Evaluation of rotavirus infection and diarrhea in Iowa commercial pigs based on an epidemiologic study of a population represented by diagnostic laboratory cases

Department of Microbiology Immunology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames 50011.

Group A, B, and C rotaviruses were identified in 9% (96/1,048) of pig fecal specimens submitted to the Iowa State University Veterinary Diagnostic Laboratory during 1987 and 1988. Six of the rotaviruses were group B, 5 were group C, and the remaining 89% were group A. Of the rotavirus cases with more than 1 serotype, 5 were multiple group A serotypes, 1 involved a group A and B serotype, and 1 included 2 group C serotypes. A retrospective epidemiologic evaluation of pig diarrhea in herds of origin was done using data obtained from the accession records of the rotavirus and 88 matched nonrotavirus pig diarrhea control cases. Herds from which rotavirus cases were derived experienced lower morbidity, mortality, and case fatality rates than matched control herds. The incidence of diarrhea decreased rapidly among all pigs from birth to 3 weeks of age. The peak incidence for piglet diarrhea occurred in February, and a moderate rise occurred in August-September. Definitive evidence for transmissible gastroenteritis virus was found in 12% of nonrotavirus cases but none of the rotavirus cases in which it was sought. Other pathogenic microorganisms were identified less frequently and inconsistently.