University of Minnesota researchers have found that pigs infected with Mycoplasma hyopneumoniae, the main cause of enzootic pneumonia, can infect other pigs for at least 200 days.
Enzootic pneumonia is a widespread respiratory disease that affects pigs worldwide. Previous studies have demonstrated that M. hyopneumoniae infection can be longer than 185 days; however, the total duration of infection has not been determined.
The purpose of the study was to determine the duration of M. hyopneumoniae infection in pigs not displaying symptoms. To achieve the goal, 60 pigs were inoculated with M. hyopneumoniae strain 232. The persistence of the organism in the respiratory tract was assessed by presence of the bacterial DNA in bronchial swabs and the ability of the infected pigs to transmit the pathogen to sentinels.
Experimentally infected pigs shed M. hyopneumoniae prior to and after the cough was observed. The organism’s DNA was detected in all experimentally infected pigs at 94 days post infection, 61% at 214 dpi and 0% at 254 dpi. Experimentally infected pigs transmitted the bacteria to sentinels at 80 and 200dpi.
Results of the study demonstrate that M. hyopneumoniae-infected pigs can be incubatory as well as convalescent carriers of the pathogen and that convalescent carriers can remain infectious for up to 200 days.