A RECENT report on new and emerging diseases published by the World Health Organisation is yet another warning bell to all countries.

With the world human population now exceeding 6,300,000,000 humans, the WHO acknowledges the near exponential growth in the human population. Therefore they expect to see far more outbreaks of infectious diseases and the emergence of new diseases that will inevitably mix between animal populations - both domestic animals and wildlife - and humans.

Neither is it a coincidence that this international warning on disease outbreaks comes at the same time that the Intergovernmental Panel on Climate Change report have given similar warning linking the human-induced climate change with the spread of serious diseases like malaria.

Even ordinary people - reflecting back on the last decade or so - would appreciate the surge in serious infectious diseases that are now stalking humans, our food-producing animals and our beleaguered wildlife.

The realisation that Australia’s animal disease quarantine was not impregnable came with the explosive outbreak of Equine Influenza last month.

We live in affluent times when very valuable stallions have joined the jet set, winging their way around the world to sow their oats during the northern hemisphere summer between February and May and, once more with feeling, in the southern hemisphere between September and December.

The Australian racing industry (harness and thoroughbred racing) - the sport of kings - is worth approximately $7.8 billion annually. And that doesn’t include the gambling revenue of $12 billion wagered on racehorses every year.

The dread this infectious disease created was the risk it posed to those billions.

In the early emergency phase of a new disease outbreak - such as Australia is currently experiencing - the imposition of no movement bans [the so-called ‘lock down’] is realistically all that could be done in a nation like Australia where there is a large and very mobile population of horse-owners and a massive racing industry.

Discounting an act of deliberate bio-terrorism, effectively the only conceivable way this disease can enter Australia is through imported horses from a country where EI is endemic (or where it’s thought it doesn’t presently exist, but does!). That place was Japan.

It is plausible that Australia’s raft of barrier quarantine safeguards & import approval protocols to prevent importing Equine Influenza might be less strictly applied when racehorses or stallions are moving from a country where EI is not active in the horse population and where you are relying on influenza vaccination to protect importing horses.

That said, the final safeguard for Australia - in the event of a horse or horses that are incubating Equine Influenza - is to keep those horses in quarantine isolation until the normal incubation period for the disease would have come and gone, and then some. And of course there is the possibility that a vaccinated horse might not show the normal high fever and typical flu-like symptoms and yet still be a carrier of the newest EI strain.

The backdrop to this story is that after Australia received some consignments of stallions from Japan, an outbreak of Equine Influenza was detected in Japan. In other words the outbreak of EI in Japan coincided with the transit of many ‘shuttle stallions’ to Australia. Between the 3 -8 of August some horses arrived from Japan and by mid-August the first reports filtered through that three stallions out of 52 at the Australian Government’s post-embarkation equine quarantine facility had become ill. Equine influenza (EI) was confirmed in these horses.

An unfortunate combination of factors has probably led to Australia’s first outbreak of Equine Influenza - (1) an asymptomatic carrier horse shedding the virus came into Australia from a country where active EI infection had not yet been detected; (2) a human who had contact with the horse shedding the virus became contaminated; (3) a failure to follow routine hygiene - such as showering, disinfecting and changing clothes -  before having direct contact with susceptible horse in another venue in Sydney (Centennial Park equestrian facility).

Being ‘free’ of any disease has its benefits AND its costs. Up-to-date international bio-intelligence on disease outbreaks is crucial. Effective national quarantine protocols are in place for specific species imported into Australia. And finally early preparedness and response in the event of an outbreak are some of those on-going costs.  Human error is the one aspect that is ALWAYS the weak link.   

Australia has been ‘the lucky country’ and doesn’t have many serious animal diseases. Our relative isolation in the world has acted as a basic quarantine, however, as the world effectively shrinks and international travel speeds up, there is increased pressure on Biosecurity and Quarantine services to keep all the bases covered.

In the 21st Century it’s impossible to manage for zero risk for each and every exotic disease we don’t want. That said, the highly contagious viral diseases with high impact get priority.

Since the mid-1990s trade liberalisation and globalisation has caused exponential movements in tradeable commodities whilst air travel now moves a staggering 2 billion people from place to place across the planet each year. Both these trends are increasing annually.

These types of statistics were the catalysts for WHO concerns about global pandemics. The highest priority would be the highly contagious [i.e. transmitted over a short distance by aerosol spread] and very virulent strains of human influenza. The concern remains that a virulent avian or animal influenza virus will jump into the human population and rapidly go global. Remember the serious outbreaks of H5N1 bird flu beginning in Hong Kong & South China in 1997 and then re-emerging in 2003 and spreading across Asia and into parts of Europe. Billions of chickens were affected or were slaughtered across Asia.

SARS (Sudden Acute Respiratory Syndrome) spilled into people in Hong Kong & China 2003 and air travel carried this viral infection to several countries. 

Just as the rapid air travel of people incubating a new highly pathogenic influenza virus is the great fear for the next human influenza pandemic, globe-trotting racehorses can inadvertently carry their own brand of influenza internationally.

EI is caused by another influenza A virus [usually the H3N8 strain]. It is explosively contagious amongst horses and when it occurs for the first time the disease can spread like foot and mouth disease of sheep and cattle.

Although imported horses are vaccinated against EI, equine vet, James Gilkerson believes that horses could have been infected with the new EI strain in Japan and arrived in Australia before the Japanese outbreak was notified. Vaccinated horses are likely to show only mild signs of infection but still could shed the virus.

EI has a relatively short incubation period of 2-6 days so usually the air transit time and the post-embarkation interval is sufficient to allow this flu disease with its fever to become obvious.

The epidemiological pattern of spread of the EI infection amongst the horses suggest that someone who had contact with horses imported from Japan between the 3 and the 8 August became contaminated and subsequently became the inadvertent source of EI transfer to an unknown number of horses at Centennial Park before the horse were transported to various locations in NSW including Maitland.

When an infected horse starts shedding the influenza virus through aerosol droplets expired in coughs and sneezes, humans working closely with horses can act as both mechanical transfer agents for the virus and, in more extreme cases, might contract horse flu themselves.

These are some of the many quarantine risk assessment issues the EI Commission headed by retired High Court judge, Ian Callinan, will need to examine.

At this stage is appears that: (1) infected horses from Japan were the source of Australia’s first outbreak of Equine Influenza; (2) the index location where the virus spread from was the Eastern Creek equine quarantine facility west of Sydney; (3) it is most likely that humans having close contact with an infected horse or horses was the source of the virus moving out of the quarantine facility into a recreational horse population and from there on into rural NSW and SE Queensland; and (4) another human contamination from virus-shedding horses at Centennial Park in Sydney transferred the virus to Randwick racehorse stables and then into the NSW thoroughbred racing industry. The latest spread has been into two thoroughbred studs in the Hunter valley.

If you think this forensic reviewing of a new emerging disease is rather academic then think again. Think Foot and Mouth Disease; think SARS and think Avian Influenza or think the next unknown viral pandemic we don’t recognise yet.

These are just a few diseases directly affecting humans and our global economies.

Spare a thought for the serious diseases that go unchecked in wildlife populations; some of these are now causing the reduction in wildlife populations and potentially driving some species to extinction.

Just as human activities are now recognised as the cause of Climate Change, new pathogens going global will be the harbinger of the 21st century. 

Don’t blame the horses but rather the Horsemen of the Apocalypse.

Forensic biologist Dr David Obendorf has written extensively for Tasmanian Times: David Obendorf

 

David Obendorf

If you think this forensic reviewing of a new emerging disease is rather academic then think again. Think Foot and Mouth Disease; think SARS and think Avian Influenza or think the next unknown viral pandemic we don’t recognise yet. These are just a few diseases directly affecting humans and our global economies.