Archive | 2021
Lateral flow assays for the detection of African swine fever virus antigen are not fit for field diagnosis of wild boar carcasses
Abstract
African swine fever (ASF) is one of the most important viral diseases of\ndomestic pigs and wild boar. Apart from endemic cycles in Africa, ASF is\nnow continuously spreading in Europe and Asia. As ASF leads to severe\nbut unspecific clinical signs and high lethality, early pathogen\ndetection is of utmost importance. Recently, “point-of-care” (POC)\ntests have been intensively discussed for the use in remote areas but\nalso in the context of on-farm epidemiological investigations and wild\nboar carcass screening. Along these lines, the INGEZIM ASFV CROM Ag\nlateral flow assay (Eurofins Technologies Ingenasa) promises virus\nantigen detection under field conditions within minutes. In the present\nstudy, we evaluated the performance of the assay with selected\nhigh-quality reference blood samples, and also with real field samples\nfrom wild boar carcasses in different stages of decay from the ongoing\nASF outbreak in Germany. While we observed a sensitivity of roughly 77%\nin freeze-thawed matrices of close to ideal quality, our approach to\nsimulate field conditions in direct carcass testing without any\nmodification resulted in a drastically reduced sensitivity of only\n12.5%. Freeze thawing increased the sensitivity to roughly 44% which\nmirrored the overall sensitivity of 49% in the total data set of\ncarcass samples. A diagnostic specificity of 100% was observed.\nHowever, most of the German ASF cases in wild boar would have been\nmissed using the lateral flow assay (LFA) alone. Therefore, the\nantigen-specific LFA should not be regarded as a substitute for any OIE\nlisted diagnostic method and has very limited use for carcass testing at\nthe point of care. For optimized LFA antigen tests, the sensitivity with\nfield samples must be significantly increased. An improved sensitivity\nis seen with freeze-thawed samples, which may indicate problems in the\naccessibility of ASFV antigen.