| apparent reinfection of enzootic-pneumonia-free pig herds: search for possible causes. | in a control scheme for enzootic-pneumonia-free herds, run by the pig health control association, a detailed study was made of 55 herds that developed enzootic pneumonia without a simple explanation. these herds were compared with 57 herds that were still free from enzootic pneumonia in mid-1984. a high standard of precautions against the risk of infection being transferred by people and fomites seemed to confer no obvious benefit. this observation was in keeping with in vitro studies which show ... | 1985 | 4024433 |