Understanding the epidemiology of African Swine
Fever and its impact on smallholders
Edward Okoth, Jocelyn Davies, Noelina Nantima, Jacqueline Kasiiti, Selestine Naliaka, Tracey May and Richard Bishop | Other team members: Beatrice Abutto, Lorna Atieno, Mike Barongo, Edwina Bochere, Eric Fevre, Samu
Machio, Yiheyis Maru, Charles Masembe, Pamela Mulema, Gideon Ndambuki, Milton Ochuka, Edwine Okuge, George Omondi, Esther Omukaga, Cynthia Onzere, Martin Wainana | hub.africabiosciences.org
Methods
Study area is in a priority region for trans-boundary
diseases (TAD) surveillance..
Cross sectional study (July-November 2012) of 683
pig keeping households in 38 villages using a 2-stage
cluster sampling design; stratified, randomised. 1100
pigs from surveyed households measured and
sampled (blood, serum, faeces).
Longitudinal study (December 2012-June 2013) of a
sub-sample of 120 households and pigs with repeat
samples at 3 months and 6 months.
• Opportunistic sampling during ASF outbreaks
• Interviews with actors in farmer networks
• Focus groups testing preliminary findings
• Analyses using complementary tools from molecular
biology, veterinary science, mathematics and social
science.
Results included here are preliminary (May 2013).
Improved understanding of African Swine Fever
(ASF) outbreaks and impacts is emerging from
preliminary analysis of data from our integrated
field study (2012/13). This is a foundation for
designing interventions to reduce ASF risk
among smallholder pig producers. It is also
contributing to international effort on vaccine
development.
Livelihoods
30% of farm households in study area keep pigs.
Diagram is aspatial. Arrows show direction of pig trade. Arrow width is proportional
to number of pigs traded over 12 months. The circle & triangle at each sampled
villagerepresent trade within the village.
Field study area Pig trading networks
Network diagram of pig trading to and from 4
sampled villages located <5km apart.
Key features of pig trading
• Most trade is within the same village
• 85% of trades are with someone known to the pig
owner.
• Trades to strangers are more prevalent during ASF
outbreaks
• Farmers in 10 sampled villages sold pigs across the
Uganda-Kenya border.
ASF incidence and impact
• Farmer interviewees said disease is the biggest risk
to their investment in pigs
• 90% of farmer interviewees had heard of ASF
This document is licensed for use under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 Unsupported License May 2013
Strategic lessons
Delivering science: Integration of multiple disciplines and approaches can help to
understand complex problems.
Developing capacity: Hands-on training in a strong research field team, such as we
achieved in the cross-sectional study, builds adaptable and sustainable research skills.
Influencing decisions: Building good relationships and networks, and early sharing of
research findings with stakeholders, is important for impact from research.
30% of farm households in study area keep pigs.
Sampled pig-keeping households own between 1 and
25 pigs, averaging 2.4 pigs.
Livelihood strategies:
• Breeding piglets for sale to other farmers, earning
USD 10 (Uganda) or USD 13 (Kenya) av. per piglet
• Rearing sub-adults for sale to butchers, earning USD
23 (Uganda) or USD 36 (Kenya) av. per animal after
5-7 months on farm
• Boar service
Average household income varies widely but income
from pigs is consistently low, (average USD 40 pa +/-
16, n=683). This indicates that poorer households are
most reliant on pigs for income.
Women have stronger roles in pig keeping than in
trade, especially in Uganda, but many households
make pig trading decisions collaboratively.
Pig keeping is dynamic. Seasonal food shortages
(January to July) accelerate the rate of pig sales.
Reducing ASF risk to smallholders
Biosecurity is the only available strategy to reduce
ASF risk and is virtually absent on every sampled
farm.
Some farmers say they could work together to
adopt our recommended simple biosecurity
practices, given advice and support.
Managing ASF risk also needs:
• incentives for farmers to report suspected ASF
outbreaks rather than sell their pigs.
• better capability for rapid confirmation of ASF
diagnosis and rapid quarantine response
Stronger market chains and more accessible feed
sources are also important to encourage farmers to
invest more in pig production and realise its
potential for enhancing food security.
Causal factors
Prevalence of ASF virus in healthy pigs is negligible in
the study area, based on molecular and serological
tests of blood samples, indicating that study area
outbreaks are caused by repeated reintroduction of
ASF virus. Tissue sampling and testing (in progress)
may show if the virus is sequestrated in tissues other
than blood.
Preliminary serological evidence suggests that
Ornithodoros ticks may be a factor in transmission
(37% of pigs tested positive for the tick exposure,
n=232, Kenya only). Until these cryptic ticks are caught
and tested it will not be clear if they are actually
carrying ASF virus.
Sales during outbreaks can readily spread infection to
other pigs through direct contact. Farmers in 16
sampled villages reported they had sold pigs during
ASF outbreaks. Seven farmers had pigs on their farm
that they said showed signs of ASF infection at the
time of sale.
Containing outbreaks through quarantine is slow,
hindered by slow confirmation of diagnosis. We have
confirmed ASF virus presence/absence in <2 hours by
running real time PCR in a pen side approach on-
farm. But capability and cost constraints need to be
overcome for application of the rapid diagnosis and
quarantine.
• 90% of farmer interviewees had heard of ASF
• 8.2% said they had ASF on their farm in 2012
• 17% of pigs owned by surveyed households in the 12
months prior to interview (n=644) died before sale or
other disposal. For >50% of these pigs, interviewees
described clinical signs that indicate ASF.
•Three confirmed outbreaks occurred in the study
region July 2012-March 2013.