Making Coccidia Less Cocky

Coccidiosis--among the top five diseases preventing weight gain in chickens--is under serious attack at two Agricultural Research Service laboratories in Beltsville, Md. A handful of ARS researchers are working with companies to develop treatments that will use the birds' own immunity against the coccidia protozoa.

Worldwide, coccidiosis costs producers some $600 million. And the problem could worsen; the protozoa are developing drug resistance.

To give producers temporary relief, the researchers developed and tested a gamma-irradiated vaccine. Mark Jenkins of ARS' Immunology and Disease Resistance Laboratory determined the radiation dose needed to weaken the live oocysts--the infectious stage of coccidia. This prevents them from reproducing and stimulates the birds' immunity.

Harry Danforth of the Parasite Biology and Epidemiology Laboratory tested the vaccine on Cornish hens at Perdue Farms, Inc., in Salisbury, Md. It reduced the amount of feed needed to raise a Cornish hen by 3 hundredths of a pound. This may seem insignificant, but could save $1 million annually in feed costs for Perdue's Cornish hens alone--and much, much more in the broiler industry.

The trouble is, the new vaccine isn't a feasible long-term solution because it requires too many oocysts, which must be grown in live chickens. Potentially more permanent controls include:

• Jenkins produced recombinant DNA that directs production of proteins from the oocysts' outer coat. Inoculated into birds, it stimulated an immune response against coccidia having the specific proteins. This gave partial protection; Jenkins wants 100 percent.

• Hyun Lillehoj of the Immunology and Disease Resistance Laboratory is collaborating with Japanese and Korean scientists on recombinant DNA for a protein that blocks another coccidia stage, the sporozoite.

• Lillehoj is in search of an umbrella protection against the six or seven coccidia species that infect chickens. Her main focus is on chicken cytokines, substances immune cells generate to communicate. So far, two are promising.

Scientific contact: Harry Danforth, ARS Parasite Biology and Epidemiology Laboratory, Beltsville, Md., phone (301) 504-8300, fax (301) 504-6273; Mark Jenkins or Hyun Lillehoj, ARS Immunology and Disease Resistance Laboratory, Beltsville, Md., phone (301) 504-8201; fax (301) 504-5306, hdanfort@lpsi.barc.usda.gov; mjenkins@lpsi.barc.usda.gov; hlilleho@lpsi.barc.usda.gov.