Astrovirus infection in hatchling turkeys: alterations in intestinal maltase activity

Two experiments were conducted to determine intestinal disaccharidase activity in 1-day-old commercial turkey poults inoculated with astrovirus. Samples of small intestines were collected on days 0.5, 1.3, and 7 after inoculation (PI) in Exp. 1 and on days 7, 10, and 14 PI in Exp. 2 and examined for specific maltase activity (SMA). Astrovirus infection was confirmed on day 7 PI by immune electron microscopy of intestinal contents. Inoculated poults developed diarrhoea and a transient, significant decrease in intestinal SMA. SMA was significantly lower in astrovirus-inoculated poults than in control poults throughout the entire small intestine from day 3 to day 7 PI. However, SMA had returned to normal in inoculated poults by day 10 PI and was significantly higher than control values in all sections of the small intestine, except in the proximal jejunum, by day 14 PI. Decreased SMA caused by astrovirus infection resulted in disaccharide maldigestion, malabsorption, and subsequent osmotic diarrhoea. As astrovirus was cleared from the intestinal tract, SMA was restored and diarrhoea was resolved.