Horses and owners should benefit
from two new ARS tests for the disease
piroplasmosis. The tests accurately detect the two different
parasitesknown as Babesia equi and Babesia
caballithat cause the disease. The tests also eliminate the need to
use live horses to produce analytical ingredients.
Piroplasmosis, also known as equine babesiosis, is not found in the United
States. But ticks capable of transmitting the disease are found at some U.S.
While the disease doesn't usually cause severe symptoms in animals that are
routinely exposed to the parasite, American horses can become very ill or die.
Those infected with B. caballi can be treated and the parasite
eliminated. No treatment has been found for B. equi infections.
Horses that enter the country for sale or competition must be declared free
of piroplasmosis. American horses that travel to foreign countries must be
retested before they can return home.
"The current test, called the complement fixation test, or CFT, has two
drawbacks," says Agricultural Research Service veterinary medical officer
Donald P. Knowles. First, he says, the test can give false negative or positive
readings, requiring additional tests for verification. That means that horses
entering the country must stay in quarantine longerdraining animals that
arrive in peak competitive condition and costing owners more in boarding costs.
Further, if one horse tests positive, other horses that came on the same plane
may also need to be retested.
Second, continues Knowles, the CFT uses infected horses to produce antigens.
Antigens are proteins in the parasites that cause horses to produce antibodies
in their blood. Although the new tests use the same antigens as the basis for
detecting the parasites, Knowles' research team developed a method for
producing them that doesn't require horses. In fact, USDA's Animal and Plant
Health Inspection Service (APHIS) originally requested that ARS develop these
tests to reduce or eliminate use of live animals. Knowles works at the ARS
Animal Disease Research Unit in Pullman, Washington.
Knowles and his colleagues with ARS and Washington State
Universitywith support from the horse industryisolated the genetic
material of each parasite and replicated it in bacteria instead of in live
horses. Then they developed new, more accurate tests using monoclonal antibody
technology. A monoclonal antibody is a laboratory-developed antibody that
reacts to only one part of a specific proteinin this case, a protein in a
ARS and WSU have applied for patents on the piroplasmosis tests. Now the
tests are undergoing validation by APHIS' National Veterinary Services
Laboratory in Ames, Iowa. The NVSL is the U.S. laboratory that determines the
piroplasmosis disease status of animals for import or export. They perform
about 32,000 piroplasmosis tests each year.
VMRD, a Pullman company that produces diagnostic test kits, has licensed the
first test, for Babesia equi, and plans to license the second. When
APHIS gives final approval, VMRD can sell the tests. "We hope the test
will be available commercially in 2 to 5 years," says Knowles.By
Kathryn Barry Stelljes,
Agricultural Research Service Information Staff.
This research is part of Animal Health, an ARS National Program (#103)
described on the World Wide Web at
Donald P. Knowles is in the
USDA-ARS Animal Disease
Research Unit, Washington State University, 337 Bustad Hall, Pullman, WA
99164; phone (509) 559-6022, fax (509) 335-8328.