DNA Probes to Identify Horse WormsBy
A new set of diagnostic probes could help save horses worldwide from
nematode parasites. The probes are being developed jointly by
Agricultural Research Service scientists
and researchers in Scotland and Australia.
As horses graze, they can accidentally swallow about 65 species of nematode
parasites (worms) lying in the grass. As many as 150,000 parasites can live in
the wall of a horse's large intestine. The parasites can cause death, weight
loss and weakness. To prevent diseases, horse owners must routinely treat their
animals with anti-parasitic drugs.
Worm resistance to anti-parasitic drugs--the only current control--is more
than 50 percent in some areas. And no drugs are available to treat nematode
larvae, the immature stage that causes blood loss and diarrhea when they emerge
from the cysts in the wall of the intestine. Available diagnostic methods come
up short. Adult nematodes can be readily identified. But this isn't possible
for eggs found in samples of horse feces or larvae cultured from these eggs.
An ARS parasitologist--the world's leading expert on these worms-- is
helping his Scottish and Australian colleagues develop the new diagnostic
probes. The probes are based on the worm's DNA sequences. So far the
researchers have developed probes to detect the adult stage of about 20 of the
65 nematode species. The scientists' ultimate goal is probes to identify egg
and larval stages. With such probes, horse owners could more selectively use
anti-parasitic drugs. This would reduce treatment cost and extend a drug's
useful life by avoiding its overuse.
Other potential uses for the probes: help researchers determine whether a
nematode is drug- resistant or is a serious pathogen; identify the predominant
species causing larval cyathostomiasis, an emerging horse disease; and evaluate
potential natural controls such as fungi that kill the worm larvae in soil.
Scientific contact: Ralph Lichtenfels, ARS,
National Parasite Collection Unit, Beltsville, MD 20705, phone (301)
504-8444, fax (301) 504-5810, firstname.lastname@example.org.