Immunosuppressive studies of an Indian chicken anaemia virus isolate in association with infectious bursal disease virus in experimentally co-infected SPF chicks

K. Dhama, J.M. Kataria, S. Arthur Sylvester, S. Tomar* and B.B. Dash
Division of Avian Diseases, Indian Veterinary Research Institute, Izatnagar - 243 122 (U.P.)
*Avian Medicine Section, Central Avian Research Institute, Izatnagar - 243122 (U.P.)

The study was conducted to ascertain the immunosuppressive effects of an infectious bursal disease virus (IBDV) in association with chicken anemia virus (CAV) in experimentally infected chicks. Briefly, 120 day-old specific pathogen free (SPF) chicks were divided into four groups (A-D). Chicks of groups A and C were inoculated intramuscularly with 0.5 ml of 10 4.5 TCID 50/0.1ml MSB1 cell culture passaged Indian CAV isolate. At 15 days post infection (DPI), the chicks of group B and C were given 10 3.5 EID 50 / 0.2 ml / Chick IBDV oculonasally. Chicks of all the groups were given NDV-F (10 6.5 EID 50 per chick, oculonasally 2-3 drops),

the next day of IBDV inoculation. The groups were reared separately under strict isolation and monitored regularly for clinical signs, lesions and mortality. Characteristic symptoms and lesions of diseases viz. CIA and IBD were observed in singly infected groups. Co-infected group showed more severe and extended lesions of disease: typically musculature hemorrhages got pronounced and later bursa became markedly atrophied Chicks remained more stunted. Putative effects of co-infection of CAV and IBDV 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 five weeks. A maximum NDV-F HI antibody titer of 2 4.6, 2 3.8 and 2 7.4 was observed in CAV, IBDV and control groups, respectively, whereas in co-infected group only a titer of 2 3.0 was achieved at 2 nd WPV. Similarly, comparative decrease in l ymphocyte proliferative responses of peripheral blood mononuclear cells reflected by the mean stimulation index values in LTT , with Con A mitogen and RDF antigen, were observed in co-infected as compared to singally infected groups.

In conclusion, chicks immunosuppressed at an early age with CAV and subsequently with other immunosuppressive pathogen (IBDV) exhibited exaggerated and extended lesions of diseases simulating field conditions along with suppressed NDV-F vaccine response.

Source : IPSACON-2005

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