EQUINE | Equine Disease Quarterly
the non-antibiotic compounds.
A recent in vivo study evaluated the intrauterine
treatment of a preformed Pseudomonas aeruginosa
biofilm with a combination of ceftiofur and tris- EDTA
or ceftiofur and tris-EDTA alone. Of five mares treated
with a combination of ceftiofur and tris-EDTA, all
effectively cleared the infection. This contrasted with
only two of five mares treated with ceftiofur and one
of five mares with tris- EDTA. The findings confirmed
greater efficiency in killing preformed biofilm within the
uterus by using a combination of antibiotic (ceftiofur)
and non-antibiotic (tris-EDTA) agents.
Advances in our understanding of the significance
of biofilms in human and veterinary medicine will in
time lead to improved diagnostics and more effective
treatment modalities. Fortunately several therapeutic
options are currently available to clinicians for the
treatment of biofilm-associated equine bacterial
endometritis.
CONTACT:
Ryan A.Ferris, DVM, MS, Dipl.ACT
[email protected]
Summit Equine Inc.
Newberg, Oregon
Tall Fescues – Endophyte-infected,
Endophyte-free, and Novel Endophyte
Tall fescue (Lolium arundinaceum) is one of the most
widely grown perennial grasses in the world and
covers approximately 37 million acres in the United
States alone. It can be infected with an endophytic
fungus (Epichloë coenophiala), which in a symbiotic
relationship with the plant produces chemicals called
alkaloids that confer benefits to the plant. This tall
fescue, native to Europe, was introduced into the United
32
States in the 1800s. In 1931, E.N. Fergus, a University
of Kentucky agronomist, collected tall fescue seed from
the Suiter farm in Menifee County, KY, on the basis of
winter hardiness, persistence in high traffic areas, and
drought resistance, giving rise to the cultivar of fescue
known as Kentucky 31 (KY31). However, some of the
alkaloids, primarily the ergot alkaloids produced by
infected plants, are detrimental to grazing animals,
including horses.
Historically, the endocrine hallmark of fescue toxicosis
in several animal species is a decrease in the circulating
concentration of the hormone prolactin. Prolactin
is secreted by the pituitary gland, and control of its
secretion is complex and not completely understood.
Prolactin exerts effects on a variety of systems
including milk production, steroidogenesis (estrogens,
progesterone and testosterone), hair growth and
shedding, libido, and synthesis of surfactant by the fetal
lungs. Importantly, prolactin may also exert an effect
on the feto-placental unit by altering steroid synthesis
and/or metabolism and maturation of the fetal adrenal-
pituitary axis, which is necessary for parturition. One
major regulator of prolactin secretion is dopamine, a
hormone produced by the hypothalamus. Dopamine,
interacts with receptors in the pituitary gland and
inhibits the secretion of prolactin.
Ergovaline is the most abundant ergot alkaloid in tall
fescue. Ergovaline, and several other alkaloids from
fescue, have similar chemical structures to dopamine
and can bind to dopamine receptors, thereby causing
a decrease in prolactin secretion, resulting in partial
or complete agalactia (the inability to produce milk)
in foaling mares. Additional problems associated with
KY31 fescue consumption in foaling mares include
altered hormone concentrations, extended gestation,
thickened placenta, placental retention, dystocia, birth
of dysmature foals, and increased foal and placental
weights. Dopamine receptors have been found in
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