Do Seropositive Wild Boars Pose a Risk for the Spread of African Swine Fever? Analysis of Field Data from Latvia and Lithuania

Abstract

In 2020, ASF occurred in wild boars throughout Latvia and Lithuania, and more than 21,500 animals were hunted and tested for the presence of the virus genome and antibodies in the framework of routine disease surveillance. The aim of our study was to re-examine hunted wild boars that tested positive for the antibodies and negative for the virus genome in the blood (n = 244) and to see if the virus genome can still be found in the bone marrow, as an indicator of virus persistence in the animal. Via this approach, we intended to answer the question of whether seropositive animals play a role in the spread of the disease. In total, 2 seropositive animals out of 244 were found to be positive for the ASF virus genome in the bone marrow. The results indicate that seropositive animals, which theoretically could also be virus shedders, can hardly be found in the field and thus do not play an epidemiological role regarding virus perpetuation, at least not in the wild boar populations we studied.

Landscape connectivity for predicting the spread of ASF in the European wild boar population

“…In fact, it must be highlighted that there are other factors that can promote the appearance and spread of ASF, for example, contaminated pork products transported by humans and consumed by wild boar can generate new notifications at great distances. In that sense, the inclusion of epidemiological models for both wild boar and domestic pigs, such as transmission dynamics 8 , wild boar—domestic pig interface 11 , 39 , as well as risk of exposure assessment analyses 30 – 32 would be highly beneficial to improve control and prevention strategies. Other transmission routes, apart from the natural spread of the disease in wild boar studied here, should be considered for such ASF plans 42 .…”

“…The intensive agriculture covers were split into two classes depending on the distance to the wild boar’s preferred covers (forests and natural areas, and extensively used farmland). We associated a lower resistance value to the agricultural areas within 2 km of the preferred covers, while larger resistance values to those farther away to consider the frequent use of agroforest mosaic habitats by the species 11 – 39 , and assuming a mean home range of 2 km radius 26 . The specific resistance values of each class can be seen in Table S1 .…”