EXPERIMENTS ON THE EPIDEMIOLOGY OF PSEUDORABIES : II. PREVALENCE OF THE DISEASE AMONG MIDDLE WESTERN SWINE AND THE POSSIBLE RÔLE OF RATS IN HERD-TO-HERD INFECTIONS

Study of the pseudorabies virus-neutralizing antibody content of pooled and individual samples of swine serum have led to the conclusion that pseudorabies is a highly prevalent, unrecognized, disease in middle western hogs. It has been shown that wild brown rats develop a fatal infection following ingestion of pseudorabies virus and that their carcasses, in turn, give rise to the disease in swine to which they are fed. It is believed that rats play a rôle in the epidemiology of porcine pseudorabies, serving as the initial source of infection for a swine herd and also as one means by which virus can be spread from farm to farm in swine herds. The experiments presented furnish further evidence that swine may serve as the source of infection for cattle.