In an interview with Farmer.pl, Professor Zygmunt Pejsak, a leading specialist in pig diseases, summarizes the experience of the past ten years of combating ASF. As he emphasizes, the road to eradicating the disease in Poland is still long and winding.
“Farmer”: Professor, let’s start with a question about what the past decade has taught us? How different are today’s methods of fighting the disease from those in 2014?
Prof. Zygmunt Pejsak: I remember perfectly well the first outbreak (then it was called a “case”) of ASF in a wild boar. Material for research from a dead body found in a frozen drainage ditch in the town of Grzybowszczyzna in the Sokółka district. We received the samples on February 14, 2014. Three days later, based on the laboratory test results, we knew that we had the ASF virus (ASFV) in Poland. Since ASF appeared in our country for the first time in history, we had no experience in combating it. What’s worse, in forecasting the development of the situation, we could only use the experience of the Spanish and Portuguese. For many reasons, the spread of ASF in those countries was different from that observed in Poland.
Methods of combating ASF have basically not changed over the last 10 years. Since the first outbreak, the administrative method of ASF eradication has been in force in Poland, throughout the European Union and around the world, which involves killing all pigs in the outbreak and disposing of the killed animals. At the beginning, we were not comprehensively prepared to eliminate herds of pigs and safely dispose of the killed animals quickly. Now we do it very efficiently.
What have we learned? First of all, our experience and information from other countries affected by the “new wave” of ASF indicate that it is possible to combat the plague provided that the first outbreak is quickly detected and the virus is prevented from spreading in the wild boar population. We didn’t make it. I hope that after 10 years of fighting ASF, we realize that the protection of pig herds against ASF can only be effective if all biosecurity principles are strictly observed. Controlling the wild boar population and finding and eliminating dead wild boars from the forest environment as quickly as possible is extremely important and significantly reduces the risk of ASFV being introduced into pig herds.
Individual countries deal with ASF differently. There are positive examples (e.g. Belgium or recently Sweden), but there are also negative ones (the Balkans, Romania, and unfortunately to some extent also Poland). According to today’s knowledge and the experience of the past 10 years, what could have been done better to contain the disease in a smaller area of our country?
The weakest link in the fight against ASF in our country, 10 years ago, was the lack of awareness of the threat of ASF spreading among most pig breeders and producers. It took us a lot of time to acquire knowledge about the principles of broadly understood biosecurity. We were unable to reasonably limit the wild boar population. To this day, the problem is to convince all interested parties that in combating ASF in the wild boar population, the most important task is to intensively search forests and fields for the presence of dead wild boars, remove and dispose of them. I have the impression that this most important element of combating ASF is chronically underestimated.
Perhaps the most controversial (although of course consistent with practice) event of this decade was the preventive slaughter of herds of pigs located near outbreaks (e.g. Lublin Province, 2016). Was this action necessary according to current knowledge? After all, preventive slaughter was later abandoned.
The veterinary administration acted in accordance with the regulations still in force today. The purpose of preventive slaughter of pigs is to reduce the possibility of spreading infections. And thus shortening the time of any restrictions related to the appearance of new ASF outbreaks. Nobody knows what the situation would be like if the preventive liquidation of herds had not been carried out. In this respect, we acted as we did everywhere. In Belgium, and many years ago in the Netherlands and France, the spread of ASF was blocked and it was quickly eradicated, primarily thanks to the preventive liquidation of all herds of pigs located close to the outbreak.
The turning point of the entire epizootic seems to be the transfer of the disease to the west of the country (November 2019). More than four years after these events, has it been possible to determine how the disease reached this region and why (unlike Belgium, the Czech Republic or recently Sweden) it was not possible to stop the localized infection in a limited area?
In the vast majority of cases, it was not possible to clearly explain why ASF moved relatively quickly over significant distances in Poland. Importantly, the causes of ASF have not been diagnosed in most outbreaks to date. This should be done on the basis of a thorough epizootic interview, conducted as soon as possible after the outbreak is detected. Unfortunately, for many reasons on both interested parties (the owner of the herd and the interviewing veterinarians – from the veterinary inspection), the collected information and often data from laboratory tests did not allow for a clear determination of how the virus was introduced into the herd. I feel that we often lacked the time and determination necessary to obtain the necessary data.
How do you assess the further development of the situation in the country? We know that in most areas, after the “first wave” passes, the disease becomes endemic. Can we realistically think about freeing the country from ASF?
In my opinion, which I have been presenting for several years, the ineffectiveness in stopping the spread of ASF in the population of pigs and wild boars in the first months and years of the epizootic leads me to the conclusion that the ASF virus from the territory of our country cannot be quickly eradicated. I believe that we can help limit the spread of ASF in the domestic pig population and thus ensure that there will be no further ASF outbreaks among pigs. This depends solely on the determination of pig producers to comply with all biosecurity rules on a daily basis. In this respect, it is important to minimize the risk associated with the circulation of the ASF virus in the population of wild boars residing in the vicinity of facilities keeping pigs; this is the responsibility of the relevant services, not pig producers. Unfortunately, we were not effective in combating the plague, especially among wild boars. It is worth recalling that outbreaks in wild boars – a total of 18,802 – were detected in as many as 14 voivodeships. As for pigs, ASF occurred in 12 voivodeships (532 outbreaks)
Taking into account the above data, it seems that there is currently no greater chance of quickly eradicating ASF in the wild boar population. Unfortunately, in many regions, the ASF virus has become endemic among wild boars and will remain there for years. We know from experience that once a pathogen has entered a population of free-living animals and its presence there has been established, it is almost impossible to eradicate it (we almost managed to do it with the rabies virus in foxes).
In one word: I hope that Poland will relatively soon be recognized as an ASF-free country in the pig population. Unfortunately, not in the wild boar population. The former can be achieved if we do not detect a single ASF outbreak in pigs for the next 12 months.
How do you assess the prospects for developing an ASF vaccine for use in wild boars? Let us recall: tests of this type of preparations began a few months ago in Hungary. Are there any reports regarding the effectiveness of this method in the field and will it potentially be a chance to control the disease in Europe?
I have been involved in issues related to the development of a vaccine against ASF for over 40 years. I remember how intensively and with the use of large resources work on this topic was carried out in Spain, and later in the USA and in many other countries of the world. For many reasons, including the complexity of the virus’s structure, no one has managed to develop a fully effective and safe biopreparation. I have attended many scientific conferences where success in this field was announced. Unfortunately, when the vaccine was transferred from the laboratory to field conditions, the effect was not satisfactory and sometimes even tragic. I believe that one day there will be a breakthrough in this area.
However, it should be remembered that the vaccine is particularly needed to combat ASF in wild boars. I am almost certain that, for epizootic reasons, the EU will not allow the use of the ASF vaccine in pigs; as is the case with vaccines against Aujeszky’s disease and classical swine fever.
For obvious reasons, it will have to be a recombinant vaccine, allowing laboratory differentiation of vaccinated and infected animals. This means that, in addition to the vaccine, an appropriate set of laboratory tests must be developed to distinguish whether the antibodies present in the blood are the result of infection with the field ASF virus or the vaccine strain. You should be aware that it will have to be a vaccine intended for oral vaccination (placed sufficiently deep underground in the environment where wild boars live). As can be seen from the above, there is still a lot to do to make a biopreparation available that can be used to effectively combat ASF.
I know everyone is waiting for the vaccine. Unfortunately, in practice, for now, the most important are biosecurity of pig herds, intensive, active search and removal of dead wild boars and controlling their population.
Thank you for the conversation.
