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Background African swine fever (ASF), a devastating viral disease of pigs, is one of the main hindrance to pig farming in sub-Saharan African. Sporadic outbreaks of the disease occur annually in various regions of Uganda most of which remain undocumented. This study employed histopathology, immunohistochemistry and conventional PCR comparatively on 290 formalin fixed paraffin embedded swine tissues in diagnosis of ASF. ASF was confirmed by conventional PCR using diagnostic primers recommended by World Organization for Animal Health, (forward primer, 5’- TGGATACCGAGGGAATAGC- 3’) and (reverse primer, 5’-CTTACCGATGAAATGATAC- 3’). Results It was found out that, more than a third of the archived pig lymphoid tissues, (lymph nodes 33.3%, 95/285 and spleen; 42.8%, 120/280) had lesions suggestive of ASF. In average, 17% and 15% of the archived samples had ASF viral DNA and antigen respectively. The positivity rate for ASF in the tested tissue samples was higher in spleen (PCR, 17.5% and IHC, 16.1%) than in other tissues. More than half (51.1%, 48/94) of the lymph nodes and 41.9% ( 49/117) of spleen tissues that had lesions suggestive of ASF tested positive for ASF using conventional PCR. Conclusion ASF is still wide spread in Uganda and is one of the major threats to pig production in the country. Immunohistochemistry other than PCR, is an effective and reliable technique for diagnosing ASF in tissues even after a long period of archiving.

International audience; BackgroundThe COVID-19 pandemic led to severe health systems collapse, as well as logistics and supply delivery shortages across sectors. Delivery of PCR related healthcare supplies continue to be hindered. There is the need for a rapid and accessible SARS-CoV-2 molecular detection method in low resource settings.ObjectivesTo validate a novel isothermal amplification method for rapid detection of SARS-CoV-2 across seven sub-Sharan African countries.Study designIn this multi-country phase 2 diagnostic study, 3,231 clinical samples in seven African sites were tested with two reverse transcription Recombinase-Aided Amplification (RT-RAA) assays (based on SARS-CoV-2 Nucleocapsid (N) gene and RNA-dependent RNA polymerase (RdRP) gene). The test was performed in a mobile suitcase laboratory within 15 min. All results were compared to a real-time RT-PCR assay. Extraction kits based on silica gel or magnetic beads were applied.ResultsFour sites demonstrated good to excellent agreement, while three sites showed fair to moderate results. The RdRP gene assay exhibited an overall PPV of 0.92 and a NPV of 0.88. The N gene assay exhibited an overall PPV of 0.93 and a NPV 0.88. The sensitivity of both RT-RAA assays varied depending on the sample Ct values. When comparing sensitivity between sites, values differed considerably. For high viral load samples, the RT-RAA assay sensitivity ranges were between 60.5 and 100% (RdRP assay) and 25 and 98.6 (N assay).ConclusionOverall, the RdRP based RT-RAA test showed the best assay accuracy. This study highlights the challenges of implementing rapid molecular assays in field conditions. Factors that are important for successful deployment across countries include the implementation of standardized operation procedures, in-person continuous training for staff, and enhanced quality control measures.