Pigs in the Savannas: Disease Threat

In the Wet Tropics feral pigs are a menace because of their impact on the rainforest. But feral pig specialist Dr Jim Mitchell says their impact on the savannas could be profound because of a disease that would be catastrophic if it got into the country: Foot and Mouth.

Feral Pig Facts

Feral pigs are a menace in Australia's Tropical Savannas as well as its rainforests Picture: Jim Mitchell

SL: Why are feral pigs such a risk with Foot and Mouth disease in the savannas?

JM: Pigs are seen as a Foot and Mouth "factory", they propagate the disease in the body and breathe it out into the air. In other words, they multiply the virus and spread it everywhere. And pigs in the dry savanna have a huge home range, especially during the dry season so they have the potential of manufacturing the virus and spreading it over large distances. Because it's so vast, some estimates say that it could be up to eight months that Foot and Mouth disease could be in the Cape before somebody found it.

SL: Is the risk of a Foot and Mouth disease outbreak increasing?

JM: I think the risks are getting higher and higher, especially with the movement of people to and fro from different parts of the world.

SL: How do you monitor whether Foot and Mouth is getting in?

JM: By testing and checking the pigs as often as possible, to try and find the disease as soon as it outbreaks, then it'll be more easier to control.

SL: How effective are current management strategies in doing that - keeping the surveillance effort up?

JM: I think they're not very effective - especially in the dry tropics. AQIS (Australian Quarantine and Inspection Service) does some testing up in Cape York but the virus could outbreak anywhere in the dry savannas for a lot of reasons and you'd never know the outbreak was there for quite a while.

SL: So how do you increase that surveillance level?

JM: Good question. I think it's probably awareness - landholder' awareness of what to look for basically. I think a lot of landholders in the dry savannas probably wouldn't know what Foot and Mouth looked like in a pig (see box). I think government departments have to push the exotic disease threat a bit more - especially in the education and extension to landholders in what to look for and how to react in the situation.

SL: Apart from the surveillance what about actual population control? Is a factor here that in the savannas pigs are seen as a resource, because there's a good market for the meat?

JM: Yeah, the wild hog market. Australia is the largest exporter of wild hog meat in the world at the moment. It exports to Germany, Italy and France and makes a lot of money over there. It's worth around $20 million to Australia each year and something like 300-400 thousand carcasses a year leave Australia.

SL: So does that dependence create problems if you're looking to reduce numbers of pigs for other reasons such as disease and environmental impact?

JM: For sure: once an animal becomes a resource it tends to be farmed and so if it's worth a lot of money they'll let the females go, or they'll let the little ones go because they know it'll be worth money the next year. But not everybody treats them as a resource; there's a lot who just want to knock out the population. Some of the other options in the dry savannas are aerial baiting which would be the most cost-effective.

SL: So do you think that's the way to go - to have a mix of some people using pigs as a resource and some people eradicating them? Will that work?

JM: Look, there are vast areas of the dry savannas that don't see any pig control whatsoever. I think until we educate the landholders into what sort of problems pigs cause - which people don't see - I don't think we'll have much effect on the populations at all. Until we get landholders on side.

Feral Pig Facts

The last population surveys in north Queensland were carried out 12 years ago which showed around two million pigs in the Cape. Jim Mitchell reckons there may be a similar number in the Top End of the NT. In the past 12 years he reckons the population may have remained static or is slowly increasing.

A feral pig sow can have up to two litters a year of 10 piglets each. That is, a maximum of 20 offspring a year! In good seasons you have to cull the population by 70 per cent every year just to keep a lid on the population.

Symptoms of Foot and Mouth disease in feral pigs include a funny walk and blisters around the mouth, tongue and feet. If landholders see such signs they should contact a vet immediately.