AUTHOR=Liao Shenquan , Lin Xuhui , Zhou Qingfeng , Wang Zhanxin , Yan Zhuanqiang , Wang Dingai , Su Guanzhi , Li Juan , Lv Minna , Hu Junjing , Cai Haiming , Song Yongle , Chen Xiangjie , Zhu Yibin , Yin Lijun , Zhang Jianfei , Qi Nanshan , Sun Mingfei 

TITLE=Epidemiological investigation of coccidiosis and associated risk factors in broiler chickens immunized with live anticoccidial vaccines in China

JOURNAL=Frontiers in Veterinary Science

VOLUME=11

YEAR=2024

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2024.1375026

DOI=10.3389/fvets.2024.1375026

ISSN=2297-1769

ABSTRACT=<p>Coccidiosis is a costly intestinal disease of chickens caused by <italic>Eimeria</italic> species. This infection is associated with high mortality, reduced feed efficiency, and slowed body weight gain. The diagnosis and control of coccidiosis becomes challenging due to the fact that chickens can be infected by seven different <italic>Eimeria</italic> species and often occur mixed-species co-infections. Grasping the epidemiology of <italic>Eimeria</italic> species is crucial to estimate the efficiency of poultry management. This study aimed to explore the distribution of <italic>Eimeria</italic> species in broiler chickens in China after administering live anticoccidial vaccines. A total of 634 samples were obtained, and the survey results showed that the prevalence of <italic>Eimeria</italic> was 86.12% (546/634), and the most common species were <italic>E. acervulina</italic> (65.62%), <italic>E. necatrix</italic> (50.95%), <italic>E. mitis</italic> (50.79%), <italic>E. tenella</italic> (48.42%), and <italic>E. praecox</italic> (41.80%). Most samples indicated mixed-species infections (an average of 3.29 species per positive sample). Notably, 63.98% of samples contain 3 to 5 <italic>Eimeria</italic> species within a single fecal sample. The most prevalent combinations were <italic>E. acervulina</italic>–<italic>E. tenella</italic> (38.96%) and <italic>E. acervulina</italic>–<italic>E. necatrix</italic> (37.22%). Statistical analysis showed that flocks vaccinated with trivalent vaccines were significantly positive for <italic>E. necatrix</italic> in grower chickens (OR = 3.30, <italic>p</italic> &lt; 0.05) compared with starter chickens, and tetravalent vaccinated flocks showed that starter chickens demonstrated a higher susceptibility to <italic>E. tenella</italic>–<italic>E. brunetti</italic> (OR = 2.03, <italic>p</italic> &lt; 0.05) and <italic>E. acervulina</italic>–<italic>E. maxima</italic> (OR = 2.05, <italic>p</italic> &lt; 0.05) compared with adult chickens. Geographically, in the case of tetravalent vaccine-immunized flocks, a substantial positive association was observed between <italic>E. necatrix</italic> infection rates and flocks from eastern (OR = 3.88, <italic>p</italic> &lt; 0.001), central (OR = 2.65, <italic>p</italic> = 0.001), and southern China (OR = 3.17, <italic>p</italic> &lt; 0.001) compared with southwestern China. This study also found a positive association between <italic>E. necatrix</italic> (OR = 1.64, <italic>p</italic> &lt; 0.05), <italic>E. acervulina</italic> (OR = 1.59, <italic>p</italic> &lt; 0.05), and <italic>E. praecox</italic> (OR = 1.81, <italic>p</italic> &lt; 0.05) infection and coccidiosis occurrence compared with non-infected flocks in tetravalent vaccinated flocks. This molecular epidemiological investigation showed a high prevalence of <italic>Eimeria</italic> species in the field. The emergent species, <italic>E. brunetti</italic> and <italic>E. praecox</italic>, might be incorporated into the widely-used live vaccines in the future. These insights could be useful in refining coccidiosis control strategies in the poultry industry.</p>