According to what the Plataforme ESA has published, researchers at the European Reference Laboratory for African swine fever (ASF), in collaboration with Latvian researchers, published, in January 2019, a study on a non-haemoadsorbent, genotype II (no-HAD) ASF virus isolated from a wild boar in Latvia in 2017. It is the Lv17/WB/Rie1 virus.
The aim of the study by Gallardo et al. (2019) was to characterise the virulence of this isolate. Under experimental conditions, two domestic pigs infected with this new no-HAD ASF virus developed a non-specific and subclinical form of the disease. Two months after the primary infection with the no-HAD strain, both pigs were resistant to the exposure (through contact) to a virulent HAD ASF virus strain (crossed protection).
According to the authors, these results show that the Latvian no-HAD strain could be used for the development of a live attenuated vaccine against genotype II ASF, such as the no-HAD OURT88/3 strain for genotype I (King et al., 2011). Also, this Latvian isolate shows the natural evolution of the ASF virus, specially the appearance of less virulent forms, such as those seen in areas where ASF has been circulating enzootically for a long time and that favour the appearance of seropositive animals (Arias et al., 2018). This local selection in some wild boar populations of a less virulent strain has been recently seen in Estonia (Gallardo et al., 2018, Nurmoja et al., 2017). It is also a phenomenon that is regularly seen in domestic pig populations in Sub-Saharan Africa (Etter et al., 2011, Quembo et al., 2014).
Thursday, February 14th, 2019/ Plateforme ESA/ France.