EPIDEMIOLOGY, PATHOGENESIS AND COUNTERMEASURES TO PREVENT AND CONTROL ENTERIC VIRUSES OF POULTRY
Location: Endemic Poultry Viral Diseases Research Unit
Title: Enteric viruses detected by molecular methods in commercial chicken and turkey flocks in the United States between 2005 and 2006
Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2008
Publication Date: June 20, 2008
Citation: Spackman, E., Pantin Jackwood, M.J., Day, J.M., Jackwood, M.W. 2008. Enteric viruses detected by molecular methods in commercial chicken and turkey flocks in the United States between 2005 and 2006. Avian Diseases. 52:235-244.
Interpretive Summary: Diseases which cause stunting and depressed growth are a major economic problem for the U.S. poultry industry because these conditions increase the feed and production costs of raising chickens and turkeys to market weight. Currently little is known about the cause of this disease, however viruses which infect the intestinal tracts of poultry are suspected to be involved. Once of the difficulties in conducting research on these diseases was that there were few detection methods for intestinal viruses of poultry, however in recent years tests for the most important diseases have been developed. With the availability of these test, which look for the virus genetic material, basic data about the prevalence of these viruses in chickens and turkeys in the U.S. can be generated. In this report intestinal tissue was obtained from 43 chicken flocks and 33 turkey flocks throughout the U.S. and was tested for the presence of each of 5 intestinal viruses. Viruses from the same family, astroviruses, were the most common in chickens and turkeys, however other viruses differed in prevalence based on species. There was no geographic pattern to virus distribution, indicating that intestinal viruses are widespread in poultry, however the clinical significance of this needs to be determined since many of the flocks were described as healthy.
Intestinal samples collected from 43 commercial broiler, and 33 commercial turkey flocks from all regions of the United States during 2005 and 2006, were examined for the presence of astrovirus, rotavirus, reovirus, and coronavirus by RT-PCR, and for the presence of groups I and II adenovirus by PCR. Phylogenetic analysis was performed to further characterize the viruses that were identified and to evaluate species association and geographic patterns. Astroviruses were identified in samples from 86% of the chicken flocks and 100% of the turkey flocks. Both chicken astrovirus (CAstV) and avian nephritis virus (ANV) were identified in chicken samples and often both viruses were detected in the same sample. Turkey astrovirus type-2 (TAstV-2) and turkey astrovirus type-1 (TAstV-1) were both found in 100% and 15.4% of the turkey flocks, respectively. In addition, 12.5% of turkey flocks were positive for ANV. Rotaviruses were present in 46.5% of the chicken, and 69.7% of the turkey flocks tested. Based upon the rotavirus NSP4 gene sequence, the chicken and turkey origin rotaviruses assorted in a species-specific manner. The turkey origin rotaviruses also assorted based upon geographical location. Reoviruses were identified in 62.8% and 45.5% of chicken and turkey flocks respectively. Based on the reovirus S4 gene segment the chicken and turkey origin viruses assorted separately and were distinct from all previously reported avian reoviruses. Coronaviruses were detected in the intestinal contents of chickens, but not in turkeys. Adenoviruses were not detected in any chicken or turkeys flocks. Of the 76 total chicken and turkey flocks tested, only three chicken flocks were negative for all viruses targeted by this study. Most flocks were positive for two or more of the viruses and overall no clear pattern of virus geographic distribution was evident. This study provides updated enteric virus prevalence data for the US using new molecular methods and reinforces that enteric viruses are widespread in poultry throughout the US, although the clinical importance of most of these viruses is unknown.