- 9 minutes
- Expertise article
- Dr. Thomasz Trela
African swine fever virus can reach a swine farm in many different ways, you have to consider every possibility and evaluate every kind of scenario when working on biosecurity against the entry of the infection. That’s the advice of Vienna-based veterinarian Dr. Thomasz Trela, who has developed personal expertise of African swine fever on farms in several countries of Europe and Asia. Here are extracts from a new podcast in which he talks about biosecurity against ASF.
You can listen the podcast episode by clicking here.
Q: On the affected farms where you've had experience, was it obvious how the African swine fever infection had entered?
A: No, in most cases we never found out how the virus came to the farm. This was true both in Europe and in Asia, so we can assume there are many introduction routes. These can involve people and vehicles --- also equipment, including field equipment such as a tractor that is parked in the middle of the farm after coming from a field populated by infected wild boar. Among other possible routes there is kitchen food waste or pork meat products and of course the risk that live infected pigs, although asymptomatic, are already shedding the virus. We have evidence, too, that feed or feed components could be a source of infection. In some countries during the summertime the small farmers use green feed materials harvested from the area around the farm. If this area is frequented by infected wild boar and the material is freshly fed to domestic pigs, the risk of infection is a very high.
Q: You suggest that wild boar could contaminate field crops and then the crops themselves or the field equipment could be the means by which the infection is carried into the farm. Has that happened in your experience?
A: Absolutely, yes. Remember that infected wild boar shed this virus in urine and faeces. By this way it can reach grass or grain and then the straw which will be used as bedding. I stress that the body of a wild boar in different stages of decomposition is always a huge risk because these cadavers contain a huge amount of the virus. Driving a tractor in a field, you can easily overlook a dead wild boar lying there and you drive over it. The bones are full of the virus. Crushing them will contaminate your tractor wheels. ASF virus is a very resistant. It can stay infective for several weeks or even months in the field. It means a wild boar which died months before can still infect your shoes.
Q: Are wild boar the biggest risk factor that allows the African swine fever virus to reach pig farms in different countries?
A: In countries with quite a big wild boar population one can probably assume that these were a source of the virus within a region. But we also have a lot of cases where the virus came with people. This virus cannot fly, it needs a carrier. Somebody has to bring it to the farm. It could be on a person or a vehicle. Another risk is when pork products are not processed at a high temperature. They may be just smoke-cured, for instance. ASF virus can stay infectious in these products for as long as six months. So the rule is, no pork at the farm.
Q: How do we stop any contact between wild boar and domesticated pigs?
A: Biosecurity is the only tool we have now to protect our pigs from African swine fever. And the first step when we are thinking about protection is a really solid fence around the farm. It should be at least two metres high and at least half a metre deep into the ground, to keep out wild boar. The gate in the fence must be both strong and properly managed, meaning that it is not left open all day and night. Keep the area around the farm and inside the fence clean, so you can see if there is anything moving around. Also, do not attract any kind of animals by leaving kitchen scraps or other garbage around the farm.
Q: Based on the lessons learned from breakdowns with the virus on Asian and European farms, what advice would you offer to a swine enterprise about operating in a location where the African swine fever virus may be present?
A: The last few years show us that what was working before may not necessarily work today against ASF. For example, decontamination is very difficult because African swine fever virus is very resistant and can stay infectious for weeks or even months. To decontaminate vehicles, during problems with porcine epidemic diarrhoea a few years ago they realised that hot air treatment after washing and disinfection was a critical point to keep the truck clean or to destroy the pathogen inside it. I think we have a similar situation with African swine fever. In disinfection, the contact time needed to destroy the virus is quite long in practical cases, more than 10 minutes. You need a temperature treatment. You need a specific disinfectant. You need the detergent to remove dirt or debris around the virus. So the process is a quite complex, time-consuming and expensive, it could be extremely challenging for smaller farmers. In real life, what we do is try to keep vehicles away from the farm, reduce vehicle traffic as much as possible and avoid any direct contact of vehicles with production zones where the pigs are located.
Q: Does that mean creating a buffer zone around the pig area?
A: Yes, an intermediate buffer zone between the perimeter fence and the super-clean production zone. It recognises that some trucks still must come close to the production area, such as when supplying feed, bringing piglets or gilts or picking up market pigs. Other vehicles may be carrying construction materials or something for maintenance. You have to manage these trucks, and because the buffer zone is already separated, you can quite easily control who is moving there and what they do. Whatever we are doing to protect the farm from ASF is also helpful against other pathogens. I would say that African swine fever is a kind of benchmark today regarding biosecurity levels, linked to its properties of being very resistant against physical and chemical factors and also due to the serious consequences of ASF infection entering the farm.
*Dr. Tomasz Trela is the technical manager for swine in Central and Eastern Europe at Boehringer Ingelheim. You can hear him being interviewed by journalist Peter Best, in the latest season of Meet The Expert swine health management podcasts presented by Boehringer Ingelheim."
