Faburay Bonto, O'Hara Kathleen, Remmenga Marta, Odoom Theophilus, Johnson Sherry, Tasiame William, Ayim-Akonor Matilda, Anderson Benita, Kwabena Amoako Kingsley, Holder Diane, Ping Wu, Zajac Michelle, O'Donnell Vivian, Xu Lizhe, Holland Robin, Brown Corrie, Levings Randall, Robbe-Austerman Suelee
Foreign Animal Disease Diagnostic Laboratory, National Bio and Agro-Defense Facility, Animal and Plant Health Inspection Service, United States Department of Agriculture, Manhattan, KS 66502, USA.
Center for Epidemiology and Animal Health, Strategy and Policy, Animal and Plant Health Inspection Service, Veterinary Services, United States Department of Agriculture, Fort Collins, CO 80523, USA.
Viruses. 2025 Aug 6;17(8):1089. doi: 10.3390/v17081089.
African swine fever (ASF) needs to be controlled, and prevention of the spread of African swine fever virus (ASFV) is dependent on enhanced surveillance and early disease detection. Commercial swine operations, especially in North America, Europe, and Asia, are characterized by comparatively large numbers of pigs, and sampling individual pigs, which represents the main strategy for current ASF surveillance, can be both costly and labor intensive. A study performed in Ghana was designed to estimate the diagnostic sensitivity of pen-based aggregate oral fluid testing for ASFV in infected pigs in a pen of 30 animals and to evaluate its utility as a tool to support surveillance of ASF in the US. This study was performed in three phases: (i) virus (Ghana ASFV24) amplification in a target host species to generate the challenge inoculum; (ii) titration of the inoculum (10% spleen homogenate) in target host species to determine the minimum dose inducing acute ASF in pigs with survival up to 5-6 days post-inoculation (dpi); and (iii) the main study, involving 186 pigs, consisting of 6 replicates of 30 pigs per pen and one seeder pig inoculated with wildtype ASFV (highly virulent genotype II) per pen. Daily sampling of aggregate oral fluids, uncoagulated blood, oropharyngeal swabs, fecal and water nipple swabs, and recording of rectal temperatures and clinical observations was carried out. The seeder pigs were each inoculated intramuscularly with 0.5 mL of the 10% spleen homogenate, which induced the desired clinical course of ASF in the pigs, with survival of up to 6 dpi. ASFV DNA was detected in the seeder pigs as early as 1 dpi and 2 dpi in the blood and oropharyngeal swabs, respectively. Transmission of ASFV from the seeder pigs to the contact pig population was detected via positive amplification of ASFV DNA in aggregate oral fluid samples at 3 days post-contact (dpc) in 4 out of 6 pens, and in all 6 pens, at 4 dpc. Testing of oropharyngeal swabs and blood samples from individual pigs revealed a variable number of ASFV-positive pigs between 3 and 5 dpc, with detection of 100% positivity between 6 and 18 dpc, the study endpoint. These findings demonstrate the potential utility of aggregate oral fluid sampling for sensitive and early detection of ASFV incursion into naïve swine herds. It also demonstrates that testing of environmental samples from the premises could further enhance overall ASF early detection and surveillance strategies.
非洲猪瘟（ASF）需要得到控制，预防非洲猪瘟病毒（ASFV）传播依赖于加强监测和早期疾病检测。商业化养猪场，尤其是在北美、欧洲和亚洲，其特点是猪的数量相对较多，对每头猪进行采样（这是当前ASF监测的主要策略）既昂贵又耗费人力。在加纳进行的一项研究旨在评估在一个有30头动物的猪栏中，基于猪栏的混合口腔液体检测对感染猪中ASFV的诊断敏感性，并评估其作为支持美国ASF监测工具的效用。这项研究分三个阶段进行：（i）在目标宿主物种中扩增病毒（加纳ASFV24）以制备攻毒接种物；（ii）在目标宿主物种中对接种物（10%脾脏匀浆）进行滴定，以确定在接种后5 - 6天存活的猪中诱导急性ASF的最小剂量；（iii）主要研究，涉及186头猪，每栏30头猪，共6个重复，每栏接种一头野生型ASFV（高致病性II型）的种猪。每天对混合口腔液体、未凝固血液、口咽拭子、粪便和饮水乳头拭子进行采样，并记录直肠温度和临床观察结果。每头种猪肌肉注射0.5 mL的10%脾脏匀浆，这在猪中诱导出了所需的ASF临床病程，接种后存活时间长达6天。在种猪中，分别在接种后1天和2天在血液和口咽拭子中检测到ASFV DNA。在接触后3天，6个猪栏中有4个猪栏的混合口腔液体样本中通过ASFV DNA的阳性扩增检测到ASFV从种猪传播到接触猪群体，在接触后4天，所有6个猪栏均检测到传播。对个体猪的口咽拭子和血液样本进行检测发现，在接触后3至5天之间，ASFV阳性猪的数量各不相同，在研究终点（接触后6至18天）检测到阳性率为100%。这些发现证明了混合口腔液体采样在敏感和早期检测ASFV侵入未感染猪群方面的潜在效用。这也表明对猪场环境样本进行检测可以进一步加强整体ASF早期检测和监测策略。
