BELTSVILLE, Md., Feb. 13—Medical veterinary officer
Donald P. Knowles has been named “Distinguished Senior Research Scientist
of the Year" by the Agricultural Research
Service for scientific leadership in developing methods to diagnose costly
animal diseases. ARS is the U.S. Department of
Agriculture’s chief scientific research agency.
“Dr. Knowles has been the driving force behind research
leading to new diagnostic tools with which we can more accurately detect
infections with disease agents such as Anaplasma marginale in cattle,
and prions associated with scrapie in sheep,” said Edward B. Knipling,
acting administrator of ARS.
Anaplasmosis is a tickborne disease caused by a parasite that
infects and destroys the red blood cells of an animal host in which it’s
transmitted. Anaplasmosis is estimated to be responsible for between 50,000 to
100,000 cattle deaths per year. Persistent infections that don’t kill the
animals can lead to poor weight gain, weakness and other complications. Cattle
that survive the initial infection become life-long carriers capable of
transmitting the parasite to other cattle.
At the ARS Pullman lab, Knowles led a team in investigating
cattle immune responses to the parasite that resulted in a new diagnostic test
that has proved more accurate than the standard method, called complement
fixation (CF) test.
Though it’s been used to check cattle prior to interstate
or international transport–such as from North America to Canada–the
CF tests has two main drawbacks. One is that it relies on the use of live
animals to obtain antigens. In this case, it is surface proteins on the
parasite that trigger antibodies in the animal’s blood. The second
drawback to using the CF tests is that they can yield misleading results, such
as “false negatives,” which allow the movement of cattle capable of
transmitting the disease.
Knowles’ lab, along with WSU collaborators, overcame the
problem by isolating and cloning one of these surface proteins, and then
developing a competitive inhibition ELISA test to check for natural antibodies
that bind to the antigen in blood samples from cattle. ELISA stands for enzyme
linked immunosorbent assay.
In collaboration with ARS, the
Canadian Food
Inspection Agency (CFIA) used the new anaplasmosis test to diagnosis
infections in cattle as well as bison. USDA’s
Animal and Plant Health Inspection
Service is also collaborating with ARS on using the test to survey cattle
in tick-infested areas of the United States. Knowles’ lab, meanwhile, is
working with WSU scientists to develop new vaccines using information on the
sequence of the Anaplasma marginale genome.
Other accomplishments that Knowles will be recognized for at the
Feb. 13 awards ceremony include:
Leadership in developing diagnostic tests for several other
agriculturally important animal diseases, including equine babesiosis
(piroplasmosis) in horses, small ruminant lentiviruses in sheep and goats,
transmissible spongiform encephalopathy (scrapie) in sheep, and bovine
spongiform encephalopathy in cattle.
Expediting collaboration with CFIA, APHIS, the National Centre
for Foreign Animal Disease in Winnipeg, Canada, and companies involved in
diagnostic kit development and distribution.
Contributing as senior inventor or co-inventor on five patents.
The most recent, filed December 2000, covers the use of monoclonal antibodies
to detect infectious agents called prions believed to cause the neurological
disease scrapie in sheep.
Providing guidance to six graduate students investigating these
animal diseases in pursuit of their M.S. or Ph.D. degrees.
Knowles is the author or co-author on 18 book chapters and 63
scientific papers. He is a member of five professional organizations, including
the American Association of Veterinary
Laboratory Diagnosticians. He earned a B.S degree in agricultural science
in 1978 and a B.S. degree in veterinary science in 1980 at the
University of Illinois, and a D.V.M. (Doctor
of Veterinary Medicine) there in 1982. He joined the ARS lab at Pullman in 1986
and earned his Ph.D. at Washington State
University in 1988.
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