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 results obtained confirmed a low pathogen load of M. hyopneumoniae, which concurred well with the decreased incidence of pneumonic lesions recorded at slaughter following the implementation of strict age segregated rearing systems (all in-all out) in Sweden during the 1990s [21, 22] as shown in Fig. 1 . It could of course, be argued that pulmonary lesions due to M. hyopneumoniae heal with time [28, 29] , and therefore, infections gained during the early rearing period could escape detection at slaughter. However, the low levels (A 450 < 1.0 in all herds) of antibodies to M. hyopneumoniae recorded show that the registrations of pneumonia were correct. Still, the slight increase of serum antibodies to M. hyopneumoniae at the end of the rearing period in herds B, C and D indicate the presence of M. hyopneumoniae in these herds, and that should not be neglected. The global market weight of pigs varies from around 80-180 kg, and is at present around 120 kg in Sweden, which is reached at an age of 6-7 months. If the market weight increase also the rearing period will be prolonged with more days at risk for each pig, which may pave the way for clinical signs of M. hyopneumoniae. Although the pathogen load differs between Sweden and Italy, it is notable that M. hyopneumoniae-like lesions were recorded in 2268 out of 4889 pigs (45.4 %) slaughtered at an age of 9-10 months in Italy [30] .