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The
Laminitis Trust Equine Cushing's Disease Trial
Report
on a trial to study the use of Vitex agnus castus extract
(Vitex4 Equids) on cases of Equine Cushing's Disease.
Robert
Eustace BVSc Cert EO Cert EP FRCVS and Susan L. Emery
The Laminitis Clinic, Dauntsey, Chippenham, Wiltshire. SN15 4JA. England
on behalf of the Laminitis Trust.
Protocol
The trial began in November 2001. The trial closed to new cases in March
2004. 120 horses and ponies are included in the study. All animals showed
clinical signs of Equine Cushing's Disease (ECD) and had blood concentrations
of endogenous ACTH (eACTH), insulin, cortisol and glucose measured before
joining the trial. Those with eACTH concentrations of greater than 50
pg/ml were eligible for inclusion in the trial. Animals were given Vitex4
Equids at the manufacturer's recommended dose rates i.e. 40 ml per day
for animals less than 800lbs, 60 ml per day for those between 800 lbs
and 1150 lbs and 80 ml per day for those over 1150 lbs. No other alterations
in the usual management was instituted and no other drugs were given to
the animals during the trial period. The only exceptions were drugs such
as acepromazine and phenylbutazone should the animals suffer laminitis.
The owners were required to submit quarterly reports as to the animal's
clinical condition, noting the following parameters; occurrence of hair
loss, diet, daily water consumption, weight (using a weightape), occurrence
of laminitis or other medical problems. In addition photographs of the
animal were also requested to accompany each report. At the end of the
12 month trial period a final report was required and a retest to measure
eACTH, insulin, cortisol and glucose.
Preliminary Results
To date 25 animals have completed their year of trial period alive and
their owners have submitted full reports including the final blood test
results. This group consisted of 13 mares and 12 geldings whose ages ranged
from 14 to 26 years. The dose was increased in four animals which had
shown no alteration in demeanour or clinical signs at the recommended
dose after 3 months of treatment. None of these received more than double
the recommended dose. 68 animals are currently part way through their
trial period. 27 animals died or were humanely destroyed during their
12 month trial period and final blood tests were not available.
Clinical signs
All owners reported improvement in the demeanour of the animals, they
became more active, less depressed and the term rejuvenated was often
used by owners. 22 owners reported that the animals shed their thick coats
during the early part of the trial period and the next year's coat was
more normal in appearance. 20 animals were reported to have shown reduced
polydipsia and hyperhidrosis. Two of the 25 animals suffered one or more
episodes of acute laminitis during the trial period. One horse which had
been dangerously aggressive showed a marked improvement within a month
of starting to receive Vitex4 Equids in the words of the owner
he is now a pussy cat!
Laboratory results
12 animals showed a reduction in eACTH during the period of the trial
though only 2 animals had final concentrations of less than 30 pg/ml.
9 animals showed an increase in eACTH and the concentration in 4 animals
did not alter during the trial.
9 animals showed
a reduction in plasma insulin concentration during the period of the trial,
7 of which had concentrations of less than 50 UIU / ml in their final
samples. 13 animals showed an increase in plasma insulin while the concentration
in 3 animals did not alter over the 12 months.
13 animals showed
a reduction in plasma cortisol over the trial period to less than 155
nmol/L in their final sample. 10 animals showed a rise in cortisol and
the plasma cortisol did not alter in 2 animals during the trial period.
Discussion
This trial is not complete and the results to date have not been subjected
to statistical analysis, yet the preliminary findings are interesting.
The majority of the 25 horses were chronic founder cases which had prior
to joining the trial suffered recurrent episodes of acute laminitis, only
two cases were so affected during the 12 month trial period. The horses
which did not survive the period of the trial were euthanased or died
due to a variety of serious systemic diseases which commonly affect geriatric
equines with ECD. In many cases inclusion in the trial was a "last
ditch" attempt which these owners were prepared to undertake. There
appears to be no trend towards normalisation of plasma concentrations
of eACTH, insulin or cortisol during the trial period, which may suggest
that the changes observed in the animals are not be related to the effects
of any of these parameters. The most consistent finding reported by the
owners was the lifting of the depression which all of these cases showed,
they became more energetic, interested in their surroundings and appeared
to enjoy life again.
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