| Abstract |
Limitations of live oocyst anticoccidial vaccines in poultry have led to a search for the new generation of anticoccidial vaccines. Several sources may influence the protective efficacy of the new generation of anticoccidial
vaccine candidates. Therefore, the objective of this study was to explore the sources influencing the protective
efficacy (in terms of the lesion score and the oocyst output) of the new-generation anticoccidial vaccine candidates from the challenge trials in chickens, using meta-analysis techniques. The overall effect size was also
estimated to get the overview of the protective efficacy. The study outcomes were the standardized mean difference (SMD) of the lesion score and the difference in mean (DM) of the oocyst output. Descriptive statistics of
the oocyst decrease ratio (%) and anticoccidial index (ACI) were also presented. Relevant citations were retrieved
from PubMed, Scopus, and Web of Science. Of 1524 retrieved citations, 63 were included for meta-analysis (60
for the lesion score and 44 for the oocyst output). Overall, the new generation of anticoccidial vaccine candidates
partially protected chickens from coccidiosis because they significantly reduced the lesion score (SMD = − 3.69,
[95% CI: − 4.08 to − 3.29], P < 0.001) with high heterogeneity (I2 = 96.85%) and the oocyst output (DM =
− 1.48, [95% CI: − 1.75 to − 1.21], P < 0.001) with high heterogeneity (I2 = 99.69%). The median oocyst
decrease ratio was 66.15% (a range from 4.27% to 95.93%, n = 125 subgroups). The median ACI was 164.71 (a
range from 50.05 to 196.40, n = 115 subgroups). Vaccine platform and route of administration were identified as
sources of heterogeneity for the lesion score and the oocyst output. However, severe publication bias threatened
validity of the lesion score outcome. After accounting for other sources of variation, the anticoccidial vaccine
candidates were shown to be less effective in reducing the oocyst output when the challenge dose, the length
between the day of last immunization and the day of the challenge, or the length between the day of the
challenge and the day of sampling, increased. In conclusion, although the new generation of anticoccidial
vaccine candidates clearly showed a partial protection of chickens from coccidiosis in experimental trials, the
protective efficacy was influenced by several sources, such as the vaccine platform and route of administration.
Sources of high heterogeneity such as protein antigens are worth exploring when additionally relevant data are
available. Therefore, additional experimental trials in chickens are required to better understand the protective
efficacy of the new-generation anticoccidial vaccine candidates. |
Publication
Journal Publication
ไทย