Submitted to: Avian Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 18, 2008
Publication Date: April 8, 2008
Citation: Pantin Jackwood, M.J., Spackman, E., Day, J.M. 2008. Pathogenesis of type 2 turkey astroviruses with variant capsid genes in 2-day-old specific pathogen free poults. Avian Pathology. 37(2):193-201. Interpretive Summary: Viral enteric diseases cause substantial economic loss to the US poultry industry. Avian astroviruses and avian rotaviruses, are commonly detected in chickens and turkeys with enteric disease, and turkey astrovirus type two (TAstV-2) are by far the most commonly detected astroviruses in turkeys. The pathogenicity of three different TAstV-2 viruses was studied in two-week-old specific-pathogen-free (SPF) turkeys. All infected poults presented diarrhea and growth depression. Virus was detected from intestinal contents and feces at 3, 7 and 14 days post-inoculation (dpi) and was also detected in blood. All birds were dehydrated, and had distended intestines filled with watery contents and undigested feed. Mild microscopic lesions were present in the intestines, and were most common in the jejunum. Viruses were demonstrated by immunohistochemistry (IHC) and by in situ hybridization (ISH) in the intestinal epithelium. Mild to moderate bursal atrophy also was observed in all TAstV-2-infected poults examined. In conclusion, different TAstV-2 viruses produce a similar enteric disease in young turkeys and may also affect the immune system of the birds by causing bursal lymphoid depletion.
Technical Abstract: The pathogenicity of three different type 2 turkey astroviruses (TAstV-2) was studied in specific-pathogen-free (SPF) turkeys. These viruses differ based on sequence analysis of the capsid gene. Poults were inoculated at two days of age and examined during 14 days for clinical signs and virus shedding. All inoculated poults presented signs of enteric disease including diarrhea and growth depression. Virus presence and shedding was detected by real time RT-PCR from intestinal contents and cloacal swabs collected at 3, 7 and 14 days post-inoculation (dpi). Viremia was also confirmed by this method. Common lesions observed at necropsy were dehydration, distended intestines filled with watery contents and undigested feed and dilated ceca with foamy contents. Microscopic lesions present in the intestines consisted of mild crypt hyperplasia, villous atrophy and lymphocytic infiltration, and were most common in the jejunum. Presence of the viruses was demonstrated by immunohistochemistry (IHC) and by in situ hybridization (ISH) in both villi and crypt enterocytes in the jejunum and, less frequently, the duodenum, ileum and ceca. Mild lesions consisting mainly in lymphocytic infiltration were also observed in other organs including pancreas, liver, and kidneys. Mild to moderate bursal atrophy occurred in all TAstV-2-infected poults examined, however no specific viral staining was observed in this organ or any other tissues examined apart from intestines. In conclusion, TAstV-2 viruses with variant capsids produce a similar enteric disease in young turkeys and may also affect the immune system of the birds by causing bursal lymphoid depletion.