Three sets of spectific primers were designed according to the previously published ITS-1 sequences of Eimeria maxima,E.tenella and E.acervulina in the GenBank.A single PCR and multiplex PCR methods were established,and used to detect the mixed samples which contained E.maxima,E.tenella and E.acervulina.The results showed that both methods amplified the special fragments with 151 bp,463 bp and 303 bp from E.maxima,E. tenella and E.acervulina,respectively,and there were no cross reactions with Sarcocystis fusiformis,Toxoplasma gondii and E.noces.The lowest concentration of DNA that could be detected was 0.5 ng.These results indicated that the multiplex PCR was a rapid,sensitive and specific method for detecting Eimeria spp.in the field.

day-old and 21-day-old Suqiu Yellow chickens were inoculated through the crop with 100 or (10 000) oocysts per bird with the eleven geographical strains of E. maxima, respectively. The estimates of oocyst production were made on 24 h fecal samples from 6 to 14 days after inoculation each day. The results showed as follows: Inoculated 100 oocysts at 7-day-old, the oocyst outputs produced from both of GZ and FY strain were the highest,while that of SH strain was the lowest. Inoculated 100 oocysts at 21 -day-old, the oocyst output from YZ strain was the highest, and that of Shanghai strain was the lowest again. Inoculated at 21 day-old and with 10 000 oocysts, the oocyst production from SZ strain was highest, and the both of LYG and YZ strains were the lowest. There was a positive relation between the oocyst output and age of chicken and the inoculated dose respectively. The patterns of oocyst shedding among all the eleven strains were similar, and the oocyst production reached its peak on the 7th day and decreased obviously on the 8th and 9th day after infection. The oocyst production was only 2 % of the total output on the 10th day, and was near to zero on the 14th day. On the 6th-8th days the oocyst output was 87 %~99 % of the total oocyst output.

Suqiu Yellow chickens were used to study the pathogenicities of eleven geographical strains of Eimeria maxima,assessed by clinical symptom,gross pathology,weight gain,lesion score and mortality.The results were as follows:The clinical symptoms and the gross intestinal pathology were similar in birds infected with all the strains and died of coccidiosis.The body weights in all infected groups were affected,and except the groups at 0.1×10~4/bird,the weight gains were significantly different from that of the control groups(P0.05).When the dose was 10×10~4/bird,the weight gains were the lowest in groups infected with Shanghai strain and the largest in groups infected with Suzhou strain and Longyan strain,but there were no significant differences(P0.05).And the lesion scores were the lowest in groups infected with Suzhou strain or Longyan strain and largest in groups infected with Yangzhou strain,but except Suzhou strain,there were no significant differences(P0.05).The infections with Yangzhou strain,Lianyungang strain,Fuzhou strain,Guangzhou strain and USA strain at dose of 10×10~4/bird caused a mortality of 20%,10%,10%,10% and 10%,respectively.It suggested that Yangzhou strain and Shanghai strain were the highest pathogenic,and Suzhou strain and Longyan strain were the least pathogenic among all the strains.