Pneumonic pasteurellosis is recognized as part of the porcine respiratory disease complex.
Pasteurellosis occurs in pigs most commonly as a complication of enzootic pneumonia; however, influenza, Aujeszky disease (pseudorabies), and infection by Bordetella bronchiseptica or Haemophilus parahaemolyticus can also cause changes in the lungs that lead to disease caused by Pasteurella spp.
Etiology of Pneumonic Pasteurellosis in Pigs
The causative organism of pasteurellosis in pigs usually is Pasteurella multocida. This bacterium rarely causes primary disease in modern pig production but is more often an opportunistic, secondary pathogen recognized as part of the porcine respiratory disease complex. Although a normal inhabitant of the porcine upper respiratory tract, P multocida can become pathogenic and causes exudative bronchopneumonia, sometimes with pericarditis and pleuritis.
The pathogenesis of pasteurellosis remains poorly understood. As part of the porcine respiratory disease complex, P multocida contributes to the progression and severity of pulmonary lesions associated with coinfecting pathogens. Its pathogenicity is mediated by a broad spectrum of virulence factors.
Primary, sporadic, fibrinous pneumonia due to pasteurellae, with no epidemiological connection to enzootic pneumonia or other types of pneumonia, also occurs in pigs.
Septicemic pasteurellosis and meningitis occasionally occur in piglets. Septicemia also occurs in adult pigs.
Nontoxigenic strains of capsular type A are the predominant isolates in cases of pneumonia. Toxigenic strains of P multocida, with or without the presence of B bronchiseptica, are associated with atrophic rhinitis.
P multocida is zoonotic and is associated with a spectrum of human disease (1, 2).
Clinical Findings of Pneumonic Pasteurellosis in Pigs
Diagnosis of Pneumonic Pasteurellosis in Pigs
Necropsy findings
Recovery of pasteurellae
Diagnosis of pasteurellosis in pigs is based on gross and histopathological findings at necropsy and identification of pasteurellae from lesions. Cytological evaluation (P multocida has a characteristic bipolar appearance under methylene blue stain), immunohistochemistry, and PCR assay can be used for diagnosis.
There are no distinctive pasteurellosis lesions in pigs. Nonspecific lesions include fibrinous and suppurative bronchopneumonia, multifocal suppuration, thickening of septa with fibrin combined with cellular infiltration, and edema.
Control of Pneumonic Pasteurellosis in Pigs
Good management practices
Antimicrobials
Control of the secondary, pneumonic form of pasteurellosis in pigs is generally based on prevention or control of enzootic pneumonia through good management practices and biosecurity measures. Early and vigorous therapy with antimicrobials, alone or in combination with sulfonamides, is indicated to prevent chronic sequelae of all forms of the disease.
Antimicrobial resistance has been noted among pasteurellae.
References
Henderson SR, Shah A, Banford KB, Howard LS. Pig trotters lung—novel domestic transmission of Pasteurella multocida. Clin Med (Lond). 2010;10(5):517-518. doi:10.7861/clinmedicine.10-5-517
Wilson BA, Ho M. Pasteurella multocida: from zoonosis to cellular microbiology. Clin Microbiol Rev. 2013;26(3):631-655. doi:10.1128/CMR.00024-13
Ono M, Okada M, Namimatsu T, Fujii S, Mukai T, Sakano T. Septicaemia and arthritis in pigs experimentally infected with Pasteurella multocida capsular serotype A. J Comp Pathol. 2003;129(4):251-258. doi:10.1016/s0021-9975(03)00040-9
de Oliveira Filho JX, Morés MAZ, Rebelatto R, et al. Pasteurella multocida type A as the primary agent of pneumonia and septicaemia in pigs. Pesqui Vet Bras. 2015;35(8):716-724. doi:10.1590/S0100-736X2015000800003
