Why Australian farmers should care about diseases we don’t have
By Linda Searle, District Veterinarian
Australia’s freedom from exotic diseases is important for many reasons, the most obvious being that if we are free from a disease then we don’t have to worry about the effects of that disease on our stock. These effects vary depending on the disease but can include the loss of production (foot and mouth disease), possible human health issues (mad cow disease) or possible massive stock mortalities (porcine epidemic diarrhea virus).
But this is definitely not the only reason that we should care about exotic diseases. Our export markets, which include animals, animal products and reproductive materials, are highly reliant on our freedom from certain diseases. The requirements vary for every country, species of animal and product and include both exotic disease and diseases that we do have in some parts of the country, but not on every farm.
So how do we know that we don’t have these exotic diseases in Australia? How can we prove to ourselves and the world at large that we don’t have these diseases? It is not good enough to simply say that we have never diagnosed the disease, therefore we don’t have it, because the response we’d get would be the same as you used to get from your mum when you told her couldn’t find your shoes – how do you know if you haven’t looked? So we look. There are dozens of surveillance programs specially designed to look for important exotic disease.
The TSE (Transmissible Spongeform Encephalopathy) surveillance program is a big one. Mad cow disease, scrapie and a few other diseases all fall under the broad category of TSE – basically any disease that is caused by a prion rather than a bacteria or a virus. We are so concerned with knowing that we don’t have mad cow disease in Australia that you will be paid $100 for a sheep and $200 for a cow to let us take the brain to a laboratory to prove that it does not have these diseases.
Now there are a couple of criteria that need to be met to be eligible for this program. The main one is that the animal was capable of having a TSE, which means that it is over 18 months for a sheep and between 30 months and nine-years-old for a cow. The animal also needed to have displayed strange neurological behavior, which it did not recover from before it died or was put down. If in doubt, ask your vet (private or government) and they will be able to tell you if the animal could be submitted through this program.
How would a disease that we don’t already have get into the country? We are quite lucky to have such a low level of disease compared with other countries, due in a large part to being an island country. Cows can’t just walk over from a neighbouring country coughing and spluttering as they go. So why should we be worried? Well, we do import animals from other countries, so there has to be quarantine procedures so we can ensure they aren’t bringing disease into the country with them. This includes companion animals as well as livestock.
But not all diseases need an animal host to get into the country.
One of the big foot and mouth disease epidemics in the UK was caused by someone picking up the food scraps from the airport and feeding it to their pigs. Foot and mouth disease virus can be contained in foodstuffs such as improperly cured salami. While any cloven-hoofed animal can get foot and mouth disease, pigs are amplifier hosts, which means that they pump out an enormous amount of the virus, which can then spread to neighbouring cows, sheep, goats and other animals. Think about all of those feral pigs out there and how quickly this disease could spread and you know why we have so many precautions in place.
As part of our many-layered approach to prevent the importation of foot and mouth disease – and its spread - we have laws on what you can feed to pigs. By stopping the consumption of prohibited feed - for example, meat and meat contaminated food scraps – we ensure that even if contaminated meat made it into Australia, it would not be eaten by pigs.
Another layer is the National Livestock Identification System (NLIS), which allows us to track the movements of animals and their possible contact with disease. This can be used for exotic diseases as well as notifiable endemic disease or residue contamination.
This is not forgetting that a hugely important layer is the education of Australian farmers about what to look out for. If you see something unusual on your farm it needs to be reported. You might think this is a hassle in the short-term, but what could you be preventing? It could be a brand-new disease or one that we haven’t had in our country or state before. The sooner we find it, the better chance we have of stopping or at least controlling it. With each day of infection, the cost of an exotic disease outbreak on our economy balloons by millions of dollars. This isn’t just loss of animals, production and the cost of eradicating the disease, but the loss of export markets and consumer confidence that can take years to re-establish.
There is an old adage in medicine that says ‘when you hear hoof beats, think horse, not zebra’, which simply means common things occur commonly. This is generally true, but it’s always a good idea to have a quick check for stripes before you get trampled.