Immunohistopathological findings in the lungs of calves naturally infected with Mycoplasma bovis

Histology and immunohistochemistry were used to analyse the lesions and distribution of Mycoplasma bovis antigen in the lungs of 18 naturally infected calves. Microscopic examination of pneumonic lungs revealed two distinct patterns of necrosis and inflammation. The first pattern was observed in six of 18 (33.3%) calves in which microscopic lesions were characterized by large irregular areas of coagulative necrosis surrounded by a dense zone of degenerated neutrophils. Moderate amounts of mycoplasmal antigen were in the centre and periphery of these necrotic foci and, to a lesser extent, in mononuclear cells of the peribronchial lymphoid tissue. The second pattern was observed in 18 of 18 (100%) calves and consisted of rounded foci of caseous necrosis composed by granular eosinophilic material surrounded by a rim of granulation tissue. Large amounts of M. bovis antigen were detected in the centre and periphery of these necrotic foci and, to a lesser extent, in the peribronchial lymphoid tissue, and alveolar and interstitial macrophages. It was concluded that both caseous and coagulative necrosis of the lung parenchyma was primarily caused by M. bovis. Infection with M. bovis should be suspected in bovine necrotic bronchopneumonia, particularly in cases in which the pulmonary necrosis is part of a pyogranulomatous inflammation centred around airways. The pattern of caseous necrosis with pyogranulomatous inflammation is characteristic of M. bovis infection while the pattern of coagulative necrosis is similar to and must be differentiated from Mannheimia haemolytica and Haemophilus somnus infection.PT: J; CR: ADEGBOYE DS, 1995, J VET DIAGN INVEST, V7, P261 ADEGBOYE DS, 1995, J VET DIAGN INVEST, V7, P333 BENNETT RH, 1977, AM J VET RES, V38, P1731 BOOTHBY JT, 1988, CORNELL VET, V76, P188 BOUGHTON E, 1979, VET B, V49, P377 BRICE N, 2000, VET REC, V146, P643 BUCHVAROVA Y, 1989, ARCH EXP VET MED, V43, P685 DUNGWORTH DL, 1993, PATHOLOGY DOMESTIC A, P539 GEARY SJ, 1981, SCIENCE, V212, P1032 GOURLAY RN, 1985, RES VET SCI, V38, P377 GOURLAY RN, 1989, VET REC, V124, P420 HAINES DM, 1991, J VET DIAGN INVEST, V3, P101 HAINES DM, 2001, CAN VET J, V42, P857 HEWICKERTRAUTWEIN M, 2002, VET REC, V151, P699 KINDE H, 1993, J VET DIAGN INVEST, V5, P194 LOPEZ A, 1986, AM J VET RES, V47, P1283 LOPEZ A, 2001, SPECIAL VET PATHOLOG, P125 LOPEZ A, 2002, 18 PAN AM C VET SCI NICHOLAS RAJ, 2003, RES VET SCI, V74, P105 POTGIETER LND, 1995, VET CLIN N AM-FOOD A, V11, P501 RODRIGUEZ F, 1996, J COMP PATHOL, V115, P151 SHAHRIAR FM, 2002, CAN VET J, V43, P863 SLAUSON DO, 1990, MECH DIS TXB COMP GE THOMAS A, 2002, VET RES COMMUN, V26, P333; NR: 24; TC: 1; J9: J VET MED A-PHYSIOL PATHOL CL; PG: 5; GA: 818KGSource type: Electronic(1