Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/31/2009
Publication Date: 3/23/2010
Citation: Spackman, E., Day, J.M., Pantin Jackwood, M.J. 2010. Astrovirus, reovirus and rotavirus concomitant infection causes decreased weight gain in broad-breasted white poults. Avian Diseases. 54:16-21.
Interpretive Summary: Viruses that affect the turkey digestive, or enteric, system can cause severe disease and cost turkey farmers money because of poor growth and higher feed costs. The exact causes of the more severe forms of enteric disease in poultry have not been well defined and are believed to be caused by viruses in many cases. Viruses from different families have been implicated as possible causes of the disease, and flocks with enteric disease frequently are infected with more than one virus at the same time. Therefore, to determine if simultaneous infection with more than one virus would effect turkey body weight and would cause illness, young turkeys were exposed to different combinations of 3 viruses collected from commercial turkey flocks in the US. Decreased body weights were observed in the virus inoculated groups as compared to control turkeys and some of the turkeys had diarrhea, however the groups which were exposed to more than one virus were not clearly more affected than those with one virus and one virus group (reovirus) did not get sick at all. The most important finding is that the group with all viruses had the lowest body-weights though-out the experiment, indicating that low body-weights can occur in the relative absence of clinical illness.
Technical Abstract: Turkey astrovirus type-2 (TAstV-2), turkey rotavirus (TRotV) and turkey reovirus (TReoV) were evaluated for pathogenesis in 3 day-old turkey poults in all possible combinations of one, two or three viruses. Body-weights were recorded at 2, 4, 7, 10 and 14 days post inoculation (PI) and were decreased through-out the experiment as compared to the sham inoculates. Although not significantly different from the other virus exposed groups, the poults exposed to all three viruses had the lowest body weights through-out the experiment. Clinical signs including huddling, diarrhea and agitation were only observed in groups exposed to TAstV-2 and/or TRotV. At 4 days PI birds from each treatment group were necropsied and pale intestines with watery contents and undigested feed were observed in the groups that were exposed to TRotV+TReoV, TRotV+TAstV-2 and the group exposed to all three viruses. Mild microscopic lesions were observed in the intestines of turkeys infected with TAstV-2, TReoV or a combination of both. In the turkeys infected with TRotV, either alone or in combination with other viruses, moderate microscopic lesions were found in all sections of the small intestine and viral antigen was identified by immuno-histochemical staining in mature enterocytes. No or very mild lesions were observed in other organs with the exception of the bursa of fabricius where mild to severe atrophy was observed in all virus-infected poults examined. Cloacal shedding of TAstV-2 and TRotV was evaluated by RT-PCR testing of cloacal swabs and minimal differences were observed among the treatment groups.