Internal Transmission

By direct contact
The most significant method of infection within the herd is transmission between pen-mates by direct nose to nose contact. Here the risk of infection is up to seven times higher than with indirect contact (see below).

Indirectly via aerosol transmission
Mycoplasma is also transmitted in farms within building via aerosols which are created in the airways of infected pigs and are spread by coughing. This means of transmission is increased in the presence of high pig density and poor ventilation and by grouping older and younger animals together. Frequently, this is how infection is maintained in a herd although usually, infection spreads only slowly through the herd.

From the sows to the piglets
Older sows generally excrete only small quantities of infection - in one study, no infection was excreted from a 8th parity sow - although young sows may excrete more. At the same time however, young sows convey a high level of maternal antibodies so providing better protection. Sow-to-piglet transmission of Mycoplasma hyopneumoniae is generally unlikely and is not possible prior to birth, via sow milk or sperm.

Transmission

The pathogen can be introduced from outside the herd or can be transmitted within the herd. Studies have demonstrated that infection with M. hyo does not generally occur before nine weeks of age.

Internal Transmission