Coccidiosis is a
parasitic disease that affects the poultry industry worldwide, having major economic impacts on poultry by reducing performance and decreasing productivity. This disease not only hinders the growth of chickens but also facilitates other epidemic diseases.
Coccidiosis is mainly controlled by prophylactic
coccidiostats administrated in the feed. However, the extensive use of these drugs has resulted in the development of drug resistance by Eimeria spp., which causes
coccidiosis. The aim of the survey was to acquire data on the prevalence of
coccidiosis and drug resistance of field isolates in chickens in China. We examined 545 farms across nine different geographic provinces over a 5-year period. These included Beijing, Sichuan, Zhejiang, Shandong, Guangdong, Fujian, Liaoning Provinces, Inner Mongolia and Xinjiang Uygur Autonomous Regions. The results indicated that oocyst per gram faeces (OPG) and
coccidiosis morbidity rate increased when non-prophylactic or low doses of
coccidiostats were used.
Coccidiosis morbidity rate in Guangdong Province was the highest, leading to greater, more frequent use of diverse types of
coccidiostats. Consequently, the Guangdong Province had the most serious drug resistance problem. In contrast,
coccidiosis morbidity rates in Inner Mongolia, Fujian and Liaoning were relatively low, leading to a reduced level of
coccidiostats use, which resulted in less drug resistance. The threshold of a
coccidiosis outbreak was an OPG level of >20000. When the OPG levels were ≥ 50000, chickens were in danger of clinical
coccidiosis, and here coccidia generated a certain degree of resistance to the
drug when administered. Coccidiostat resistance started to appear when the OPG level reached ca. 20000 using 2 mg kg(-1)/5 mg kg(-1), respectively, of
maduramycin, whereas 5 mg kg(-1) of
maduramycin developed severe drug resistance.