OS20 Online 8 December Poster

1. 1EuFMD | Open Session special edition | #OS20se
Patrick Bastiaensen
World Organisation for Animal Health
IS AFRICAN SWINE FEVER RETURNING TO AFRICA ?
A back-of-the-envelope analysis of 15 years of WAHIS data.

2. 2EuFMD | Open Session special edition | #OS20se
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Figure 1. Immediate notifications (three-year rolling average)
WAHIS-based* data since its inception in 2005 indicate that
“exceptional epidemiological events” related to ASF in Africa, i.e.
mostly outbreaks, have been reported at a consistent, low rate, until
2017 – 2018, when the number of such “immediate notifications”
started to increase, pointing to a higher number of outbreaks of an
epizootic nature, either in new territories, i.e. new areas within
countries or introduced into hitherto free countries.
(*) OIE World Animal Health Information System
Several hypotheses have been explored to
explain this apparent increase, looking at whether
this could be a reflux of the Georgia strain into
Africa, e.g. from Europe or Asia, or whether other
explanations could be considered, i.e. increased
awareness of the ASF situation in a traditionally
enzootic ‘silent’ system, or a genuine increase in
domestic outbreaks, possibly due to an increase
in the domestic pig population in Africa.

3. 3EuFMD | Open Session special edition | #OS20se
Map 1. Map of countries
reporting ASF through
immediate notifications to the
OIE (WAHIS) since 2005.
Circled are Cabo Verde
(west) and Mauritius (east).
When studying the WAHIS six-monthly
reports, where countries report on ASF
mostly as an enzootic disease, the picture
is blurred by a small number of (often small)
countries, reporting a high number of
outbreaks for a while and then interrupting
these reports, without clear indication of the
epidemiological evolution, e.g. eradication.
A second analysis of population numbers,
submitted as part of the WAHIS annual
reports, reveals that some countries having
reported ASF outbreaks have experienced
spectacular increases in pig population
numbers over the last decade, as high as
+500% in Malawi, +600% in Senegal and
+2,400% in Chad (55% on average).
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** Penrith, Mary-Louise, Duarte Bastos, Armanda, Etter, Eic M.C. &
Beltrán-Alcrudo, Daniel (2019). Epidemiology of African swine fever
in Africa today: Sylvatic cycle versus socio‐economic imperatives.
Transbound Emerg Dis. 2019;66:672–686. DOI:
10.1111/tbed.13117
Combined with the fact that genotype II, linked to the Georgia
strain, in a 2018 Africa review by Penrith et al.** is still only
being reported in the initial countries-of-origin, along with
Mauritius (2007 – 2008 outbreaks), leads one to conclude that
the higher number of outbreaks is likely the result of an
unprecedented increase in pigs being farmed on the continent.

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8, 10, 15, 17 December 2020
EuFMD / Open Session