However, the association between E. maxima and increased mortality was not seen in broilers that received an anticoccidial medication instead of vaccination, said Mark Jenkins, PhD, a microbiologist with the USDA’s Agricultural Research Service.

In addition, there was no correlation between mortality and other coccidial species — E. acervulina, E. tenella or E. praecox — whether broilers were vaccinated or treated with an anticoccidial, he said of the study, conducted with Mountaire Farms.

During the study, investigators tracked the species and concentration of Eimeria on commercial broiler farms for 2 years. They also looked at broiler performance.

“These data support observations that E. maxima is an important cause of mortality, probably due to it predisposing chicks to necrotic enteritis,” Jenkins said.

Although E. maxima-oocyst levels correlated with mortality, they did not correlate with broiler performance as measured by average daily weight gain and feed conversion ratio at 7 to 8 weeks, a finding Jenkins said was “of interest.”