Outbreak investigations of Actinobacillus pleuropneumoniae serotype 15 in central Iowa in the winter of 2021-2022

From November 2021 to January 2022, 20 growing-pig sites in central Iowa reported severe clinical respiratory disease and weekly mortality of up to 50%. Actinobacillus pleuropneumoniae serotype 15 was identified as the causative agent of the clinical disease. Given that A pleuropneumoniae serotype 15 has been infrequently diagnosed in the United States, an outbreak investigation was conducted to explore biosecurity hazards and epidemiological aspects associated with the surge of cases. The investigations revealed that all farms had significant gaps in biosecurity and relied heavily on third-party service providers, which may have contributed to the pathogen spread.