Mycoplasma Hyopneumoniae

Mycoplasma hyopneumoniae is a species of bacteria known to cause the disease Porcine Enzootic Pneumonia, a highly contagious and chronic disease affecting pigs (Whittlestone, 1979). As with other mollicutes, M. hyopneumoniae is gram positive, small in size (400 - 1200 nm), has a small genome (893 - 920 kilo-base pairs (kb)) and lacks a cell wall (Tajima et al., 1982). It is considered to be difficult to grow in laboratories due to its complex nutritional requirements and the high chances of contamination associated with mycoplasma culture. To successfully grow the bacterium, an environment of 5-10% carbon dioxide is required, and the medium should demonstrate an acid colour shift.

This bacterium is a concern in the livestock industry as it causes a significant reduction in the growing weight of pigs. Losses in the U.S.A. have been previously estimated at 200 million to 1 billion dollars per annum (Clark et al., 1991). Porcine enzootic pneumonia is endemic worldwide and M. hyopneumoniae is present in almost every pig herd (Minion, 2002). Treatment of this disease is limited to antibiotics, which are currently ineffective as they do not completely remove the infection. Vaccines have been found to reduce the severity of the disease but do not prevent the disease from occurring in infected pigs (Haesebrouck, et al., 2004).