Assessment of real-time PCR test in oral fluid samples for screening the serotypes of Actinobacillus pleuropneumoniae circulating in swine herds

Abstract

Actinobacillus pleuropneumoniae is the etiological agent of porcine pleuropneumonia, causing remarkable economic losses in the global swine industry. The diversity of A. pleuropneumoniae is generally determined through serotype identification, which is commonly employed for control strategies and surveillance. However, serological methods currently in use still have significant limitations. This study explores the use of real-time polymerase chain reaction (qPCR) to detect circulating serotypes of A. pleuropneumoniae in non-diseased swine herds through testing of oral fluids. The study included three A. pleuropneumoniae-positive and three A. pleuropneumoniae-negative farms located in Quebec, Canada. Tonsil brushings, microbiological growths, and oral fluids were analyzed using qPCR to detect A. pleuropneumoniae and its distinct serotypes. Serological tests were performed using the LPS ELISA available at that time. In negative farms the absence of A. pleuropneumoniae and any serotype confirmed the specificity of the method. Positive farms, on the other hand, confirmed also the sensitivity of the analysis, with oral fluid samples consistently yielding positive results for the serotypes identified by ELISA. The qPCR test conducted on oral fluids offers a noninvasive and cost-effective method for monitoring, complementing traditional serological techniques. It provides qualitative information about serotype distribution, facilitating proactive surveillance and control strategies.

Keywords: Actinobacillus pleuropneumoniae; Oral fluid; Real-time PCR; Serotype.