Studies on immunosuppressive effect of commonly used Gumboro vaccines in broiler chickens
Abstract
The study was divided in to three experiments. In experiment-I 215 day- old broiler chicks were divided in to 5 groups A, B, C, D and E. Group A was kept as unvaccinated control. Groups B, C, D were divided into three subgroups each. Ist subgroups were given IBD vaccine; IInd subgroups were given IBD vaccines with NDV vaccine. Third subgroups were given IBD vaccine, NDV vaccine and supplemented with Levamisole @ 7.5 mg/ kg body weight & vitamin E @ 25mg / bird /day from day 13 to day 17 of age. Group E was subdivided into two subgroups EI&EII. EI served as NDV control and EII group was primed with live B 1 NDV strain and boosted with killed NDV on day 8 of age. In other subgroups live NDV vaccination was done with Lasota strain on day 5 of age followed by booster vaccination on day 21 of age. Three commercial IBD vaccines (vac1, vac2 & vac3) were given on day 14 of age in groups B, C&D, respectively.
Various parameters like clinical signs, gross lesions, HI titers due to NDV, IBDV ELISA titers, body weight, bursa and spleen index, bursa spleen and thymus lesion scoring was done to assess the role of three IBD vaccines in causing immunosuppression.
Clinical signs were not produced by any of vaccines. Some haemorrhagic spots were observed in thigh muscles in IBD vaccine3 inoculated groups on day 21 and 28. Body weights were significantly reduced in nonsupplemented subgroups inoculated with IBD vaccine1 & IBD vaccine3. Vaccine 2 did not cause significant decrease in HI titers whereas the HI titers against NDV were significantly lower in vac1&3 inoculated subgroups, which were not supplemented by immunomodulators, on the other hand highest ELISA titers against IBDV were produced by IBD vaccine3 followed by IBD vaccine1&2.
All the three vaccinal strains caused significant decrease in bursal index to a varying degree. Supplementation of immunomodulators caused significant increase in bursal indices. There was no effect on spleen indices by different vaccines. Vaccines 1 and 3produced thymic lesions but these were absent in vac2-inoculated groups. Maximum bursal and spleen lesions were produced by vac3 followed by vac1 and 2. Thymic lesions were absent in vac2 inoculated groups but present in vac1 and 3 inoculated groups. Supplementation of immunomodulators decreased the severity of lesions in all the subgroups.
Twenty chicks from 3 hatcheries were bled on day 1 of age to know the status of maternal antibodies against IBDV and NDV. Chicks from hatchery I had significantly lower HI titers against NDV but higher IBDV antibody titer as compared to hatchery II and II. Maternal antibody titers against NDV were 5.57±1.38, 13.14±1.94 and 12.00±2.6 in three hatcheries, respectively. Against IBDV maternal antibody titers were 5161.00±197.84, 3307.00±400.79 and 3645.21±242.21 in hatchery I, II and III, respectively. Five blood samples were collected from 15 farms each to know the IBD and NDV vaccinal response under field conditions. There was lot of variation in NDV and IBDV antibody titers. Some IBDV strains produced higher IBDV ELISA titers but at the same time caused decrease in HI titers against NDV.
On the basis of these studies it can be concluded that the practice of vaccinating against IBD at day13-14 of age in the field still holds good and farmers should be advised to supplement the chicks with immunomodulators from 13 to 17 day of age to ameliorate immunosuppressive effect of intermediate and intermediate plus vaccines.
Description
Keywords
null