African swine fever (ASF) is a severe hemorrhagic disease of suids caused by the African swine fever virus (ASFV). In 2023, the introduction of genotype II ASFV into Lombardy was a cause for serious concern; the region is home to approximately 50% of the national pig population and is of economic importance to the processing industry of the entire country. Since then, two ASF epidemics have resulted in a total of 30 outbreaks in domestic pigs in the same areas of Lombardy, where the disease is endemic in wild boars. The results of the control activities conducted in the affected areas seem to indicate the establishment of self-sustaining infection cycles in the wild boar population with spillover and spillback events occurring between wild boars and domestic pigs. This manuscript describes some epidemiological features of the ASF epidemics in Lombardy with the aim of providing useful information to combat the disease.

In 2023, ASF was recognized in Lombardy in wild boars, but shortly thereafter the disease was also identified in pig farms, with serious economic repercussions for the entire national pig sector. To identify factors related to the introduction of the infection into pig farms, a case–control study was conducted with the aim of gaining knowledge on the risk and protective factors involved in the introduction of the ASF virus into intensive pig farms. To this end, a questionnaire was developed on risk factors related to ASFV transmission into pig farms and on good management and biosecurity practices. The results of the study showed that measures aimed at strengthening the segregation of the farm from the external environment (external biosecurity), such as the mandatory passage through a hygiene lock upon entry, the presence of a hygiene lock for farm personnel and external visitors, the presence of special equipment and disinfection points at the entrance to the sheds, the loading of dead pigs outside the animal housing area and the ownership of non-adjacent agricultural land, were associated with a reduced risk. This information, if effectively communicated, could be of direct practical value to farmers to ensure the successful implementation of farm biosecurity.