Detection of Actinobacillus pleuropneumoniae in oral-fluid samples obtained from experimentally infected pigs

The use of cotton ropes has been recently proposed to collect oral fluids from pigs as a method to detect and monitor viral infections in swine populations. However, its use for detection and monitoring of swine bacterial pathogens by polymerase chain reaction (PCR) has not been assessed. In this study, oral-fluid testing for diagnosis of Actinobacillus pleuropneumoniae was evaluated over time, utilizing samples from experimentally infected pigs. Eighty pigs were randomly assigned to experimental groups infected with A pleuropneumoniae serovars 1, 3, 5, 7,10, 12, or 15 and a non-inoculated control group. Oral fluids and blood samples were collected prior to infection, 1 day post infection, and weekly thereafter for 7 consecutive weeks. Oral fluids were tested for A pleuropneumoniae, Haemophilus parasuis, and Streptococcus suis by specific PCR tests offered by the Minnesota Veterinary Diagnostic Laboratory. Actinobacillus pleuropneumoniae was detected on days 1 and 7 post infection, whereas H parasuis and S suis, normal colonizers of the swine respiratory tract, were detected at all time points. These results indicate that oral-fluid testing has the potential to be a screening tool for detection of swine bacterial pathogens. Field studies are indicated to explore this potential further.