Muhangi Denis, Masembe Charles, Emanuelson Ulf, Boqvist Sofia, Mayega Lawrence, Ademun Rose Okurut, Bishop Richard P, Ocaido Michael, Berg Mikael, Ståhl Karl
Department of Wildlife and Aquatic Resources, College of Veterinary Medicine, Animal Resources and Biosecurity, Makerere University, P. O. Box 7062, Kampala, Uganda.
Department of Biological Sciences, College of Natural Sciences, Makerere University, P. O. Box 7062, Kampala, Uganda.
BMC Vet Res. 2015 May 13;11:106. doi: 10.1186/s12917-015-0426-5.
African swine fever (ASF) is a fatal, haemorrhagic disease of domestic pigs, that poses a serious threat to pig farmers and is currently endemic in domestic pigs in most of sub-Saharan Africa. To obtain insight into the factors related to ASF outbreaks at the farm-level, a longitudinal study was performed in one of the major pig producing areas in central Uganda. Potential risk factors associated with outbreaks of ASF were investigated including the possible presence of apparently healthy ASF-virus (ASFV) infected pigs, which could act as long-term carriers of the virus. Blood and serum were sampled from 715 pigs (241 farms) and 649 pigs (233 farms) to investigate presence of ASFV and antibodies, during the periods of June-October 2010 and March-June 2011, respectively. To determine the potential contribution of different risks to ASF spread, a questionnaire-based survey was administered to farmers to assess the association between ASF outbreaks during the study period and the risk factors.
Fifty-one (21 %) and 13 (5.6 %) farms reported an ASF outbreak on their farms in the previous one to two years and during the study period, respectively. The incidence rate for ASF prior to the study period was estimated at 14.1 per 100 pig farm-years and 5.6 per 100 pig farm-years during the study. Three pigs tested positive for ASFV using real-time PCR, but none tested positive for ASFV specific antibodies using two different commercial ELISA tests.
There was no evidence for existence of pigs that were long-term carriers for the virus based on the analysis of blood and serum as there were no seropositive pigs and the only three ASFV DNA positive pigs were acutely infected and were linked to outbreaks reported by farmers during the study. Potential ASF risk factors were present on both small and medium-scale pig farms, although small scale farms exhibited a higher proportion with multiple potential risk factors (like borrowing boars for sows mating, buying replacement from neighboring farms without ascertaining health status, etc) and did not implement any biosecurity measures. However, no risk factors were significantly associated with ASF reports during the study.
非洲猪瘟（ASF）是家猪的一种致命性出血性疾病，对养猪户构成严重威胁，目前在撒哈拉以南非洲大部分地区的家猪中呈地方流行状态。为深入了解农场层面与ASF疫情相关的因素，在乌干达中部一个主要生猪产区开展了一项纵向研究。调查了与ASF疫情相关的潜在风险因素，包括可能存在表面健康但感染了非洲猪瘟病毒（ASFV）的猪，这些猪可能成为病毒的长期携带者。分别在2010年6月至10月和2011年3月至6月期间，从715头猪（来自241个农场）和649头猪（来自233个农场）采集血液和血清，以调查ASFV和抗体的存在情况。为确定不同风险因素对ASF传播的潜在影响，对养殖户进行了基于问卷调查的调查，以评估研究期间ASF疫情与风险因素之间的关联。
分别有51个（21%）和13个（5.6%）农场报告在过去一到两年以及研究期间其农场发生了ASF疫情。研究前ASF的发病率估计为每100个猪场年14.1例，研究期间为每100个猪场年5.6例。使用实时PCR检测，三头猪的ASFV呈阳性，但使用两种不同的商业ELISA检测，没有一头猪的ASFV特异性抗体呈阳性。
基于血液和血清分析，没有证据表明存在病毒的长期携带猪，因为没有血清阳性猪，仅有的三头ASFV DNA阳性猪为急性感染，且与养殖户在研究期间报告的疫情有关。中小型猪场均存在潜在的ASF风险因素，尽管小型猪场存在多种潜在风险因素（如为母猪配种借公猪、从邻近农场购买后备猪而未确定健康状况等）的比例更高，且未实施任何生物安全措施。然而，在研究期间，没有风险因素与ASF报告显著相关。
