & nervous symptoms.

 Symptoms can include Fever, increased heart rate, discomfort/weight shifting between legs (both fore and hind limbs), depression, rapid deterioration, usually with respiratory and/or nervous signs.

 Respiratory signs can include: respiratory distress, increased respiratory rates, nasal discharge—can be initially clear progressing to stable white froth & /or stable blood-stained froth

 Nervous signs can include : ‘wobbly gait’ , altered consciousness—apparent loss of vision in one or both eyes, aimless walking in a dazed state, head tilting,  circling, muscle twitching, leakage of urine, inability to rise, facial paralysis and/or a locked jaw, spasms of the jaw or involuntary chomping, seizures.

 Other symptoms seen in horses with HeV infection: unexplained horse deaths, facial swelling & /or swollen lips, teeth grinding, muscle trembling, altered gait or high stepping, wide based stance, anorexia, red gums, colic-like signs (rolling and thrashing), straining with difficulty passing manure, difficult urination (in both males & females),  protruding penis, hot hooves & bad breath

 Because the virus can transmit to quickly, and horses die so quickly , urgent veterinary attention is required. Do not delay!

 THE VIRUS…..

HeV is a fragile virus & is very susceptible outside the host to high temperatures and drying,  & varying susceptibility to pH changes. It usually has a short life (hours) outside the body & becomes non-infectious when treated with soap and detergents. However, in some experimental circumstances the virus can survive longer, up to four days at 22 degrees Celsius in pH neutral bat urine. Virus survival on mango flesh extended the virus life up to 2 days, and lychee juice up to 3 days.

 INCUBATION & TRANSMISSION IN THE HORSE….

In experimentally infected horses the incubation period has ranged between 3–11 days. In naturally infected horses, the attributed incubation period has ranged between 5–16 days. The time period from illness to death averages a little over two days from first signs to death.

Up to 20 % of horses can survive acute infection.

 Cases are typically horses paddocked or kept outside in areas attractive to flying foxes. Horse-to-horse transmission of HeV appears higher in stabled horses compared to a paddock situation. In paddock situations to date 65% of cases have involved one infected horse that died without any in-contact horses becoming infected. HeV has potential to spread to other horses through direct contact with infectious body fluids or excreta, or through indirect contact via contaminated fomites, including human transfer.

INFECTION IN HUMANS, DOGS, CATS, FERRETS, HAMSTERS, & OTHER SPECIES… 

Experimental research has found that cats, pigs, hamsters, ferrets, African Green Monkeys, guinea pigs & mice can be infected with HeV & die. However, rats, rabbits and a dog developed antibodies but not symptoms when exposed to HeV.   In July 2011, test results showed antibodies to HeV in a dog on a property in Queensland with no symptoms & no virus. In July 2013 a dog was confirmed to be infected with HeV on a property in New South Wales.

 Both cases of HeV infection in dogs were on properties where HeV infection had been found in horses & where there was close contact between the dog and horses. The few cases of HeV infection in dogs suggest that dogs cannot become ill.

 Seven cases of human infection with HeV have been recorded. All cases had a high level of exposure with blood or body fluids from an infected horse. Four people died – a case fatality rate of 57% . Human infection may have from a horse in the late incubation period, i.e. up to 72 hours before symptoms in the horse. What little data is available suggests that human infection is by direct contact with infected tissues or secretions.

 THE HENDRA VACCINE…

A genetic vaccine for HeV was released commercially in November 2012.  The vaccine works by stimulating the production of antibodies that neutralise HeV so it can’t attach to cells, preventing infection. 

In studies on the vaccine, there was no evidence of viral shedding by immunised horses after HeV virus was given to the horses & no evidence that the virus had infected the animal.

 In field trials, horses were given two single doses of the vaccine by intramuscular injection on Days 0 and 21.1%of vaccinated animals in both trials produced significant antibody and were protected from challenge with HeV virus.

Vaccination is the single most effective way of reducing the risk of HeV infection in horses. Human infection & death have occurred following high-level exposure to body fluids from an infected horse. Vaccinating horses is an important measure to prevent this occurring & provides a public health & workplace health & safety benefit. Widespread vaccination of horses will significantly reduce the number & risk of human exposures.

Similar to all vaccines, no one vaccine can be 100% effective in all animals on all occasions, therefore it is critical that people in contact with horses continue to practice good biosecurity and hygiene, even if a horse is vaccinated. Veterinarians have to be specially trained in order to administer the vaccine because it is still classified as experimental.

 The HeV vaccine not only protects horses from infection, but breaks the cycle of virus transmission from horses to humans. If you value your family, staff and veterinarian, get your horses vaccinated.

 PROTECT YOUR SAFETY!

Hendra virus can KILL humans. If your horse is ill, adopt standard precautions, for all contact with horses, even for horses that aren’t sick. This includes:

  • Cover any cuts & abrasions you have with a water-resistant dressing & adopt personal hygiene, including hand hygiene before & after horse contact, between horses & after removing PPE.
  • Wear PPE including disposable gloves for contact with blood, body fluids, excretions, non-intact skin & mucous membranes, & protective clothing & facial protection where there is a risk of droplets, splashes, & sprays of blood & body fluids.
  • afe handling, transport, storage & cleaning of contaminated clothing & other laundry
  •  Safe handling & disposal of animal excreta & stable manure.
  •  Stable hygiene & environmental cleaning using appropriate cleaning agents & disinfectants
  •  Isolate sick or dead horse from all people, all other horses & all other domestic animals on the premises & from the public
  • If necessary seek advice from your lovel DPI or Biosecurity Queensland about disposal of any dead horses if they die before sample results confirm that it’s not Hendra, & ensure the disposal contractor is aware of the risk.
  • Ensure the health & safety of any person at the premises who helps you with the horses, or with a veterinary assessment or procedure (e.g. restraining the horse) & ensure that they understand yourinstructions for their health and safety
  • Perform hand hygiene & treat tissues, blood and other body fluids (especially respiratory& nasal secretions & saliva) & excretions as potentially infectious.

 PPE should include: impervious rubber boots, splash-proof overalls (long sleeves with a hood) or cotton or disposable overalls with impervious or splash-proof apron, disposable impermeable gloves (nitrile gloves recommended), double-gloved, a face shield or safety eyewear (to protect against facial splashing) & a respirator (P2 standard). Be careful not to overheat when wearing PPE.

 IF YOU ARE ACCIDENTALLY EXPOSED TO INFECTIOUS MATERIAL….

Use soap & water to wash off contamination—shower if possible, & seek urgent medical advice. Minimise any further exposure by withdrawing to a safe area & advising other people to do the same.

SUITABLE DISINFECTANTS…. 

Suitable disinfectants include: soaps and detergents, Virkon®, hypochlorites, iodophors/iodine (Betadeine etc), chlorhexidine (Savlon/Hibiclens), quaternary ammonium compounds. Note that household bleach is NOT on this list, &  that for most disinfectants thorough cleaning is required before use.

 

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