There are three recognized Mycoplasma spp. Mycoplasma are very small and readily pass through ordinary bacterial filters. In addition, mycoplasma are difficult to grow in the laboratory. For these reasons, it was originally assumed that mycoplasmal pneumonia was a virus. Mycoplasmal pneumonia affects pigs of all ages, starting with those as young as 7-10 days of age.
Mycoplasmal pneumonia is a chronic disease.
A high percentage of the pigs are affected, but the death loss is low. Pigs usually show first signs of the disease between 3 and 10 weeks of age. The incubation period is 10 days or more after exposure to carrier swine. The pigs have a dry, nonproductive cough that is most noticeable after exercise. Pigs may cough for only 1-3 weeks, or the coughing may persist indefinitely.