Immunostimulating potentials of methanolic extract of <i>Plectranthus parviflorus</i> in chickens vaccinated against Newcastle disease and Infectious bursal disease

Abstract

Outbreaks of Newcastle disease (ND) and Infectious Bursal disease (IBD) have been reported in vaccinated poultry flocks in many countries highlighting the need for the administration of immunostimulants to improve immunity in such birds. The immunomodulatory effects of methanol leaf extract of plectranthus parviflorus on ND and IBD antibody titre was investigated. One hundred day-old cockerels were randomly assigned into five groups each, A-E and A1-E1 for Newcastle disease and Infectious bursal disease studies respectively. Groups A and A1 were control groups and received water only while groups B and B1 received LaSota and IBD intermediate plus ® vaccine respectively. Groups C and C1, D and D1 were administered 100mg/kg and 200mg/kg of Plectranthus parviflorus orally for three days before vaccination respectively, while groups E and E1were given 100mg/kg of the extract orally three days post vaccination. Blood samples were obtained via jugular vein at day-old and 14 days as well as on days 7, 14 and 21 post vaccination. Haemagglutination- inhibition (HI) test and enzyme linked immunosorbent assay (ELISA) were used to assay the antibody titre against ND and IBD respectively. A decline in maternal antibody over 14 days was observed for antibody titre against Newcastle disease and infectious bursal disease from 6.1 to 1.8 geometric mean (log2) and (1043.37±2.1) to (524.48±2.7) respectively. Group D was observed to have a significant titre value of 2.3 and 3.7 geometric mean (log2) 14 and 21 days post ND vaccination while group D1 also had a significant increase (1037.90±3.6) titre 14 days post-vaccination. This study showed that plectranthus parviflorus extract had a significant effect on Newcastle disease and Infectious bursal disease humoral response when administered orally at 200mg/kg before vaccination with ND and IBD vaccines respectively.