Evaluation of a Universal Subunit Eimeria spp. Vaccine

Diseases associated with animal production and presently controlled by antibiotics represent a critical area for research and development. Coccidial infections in poultry have long been controlled by ionophores and/or coccidiostats and today these treatments have come under increased scrutiny by regulatory agencies and consumers. Additionally, traditional coccidia vaccines are limited to combining individual strains of attenuated oocysts; individual strains typically provide no cross-protection against other Eimeria strains. Therefore, there is a critical need for the development of new technologies to control Eimeria spp. Optimally, these new technologies should address and overcome concerns of both cross-protection and the one vaccine strain per species protection model.  We have developed a novel vaccine platform, BTVCx, that incorporates a subunit/epitope sequence, common for all Eimeria spp. (broad spectrum), into an inactivated orally administered vaccine that protects poultry against coccidiosis by inducing mucosal immunity. BTVCx was evaluated in two separated mixed-Eimeria spp. challenge trials at Southern Poultry Research (Athens, GA). For each experiment, 1000 day of hatch chicks (Cobb 500) were randomly assigned to either the control non-treated group (Ctl) or the treated group (n=50/pen 10 replicate pens/group) that received BTVCx (0.2ml/bird/oral gavage) on d2 and 16 of life. On day 28 (exp1) or d21 (exp2), birds were challenged with a combination of E. acervuline (EA), E. maxima (EM), and E. tenella (ET). Six days post challenge, 5 birds/pen birds were sacrificed, group weighed, and coccidial lesion scored according to the Johnson-Reid scale wherein 0 is normal and 1, 2, 3, or 4 indicate increasing severity of infection. On d28 (experiment 1) or d27 (experiment 2), fresh fecal samples were collected from each pen determine the degree of oocysts shedding/cycling. Results showed significant reductions in lesions scores in both experiments 42% for experiment 1 and 45% for experiment 2 (36/39%EA, 43/39%EM, 60/66%ET, respectively) and total oocyst shedding was reduced 42% in experiment 1 and 65% in experiment 2 (40/75%EA, 68/85%EM, 40%ET, respectively). In a third challenge experiment (see experimental design above), BTVCx was compared to a Ctl group and commercial coccidia vaccine group (Vx):  Productive parameters (Adjusted Feed Conversion Rate (FCR) and Average Weight Gain (DWG)) were measured throughout the course of the experiment.  At the conclusion of the experiment (d42) statistical differences were observed in DWG and FCR when comparing the BTVCx group and the Vx group with the Ctl group; birds receiving BTVCx weighed an average of 87g/bird more than the Ctl group and feed conversion improved by 84 points. These data taken together indicate the potential of BTVCx as an alternative control strategy for coccidiosis.   
 
Keywords: Vaccine, Coccidia, Alternative, Eimeria, Poultry.

Abstract presented at the 3rd International Symposium on Alternatives to Antibiotics 2019.