Protective immunity in broiler chickens elicited by live commercial coccidia vaccines (LCV) against recent field isolates and vaccines

Abstract

Use of live commercial coccidia vaccines (LCV) have proven to be important for control of coccidiosis in broilers, however LCV from different companies can vary. The objectives of this study were to measure the level of protection provided by five LCV against homologous and heterologous challenges at 20, 26 and 33 days of age and measure the level of protozoa parasite infection for each isolate in coccidia naïve chickens via wet mount smears. A Randomized Complete Block design with six vaccine treatments (a non-vaccinated, Con and vaccines A-E) was used. The dependent variables were weight gain and microscopic parasitic scores (MS). Vaccination was performed via coarse spray (d0). Birds were challenged on 20, 26, and 33 d of age with 3-5 field isolates and a homologous antigen. Four to five birds were challenged for each field isolate and homologous antigen. MS were determined 6 d post challenge. The d 26-32 and d 33-39 average gains of the Con treated broilers were lower (P ≤0.05) compared to the gain of broilers from the LCV treatments. The MS of the birds that were immunized with vaccines C, D, and E and challenged on d 20 with E. tenlla were 96, 83, and 92% numerically reduced, however this reduction was not significant. Similar results of MS were detected from the d 26 and 33 challenges. The average gain of broilers may be improved when LCV are used, however protection varies depending on Eimeria species challenged and the age of the broilers.