Evaluation of a transmissible gastroenteritis virus eradication program in a breeding stock supply herd

ndemic transmissible gastroenteritis (TGE) is defined as the persistence of the TGE virus (TGEV) and disease in a herd. Endemic infection is a common sequel to a primary outbreak in herds of more than 300 sows.1 In these herds, the main clinical findings are diarrhea, primarily in suckling piglets (from 6 days old to about 2 weeks after weaning); diarrhea among recently weaned pigs; and discrete episodes of overt clinical recrudescence in part of the herd. The endemic disease may be mild or inapparent for much of the time. In some herds, the predominant clinical finding is a mild diarrhea in suckling piglets from about 6 days old. In other herds, the disease ‘break’ occurs primarily during the postweaning period.2 Pigs in some herds have diarrhea both before and after weaning. Adult pigs usually are not sick. However, occasionally there is diarrhea in gilts or sows housed in the same farrowing room as piglets with diarrhea during periods of recrudescence. During a typical recrudescence, piglet mortality is usually 10% of that during the initial outbreak. The presence of finishing pigs results in a significantly greater incidence of disease relapse in larger herds.1 The timing of the periods of disease recurrence almost invariably occurs within about 9 months of the end of the primary outbreak, and most within about 4 months. Some herds have several episodes of disease relapses, usually at intervals of 3 or 4 months, while others experience only a single recurrence.