The challenge of detecting herds sub-clinically infected with Actinobacillus pleuropneumoniae

•PCR techniques should be applied to serotype Actinobacillus pleuropneumoniae strains.•Serology should be used to perform routine surveillance of possibly infected herds.•Species-specific or serotype-specific tests may be used for different purposes.•Well-validated molecular tests should be used to identify carrier animals.

The introduction into a naïve herd of animals sub-clinically infected with Actinobacillus pleuropneumoniae (App) is frequently the cause of clinical pleuropneumonia and the identification of such infected herds is a priority in the control of disease. Different serological tests for App have been developed and a number of these are routinely used. Some are species-specific whereas others identify more specifically the serotype/serogroup involved which requires updated information about important serotypes recovered from diseased pigs in a given area/country. Serotyping methods based on molecular techniques have been developed lately and are ready to be used by most diagnostic laboratories. When non-conclusive serological results are obtained, direct detection of App from tonsils is sometimes attempted. This review addresses different techniques and approaches used to monitor herds sub-clinically infected by this important pathogen.