| Coccidiosis causes serious economic losses on the global breeding industry every year.It can cause enteritis with high mortality to various subclinical diseases,among which the most pathogenic is Eimeria tenella.However,the pathogenicity of Eimeria tenella varies among different geographical strains.At present,the pathogenicity and drug resistance of Eimeria tenella in Yiwu,Zhejiang province have not been reported in China.In this study,prevalence of chicken coccidiosis was investigated by microscopic examination of samples collected from 10 chicken farms in zhejiang province.The total positive rate was 53.0%(265/500)in 10 chicken farms.Infection rates were as follows:98.0%(147/150)of chickens on 40 days,40.5%(81/200)on 60-85 days and24.6%(37/150)on 90 days.The positive rate of free-range rearing was 82.0%(164/200)being higher than that of free-range rearing 33.7%(118/350).Eimeria tenella was isolated from cecal samples of chickens in Jinhua County,Yiwu City,Zhejiang Province by single oocyst isolation technique,and was inoculated SPF chickens for passage and identification.Then,the isolated strains were inoculated with 5×10~5,5×10~4,5×10~3,5×10~2 sporulated oocysts,respectively,and the pathogenicity of Eimeria tenella isolates was preliminarily studied by animal experiments.Finally,drug resistance was tested with 6 anticoccidial drugs with feed premixes.The oocysts isolated from cecum of chickens in Yiwu were identified as Eimeria tenella by passages.The results of pathogenicity were as follows:1)5×10~2group:no death and no;2)5×10~3and 5×10~4group:mortality rates were 20.0%and40.0%with much blood in feces;3)5×10~5 group:all chickens were dead and weight gain was decreased with severe diarrhea with much blood in feces.Eimeria tenella(Yiwu strain)had no drug resistance to Sulfachloropyrazine sodium with mild resistance to Toltrazuril,Clopidol and Amprolium and moderate resistance to Salinomycin and Nicarbazin.In conclusion,had the highest rate of coccidiosis found in chickens under 40days of age with the positive rate of free-range rearing being higher than that of flat rearing.The Eimeria tenella(Yiwu strain)isolated from the cecum of infected chickens in Yiwu city were highly pathogenic,which were most sensitive to Sulfachloropyrazine sodium. |
