You may want to read the paragraph under diagnosis in this article:
https://www.merckvetmanual.com/poultry/coccidiosis/overview-of-coccidiosis-in-poultry
Here are some more good articles:
https://ucanr.edu/sites/poultry/files/201392.pdf
https://www.farmhealthonline.com/US/disease-management/poultry-diseases/coccidiosis-in-poultry/
http://www.poultryhub.org/health/disease/types-of-disease/coccidiosis/
https://www.merckvetmanual.com/poultry/coccidiosis/overview-of-coccidiosis-in-poultry
Here are some more good articles:
https://ucanr.edu/sites/poultry/files/201392.pdf
https://www.farmhealthonline.com/US/disease-management/poultry-diseases/coccidiosis-in-poultry/
http://www.poultryhub.org/health/disease/types-of-disease/coccidiosis/