Biological Characteristics of Chinese Precocious Strain ofEimeria acervulinaand Its Immune Efficacy Against Different Field Strains

Abstract

In this study, the biologic characteristics of one experimental precocious strain of Eimeria acervulina and seven field isolates from different geographic locations in China were compared, and the immune efficacy of two precocious strains against coccidiosis in chickens was assessed to explore their potential use as coccidiosis vaccines. All the different strains were purified by single oocyst separation and their monospecificity was confirmed using E acervulina-specific PCR assays. The average sizes of E. acervulina oocysts were 18.28-20.19 X 14.09-14.79 microm and the shape indexes were from 1.28 to 1.40. The prepatent periods ranged from 93 to 115 hr, except for the Heyuan precocious strain (HYP; 75 hr). Chickens infected with Huadu field strain (GHD) produced the highest oocyst output whereas HYP induced the lowest level. When inoculated with 50,000 sporulated oocysts or more, the average weight gains of infected chickens were reduced, with apparent clinical symptoms. To assess the immunogenicity of precocious strains HYP and Baoding (BDP), birds were orally immunized and challenged with seven different field strains of E. acervulina. Body weight gain, fecal oocyst output, and gut lesion scores were compared to evaluate their vaccine potential. The results showed that the average body weight gains of chickens in all the vaccinated and challenged groups were higher than those of nonvaccinated and challenged groups. In general, oocyst shedding was reduced 34.39%-95.31% and gut lesion scores decreased 31.03%-86.21% compared with unvaccinated and challenged control chickens. In summary, this study indicated that the precocious strains of E. acervulina could induce a protective immune effect with various responses against coccidiosis caused by different field strains.

Are Eimeria Genetically Diverse, and Does It Matter?

“…Similarly, just four nucleotide polymorphisms exist between EmAMA-1 coding sequences from the E. maxima Houghton and Weybridge laboratory strains, two causing non-synonymous changes, one situated in the putative pro-domain and one located in domain 1 [9,66]. Nonetheless, despite such limited diversity within the coding region of at least one vaccine candidate, strain specific immune escape has been reported in vivo for E. acervulina [67,68], E. mitis [69], E. maxima [70] and E.…”

Diagnosis and control of chicken coccidiosis: a recent update

“…As against the background of allelic polymorphism among AMA-1 which has limited their use in P. falciparum, AMA-1 is a potential candidate for E. tenella vaccine due to its inhibitory capacity on parasite invasion (Jiang et al 2012). Although low level of allelic polymorphism has been reported among AMA-1 of E. tenella and E. maxima, in vivo studies have also shown some degree of strainspecific immune escape (resistance) among the vaccine candidate for E. tenella, E. acervulina and E. maxima (Awad et al 2013;Healer et al 2004;Smith et al 2002;Wu et al 2014). Therefore, allelic diversity in this candidate vaccine antigen is a potential constraint to the effectiveness of subunit vaccine use against coccidiosis in poultry.…”