Some 12,000 foals are born in
Kentucky each year, and an average
of 110 cases of placentitis occur
| Some mares grazing the rolling,
idyllic hills of Kentucky may produce foals destined to become prize
racehorses. Or, in their last month of pregnancy, the mares may be stricken
with a disease called nocardioform placentitis, causing weak or stillborn
The bacterium that causes the disease, Crossiella equi, was recently
named by ARS microbiologist David P.
Labeda, at the National Center for Agricultural Utilization Research, Peoria,
Illinois. Labeda has been collaborating with veterinary researchers at the
University of Kentucky's Livestock Disease Diagnostic Center, Lexington, to
learn more about the nature of C. equi and find some practical
horse-husbandry solutions to the problem.
"We're puzzled," says Labeda, "as to how C. equi finds
its way to its infection site."
Since 1986, nocardioform placentitis has dashed many dreams for prize-winning
horses in Kentucky. The disease causes lesions in the placentathe
nourishment highway between the mare's uterus and the fetuswhich prevent
the fetus from growing strong. Annually, the number of U.S. cases of
nocardioform placentitis, all occurring in Kentucky, fluctuated between 2 and
32. But during the wet-weather years of 1998 and 1999, it shot up to 94 and 144
cases, respectively. Some 12,000 foals are born in the region each year, and an
average of 110 cases of placentitis occur from all causes annually.
In 1999, University of Kentucky researchers found that DNA sequences in C.
equi corresponded to several DNA sequences that Labeda had determined for a
bacterium he named C. cryophila during a study of bacteria in the family
Though C. cryophila and C. equi are closely related, only C.
equi has been implicated in an animal disease. It thrives in warm
temperatures and on many carbon-rich materials.
Yet, in animal experiments at the University of Kentucky, the scientists have
been unable to use C. equi to induce nocardioform placentitis in a
horse. The researchers are trying to determine the life stage in which the
bacterium is infective and whether it becomes motile enough to reach the horn
of a mare's uterus.
Fortunately, C. equi succumbs to most antibiotics, and the disease has
so far stricken only a small percentage of horses. For these reasons, says
Labeda, it would be inappropriate to indiscriminately use antibiotics to
prevent the disease in all horses that might become infected.By Ben
Hardin, formerly with ARS.
This research is part of Plant, Microbial, and Insect Genetic Resources,
Genomics, and Genetic Improvement, an ARS National Program (#301) described on
the World Wide Web at http://www.nps.ars.usda.gov.
David P. Labeda is with
the USDA-ARS National Center for
Agricultural Utilization Research, 1815 N. University Street, Peoria, IL
61604; phone (309) 681-6397, fax (309) 681-6672.