What makes ASF so difficult to eradicate?

Based on experiences, knowledge and data gained from the current epidemic this review highlights some recent developments in the epidemiological understanding of ASF.
calendar icon 18 January 2019
clock icon 3 minute read

Authors Erika Chenais, Klaus Depner, Vittorio Guberti, Klaas Dietze, Arvo Viltrop and Karl Ståhl

The qualities of the three epidemiological traits contagiousity, tenacity, and case fatality rate make ASFV efficient in both persistence and transmission. The high tenacity ensures long term persistence in the environment, high case fatality rate makes the virus largely available, and the relatively low contagiousity prevents the complete depletion of the host population. The interaction of these three parameters maximise both local persistence and geographical spread of the virus making its eradication a challenge.

The disease does not show a typical epidemic pattern with either self-limiting localised epidemics or wider spread through an epidemic wave [1]. Both these patterns would probably require higher contagiousity. The patterns usually observed in endemic settings, with a constant circulation or presence of pathogens in the target population [1], is also not observed.

With a high case fatality rate and the probable absence of a long-lasting carrier status, ASFV cannot be maintained independently in an active circulation over a longer time despite the high reproductive capacity of wild boar. This leaves us the epidemiological scenario of a reservoir-facilitated perpetuation leading to an endemic state.

With the absence of the reservoir hosts, African wild suids or Ornithodoros spp. ticks, the habitat as such, including the contaminated carcasses have to be considered as pathogen reservoir leading to the observed endemic setting with extended transmission intervals.

Apart from the wild boar population and the habitat, the current epidemic recognises humans as the main responsible for both long distance transmission and virus introduction in the domestic pig farms. Thus it becomes crucial to include social science when planning prevention-, control-, or eradication measures. By considering only the biological particularities of the disease, contagiousity, tenacity and case fatality rate, but ignoring the human aspects, the epidemic will not be controlled.

Erika Chenais, Klaus Depner, Vittorio Guberti, Klaas Dietze, Arvo Viltrop and Karl Ståhl (2019). Epidemiological considerations on African swine fever in Europe 2014–2018. Porcine Health Management, 5:6.

[1] Dicker R, Coronado F, Koo D, Parrish RG. Principles of epidemiology in public health practice. Atlanta: US Department of Health and Human Services; 2006.

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