Scientist Sleuths in Pursuit of Racehorse
Disease By Jan
December 13, 2001
Scientists have characterized the bacterial culprit behind
nocardioform placentitis, a reproductive disease of thoroughbred racehorses
thats caused hundreds of cases of weakened or stillborn foals on farms in
Kentuckys Bluegrass region since 1986.
Genetic analysis of the bacterium led scientists to conclude it
is a new species in the genus Crossiella, named C. equi. The
accomplishment narrows down the list of potential suspects veterinary
scientists have to check when diagnosing horses or researching the nature of
the disease for clues on how it might be prevented using antibiotics, new
animal husbandry practices, or other measures.
There were 144 U.S. cases of nocardioform placentitis in 1999
and 48 in 2000, all on central Kentucky farms. The disease is characterized by
lesions that compete for nutrients flowing across the placenta to the
developing fetus from the mares uterus. This can result in an aborted
fetus during late gestation, or a weak or stillborn foal.
Michael Donahue and colleagues at the University of Kentuckys
Diagnostic Center in Lexington noticed portions of C. equis
genetic code matched those of other bacterial strains in a collection
maintained by microbiologist David Labeda at the
Agricultural Research Service.
Labeda oversees the Actinobacterial Germplasm Collection at
ARS National Center for Agricultural
Utilization Research, Peoria, Ill. Through careful analysis of the genetic
sequences, and comparison with another closely-related species, C.
cryophila, the scientists determined that the equine isolates were indeed a
member of the genus Crossiella--albeit a new species (C.
equi)--and one of the few actinomycetes known to cause animal disease.
But theres much still to learn about C. equi, notes
Labeda. One critical piece of intelligence in the fight against nocardioform
placentitis will come from studies revealing where and how the bacterium lives
in the environment, and at what life stage. Also important is determining how
the bacterium finds its way into the mares uterus and causes infection. A
story appears in the December issue of Agricultural Research
ARS is the U.S. Department of
Agricultures chief scientific agency. In Peoria, Labeda works in the
ARS center's Microbial Genomics and
Bioprocessing Research Unit.