'Home Grown' And Exotic Diseases
by Wendy Elks

On the Queen’s Birthday holiday in 2006, Queenslander Jennifer Crane noticed something wrong with her 18-year-old Thoroughbred gelding, Clive. The ex-galloper, dressage, show and now pleasure horse, was lying down at an unusual time in an unusual place and when he stood he looked uncomfortable. Suspecting a chill in the back, Jennifer stabled him and called the vet. Early next day Clive was treated for colic, though from his raised temperature, swollen jaw and red gums, Dr Rebekah Day of Range Veterinary Practice in Peachester knew something else was going on. During the day, Clive worsened and didn’t want to eat. The vet visited twice more, treating him for muscle spasms and trying to pinpoint the cause of his swollen face. He continued to deteriorate and Rebekah Day took blood and urine samples. By Wednesday Clive was much worse, looking terrible, with bloodshot eyes and panting like a dog. He went down as the vet arrived again, and died soon after.

Hendra Virus Suspected
Jennifer’s horse had suffered a dramatic and agonising death, within two days of being well and happy. She walked the paddocks in shock, looking for likely causes, e.g. toxic plant poisoning, while Rebekah Day hassled the Queensland Department of Primary Industry (DPI) for the test results. Rebekah suspected the rare Hendra virus, and 10 days later the DPI, who’d been sceptical, confirmed this. With a positive Hendra diagnosis, Queensland Health had to become involved and anyone who’d been in contact with the horse tested for the disease. Three tests, three weeks apart were necessary: on top of the 10 days it had taken to reach a diagnosis, this meant that for more than two months Jennifer Crane and her veterinarian lived in fear of contracting the disease. Both were cleared, but to this day they must be watchful for unusual symptoms.

In June 2008, veterinarian Ben Cuneen died after a Hendra outbreak at Redlands Veterinary Clinic, along with four out of nine horses that contracted the disease. A nurse survived after spending weeks in hospital; she has still not completely recovered and remains under treatment. Once again, Hendra wasn’t immediately identified. Another, unrelated outbreak also occurred, at a property in Proserpine. Dr Cuneen was the third human fatality directly linked to Hendra. Trainer Vic Rail died of the disease in 1994 - the first known ‘spill-over’ into the human population, in the Brisbane suburb of Hendra. A year later, Mackay sugarcane farmer Mark Preston died after being involved in a post-mortem on an infected horse. With 12 years between these deaths, it’s not surprising that health authorities didn’t immediately suspect Hendra.

The human deaths were contracted through occupational exposure, but it’s important to know that any person could pick up the virus through direct contact with an infected horse or pony. As Hendra symptoms mimic snake bite, toxic plant poisoning and other, unrelated diseases, there is a possibility some cases have gone unnoticed, although Barry Smyth of the Equine Veterinarians Association and Australian Horse Industry Council suggests this is unlikely as, in the thousands of horses tested before export from Australia in the last 13 years, none has been detected.

While Hendra does have a low contagion level, there’s a very real possibility that this could change. Dr Linfa Wang of the CSIRO’s Australian Animal Health Laboratory says that the symptoms of the Redlands Hendra outbreak weren’t typical because the disease exhibits genetically variable virus strains.

Extensive studies carried out by the Australian Biosecurity CRC partnership have shown that all four flying fox species in Australia can carry Hendra, with between 10% and 40% exposed to the disease during their lives. “…they (bats) show little to no clinical sign of the disease…(but) in horses and humans Hendra replicates to very high levels”.

So far there’ve been no known cases of direct transmission from bat to human; researchers suspect that horses pick up the virus from feed contaminated with flying fox secretions – urine, saliva and possibly birthing fluids. It’s thought that in times of stress such as drought, habitat loss, or even pregnancy, susceptible bats may be more prone to the disease, and with increased contact with domestic animals and humans as the bats colonise suburban and semi-rural areas in search of food, a ‘spill-over’ effect can occur. Thankfully Hendra is far less transmissible than equine influenza, but its rarity and association (so far) with a tropical climate can bring about complacency. Dr Wang says, “If a more contagious strain (of Hendra) appeared, we would have a serious and potentially global problem on our hands.”

CEM in USA
Currently in the US, bio-security organisations are losing the battle against an outbreak of another equine disease, contagious equine metritis (CEM). I8 stallions in 6 states and 5 mares in 3 states have confirmed CEM-positive by the USDA’s National Veterinary Services Laboratories, and locations have been confirmed for 797 other horses exposed to Taylorella equigenitalis, the bacterium that causes CEM, a sexually transmitted disease that can cause sterility and abortions if untreated. The cost of tracking and treating the disease will be enormous, and the number of horses exposed and its geographical spread keeps growing. The precise origin of the outbreak remains to be determined.

TRANSMITTING INFECTIONS
As Jennifer Crane points out, media coverage of equine disease outbreaks is usually fairly cold-blooded, talking mostly about the financial implications for the racing industry. But diseases such as Hendra can strike any horse, and the emotional, financial and personal cost to the owner can be high, and potentially life-threatening. It cannot be emphasised enough that all equine-related workers and horse owners should be watchful for unusual symptoms, and always maintain safe practices when handling or treating horses with any kind of infection. Before this event, Jennifer, who lives on the Queensland Hinterland, had never heard of Hendra. She was aware that a colony of flying foxes in the nearby forest sometimes camped in trees near the paddock fence, but she wasn’t aware that transmissible diseases can pass from bats to horses. She and others have since worked with the Queensland DPI (or DEEDI, as it is now known) and Biosecurity Queensland to develop an up-to-date fact sheet on Hendra; this and other infectious disease guidelines can be viewed on the Queensland Horse Council website: www.qldhorsecouncil.com.

NO PROTECTION FROM FUTURE DISEASE OUTBREAKS
Last year, the Redlands Veterinary clinic was reported in The Age newspaper as being set to close, its reputation permanently – and undeservedly - damaged by association with the Hendra virus. This demonstrates the on-going cost of the aftermath of a disease outbreak. As usual, prevention is better than the ‘cure’ - the enormous expense of tracking, containing and treating an infectious disease outbreak. The Australian Government covered these costs in the 2007 EI outbreak after its quarantine practices were found to be implicated, but this is unlikely to be repeated. The costs to the Australian taxpayer are staggering: around $500 million, not including State government and industry contributions, costs associated with the 7-month long Callinan Inquiry, and subsequent changes to quarantine and biosecurity procedures. This also does not take into account the massive financial impact on the racing and leisure/pleasure/sport-horse industries.

With the Horse Disease Levy Bill recently defeated in the Senate, all horse-owners must consider what can be done to protect the future of Australia’s equine industry. Currently there is no horse levy system in place and therefore the horse industry cannot become a party to the Emergency Animal Disease Response Agreement, like all other livestock owners. This means there is no guarantee of government assistance for a future emergency disease outbreak and all horses and horse owners are fully exposed to the potential consequences and costs.
These important issues will be explored in future issues of Hoofbeats.

For information on the Animal Disease Response Agreement, or to receive updates via email on the horse industry in Australia, register on the Australian Horse Industry Council website: www.horsecouncil.org.au