Update on Mycoplasma hyopneumoniaeinfections in pigs: Knowledge gaps for improved disease control

Abstract

Mycoplasma hyopneumoniae(M. hyopneumoniae) is the primary pathogen of enzooticpneumonia, a chronic respiratory disease in pigs. Infections occur worldwide andcause major economic losses to the pig industry. The present paper reviews the cur-rent knowledge onM. hyopneumoniaeinfections, with emphasis on identificationand analysis of knowledge gaps for optimizing control of the disease. Close contactbetween infected and susceptible pigs is the main route ofM. hyopneumoniaetrans-mission. Management and housing conditions predisposing for infection or diseaseare known, but further research is needed to better understandM. hyopneumoniaetransmission patterns in modern pig production systems, and to assess the impor-tance of the breeding population for downstream disease control. The organism isprimarily found on the mucosal surface of the trachea, bronchi and bronchioles. Dif-ferent adhesins and lipoproteins are involved in the adherence process. However, aclear picture of the virulence and pathogenicity ofM. hyopneumoniaeis still missing.The role of glycerol metabolism, myoinositol metabolism and theMycoplasmaIgbinding protein—MycoplasmaIg protease system should be further investigated fortheir contribution to virulence. The destruction of the mucociliary apparatus,together with modulating the immune response, enhances the susceptibility ofinfected pigs to secondary pathogens. Clinical signs and severity of lesions dependon different factors, such as management, environmental conditions and likely alsoM. hyopneumoniaestrain. The potential impact of strain variability on disease sever-ity is not well defined. Diagnostics could be improved by developing tests that maydetect virulent strains, by improving sampling in live animals and by designing ELI-SAs allowing discrimination between infected and vaccinated pigs. The currentlyavailable vaccines are often cost-efficient, but the ongoing research on developingnew vaccines that confer protective immunity and reduce transmission should becontinued, as well as optimization of protocols to eliminateM. hyopneumoniaefrompig herds.