African Swine Fever Outbreaks in Lithuanian Domestic Pigs in 2019

While numerous risk factors of African swine fever (ASF) transmission to domestic pigs have been described, ASF virus introduction has often not been traced back to one single defined cause. The large number of ASF outbreaks that occurred in domestic pigs in Lithuania from 2014 through to 2018 raised the question regarding whether outbreak-specific risk factors and transmission routes could be identified. Therefore, a prospective matched case-control study was designed. Data from 18 outbreaks that occurred in Lithuanian in 2019 and 36 control farms were analyzed. Conditional multivariable logistic regression showed that two or more visits by veterinary inspection of a farm had a significant preventive effect on the occurrence of ASF on a farm (Odds ratio (OR) 14.21, confidence interval (CI) 1.09-185.60 for farms not inspected vs. farms inspected twice or more a year), while certain practices (e.g., mushroom picking, sharing equipment, etc.), which might facilitate the indirect introduction of ASF from fields and forests into piggeries, significantly increased the odds of an outbreak (OR 5.18, CI 1.10-24.44). The results of the study highlight the importance of veterinary inspections for increasing the biosecurity level on pig farms and the awareness of ASF. The knowledge on potential protective and risk factors may help to improve the prevention and control of ASF outbreaks in domestic pig farms in Lithuania and other affected countries.