Serological patterns of Actinobacillus pleuropneumoniae, Mycoplasma hyopneumoniae, Pasteurella multocida and Streptococcus suis in pig herds affected by pleuritis

Wallgren, Per; Nörregård, Erik; Molander, Benedicta; Persson, Maria; Ehlorsson, Carl-Johan

The increased number of transmissions between pigs may increase the influence of other microbes. M. hyopneumoniae and A. pleuropneumoniae are important pathogenic microbes, but co-infections may intensify or prolong clinical signs of respiratory disease [8] [9] [10] [11] . It has also been observed that the incidence of respiratory illness may vary with season [12] . Therefore, infections in the respiratory tract of grower pigs have become regarded as a syndrome rather than linked to single microorganisms [11, 13, 14] . This syndrome is referred to as the porcine respiratory disease complex (PRDC). As stated above PRDC is regarded to be dominated by bacterial species, and important primarily pathogenic bacterial species include M. hyopneumoniae [1] [2] [3] and A. pleuropneumoniae [4] [5] [6] . The frequent demonstration of interferon-α in serum in growers during the first week after arrival to fattening herds [15, 16] suggest that PRDC can be associated with viral infections, and that PRDC can also include the influence of secondary invaders such as Pasteurella spp [17, 18] .