African swine fever (ASF) is a contagious viral disease, which can cause up to 100% mortality among domestic pigs. In Uganda there is paucity of information on the epidemiology of the disease, hence a study was carried out to elucidate the patterns of ASF outbreaks. Spatial and temporal analyses were performed with data collected monthly by the district veterinary officers (DVOs) and sent to the central administration at MAAIF from 2001 to 2012. Additionally, risk factors and the associated characteristics related to the disease were assessed based on semistructured questionnaires sent to the DVOs. A total of 388 ASF outbreaks were reported in 59 districts. Of these outbreaks, 201 (51.8%) were reported in districts adjacent to the national parks while 80 (20.6%) were adjacent to international borders. The number of reported ASF outbreaks changed over time and by geographical regions; however, no outbreak was reported in the North-Eastern region. ASF was ranked as second most important disease of pigs, and it occurred mostly during the dry season ( ). Pig movements due to trade (OR 15.5, CI 4.9–49.1) and restocking (OR 6.6, CI 2.5–17.3) were the major risk factors. ASF control strategies should focus on limiting pig movements in Uganda. 1. Introduction African swine fever (ASF) is a highly fatal disease of domestic pigs and can cause mortality of up to 100% of affected pigs [1]. The disease is caused by double-stranded DNA virus with an icosahedral symmetry that belongs to genus Asfivirus and family Asfarviridae [2]. Since its first description in Kenya in the early 1920s [3], the disease has been reported in several countries around the world, remaining endemic in Sardinia, and in 2007 outbreaks was reported in Georgia, Russia, and neighbouring countries [4]. The epidemiology of ASF is complex, transmission is direct and vector-borne, and the disease has well-recognized sylvatic and domestic cycles. In sub-Saharan Africa, ASFV is maintained by long-term, inapparent infection of wildlife hosts such as bush pigs (Potamochoerus porcus) and warthogs (Phacochoerus africanus) which are infected via tick bites of the argasid tick vector (Ornithodoros complex) [5]. ASF is highly contagious and is transmitted by direct contact between infected pigs and susceptible ones or by contact with or ingestion of infectious secretions/excretions. The virus is highly resistant in tissues and the environment, contributing to its transmission over long distances through swill feeding and fomites (e.g., contaminated material, vehicles, or visitors to pig premises) [6]. In
References
[1]
M.-L. Penrith, G. R. Thomson, A. D. S. Bastos et al., “An investigation into natural resistance to African swine fever in domestic pigs from an endemic area in southern Africa,” OIE Revue Scientifique et Technique, vol. 23, no. 3, pp. 965–977, 2004.
[2]
L. K. Dixon, J. M. Escribano, C. Martins, D. L. Rock, M. L. Salas, and P. J. Wilkinson, “Asfarviridae,” in Virus Taxonomy, C. M. Fauquet, M. A. Mayo, J. Maniloff, U. Desselberger, and L. A. Ball, Eds., Report of the ICTV, London, UK, 8th edition, 2005.
[3]
R. E. Montgomery, “On a form of swine fever occurring in British East Africa (Kenya Colony),” Journal of Comparative Pathology, vol. 34, pp. 159–191, 1921.
[4]
R. J. Rowlands, V. Michaud, L. Heath et al., “African swine fever virus isolate, Georgia, 2007,” Emerging Infectious Diseases, vol. 14, no. 12, pp. 1870–1874, 2008.
[5]
W. Plowright, J. Parker, and M. A. Peirce, “African swine fever virus in ticks (Ornithodoros moubata, murray) collected from animal burrows in Tanzania,” Nature, vol. 221, no. 5185, pp. 1071–1073, 1969.
[6]
P. J. Wilkinson, “African swine fever virus,” in Virus Infections of Porcines, M. B. Pensaert, Ed., pp. 17–35, Elsevier Science Publishers, Amsterdam, The Netherlands, 1989.
[7]
B. A. Lubisi, A. D. S. Bastos, R. M. Dwarka, and W. Vosloo, “Molecular epidemiology of African swine fever in East Africa,” Archives of Virology, vol. 150, no. 12, pp. 2439–2452, 2005.
[8]
E. C. Anderson, G. H. Hutchings, N. Mukarati, and P. J. Wilkinson, “African swine fever virus infection of the bushpig (Potamochoerus porcus) and its significance in the epidemiology of the disease,” Veterinary Microbiology, vol. 62, no. 1, pp. 1–15, 1998.
[9]
D. Muhanguzi, V. Lutwama, and F. N. Mwiine, “Factors that influence pig production in Central Uganda—case study of Nangabo Sub-County, Wakiso District,” Veterinary World, vol. 5, no. 6, pp. 346–351, 2012.
[10]
UBOS/MAAIF, Uganda Census of Agriculture 2008/2009, 2009.
[11]
C. P. K. Basalirwa, “Delineation of Uganda into climatological rainfall zones using the method of principal component analysis,” International Journal of Climatology, vol. 15, no. 10, pp. 1161–1177, 1995.
[12]
R. Likert, “A technique for the measurement of attitudes,” Archives of Psychology, vol. 22, no. 140, pp. 1–55, 1932.
[13]
J. M. Bland and D. G. Altman, “Statistics notes. The odds ratio,” British Medical Journal, vol. 320, no. 7247, article 1468, 2000.
[14]
C. Rutebarika and A. O. Ademun, Overview of African Swine Fever (ASF) Impact and Surveillance in Uganda. During African Swine Fever Diagnostics, Surveillance, Epidemiology and Control: Identification of Researchable Issues Targeted To the Endemic Areas Within Sub-Saharan Africa, 2011.
[15]
Office International des Epizooties (OIE), Manual of Diagnostic Tests and Vaccines For Terrestrial Animals, 2010.
[16]
P. J. Wilkinson, “The persistence of African swine fever in Africa and the Mediterranean,” Preventive Veterinary Medicine, vol. 2, no. 1–4, pp. 71–82, 1984.
[17]
M.-L. Penrith and W. Vosloo, “Review of African swine fever: transmission, spread and control,” Journal of the South African Veterinary Association, vol. 80, no. 2, pp. 58–62, 2009.
[18]
A. Muwonge, H. M. Munang'andu, C. Kankya et al., “African swine fever among slaughter pigs in Mubende district, Uganda,” Tropical Animal Health and Production, vol. 44, no. 7, pp. 1593–1598, 2012.
[19]
L. Bj？rnheden, “A study of domestic pigs, wild suids and ticks as reservoirs for African swine fever virus in Uganda,” Institutionen F？r Biomedicin Och Veterin？r Folkh？lsovetenskap, 2011.
[20]
J. Ravaomanana, F. Jori, L. Vial et al., “Assessment of interactions between African swine fever virus, bushpigs (Potamochoerus larvatus), Ornithodoros ticks and domestic pigs in north-western Madagascar,” Transboundary and Emerging Diseases, vol. 58, no. 3, pp. 247–254, 2011.
[21]
J. M. Sánchez-Vizcaíno, L. Mur, and B. Martínez-López, “African swine fever: an epidemiological update,” Transboundary and Emerging Diseases, vol. 59, no. 1, pp. 27–35, 2012.
[22]
S. Costard, B. Wieland, W. de Glanville et al., “African swine fever: how can global spread be prevented?” Philosophical Transactions of the Royal Society B, vol. 364, no. 1530, pp. 2683–2696, 2009.
[23]
E. Tejlar, Outbreaks of African Swine Fever in Domestic Pigs in Gulu District, Uganda, 2012.
[24]
C. Gallardo, A. R. Ademun, R. Nieto et al., “Genotyping of African swine fever virus (ASFV) isolates associated with disease outbreaks in Uganda in 2007,” African Journal of Biotechnology, vol. 10, no. 17, pp. 3488–3497, 2011.
