The role of type-2 turkey astrovirus in poult enteritis syndrome

An experimental study was conducted to determine the comparative pathogenicity of type-2 turkey astrovirus (TAstV-2) obtained from turkey flocks afflicted with poult enteritis syndrome (PES) and from turkey flocks displaying no apparent signs of infection. In total, ninety 7-d-old poults, which tested negative for the presence of astrovirus, rotavirus, coronavirus, and reovirus by reverse transcriptase (RT) PCR, were divided evenly into 3 groups: A, B, and C. Birds in group A were inoculated orally with turkey astrovirus-positive intestinal contents from birds affected with PES. Group B received turkey astrovirus-containing intestinal contents from apparently healthy flocks. Group C served as a negative control and was given PBS. Clinical signs of diarrhea, depression, and dullness were observed in group A. Birds in group B also showed clinical signs similar to those in group A, although the signs were milder in nature. Birds in group C did not show any clinical signs. At 16 d postinoculation, the BW of birds in group A was significantly lower than that of birds in groups B or C. In addition, the bursa size was reduced in group A, but not in groups B or C. Birds in groups A and B, but not in group C, were found to shed turkey astrovirus in their feces, as detected by RT-PCR. These results provide a preliminary indication that TAstV-2 from PES birds may be more pathogenic than TAstV-2 from apparently healthy poults. Further studies are needed to determine if pathogenic and nonpathogenic strains of TAstV-2 exist in the environment. These results also reinforce our previous observations that astrovirus is involved in PES, causing significant retardation in growth and weight gain.