The pfhA region, consisting of the genes tpsB1, tpsB2, pfhA1 and pfhA2, is related to the pathogenicity of P. multocida type A. The highly pathogenic strains produce necrotic bronchopneumonia, fibrinous pleuritis and pericarditis in pigs and can be identified by PCR of the pfhA2 gene. This evidence concerns the gene TPSB2 and pericarditis.