Mannheimiosis

Mannheimiosis bovina
Mannheimia haemolytica (Mh) is the most pathogenic bacteria associated with bovine pneumonic pasteurellosis (mannheimiosis); furthermore, it is the most importanteconomic loss disease in beef cattle, and the second one after gastrointestinal diseases mainly in less than a year old dairy heifers. It is a common and important opportunistic agent in bovinenasopharynx. Stress immunosuppression or the infection caused by respiratory viruses or Mycoplasma spp, lead to its establishment and multiplication in lung tissue. A1 and A6 are the most frequentserotypes in pneumonic injuries, and A1 and A2 in the nasopharynx of healthy bovine. Among the Mh virulence factors, leukotoxin is the most important one; its primarily toxic effect isprimarily against leukocytes in ruminants. A better understanding of the epidemiology and the importance of Mh species requires new identification criteria that include molecular techniques, as wellas more sensitive procedures regarding biochemical and immunological isolation and identification. Antimicrobial efficacy, as prophylactic or therapeutical agents, has been very variable dueto diagnosis inaccuracies and to the increase of multi–resistant strains. There is a varied range of bacterins that have been used over the last decades; the efficacy of many of them has beenquestioned as they only protect partially and some of them might even increase the morbility. Vaccines with a supernatant culture containing leukotoxin and other soluble antigens, or isolatedbacterial extracts or combined with bacterins, have been recently developed showing satisfactory results. Efficient prevention and control of bovine mannheimiosis should be supported by areliable diagnosis, use of vaccines and efficient therapeutic measurements, together with good management practices.
Key words: Bovine Mannheimiosis, Etiology, Prevention and Control, Bovines.