Putative Role of Arthropod Vectors in African Swine Fever Virus Transmission in Relation to Their Bio-Ecological Properties

Abstract

African swine fever (ASF) is one of the most important diseases in Suidae due to its significant health and socioeconomic consequences and represents a major threat to the European pig industry, especially in the absence of any available treatment or vaccine. In fact, with its high mortality rate and the subsequent trade restrictions imposed on affected countries, ASF can dramatically disrupt the pig industry in afflicted countries. In September 2018, ASF was unexpectedly identified in wild boars from southern Belgium in the province of Luxembourg, not far from the Franco-Belgian border. The French authorities rapidly commissioned an expert opinion on the risk of ASF introduction and dissemination into metropolitan France. In Europe, the main transmission routes of the virus comprise direct contact between infected and susceptible animals and indirect transmission through contaminated material or feed. However, the seasonality of the disease in some pig farms in Baltic countries, including outbreaks in farms with high biosecurity levels, have led to questions on the possible involvement of arthropods in the transmission of the virus. This review explores the current body of knowledge on the most common arthropod families present in metropolitan France. We examine their potential role in spreading ASF—by active biological or mechanical transmission or by passive transport or ingestion—in relation to their bio-ecological properties. It also highlights the existence of significant gaps in our knowledge on vector ecology in domestic and wild boar environments and in vector competence for ASFV transmission. Filling these gaps is essential to further understanding ASF transmission in order to thus implement appropriate management measures.

Mechanical transmission of African swine fever virus by Stomoxys calcitrans : Insights from a mechanistic model

“…partially fed with infectious blood) transmits the virus to a susceptible pig during a subsequent blood‐feeding attempt (parameter b 1 in the current model). It is also necessary to describe quantitatively the populations of blood‐feeding arthropods in outdoor pig farms and to identify farm characteristics that influence stable fly densities (Bonnet et al., 2020). Indeed, the literature related to the presence of stable flies in pig farms was very scarce, as we found only one publication on the subject (Moon et al., 1987).…”

“…Stable flies feed frequently, with a time duration between two blood meals reported between four hours and four days (Salem et al., 2012). Due to the pain generated by a bite, stable flies’ blood meals are generally interrupted and split into five to 20 attempts, depending on host reactivity (Bonnet et al., 2020). Therefore, it was assumed that stable flies could make on average between two and 10 blood‐feeding attempts during a day, that is between 0.2 and 0.8 hr −1 during the biting activity period, leading to an average of 0.5 hr −1 .…”

9. African swine fever epidemiology, surveillance and control

“…ASFV has been found in hog lice (Haematopinus suis) collected from experimentally infected pigs. Hog lice normally spend their entire brief lives on the same pig and would only be transferred to another pig by close contact (Bonnet et al, 2020). It is unlikely that they have any epidemiological significance.…”

Research priorities to fill knowledge gaps in the control of African swine fever: possible transmission of African swine fever virus by vectors

“…There are very limited quantitative data on host preferences of vectors and their biting rates on both free roaming wild boar near farms and domestic pigs in backyard, medium‐sized or large production farms in ASF‐affected areas (Bonnet et al., 2020). Some blood‐sucking vectors (e.g.…”