COCCI People - Dr Harry Danforth

Dr. Harry Danforth has devoted his career to controlling coccidiosis in poultry

Dr. Harry Danforth

Asatisfying life's work sometimes comes about by chance, and so it has been for Dr. Harry Danforth, a research microbiologist who has made invaluable contributions to the control of coccidiosis in poultry.

It started when he was a college undergraduate and found a course in parasitology to be particularly interesting. Danforth was fascinated by the interaction between parasites and their host.

Parasites in humans might have been just as interesting, but as he pursued his higher education, including a Ph.D. in biology, "I met people in the field of veterinary parasitology willing to take on a young kid," he recalls. "The veterinary part came about by chance."

Since 1980, Danforth has been with the United States Department of Agriculture. He currently works at the Parasite Biology and Epidemiology Laboratory in Beltsville, Md., outside Washington, D.C., and lives nearby with wife Charla.

Works Enabled Vaccine Development

Danforth's accomplishments as a scientist have been impressive. He has published over 200 peer-reviewed manuscripts, book chapters and abstracts and currently holds 13 cooperative research agreements with vaccine and pharmaceutical companies.

He has extensively researched monoclonal antibodies against avian coccidia and is credited with developing the first genetically engineered antigen that provides immunity against coccidiosis affecting poultry.

"It was the production of monoclonal antibodies against parasites that made it possible to produce antibodies that would trigger an immune response to coccidia in chickens," says Danforth.

"Then we started to work with the delivery of live coccidia vaccines. We found that you could use drug-sensitive coccidia to vaccinate birds and change the sensitivity of the coccidia on the floor of growout houses," he says.

As far back as the 1970s, Danforth says he foresaw that the effectiveness of anticoccidials could be problematic. "Ionophores were emerging and they were effective, but coccidia had already shown resistance to all other drugs for coccidiosis. I figured it was a matter of time before resistance also occurred with the ionophores, and that immunology was the future of coccidiosis control," Danforth says.

Recent research by Danforth has demonstrated that vaccinating with a live oocyst vaccine renews the sensitivity of coccidia to the widely used ionophore salinomycin.

Vaccination also changes the composition of oocysts in the field and their ability to cause intestinal damage, his research shows. For example, after the use of Coccivac-B, a live-oocyst vaccine, an aggressive Eimeria tenella strain disappeared altogether, and lesions due to other species of Eimeria were minimized.

Predicts Change

Many poultry producers are not using coccidiosis vaccines, Danforth says, because they can still control coccidiosis with in-feed anticoccidials. But he believes that's going to change with time.

"In-feed anticoccidials have been good over the years and are simple to use. You just mix it into feed at the feed mill and treat flocks across the board.

"But resistance has become even more of a problem and there are no new anticoccidials being produced. Producers are going to look to vaccines to control coccidiosis. Vaccination is a good adjunct to anticoccidial treatment," he says.

Initially, producers may not depend entirely on vaccines, but more will at least incorporate vaccination into their coccidiosis control programs, he says. "In the immediate future, there will be more vaccination with live oocysts and, further into the future, other types of coccidiosis vaccines."

Consumer demand for birds raised without drugs will contribute to the trend to vaccinate and capitalize on natural immunity, although in the United States, that demand isn't as strong yet as it is in Europe, Danforth says.

Down the road, as there is a greater understanding of how vaccines work, he says, the pendulum will swing and vaccination will be the primary way that poultry producers control coccidiosis, he predicts.

Clear Mission

Today, Danforth is spending more time in an office directing research than he is in the lab. It's a far cry from the small farming community in Illinois where he grew up, but Danforth says he gets out as often as possible to visit with poultry producers, particularly in the nearby Delmarva Peninsula, and with veterinarians in charge of flock health.

Whether he's in the office or the lab, however, Danforth says he likes his work, and his mission to advance the science of coccidiosis management.

Coccidiosis research, he says, gives poultry producers new direction and possibilities for coccidiosis control. "It helps them take the technology we have and apply it so we will continue to have good flock performance and control of a potentially economically devastating disease."

One of the reasons further advancements in coccidiosis control can be expected, says Danforth, is due to the attitude of the poultry industry.

"I applaud the poultry industry for its willingness to try new things," he says. "People in the industry are highly progressive. They are always open to new ideas and are highly adaptable. I find that refreshing. I really want to thank them for their cooperative attitude."

Editor's note: This is the first in a series of features about professionals who are making important contributions in the field of coccidiosis control.

Source: CocciForum Issue No.2, Schering-Plough Animal Health.

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