The carrier state in cattle in foot-and-mouth disease

Abstract

Extract

The possibility of cattle recovering from foot-and-mouth disease and subsequently transmitting it to susceptible animals has been a matter of speculation for some considerable time. This has been particularly so in outbreaks of the disease in which the origin could not be explained in any other way. To cite a few instances, during the winter of 1893–4 in Denmark, foot-and-mouth disease reappeared on four large farms on which outbreaks had taken place from 6 to 12 months previously. In each case, it was observed that only newly purchased calves and cattle introduced since the previous outbreak became affected. The disease was stamped out by killing all the new cattle, but, in spite of this, a third outbreak occurred 12 months after the second outbreak on one of the farms when new cattle were again introduced, affecting only the new animals (Anon., 1901; Bang, 1912). The source of infection could not be determined, particularly as the rest of the country had been free of the disease during the period.