The Piglet As A Model Of Norwalk Gastroenteritis

Abstract

Norwalk-like viruses (NLV) are the most important cause of acute gastroenteritis in humans. However, little is known about their pathogenesis since no cell culture or animal model is available yet. Therefore, we have investigated if young piglets would be a suitable model to study NLV pathogenesis. Sixteen &#8764;21-d-old piglets were orally gavaged with 3 doses of the NLV prototype strain (Norwalk virus; strain 8FIIb) previously confirmed to be infective for human volunteers. Stool samples were collected daily to assess viral shedding. Exposure to Norwalk virus had no detectable effect on pig growth. Using RT-PCR, viral NV-RNA was detected in two (high dose) of the twelve pigs gavaged with virus. In a second study, colostrum-deprived newborn piglets were orally gavaged with either the human strain (8FIIb, n=4), swine calicivirus (n=6) or a saline control (n=5). Neither swine calicivirus nor Norwalk virus could be detected by RT-PCR in any stool samples. At day 4 post infection intestinal samples were collected for histological and biochemical evaluation. Differences in diarrhea score and intestinal lactase activity were not detected, but weight gain of pigs infected with the swine calicivirus (158 g/d) was lower (P<0.05) than control pigs (280 g/d). In addition, there was a 49% reduction in ileal villus height in the swine calicivirus group (P<0.05). These results are consistent with swine calicivirus-induced villous atrophy, and attendant reduction in nutrient absorption.