Estimating the Basic Reproductive Number (R0) for African Swine Fever Virus (ASFV) Transmission between Pig Herds in Uganda.
African swine fever (ASF) is a highly contagious, lethal and economically devastating haemorrhagic disease of domestic pigs. Insights into the dynamics and scale of virus transmission can be obtained from estimates of the basic reproduction number (R0). We estimate R0 for ASF virus in small holder, free-range pig production system in Gulu, Uganda. The estimation was based on data collected from outbreaks that affected 43 villages (out of the 289 villages with an overall pig population of 26,570) between April 2010 and November 2011. A total of 211 outbreaks met the criteria for inclusion in the study. Three methods were used, specifically; (i) GIS- based identification of the nearest infectious neighbour based on the Euclidean distance between outbreaks, (ii) epidemic doubling time, and (iii) a compartmental susceptible-infectious (SI) model. For implementation of the SI model, three approaches were used namely; curve fitting (CF), a linear regression model (LRM) and the SI/N proportion. The R0 estimates from the nearest infectious neighbour and epidemic doubling time methods were 3.24 and 1.63 respectively. Estimates from the SI-based method were 1.58 for the CF approach, 1.90 for the LRM, and 1.77 for the SI/N proportion. Since all these values were above one, they predict the observed persistence of the virus in the population. We hypothesize that the observed variation in the estimates is a consequence of the data used. Higher resolution and temporally better defined data would likely reduce this variation. This is the first estimate of R0 for ASFV in a free range smallholder pig keeping system in sub-Saharan Africa and highlights the requirement for more efficient application of available disease control measures.
Department of Academic Registrar (ICT Division), Makerere University, Kampala, Uganda; International Livestock Research Institute, Nairobi, Kenya.
Mike B
MB
Barongo
Department of Disease Control and Epidemiology, National Veterinary Institute, Uppsala, Sweden.
Karl
K
Ståhl
International Livestock Research Institute, Nairobi, Kenya.
Bernard
B
Bett
International Livestock Research Institute, Nairobi, Kenya.
Richard P
RP
Bishop
International Livestock Research Institute, Nairobi, Kenya.
Eric M
EM
Fèvre
Ministry of Agriculture, Animal Industry and Fisheries, Entebbe, Uganda.
Tony
T
Aliro
International Livestock Research Institute, Nairobi, Kenya.
Edward
E
Okoth
Department of Biological Sciences, College of Natural and applied Sciences, Makerere University, Kampala, Uganda.
Charles
C
Masembe
Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.
Darryn
D
Knobel
International Livestock Research Institute, Nairobi, Kenya; Department of Mathematics, Faculty of Science, Gulu University, Gulu, Uganda.
Amos
A
Ssematimba
D000357:African Swine Fever / Q000453:epidemiology* / Q000635:transmission*; D000358:African Swine Fever Virus; D000818:Animals; D050936:Basic Reproduction Number; D004196:Disease Outbreaks; D015233:Models, Statistical; D012621:Seasons; D034421:Sus scrofa; D013552:Swine; D014454:Uganda / Q000453:epidemiology