Review on anticoccidial vaccine development for chickens: Past progress, modern methods, and production bottlenecks

Poultry coccidiosis is an economically significant intestinal disease caused by parasitic protozoa in the genus Eimeria. Developing Eimeria vaccines is a possible way to control and prevent coccidiosis. This review discusses the different methods and challenges of anticoccidia vaccine production for poultry. The production of anticoccidial vaccines involves several methods with challenges. Live Eimeria vaccines are produced using non-attenuation without any alteration or modifications in terms of pathogenicity, and attenuation methods reduce virulence through serial passage in embryonated eggs or chickens, irradiation, chemicals, heat, and live strains tolerant of ionophores. Both non-attenuation and attenuation methods are challenge, including the need for chickens' infection to produce oocysts, high cost, and quality control tests for ensuring vaccine safety. To minimize the challenge of live vaccine production, use recombinant deoxyribonucleic acid (DNA) technology. Unlike conventional whole-cell vaccines, non-replicating subunits only contain the pathogen antigenic parts for the subunit vaccine and genetic materials for DNA vaccine production and are cloned in the presence of a harmless plasmid vector or with a harmless adjuvant. The genetic and antigenic diversity among and within species of Eimeria, chicken flocks and locations, and complex life cycle of the Eimeria species make the development of DNA and recombinant vaccines extremely difficult. Challenge infection effects in immunized chickens are determined by weight gain, feed conversion efficiency, oocyst production, and intestine lesions, but there is a lack of immunological assays for accurately predicting studies for laboratory and field trials and standard guidelines for modern poultry vaccine production in Eimeria. The production of a safe and effective vaccine against coccidiosis in poultry is crucial for minimizing economic losses and enhancing animal welfare. To select the appropriate anticoccidial vaccine development methods and assess the challenges faced, more research should be done.