Transmission routes of African swine fever virus to domestic pigs: current knowledge and future research directions

African swine fever (ASF) is a major threat to the pig industry in Europe. Since 2007, ASF outbreaks have been ongoing in the Caucasus, Eastern Europe and the Baltic countries, causing severe economic losses for many pig farmers and pork producers. In addition, the number of ASF cases in wild boar populations has dramatically increased over the past few years. Evidence supports direct contact with infectious domestic pigs and wild boars, and consumption of contaminated feed, as the main transmission routes of ASF virus (ASFV) to domestic pigs. However, significant knowledge gaps highlight the urgent need for research to investigate the dynamics of indirect transmission via the environment, the minimal infective doses for contaminated feed ingestion, the probability of effective contacts between infectious wild boars and domestic pigs, the potential for recovered animals to become carriers and a reservoir for transmission, the potential virus persistence within wild boar populations and the influence of human behaviour for the spread of ASFV. This will provide an improved scientific basis to optimise current interventions and develop new tools and strategies to reduce the risk of ASFV transmission to domestic pigs.ISSN:0042-490

Scientific Opinion on African swine fever

The risk for endemicity of ASF in the eastern neighbouring countries of the EU and spread of ASFV to unaffected areas was updated until 31/01/2014. The assessment was based on a literature review and expert knowledge elicitation. The risk that ASF is endemic in Georgia, Armenia and the Russian Federation has increased from moderate to high, particularly due to challenges in outbreak control in the backyard production sector. The risk that ASFV will spread further into unaffected areas from these countries, mainly through movement of contaminated pork, infected pigs or contaminated vehicles, has remained high. In Ukraine and Belarus, the risk for ASF endemicity was considered moderate. Although only few outbreaks have been reported, which have been stamped out, only limited activities are ongoing to facilitate early detection of secondary spread. Further, there is a continuous risk of ASFV re-introduction from the Russian Federation, due to transboundary movements of people, pork or infected wild boar. The number of backyard farms is greatest in the west of Ukraine and westwards spread of ASFV could result in an infected area near the EU border, difficult to control. In Georgia, Armenia and the Russian Federation, the risk for endemicity of ASF in the wild boar population is considered moderate, mainly due to spill-over from the domestic pig population, whereas in Ukraine and Belarus this was considered to be low. In those areas in the Russian Federation where wild boar density is high, this risk may be higher. Intensive hunting pressure in affected wild boar populations may increase the risk for spread, possibly with severe implications across international borders. The risk for different matrices to be infected/contaminated and maintain infectious ASFV at the moment of transportation into the EU was assessed and ranged from very high for frozen meat, to very low for crops

Basic reproduction number for certain infectious porcine diseases: estimation of required level of vaccination or depopulation of susceptible animals

Basic reproduction number (R0) is one of the fundamental quantitative characteristics in epidemiology of infectious human and animal diseases. This parameter reflects the biological properties of the infectious agent, the social and economic aspects of animal husbandry, natural factors associated with the habitat of the animal population invaded by the virus (microorganism), as well as the effectiveness of methods selected for infection control, in particular, the implementation of preventive measures; it also allows foreseeing the number and probability of occurrence of new secondary outbreaks in the area at risk of the disease spread. The paper presents data on the estimation of basic reproduction number (R0) for a range of infectious porcine diseases. A systematic analysis has been undertaken with respect to the publications available on the estimation of R 0 for various virus isolates of African swine fever, classical swine fever, foot-and-mouth disease, porcine reproductive and respiratory syndrome, Aujeszky’s disease, hepatitis E, encephalomyocarditis, porcine circovirus type 2, as well as pleuropneumonia associated with Actinobacillus pleuropneumoniae, and diseases caused by pathogenic isolates of Mycoplasma hyopneumoniae. Based on the obtained R0 values, recommendations for the veterinary services are made on preventive vaccination of pigs against the above mentioned diseases in the areas at risk of infection spread. The necessary conditions for wild boar depopulation aimed to prevent new African swine fever outbreaks are identified, namely, the elimination of at least 75% of the wild boar population living in the risk zone within the period of time equal to one infectious period

EXPERT RISK ASSESSMENT OF FMD INTRODUCTION TO THE RUSSIAN FEDERATION FROM INFECTED COUNTRIES

Predictive assessment of possible risks of FMD introduction from neighboring countries to the territory of eight RF Federal Districts was presented. The risk quantitative parameters were determined by experts, specialists in the field of FMD epidemiology. To implement the expert survey method most significant routes of infection introduction to the RF were determined. The experts performed FMD introduction risk assessment for each federal district and determined its score. As a result of statistical analysis the greatest probability was determined for the Far-Eastern Federal District. The North Caucasus and Siberian Federal Okrugs demonstrate lower probability. Basing on the obtained data the major routes of FMD introduction to the territory of the country were determined. Preventive vaccination of susceptible animal population is carried out in order to prevent FMD occurrence and spread in the zones at risk of its introduction. It is aimed at FMD outbreak prevention in the specified RF Subjects by inducing protective immunity in at least 81% of immunized cattle and at least 95% of immunized pigs

Spatio-temporal modeling of the African swine fever epidemic in the Russian Federation, 2007-2012

© 2014 Elsevier Ltd. In 2007 African swine fever (ASF) entered Georgia and in the same year the disease entered the Russian Federation. From 2007 to 2012 ASF spread throughout the southern region of the Russian Federation. At the same time several cases of ASF were detected in the central and northern regions of the Russian Federation, forming a northern cluster of outbreaks in 2011. This northern cluster is of concern because of its proximity to mainland Europe. The aim of this study was to use details of recorded ASF outbreaks and human and swine population details to estimate the spatial distribution of ASF risk in the southern region of the European part of the Russian Federation. Our model of ASF risk was comprised of two components. The first was an estimate of ASF suitability scores calculated using maximum entropy methods. The second was an estimate of ASF risk as a function of Euclidean distance from index cases. An exponential distribution fitted to a frequency histogram of the Euclidean distance between consecutive ASF cases had a mean value of 156. km, a distance greater than the surveillance zone radius of 100-150. km stated in the ASF control regulations for the Russian Federation. We show that the spatial and temporal risk of ASF expansion is related to the suitability of the area of potential expansion, which is in turn a function of socio-economic and geographic variables. We propose that the methodology presented in this paper provides a useful tool to optimize surveillance for ASF in affected areas