Overview of <em>Mycoplasma bovis</em> Infection in Dairy and Beef Cattle

Mycoplasma bovis is an economically important disease in dairy and feedlot cattle; the annual loss was calculated as 140 million USD in the USA. Mycoplasma bovis is a common bacterium found in mucous membranes in different animal species, including the respiratory tract, urogenital tract, and gastrointestinal tract. Mycoplasma bovis is a highly contagious disease with an over 70% infection rate. The disease prevalence of M. bovis infection is varied widely and high nasal prevalence was reported among young calves. The mortality were reported in 2-6 weeks of old calves while the peak clinical incidence was at the age of one month. Mycoplasma bovis is colonized in normal respiratory mucosae and tonsils. The clearance of the organism takes for a long period in cattle, it is for a couple of months to a number of years in the mammary gland. Mortality of Mycoplasma bovis infection is varied from herd to herd and location to location. Mycoplasma bovis has been isolated from milk, conjunctiva, semen, and vaginal secretions. The organism is excreted through milk either intermittently or continuously, even in sub-clinical infection. Airborne transmission is the main route of infection in the susceptible bovine host. An animal that sheds M. bovis is the main source of infection within a herd. The bacterium is excreted in colostrum, vaginal secretion and in respiratory secretion of infected cows. The pathogenesis of Mycoplasma bovis has been poorly understood or partly investigated in cattle. Both conventional and molecular methods are there to identify the organism with high analytical sensitivity and specificity. Both 16S rDNA and 23S rDNA targets are used to differentiate Mycoplasma from other possible microorganisms. The immunohistochemistry, in situ hybridization and histopathology, have also been optimized as diagnosis of Mycoplasm bovis infection in cattle. Serological diagnosis is also considered a cost-effective method to identify the seropositive animal. ELISA test has been optimized for field samples of both serum and milk. Three main mechanisms have been able to control or prevent Mycoplasma bovis infection in cattle farming such as sanitary control measures, antimicrobial therapy and vaccination.