Astrovirus infection in hatchling turkeys: histologic, morphometric, and ultrastructural findings

In 3 experiments, 2- or 5-day-old commercial turkey poults were inoculated orally with astrovirus and examined for clinical signs and for gross and microscopic lesions for 14 days. By day 2 after inoculation (PI), inoculated poults had developed diarrhoea, generalized loss of intestinal tone, and dilated caeca that contained light-yellow fluid and gas; these changes persisted until day 10 PI. Mild crypt hyperplasia was the only change seen by light microscopy, and it was first noted in the proximal jejunum on day 1 PI, in the distal jejunum and ileum on day 3 PI, and in the duodenum on day 5 PI. A significant increase in crypt depth and area was detected by image analysis on day 3 PI. Electron microscopy identified intracytoplasmic aggregates of astrovirus in enterocytes on the sides and base of villi in the ileum and distal jejunum on day 3 PI. It was concluded that astrovirus caused lesions and replicated in both upper and lower segments of the small intestine in turkey poults.