Age dependent resistance to transmissible gastroenteritis of swine (TGE). I. Clinical signs and some mucosal dimensions in small intestine.

Pigs were exposed to transmissible gastroenteritis (TGE) virus when three days old or when 21 days old. Diarrhea was earliest in onset, most frequent, most profuse and most prolonged in the youngest group. Pigs exposed when three days old also had a higher case fatality rate than those exposed when 21 days old. The histological response of both groups to exposure was atrophy of villi and hyperplasia of crypts in jejunum and ileum. However, from days three to seven post-exposure, when most fatalities occurred in the younger group, atrophy of villi was both more intensive and extensive in the younger group. Hyperplasia of crypts was also greater and more prolonged in the younger group. Regeneration of atrophic villi was more rapid in jejunum than ileum in both groups. Results were interpreted to indicate two populations, with different rates of regeneration, in the 21-day old group. Based on this interpretation, regeneration of villi was more rapid in one population from the 21-day old group than in the three-day old group. The length of villi and depth of crypts in control pigs varied longitudinally (i.e. from site to site) in the intestine, within each age group. Length of villi and depth of crypts in control pigs also varied with age.