To support control and eradication programs, an appropriate diagnosis should involve the use of virus and antibody detection tests. As highlighted by EFSA Expert opinion (EFSA Journal 2021; 19 (1):6402) the PCR test in blood or organs (spleen, lymph nodes, tonsil, kidney, bone marrow) samples is the recommended technique for early detection of the virus. PCR test is the only test to be used for authorized movements from restricted zones as referred in the EU 2021/605 of 7 April 2021 laying down special control measures for African swine fever.
Figure→ Dynamic of African swine fever virus infection with respect to the different clinical forms.
Sampling and shipping guidelines can be found in the World Organisation for Animal Health (WOAH) Manual of Diagnostic Tests and Vaccines for Terrestrial Animals (Chapter 3.9.1, 2021 on line edition). The selection of which test to use depends on available matrices, the purpose of the testing (surveillance, eradication, diagnosis, confirmation), as well as the ASF epidemiological status of the country (region) or stage of the epidemic in the region.
ASF diagnosis workflow in case of ASF suspicion
Laboratory testing requires well-defined laboratory contingency plan (LCP) with a detailed description of a simplified workflow that will provide rapid tools to demonstrate freedom from disease after an outbreak.
Interpretation of the ASF diagnostic results
Taken together, sensitive, specific and robust laboratory diagnostic assays are available but, as for any other disease, there is not a single test being 100% reliable (sensitive and specific). For this reason, final diagnosis should be based on the interpretation of the results derived from the use of appropriate samples and validated tests in combination with the information coming from disease epidemiology, scenario, and the clinical signs. A thorough understanding of the viremia and antibody seroconversion timing during ASFV infection is a prerequisite to infer the dynamic of the infection in the investigated areas and to support control and eradication programs.
A review about the different methods for ASF virus, genome and antibody detection is available in “Update of the methods for African swine fever diagnosis in clinical samples” and at "African swine fever (ASF) diagnosis, an essential tool in the epidemiological investigation".