Enzootic pneumonia in feeder pigs: Observations on causal factors.

A number of factors were studied in eight feeder pig herds, affected with severe or mild enzootic pneumonia, in order to identify those associated with this disease. Piggeries with poor facilities and management and where procurement of piglets was from sales barns were more severely affected with enzootic pneumonia than were those with good facilities and where pigs originated directly from breeding units. Serological tests and virus isolation revealed that all herds had been exposed to Mycoplasma hyopneumoniae and to many viruses; transmissible gastroenteritis virus infection was the only viral infection that was apparently associated with the severity of enzootic pneumonia and the performance observed in the herds.