Immunosuppressive studies of an Indian avian reovirus isolate in association with chicken anaemia virus in experimentally co-infected chicks

Nitin Bhardwaj, J.M. Kataria, K. Dhama, S. Arthur Sylvester and S. Rahul
Division of Avian Diseases Indian Veterinary Research Institute, Izatnagar - 243 122 (U.P.)

The study was conducted to ascertain the immunosuppressive effects of an Indian avian reovirus (ARV) isolate in association with chicken anemia virus (CAV) in experimentally infected chicks. Briefly, 150 clinically healthy day-old broiler chicks were divided into five groups (A-E), with 30 chicks each. Chicks of group A and C were inoculated intramuscularly with 0.5 ml of 10 4.5 TCID 50/0.1 ml of MSB1 cell culture passaged Indian CAV isolate. At 10 days post infection (DPI), the chicks of group B and C were given 0.2 ml of 10 6.5 EID 50/ml of ARV isolate VA-1 by footpad route. Chicks of groups A-D were vaccinated occulonasally with 10 6.5 EID 50/chick of NDV-F. The chicks of group E served as uninfected unvaccinated controls. The groups were reared separately under strict isolation and monitored regularly for clinical signs, lesions and mortality. Characteristic symptoms and lesions of diseases viz. chicken infectious anemia and reoviral arthritis were observed in singly infected groups. Co-infected group showed more severe and extended lesions of disease: r eoviral lesions were more severe and pronounced. Putative effects of co-infection of CAV and ARV on the immune system of chicks were monitored for humoral and cell-mediated immune responses (HIR, CMI) by haemagglutination inhibition (HI) and lymphocyte transformation test (LTT), respectively, at various weeks post vaccination (WPV). Co-infected chicks showed marked suppression of both HIR and CMI responses during the entire observation period of 4 weeks. A maximum NDV-F HI antibody titre of 2 5.3, 2 4.5 and 2 7.2 was observed in CAV, reovirus and control groups, respectively, whereas in co-infected group only a titre of 2 3.9 was achieved at 2 nd WPV. Similarly, comparative reduced l ymphoproliferative responses of peripheral blood mononuclear cells reflected by the mean stimulation index values in LTT were observed in co-infected groups for both specific (NDV-F) and non-specific (Con-A) stimulations. In conclusion, the c hicks infected at an early age with CAV and subsequently with ARV exhibited exaggerated and extended lesions of diseases along with suppressed NDV-F vaccine responses.

Source : IPSACON-2005

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