Eimeria acervulina is the coccidial parasite usually associated with necrotic enteritis, but recent research indicates that Eimeria maxima may be the more worrisome culprit.

In a study designed to examine the association between necrotic enteritis (NE) and Eimeria, broilers infected with various Eimeria species were challenged with Clostridium perfringens, the cause of necrotic enteritis.

Damage to the intestinal tract from E. maxima, E. acervulina and E. praecox worsened the pathogenic effects of C. perfringens, leading to NE, and except for E. praecox, all birds with Eimeria and C. perfringens experienced significantly decreased weight gain.

Infections with E. maxima, however, “greatly increased the probability of NE over the other species,” and E. maxima had a much higher potential for causing mortality from NE than E. acervulina, Dr. Greg Mathis and colleagues found.

“We got almost 45% mortality from NE in broilers with E. maxima compared to about 5% in birds with E. acervulina,” Mathis said in Seattle at the annual meeting of the American Association of Avian Pathologists, where the results of the study were presented.

'You've got to control E. maxima'

What are the implications of the findings for broiler producers? “You’ve got to control E. maxima to hold down NE,” the researcher said.

If producers vaccinate for coccidiosis control, “get the vaccination program in as early as you can and get it as uniform as you can. By 18 or 20 days, E. maxima will be gone and you shouldn’t have a problem,” Mathis said.