Making Coccidia Less Cocky
February 19, 1999
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
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
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
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,