Transmission of African swine fever virus from infected pigs by direct contact and aerosol routes

In 2014, African swine fever virus (ASFV) was introduced into the Baltic states and Poland. Since then, the disease has continued to spread within these regions, and recently, cases were reported in the Czech Republic and Romania. Currently, there is an increasing risk of ASFV introduction into Western Europe. Hence, there is an urgent need to assess current contingency plans. For this purpose, knowledge of modes-of-transmission and clinical outcome in pigs infected with new European ASFV strains is needed. In the present study, two experiments were conducted in pigs using an isolate of ASFV from Poland (designated here POL/2015/Podlaskie/Lindholm). In both studies, pigs were inoculated intranasally with the virus and contact pigs were exposed to the experimentally infected pigs, either directly (contact within and between pens) or by air. Pigs exposed to the virus by intranasal inoculation, by direct contact to infected animals and by aerosol developed acute disease characterized by viremia, fever and depression. Infectious virus was first detected in blood obtained from the inoculated pigs and then sequentially among the within-pen, between-pen and air-contact pigs. ASFV DNA and occasionally infectious virus was found in nasal-, oral-, and rectal swabs obtained from the pigs, and ASFV DNA was detected in air samples. No anti-ASFV antibodies were detected in sera. In conclusion, the study shows that the currently circulating strain of ASFV can be efficiently transmitted via direct contact and by aerosols. Also, the results provide quantitative transmission parameters and knowledge of infection stages in pigs infected with this ASFV

New legal regulations aimed at controlling the growing problem of antimicrobials resistance in the environment of farm animals

The era of using antibiotics as panaceum for nearly all bacterial diseases is slowly fading to the past. The accelerated increase of antibiotic drug resistance (AMR), in many cases, the loss of an antibiotics effectiveness in both animals and humans, is the main reason. Stringent drug registration procedures, more accurate pre-registration clinical trials are associated with an the increase of registration and manufacturing costs, meaning that less drugs containing new active substances appear on the market. Additionally, medicines for humans have priority over veterinary medicines in access to innovative molecules. European Union legislation responds well to these trends. Since the end of the 1990s, legal acts have appeared to support direction of sustainable development, including sustainable animal production. They apply to all member countries. Initially issued in the form of directives, i.e. recommendations, they have recently been replaced by regulations, i.e. acts with the force of law directly applicable in all Member States. In this article, legal issues related to the aspects of protecting antimicrobials against unreasonable use for livestock are presented and discussed

African swine fever in Poland in 2014-2021 - why we can’t manage?

African swine fever (ASF), has been a major problem for the pig industry in Poland for the last seven years. In spite of measures taken to eradicate the disease in wild boar population, from year to year, new peaks in number of cases are reported. As a consequence, the number of outbreaks in pigs is also growing. The main constrains of ASF eradication in Poland could be high density of wild boar in ASFaffected regions. Other factors, like long-distance ASF spread to new regions of the country, are mainly caused by human activity and a lack of awareness of potential disease harassment to pig production. In the of pig holdings, the only effective measure in ASF prevention is strict biosecurity rules. Despite many efforts to implement these measures, the disease occurred in a number of voivodeships, primarily in eastern Poland, but starting from 2019, also in the western part of the country, close to the German border. Further recommendations to eradicate ASF in Poland or at least minimize the economic loss caused by ASF in pig sector, include effective wild boar management strategies, along with the adoption of necessary biosecurity measures by all pig producers. The only solution for sustainable pig production seems to be the strict collaboration between pig producers, veterinary inspection and hunting association. Similarly, efforts undertaken to develop an effective vaccine should be based on close collaboration between different international research teams

Wild boar as the most important reservoir and vector of transmission of the African swine fever virus; why do we have to restrict their population

Basing on Polish experience of about 5 years (since the presence of the African swine fever (ASF) in this country, starting from February 17th, 2014) and in accordance with literature the importance of the disease in wild boar is charaterised. ASF belongs to the most dangerous, very contagious diseases occurring in domestic swine and wild boar in Eurasia. In Europe, including Russia, Ukraine, Belarus, Lithuania, Latvia, Estonia, Poland, Romania, Hungary, Bulgaria, Czech Republic and Belgium ASF is existing at present and was diagnosed for short time in the frame of the Eurasian pandemy. There is a serious concern of spreading of the virus of ASF (ASFV) to other countries of Europe, not only by wild boar. However the reservoir of ASFV in this animal is playing a very important role in the maintenance of the virus and infection of pigs. Long lasting existence of ASFV in the environmnent is connected with the very high resistance to antiviral environmental factors. Following the lack of an effective immunogenic vaccine against ASF the disease can only be controlled by administrative measures. Additionally the important and recommended procedure is the significant reduction of the wild boar population. Probability of eradication of ASFV from wild boar is increased after adding quick carcass removal simultaneously by respecting biosecurity rules. If effectively implemented, fencing is more useful to delineating zones rather than adding substantially to increased efficiency of ASF control. However, segments of fencing will be particularly usefull in theses areas, where carcasses removal or intensive hunting is difficult to implement

Vaccine against African swine fever

African swine fever (ASF), occurring for many years, is at present the most significant viral disease of swine and wild boar. Despite of the situation, defined as a large epidemic or even pandemic, a vaccine is not yet available, It has been claimed that live, attenuated anti-ASF vaccines are most promising products on the way to control the disease. However the safe and effective vaccine is yet to be obtained. The current status in the field of ASFV vaccine development is encouraging, since ASFV strain(s) have been obtained, that have their virulence genes deleted. Deletion of ASFV genes that inhibit host antiviral type I interferon responses is considered as the most effective strategy to attenuate the virus. Deleted, live vaccinal strain(s) are still able to replicate and encode immunogenic antigens thus induce protective immunity in swine. However, a licensed cell line in which live, attenuated virus (LAV) can be propagated and produced on a large scale, is still not available. Concerning wild boar, the natural reservoir of ASFV, while developing live vaccine for swine protection, rigorous conditions for its safety and efficacy are strongly required

Ethical and economical aspects of wild boar depopulation in attempts of ASF eradication

African swine fever has emerged in Poland on 14 February 2014. Until the end of July 2021, 12 764 outbreaks in wild boar and 400 outbreaks in domestic pigs have been notified. However, despite the reliable experience gathered during the last 7 years of ASF epizootics in Poland, it is not sufficient enough to prevent further spillover of disease to the distant regions of the country. The most significant aspect of ASF eradication in Poland, is the uncontrolled spread of ASF in the wild boar population. It is important to mention, that the emergence of ASF in wild boar population on that scale has not been identified before, during the disease epizootic in any European or Southern America country. Therefore, the measures undertaken to combat ASF in wild boar are not fully efficient. The ethical concerns, related to massive hunting in order to stop further ASF spread, are raised by pro-ecological societies. According to the food production authorities in Europe, including the European Food Safety Agency (EFSA), one of the most important efforts to reduce further ASF spread and risk of its transmission to domestic pig sector, should be intensive reduction of wild boar population. Taking into account the range of economical loss, due to the ASF emergence in domestic pigs and stamping out of hundreds or thousands pregnant sows, seems not to be not considered by a number of people from pro-ecological societies. Meanwhile, the effective reduction of wild boar population is extremely difficult or even impossible. The most stringent measures of wild boar depopulation may only result in a decrease of 50-60 percent of the entire wild boar number. In contrast, the recovery of wild boar population may reach 300 percent annually. There is no doubt, that wild boar for many years, and perhaps decades, will remain in Europe, including Poland, as the main reservoir of ASFV, and thus a constant epizootic threat for swine production. Other agricultural aspects related to the intensive cultivation of maize and rape, should be reconsidered due to their important influence as a convenient and protein-rich natural feed for wild boar. The success of ASF eradication in Belgium and the Czech Republic shed light on the possibilities of control of this disease in any country of Europe. However, taking into account the focal introduction of ASF to the above-mentioned countries, the strategy of ASF eradication in multi-site affected country as Poland, should be carefully modified and applied as an individual approach