A Review of African Swine Fever and the Potential for Introduction into the United States and the Possibility of Subsequent Establishment in Feral Swine and Native Ticks
African swine fever (ASF) is caused by African swine fever virus (ASFV), which can cause substantial morbidity and mortality events in swine. The virus can be transmitted via direct and indirect contacts with infected swine, their products, or competent vector species, especially Ornithodoros ticks. Africa and much of Eastern Europe are endemic for ASF; a viral introduction to countries that are currently ASF free could have severe economic consequences due to the loss of production from infected animals and the trade restrictions that would likely be imposed as a result of an outbreak. We identified vulnerabilities that could lead to ASFV introduction or persistence in the United States or other ASF-free regions. Both legal and illegal movements of live animals, as well as the importation of animal products, byproducts, and animal feed, pose a risk of virus introduction. Each route is described, and current regulations designed to prevent ASFV and other pathogens from entering the United States are outlined. Furthermore, existing ASFV research gaps are highlighted. Laboratory experiments to evaluate multiple species of Ornithodoros ticks that have yet to be characterized would be useful to understand vector competence, host preferences, and distribution of competent soft tick vectors in relation to high pig production areas as well as regions with high feral swine (wild boar or similar) densities. Knowledge relative to antigenic viral proteins that contribute to host response and determination of immune mechanisms that lead to protection are foundational in the quest for a vaccine. Finally, sampling of illegally imported and confiscated wild suid products for ASFV could shed light on the types of products being imported and provide a more informed perspective relative to the risk of ASFV importation.
Key Points
• African swine fever (ASF) is caused by African swine fever virus (ASFV), which is the only known arthropod-borne DNA virus.
• Currently, ASF is not present in the United States, but it is a high consequence, foreign, notifiable swine disease, and the economic consequences associated with an introduction could be catastrophic.
• The virus is endemic in many parts of the world, including most of sub-Saharan Africa, the island of Sardinia, and parts of the Caucasus region and Eastern Europe.
• The routes of concern for the introduction of ASF into the United States are the legal or illegal importation of live animals (or their products) or a bioterrorism event.
• Introduction or spillover events from domestic swine into feral swine populations would substantially complicate the eradication process as would infection in native Ornithodoros tick species.
• Currently, there is no ASF vaccine approved for use.
• Future research should involve (1) laboratory feeding experiments to evaluate multiple species of North American Ornithodoros ticks that have yet to be characterized, (2) expanded analyses to explore the distribution and host preferences of competent soft tick vectors in relation to high pig production regions as well as high densities of feral swine, (3) characterization of antigenic viral proteins that contribute to a host immune response and determination of immune mechanisms that lead to protection, (4) expanding classical swine fever slaughter surveillance and random blood collections to include screening for ASFV, in the event of an increased risk of viral introduction, and (5) sampling of wild suid products that were illegally imported and confiscated for the detection of ASFV.
Authors: Vienna R. Brown, Sarah N. Bevins
Source: https://www.frontiersin.org/
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