Mannheimia haemolyticaand bovine respiratory disease

Abstract

Mannheimia haemolytica is the principal bacterium isolated from respiratory disease in feedlot cattle and is a significant component of enzootic pneumonia in all neonatal calves. A commensal of the nasopharynx, M. haemolytica is an opportunist, gaining access to the lungs when host defenses are compromised by stress or infection with respiratory viruses or mycoplasma. Although several serotypes act as commensals, A1 and A6 are the most frequent isolates from pneumonic lungs. Potential virulence factors include adhesin, capsular polysaccharide, fimbriae, iron-regulated outer membrane proteins, leukotoxin (Lkt), lipopolysaccharide (LPS), lipoproteins, neuraminidase, sialoglycoprotease and transferrin-binding proteins. Of these, Lkt is pivotal in induction of pneumonia. Lkt-mediated infiltration and destruction of neutrophils and other leukocytes impairs bacterial clearance and contributes to development of fibrinous pneumonia. LPS may act synergistically with Lkt, enhancing its effects and contributing endotoxic activity. Antibiotics are employed extensively in the feedlot industry, both prophylactically and therapeutically, but their efficacy varies because of inconsistencies in diagnosis and treatment regimes and development of antibiotic resistance. Vaccines have been used for many decades, even though traditional bacterins failed to demonstrate protection and their use often enhanced disease in vaccinated animals. Modern vaccines use culture supernatants containing Lkt and other soluble antigens, or bacterial extracts, alone or combined with bacterins. These vaccines have 50-70% efficacy in prevention of M. haemolytica pneumonia. Effective control of M. haemolytica pneumonia is likely to require a combination of more definitive diagnosis, efficacious vaccines, therapeutic intervention and improved management practices.

Manejo do complexo respiratório bovino em confinamento: Revisão

“…Bezerros que atravessam longas distâncias são expostos a fatores estressantes como a inalação de fumaça de óleo diesel, desafios térmicos extremos e até mesmo desidratação, fome e exaustão (Rice et al, 2007).…”

“…O desafio alimentar para um ótimo desempenho, o ambiente empoeirado, água diferente a que estavam acostumados, formação de lotes de bezerros de origens distintas, entre outras mudanças radicais sofridas, torna-se assim o animal ainda mais susceptível ao contágio da CRB (Srikumaran et al, 2007, Rice et al, 2007.…”

“…As neuraminidases são responsáveis pela redução da viscosidade do muco respiratório, abrindo passagem para a entrada das bactérias no parênquima das vias respiratórias. Os lipopolissacarídeos irão gerar hemorragia, edema, hipóxia e inflamação aguda e as leucotoxinas são responsáveis pela lise dos leucócitos dos bovinos, sendo esta última, o principal fator de virulência (Rice et al, 2007).…”

Acute Die-off of Chamois (Rupicapra rupicapra) in the Eastern Austrian Alps due to Bacterial Bronchopneumonia withPasteurellaceae

“…Nonetheless, they may cause severe disease and great economic losses (Radostits et al 2000). In cattle (Bos taurus), Mannheimia haemolytica is one of the most common pathogens associated with respiratory tract diseases, especially in young or recently transported animals (Rice et al 2007). Mannheimia glucosida is frequently isolated from ovine species (Caprinae), can be isolated from bovine species (Bovinae), and is similarly associated with respiratory diseases (Angen et al 1999;Kehrenberg et al 2001).…”

Paleic acid, a fatty acid from Paenibacillus sp.: taxonomy, fermentation, isolation, structure determination, and anti-Mannheimia and -Pasteurella activity

“…Paleic acid (1) showed MIC values of 100, 100 and 4100 mg ml À1 against S. aureus FDA209P, Smith and MS9610, respectively.…”