Effect of age on susceptibility of pigs to Mycoplasma hyopneumoniae pneumonia.

The effect of age on susceptibility of pigs to Mycoplasma hyopneumoniae was compared in 2 experiments. In experiment A, pigs 3, 6, and 12 weeks of age were contact-exposed to pigs with established M hyopneumoniae infection for 27 days and then evaluated for pneumonia at necropsy done at 42 days after exposure began. In experiment B, pigs 3 and 11 to 12 weeks of age were contact-exposed for 20 days and then placed in separate, isolated hog houses until necropsy was done at 49 days after exposure began. Evaluations at necropsies revealed that no differences existed between age groups concerning occurrence or severity of pneumonia. Likewise, immunofluorescence and culture evaluations of lung tissue revealed that no significant differences existed among age groups concerning detection of M hyopneumoniae or time of seroconversion to the organism. Under conditions of this study, no differences were detected in susceptibility of pigs between 3 and 12 weeks of age.