African swine fever: how can we stop it from spreading?

frican swine fever (ASF) does not of (edible) materials, that either has been in need an introduction. The contact with pork or contains ingredients of Acharacteristics of the virus have been pork origin, that is transported over the described in numerous scientific articles. globe, combined with the presence of an The epidemiology of the recent spread has ASF naïve pork (and wild boar-) population been studied in great detail. All the details that encounters possible ASF infected about how genotype II of this ASF virus is materials, makes control of ASF very difficult. travelling around the globe are well known. Journals, magazines, and websites have been full of reports over the alarming situation in Domestic pigs versus wild boar (or a steadily increasing number of countries. feral pigs) There are also success stories but they are few. Most reports are dramatic when The role of domestic pigs in the describing the economic damage, the social epidemiology of ASF differs from the role of disruption in rural areas, the psychological wild boar or feral pigs. impact on pig farming communities, the In wild boar an ASF reservoir will be empty shelves signalling the reducing pork created by continuous infection, which supply in bigger cities of China, etc. Is there might lead to infections in the domestic nothing that can be done to stop this population. In countries where the soft tick tragedy? is present, the tick will act as an reservoir. Delicious pork meat. The whole industry When the wild boar gets sick it will seek must ensure that it is free of ASF virus. shelter and in the case of ASF, it will die in by Alex Eggen, the sheltered place. This can be in the forest AEVC BV, The Netherlands. but also inside a corn field, contaminating [email protected] very pathogenic. Close to 100% of the ASF the harvested corn. When that harvested virus affected pigs die within 10 days. The feed is fed within a short period after the immune apparatus of the pigs has no chance harvest, domestic pigs can be infected. Before trying to answer this question, to provide any sort of immunity against ASF In countries where biosecurity is at a high some aspects involved in the spread need to virus in that short period of time. level (for example Belgium, Czech Republic be considered. It all starts with the virus, The percentage of ASF seropositive wild and Poland) and harvested feed is only fed secondly the role of domestic pigs and wild boars is still very low (<2.0%). This can be some months after harvesting, only very boars, and last but not least it is the human considered a good sign because no ASF virus seldom will the wild boar population act as involvement that has proven to be a crucial carriers are present. But on the other hand, a source of infection for the domestic aspect in the control programme. because there is no immune population, the population. infection will not die out by itself. There will The situation is totally different when the be always naïve animals. ASF virus infects the domestic pig African swine fever virus The ASF virus is also a bug of ‘steel’. It can population. Now there are a lot of survive for long periods in all kind of edible possibilities for direct and indirect contact The structure of ASF was recently detected materials. The OIE has issued a study on the between the infected population and the by using electron microscopy. A quote from survival of ASF virus in different materials non-infected domestic pig population. researchers stated that ‘the cryo-EM and Kansas State University determined the The current global spread of the ASF virus structure of African swine fever virus half-life of ASF virus in feed ingredients. in the domestic population is almost unravels a unique architecture comprising Both revealed that all materials tested exclusively caused by material of domestic two icosahedral protein capsids and two under their conditions can be a prolonged pig origin. Even a number of infections in the lipoprotein membranes. This high-level source of ASF virus infection. Epidemiology wild boar population can be traced back by organisation confers to ASFV a unique could not demonstrate any evidence of making infected domestic pork material architecture among the nucleocytoplasmic airborne infection, which should make accessible to these wild boar. large DNA virus (NCLDV) that likely reflects control easier. In conclusion, many attempts are made to the complexity of its infection process and There are promising reports on the reduce the wild boar population in order to may help explain current challenges in its development of a vaccine. But here caution control the spread of ASF, while the main control’. is in place because there are still many source of ASF virus for both the domestic The genotype II of ASF virus affecting pigs questions to be answered and regulations to pig as well as the wild boar population, are is not very contagious and direct contact is be altered before it can be used. products made of the ASF virus infected needed. It is far less contagious than, for In summary, the combination of a virus domestic pig population. Only seldom are example, CSF or FMD virus, but the virus is that will survive for longer periods in all kind Continued on page 9

International Pig Topics • Volume 35 Number 2 7 Continued from page 7 also not in the feed chain for animals. If the focus on ASF virus freedom in the wild boar ASF virus infected wild boar products industry cannot control the risk that some population or eradicating the wild boar involved. This makes controlling ASF of the parties involved are willing to take, population, as some states in the USA are infection in pigs a problem for the industry ASF will continue to spread around the currently investigating. keeping domestic pigs. Why is this such a globe. Border control of possible ASF infected problem? The risks are clearly identified and materials is essential. This is not only for free reported in all kinds of communication countries on incoming goods, but ASF materials. However, discipline to adhere to infected countries also have a global Human involvement in controlling the recommendations and control of proper obligation to help in controlling the spread the spread of ASF execution is often lacking. This is mostly of ASF virus by checking outgoing goods. fuelled by a loss of income when applying At ESPHM2018, the keynote lecturer in the the no-ASF-virus-spreading-risk attitude. On ASF session posed the title ‘ASF is a human the other hand, providing financial Conclusion driven disease’ to the audience. Dr Klaus compensation might lead to over reporting, Depner, and also other scientists, tried to which is another typical human peculiarity. Yes, ASF virus spread can be stopped. make it clear that the human factor is an In countries with low biosecurity standards Spreading is 100% a human activity and so is extremely complicated matter. and greater backyard farming or outdoor its control. The industry supplying services There are many different individual aspects production, ASF will enter the domestic pig and ingredients, the pork producers that play a role when small scale pig farmers, population first, mainly by swill feeding, and themselves and the pork processing industry small scale meat processors and meat from there it will enter the wild boar or feral need to all be convinced that they can do it traders get confronted with a possible loss pig population because of unsuitable, together. Their work must be coordinated of income. lacking or insufficient rendering capacity. and they should take a no-risk approach. There are many examples reported, These countries will focus on ASF virus When all ASF infected material is kept including a director of a zoo who bought freedom in the domestic population. away from the domestic pig population, no tons of pork from (ASF infected) Vietnam In countries with high biosecurity new cases will occur. because the zoo was losing money and the standards, ASF might enter the wild boar Early diagnosis (on-site PCR test), the animals needed to be fed. This was done in population through international travellers correct disposal of all pigs on infected an attempt to survive and they were willing coming from countries where risks are taken. farms, proper disinfection and strictly to take risks to do so. In these, often more sophisticated countries, adhering to restocking procedures, frequent But this is the key message: in the case of an increasing level of outdoor production is checking of meat processing plants and controlling the spread of ASF the industry present. This has to stop immediately. meat on the market, are just a few of the cannot take any risk. ASF virus infected pork Contact between wild boar and outdoor recommendations. should never end up in any of the food raised domestic pigs cannot be prevented by In a no-risk scenario, a comprehensive list chains. Not in the human food chain but any (affordable) means. These countries will is a long one! n

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