Rotaviral Enteritis in Pigs
Rotaviral enteritis is a common disease of the small intestine of pigs. All ages are susceptible, but significant diarrheal disease usually is seen in nursing or post-weaning pigs.
The causal rotavirus infects and destroys villous enterocytes throughout the small intestine, but lesions are most severe in the middle third of the intestine. Loss of villous epithelium results in partial villous atrophy, malabsorption, and osmotic diarrhea. Four antigenic groups (A, B, C, E) of rotavirus are found in pigs. They are easily spread by direct contact. Healthy carrier sows may be fecal shedders during the periparturient period, thereby exposing their litters to infection.
If neonatal pigs do not receive protective levels of maternal antibody, they are likely to develop profuse watery diarrhea in 12–48 hr. More commonly, the infection is endemic in a herd, and sows have varying levels of antibody in the colostrum and milk, which provide varying degrees of passive protection to nursing pigs. Diarrhea often begins in pigs 5 days to 3 wk old or immediately after weaning. The feces of nursing pigs often are yellow or gray and pasty in the early stages and progress to gray and pasty after ~2 days. Diarrhea persists for 2–5 days. Diarrheic pigs become gaunt and rough-haired, but mortality usually is low. Weaned pigs have watery feces that contain poorly digested feed. Weaners become inappetent and noncompetitive, which results in emaciation, stunting, and probably predisposition to pneumonia and other diseases.
Laboratory procedures are required. Confirmation is based on histologic demonstration of villous atrophy in the jejunum, electron microscopic demonstration of virions in the intestinal contents, PCR, and immunodiagnostic procedures to demonstrate viral antigen in the intestinal mucosa or feces. Differential diagnoses include endemic transmissible gastroenteritis, porcine epidemic diarrhea, Isospora suis enteritis, and enteric colibacillosis.
There is no specific treatment. Minimizing heat loss and providing adequate water to maintain hydration are helpful. Concurrent infection by enterotoxigenic Escherichia coli is common; therefore, antibiotic therapy may reduce mortality. Providing diarrheic weaned pigs with a warm, dry, draft-free environment and frequent limited feedings help prevent starvation, secondary diseases, and permanent stunting. Vaccine for group A rotavirus appears beneficial when given to sows before farrowing. Vaccines for groups B, C, and E have not been developed because of difficulty in virus propagation. A serotyping scheme based on virus neutralization indicates a lack of cross-protection between isolates within groups.