African swine fever and experiences from affected countries

Although only two years have passed since the last IPVS congress in Chongqing (China), the global swine industry has been completely transformed by the emerged threat of African swine fever (ASF). The introduction of ASF to South East Asia, especially to China, has altered perceptions of ASF. On one hand, the massive scale of the outbreak in the People Republic of China (PRC) has given the perception that the situation in many countries is not so severe. On the other, China's huge effort in ASF outbreak mitigation has dramatically increased attention to the ASF problem and the number of research projects in the country: in 2019 alone, more ASF diagnostic kits have been developed and applied to the field conditions than in previous over 100 years. These new approaches to ASF diagnostics and surveillance need to be assessed. 

Several recent publications suggest that commercial ASF vaccines will be soon available. Now is the time to start discussions with the swine industry on possible strategies for ASF vaccination and the future role of ASF vaccines as a measure for ASF. 

2018-2019 brought a little new to ASF epidemiology. The experience of affected countries confirms again and again that low biosecurity level of pig farms continues to play the most crucial role in introducing and spreading of ASF to new areas. In China, the increasing risk of ASF introduction and the tremendous consequences were evident for many years prior to the outbreak. 

The last two years did indicate a paradox of biosecurity issues. All agree that to reduce ASF risks, biosecurity across the industry needs to be improved, including a reduction in the number of backyard farms. However, we saw very few examples of countries sufficiently investing in pig production systems prior to ASF introduction. Still, adequate changes in the pig industry began only after ASF spread within the country. Such reactive policies only multiply the costs of upgrading the biosecurity infrastructure of the industry, including losses from ASF itself. From the epidemiological point of view, ASF is much easier to control and eradicate, especially in the domestic pig population, than are other significant swine diseases - PPRS for example. But the number of effort and efficacy to control ASF depends mostly on economic drivers in the country and/or region. 

Finally, ASF reporting needs to consider the potential for transboundary spread of ASF through and in wild boar. Recent situations in Indonesia and Denmark, where pig carcasses floating on the sea reached the coasts of ASFfree countries, did not affect the ASF free status of those countries. This kind of cases needs to be foreseen by legislations. Given the situation, it might be effective to provide an incentive for countries to stimulate them to be transparent when reporting potential cases of ASF. 

African swine fever outbreaks have been reported in Russia since 2007. Despite all measures taken, 1527 outbreaks have been detected from the initial outbreaks in Russia to the end of 2019 - including 912 in domestic pig populations and 615 in wild boars. Recently, some measures have been taken in the Russian Federation to reduce the morbidity from ASF. A decree by the Government of the Russian Federation has been issued to enact a plan for ASF control. The veterinary rules and regulations have been updated by the order of the Ministry of Agriculture of the Russian Federation. These rules include requirements for keeping pigs, diagnostics, preventive and control measures, and other restrictions aimed at preventing the spread and elimination of ASF outbreak. The main requirements presented in published documents include the organization of full cycle of pig production, ensuring a high level of biosecurity at all enterprises on breeding and slaughtering of pigs and processing of pig production, traceability of animals and products, reduction the density of wild boar population in the threatened zones, and mandatory reporting to the state veterinary service about all cases of suspicion of ASF. The electronic traceability system “Mercury” of livestock products has been launched. Despite these recent mitigation efforts in Russia, the foci of ASF have continued to expand. 

In 2016, in the territory of the Russian Federation, ASF was detected in domestic pigs in 215 localities (239 foci) in 26 of 85 regions of Russia, and there were 527 cases of ASF in wild boar (65 locations, infected objects) in 17 regions. According to the Federal Service for Veterinary and Phytosanitary Surveillance, the economic losses were estimated at 24.8 million Euros. In 2017, 150 affected locations (165 foci) were notified in domestic pigs in 23 regions of Russia, and there were 330 cases of ASF in wild boar (102 affected locations and 11 foci). 

In 2018, the number of outbreaks in domestic pigs reduced: 56 affected locations and 21 infected objects in 18 regions of Russia and 143 cases in wild boar. However, in 2019 the situation in domestic pigs got worse (79 notifications). It was caused mainly by ASF outbreaks emerged in the Far East, in the area bordering with China. Primary outbreaks were registered mostly in the backyards of the Amur region, and later in Primorsk Territory, Khabarovsk region, and the Jewish Autonomous Region. ASF has been detected both in domestic and wild bigs populations. According to the regional veterinary services, the primary causes of rapid ASF spread in Russian territories bordering with China include the low level of biosecurity of pig farms, the high number of completely unprotected backyards and high density of wild boar.

At the Federal Research Centre for Virology and Microbiology, we sequenced the genomes of ASFV isolates from this area. Sequenced genome regions of the isolates were identical to those from ASFV isolates from Belgium, China, and Georgia available in Genbank.

It is also worth mentioning that in some regions in wild boar of the same area the period between ASF notifications is more than 6 months, and this phenomenon cannot be explained by the reintroduction of the virus.

Since the beginning of the epidemic, another serious problem related to ASF spread is the uncontrolled movement of pork products contaminated with the virus (or its genome) from affected (which are not always declared by the owner to the veterinary service timely) pig farms to long-distant areas. The presence of ASFV DNA can be considered as an indicator of the efficiency of the ASF control system in a country. In 2019 in the Russian Federation, there were 2 cases when ASFV genome DNA was spread widely by pork products. In the first case from (October 2019), the batches of pork products produced from infected pigs were shipped from Kaluga region to 39 regions of Russia. In another case, bathes of pork products delivered from infected pigs and containing ASFV DNA were shipped from the Stavropol region to other 18 regions of Russia.

After more than ten years of African swine fever virus circulation in Russia, the national pork industry is in very good shape. The latest USDA forecasts suggest that Russia’s domestic pork production is set to increase by 2.7% year-on-year in 2019, to finish at 3.24 million tonnes (cwe). Consumption is predicted to be slightly above this during 2019 at 3.31m tonnes (cwe). 

In 2020, the USDA anticipates that Russia’s domestic production will grow to equal its domestic consumption levels. Both are forecast to reach 3.33m tonnes in 2020. The domestic pig herd in Russia is forecast to reach 23.6 million head during 2019, making it one of the largest pig herds globally. 

Past years confirm that ASF is a "trade" disease, and for many countries without export ambitions, the role of ASF is overestimated. 

Based on the information from the OIE reporting system, there have been no recent cases of ASF reported in Transcaucasian Countries and Belarus. Recently, the Czech Republic and Estonia declared their freedom from the disease in wild boar and domestic pig populations. Based on that, we could conclude that the eradication ASF can be achieved even without a vaccine. 

Recent studies have shown that all the field strains isolated in the Russian Federation in 2019 induce in bioassays the same high level of pathogenesis and acute (up to 21 days, including incubation period) course of the disease in domestic wild pigs as Georgia 2007 reference strain does. Given such short length of the course of the disease, two possible explanations for the phenomenon of 6-months interval between detections in the same wild boar subpopulation can be proposed: 1) unknown reservoirs of the virus in the environment or 2) the weakness of the surveillance system and hidden circulation of the virus in this area. 

As some recent surveys have shown, there are still many knowledge gaps about ASF. Many scientific projects and scientists all around the world are working actively to fill in these gaps. To consolidate these research efforts the Global African Swine Fever Research Alliance (GARA) was established in 2014. GARA has a mission of establishing and sustaining global research partnerships that will generate scientific knowledge and tools to contribute to the successful prevention, control and where feasible eradication of African Swine Fever (ASF). GARA aims to expand ASF research collaborations worldwide and maximize the use of resources and expertise to achieve its five strategic goals: 

1. To facilitate research collaborations and serve as a communication gateway for the global ASF research community. 

2. To conduct strategic research to increase our understanding of ASF. 

3. To develop the next generation of control measures and strategies for their application. 

4. To determine the social and economic impacts of the new generation of improved ASF control 

5. To provide evidence to inform the development of policies for the safe trade of animals and animal products in ASF-endemic areas. 

Additional information on the GARA Project and the work of the Alliance can be found on the website: http://www.ars.usda.gov/GARA.