FMD - Consequences of its Spread in Australia06 November 2012
Paul Freeman, Regional Veterinary Officer at Wollongbar, explains foot and mouth disease (FMD) and the consequences of its spread in Australia.
Foot and mouth disease (FMD) is an acute, highly contagious viral disease of domestic and wild cloven-hoofed animals (ungulates). The disease is characterised by the formation of vesicles (fluid-filled blisters) and erosions in the mouth and nostrils, on the teats, and on the skin between and above the hoofs. FMD may cause serious production losses and is a major constraint to international trade in livestock and their products. It does not occur in Australia.
Because an outbreak of FMD in Australia would result in the closure of most of our meat, dairy and wool export markets until the outbreak was eradicated, the social and economic costs of an FMD outbreak in Australia would be huge. Herds and flocks would be destroyed and sales of animals and animal products restricted until the disease was eradicated which would be devastating for individual farmers. Unlike the United Kingdom or South Korea, Australia is a major exporter of livestock and livestock products so the impact of an FMD outbreak would be catastrophic for our economy.
The Australian Bureau of Agricultural and Resource Economics and Sciences (ABARES) recently costed a small scale three month outbreak at $7.1billion while a 12 month duration large scale outbreak was estimated to cost $16 billion. The UK outbreak in 2001 is estimated to have cost the UK economy about $10 billion while the recent outbreak in South Korea resulted in destruction of 25 per cent of the national cow and swine herd.
What causes FMD?
FMD is caused by a virus of which there are 7 serotypes: Types O, A, C, SAT1, SAT2, SAT3 and Asia 1. Infection with one serotype does not offer any cross protection against another serotype. Within these serotypes there are over 60 strains which vary in the level of cross protection they offer against other strains, depending on how immunologically similar they are.
The practical implication of this is that vaccines usually have to be manufactured to match the specific FMD serotype and strain causing the outbreak.
Which species are affected?
Most cloven footed animals are susceptible to FMD infection including both domestic and wild animal species. FMD does not affect humans, horses, or companion animals such as dogs and cats. Cattle, sheep, goats, pigs and buffalo are the usual domesticated livestock species affected while more than 70 species of wildlife can also be infected experimentally. Species vary between each other in their susceptibility to infection, the clinical signs displayed and their ability to transmit infection. For instance camels, alpacas and llamas would need to be considered in an FMD outbreak but appear somewhat resistant to field infection. Deer also vary between species in their susceptibility but clinical cases have been seen in some outbreaks.
Generally wildlife become infected from contact with infected livestock and have only rarely been implicated in spreading infection. The exception is in Africa where African Buffalo can be long term carriers of FMD virus and have played a role in spreading infection throughout sub Saharan Africa. Australian native species have been tested for susceptibility to infection and are regarded as unlikely to be involved in the spread of FMD. However, feral pigs, goats and camels would pose a major risk for spreading FMD.
What are the symptoms?
The symptoms can vary from mild to severe. Blisters or vesicles developing on the feet, mouth and teats which rupture leaving raw ulcers are the most characteristic lesion. Lameness, excess salivation and fever are often seen. However as mentioned earlier the clinical expression of infection varies between species according to the dose and strain of the virus. For instance some O strains have caused barely noticeable illness in cattle and buffalo while causing classical severe illness in pigs in contact with infected stock. Sheep and goats generally show fairly mild signs when infected which may be missed if not examined carefully. Because the disease is very contagious the number of animals in a herd that become infected may approach 100 per cent, but deaths are unusual except in young animals.
The incubation period can be as short as 24 hours or as long as 14 days and varies between species and the dose and strain of the virus involved in the outbreak.
How long does the virus persist in the environment?
Under cool moist conditions the FMD virus can survive for up to 6 months. The virus does not survive for long in hot dry conditions. It can survive for extended periods in hides, some dairy products, and in chilled, cured or salted meats. The strict quarantine conditions on bringing animal products into Australia are in part to protect against the introduction of FMD virus in these types of products.
How is it spread?
Infected animals shed the virus in expired air, urine, faeces, milk, saliva and semen and the virus can be shed by infected animals for up to 4 days before any symptoms are noticed. Indirect transmission of infection can also occur when vehicles, clothing, hands or feedstuffs get contaminated with the virus and then come in contact with susceptible animals. Windborne spread can occur and has on several occasions caused transmission of the virus over significant distances.
The various ways FMD virus may be spread and the high level of contagiousness make it one of the most feared animal diseases. In the UK outbreak in 2001 the movement from saleyards of infected sheep before they displayed any symptoms resulted in the spread of infection very rapidly throughout the country and vastly increased the size of the outbreak.
Spread of FMD by feral animals is a major risk in Australia. There are large populations of feral pigs, goats and camels in many areas of Australia and FMD would be difficult o eradicate once it got established in feral animals.
Where does it occur in the world?
FMD is endemic in many parts of Africa, Asia, Eastern Europe, the Middle East and South America. It is not present in Indonesia or New Guinea nor in the South Pacific islands. Both Australia and New Zealand are free from FMD.
How would FMD get into Australia?
Feeding food refuse (swill) to pigs is thought to have started the FMD epidemic United Kingdom in 2001. New South Wales and all other Australian states and territories have strict laws that prohibit the feeding of food scraps or refuse to animals. To help avert the establishment of FMD and other diseases in Australia, it is important to prevent pigs (including wild pigs) from gaining access to food scraps. Rubbish tips and ports are monitored regularly to ensure that food scraps do not end up being fed to livestock.
Importing or carrying FMD contaminated food products is the most likely route for FMD entry in to Australia. The widespread availability of international air travel has increased the risk of FMD contaminated products entering Australia. Australia has strict quarantine requirements to mitigate this risk.
What action would occur in Australia if FMD was to occur?
Australia has nationally agreed response plans for animal emergency diseases such as FMD called AUSVETPLANS. For an FMD outbreak the response would focus on stopping the spread of infection by:
- controlling the movements of animals and their products by quarantine;
- using strict hygiene procedures when working with animals and their products;
- slaughtering infected and at risk animals; and
- strategic vaccination using strain specific vaccines.
The National Livestock Identification System (NLIS) would play a key role in tracing animal movements rapidly as speed is the key to limiting the spread of FMD. It would be important to not allow infection to get established in feral animals as that would make eradication more difficult.
Reporting possible FMD
Early diagnosis is the key to controlling FMD.
If you suspect FMD you should immediately notify in one of the following ways:
- Call the emergency animal disease hotline – 1800 675 888 – which is monitored 24 hours a day, or
- Phone a Livestock Health and Pest Authority (LHPA) District Veterinarian or Ranger, or a NSW Department of Primary Industries (NSW DPI) veterinarian or regulatory officer.
Every year vets investigate a number of suspicious disease cases where the clinical signs are serious enough to warrant samples being sent to the Australian Animal Health Laboratory (AAHL) at Geelong for FMD exclusion.November 2012 © State of New South Wales, Australia.