Behaviour of free ranging wild boar towards their dead fellows: potential implications for the transmission of African swine fever.

Carolina Probst,Anja Globig,Bent Knoll,Franz J Conraths,Klaus Depner

doi:10.1098/rsos.170054

Abstract

The behaviour of free ranging wild boar (Sus scrofa) towards carcasses of their conspecifics potentially infected with African swine fever (ASF) may significantly influence the course of an ASF epidemic. This study aims to better understand the behaviour of wild boar towards their dead fellows. Thirty-two wild boar carcasses on nine study sites in northeast Germany were monitored under field conditions by photo-trapping from October 2015 until October 2016. During this period, a total of 122 160 pictures were taken, thereof 16 111 pictures of wild boar. In both winter and summer, wild boar seemed to be particularly interested in the soil next to and underneath the carcasses. About one third of the visits of wild boar led to direct contact with dead conspecifics. The contacts consisted mostly in sniffing and poking on the carcass. Under the given ecological and climatic conditions, there was no evidence for intra-species scavenging. However, piglets were observed several times chewing bare bones once skeletonization of the carcasses was complete. It must be assumed that all these types of contact may represent a risk of transmission. Both the high tenacity of ASF virus and the long time wild boar carcasses can remain in the environment, allow the persistence of the virus for several months or even years. We therefore consider the rapid detection and removal (or destruction on the spot) of contaminated carcasses as an important control measure against ASF in wild boar.

Highlights

African swine fever (ASF) is a notifiable viral disease of domestic and feral pigs (Sus scrofa), and is a major threat to animal health and trade for many European countries [1]
An ASF epidemic currently occurs in northeastern parts of the European Union and has spread locally in the wild boar population
Since the detection of the first ASF case in wild boar in Lithuania in late January 2014, more than 4180 cases have been reported in the Baltic States (Estonia, Latvia, Lithuania) and Poland [2]

Summary

Introduction

African swine fever (ASF) is a notifiable viral disease of domestic and feral pigs (Sus scrofa), and is a major threat to animal health and trade for many European countries [1]. An ASF epidemic currently occurs in northeastern parts of the European Union and has spread locally in the wild boar population. Most ASF positive wild boar were not detected by active surveillance (hunted), but by passive surveillance (animals found dead) [3]. Two main scenarios were forecasted: due to the high virulence of the virus, ASF could spread so rapidly that it would quickly exhaust the susceptible population and fade out, or it could cause an epidemic wave that rapidly moves westwards. For the spread of ASF into free areas, direct contact with contaminated carcasses is regarded as one of the most important risk factors [8,9,10]

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