| dc.description.abstract | Imported live attenuated infectious bursal disease (IBD) vaccines have been linked to vaccine failures in layers and broilers and associated with immune suppression, and sub-optimal immune responses. In addition, there is no vaccination regime for indigenous chicken in Kenya. This study investigated the effects of aqueous extracts of stinging nettle (Urtica dioica) and neem (Azadirachta indica), in modulating the immune response to an imported live attenuated (D78) and a locally-derived killed (K1) IBD vaccine in indigenous chicken. Two composite controlled experiments were conducted using a total of one hundred and four (104) specific-antibody-negative (SAN) indigenous chicks. The first involved: propagation of local IBD virus isolates; quantification of the virus content and preparation of the inactivated K1 IBD vaccine by formalin inactivation. Forty four (44) 4-week-old indigenous chicks, divided into 5 groups, were used to propagate four local IBD virus isolates; one being a control group. The second involved: establishing immune-stimulating effects of stinging nettle and neem, assessing immunosuppressive effects of the live attenuated D78 IBD vaccine and coming up with a vaccination regime for indigenous chickens. Sixty (60) SAN indigenous chicks were divided into 3 composite treatment groups (Group 1A, B, C, D & E, Group 2A, B & C and Group 3A, B, C, D, E, F and G). Each of the 15 sub-groups were inoculated with D78, K1 and D78 + K1 as follows: imported D78 and local K1 IBD vaccines were given to group 1A, 1C & 3A and 2A-C, 3B (at 14, 28 days of age) respectively. A combination of D78 and KI vaccines was given to group 1B (at 14, 28 days of age) and 30 days apart for group 1D-E (D78 priming at 14, 21 days and booster K1 at 44 days of age). Live Newcastle disease (ND) La Sota vaccine was given to group 1A-E, 2A-C, 3C and 3D (at 21, 35 days of age). Stinging nettle was given in water to groups 1B, 1E, 2B, 3E and neem to groups 1C, 1D, 2C, 3D and 3F. Group 3G acted as the unvaccinated and unsupplemented control. Immune response to the two IBD vaccines was assessed by indirect ELISA. Immunosuppression was assessed using hemagglutination inhibition (HI) titres. Effects on chicken health and growth was assessed by monitoring differential leucocyte counts, heterophil-lymphocyte ratios (H/L ratios), total plasma protein, packed cell volume, glucose concentration and weight gain.
The imported live D78 IBD vaccine had a faster onset of higher antibody titres compared to the local inactivated K1 IBD vaccine when given alone. Stinging nettle was better than neem in enhancing IBD antibody response beyond the protective threshold titre level of 3.18 log10 in groups receiving a combination of the two IBD vaccines. The highest (4.103 log10) and most persistent (˃3.8log10) mean antibody titres were seen in group 1E supplemented with stinging nettle and group 1D (3.835 log10) supplemented with neem, both received a combination of the IBD vaccines 30 days apart. The live attenuated D78 vaccine was moderately immunosuppressive while the local inactivated K1 vaccine had neither adverse reactions nor immunosuppressive effects. Neem and stinging nettle supplementation enhanced HI ND antibody response in groups receiving a combination of the two IBD vaccines; however, neem reversed the immunosuppressive effects of the live D78 IBD vaccine in group 1C (D78 + ND + Neem). High initial increases in mean relative counts of lymphocytes corresponded to high plasma protein levels in groups receiving a combination of the two IBD vaccines (1D). There was a significant (p˂0.05) negative correlation between H/L ratio and total plasma protein (r = -0.61) in group 2A (K1 + ND). Higher body weight gains were associated with groups receiving a combination of the two IBD vaccines and D78 vaccine alone compared to groups receiving the local killed K1 vaccine alone. Adoption of a prime-boost program comprising a combination of the two IBD vaccines plus supplementation with either stinging nettle or neem is recommended. The K1vaccine should, however, be further evaluated for protection of indigenous chicken against challenge with virulent IBD virus. | en_US |
