M. hyopneumoniae is present in all countries of the world where a significant pig industry exists. The very high prevalence, coupled with the associated financial losses, make this organism one of the most important for pig veterinarians and producers.
M. hyo is the primary respiratory pathogen and the causative agent of Enzootic Pneumonia (EP). M. hyo damages local defence mechanisms in the lung and has an immuno-depressant effect. This allows the entry of other pathogens which colonise lung tissue and may produce harmful toxins. EP is primarily a problem of grow-finish pigs but pigs as young as a few weeks of age or adults may be affected, particularly in a recently infected herd. However experimental infection of pigs with M. hyo alone usually produces coughing with little or no impact on performance.
The term Porcine Respiratory Disease Complex (PRDC) is used to describe new and severe problems observed in finishing units where M. hyo and PRRS virus play a significant role.
 |
 |
 |
Mycoplasmas  colonise the respiratory tract... |
damage cilia and cells and... |
allow P. multocida  and other secondary pathogens to invade |
US research has demonstrated that M. hyo enhances the severity and duration of PRRS virus induced pneumonia [?].
Swine influenza virus, porcine circovirus type 2 (PCV-2), Pasteurella multocida, Actinobacillus pleuropneumoniae, Streptococcus suis and Haemophilus parasuis also often contribute to the syndrome.
Denagard has been shown to be one of the most potent antibiotics against M. hyo. However, in PRDC the wide range of bacteria/mycoplasma involved are best controlled in-feed by the synergistic broad spectrum combination of Denagard and chlortetracycline [?] or doxycycline [?] premixes.
| 
