New Sweet Itch Vaccine Trial:
2007
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PROGRESS WITH THE TREATMENT OF SWEET-ITCH
(Professor Stanford has prepared the following note, giving further
information about the trials):
Sweet-itch is a problem caused by an excessive reaction to the
bites of midges. It begins with an intolerably itchy allergic
reaction to the saliva of the midge, which is then followed by
an autoimmune over reaction as the horse's immune system attempts
to right the original wrong. During this process thickening and
ulceration of the skin occurs and this only returns to normal
at the end of the midge season. Both the allergy and the autoimmunity
are caused by a dysregulation of the immune system to a mode known
as Th2. Treatments which causes the immune system to return to
the positive mode, known as Th1, are likely to be successful.
This has already been accomplished in human medicine in eczema
and asthma, using a very similar approach.
Over the past 3-4 years we have been working on developing a simple
and safe product, based on a suspension of heat-killed bacilli
of a carefully selected species. This modulates the immune response
from the dysregulation that leads to sweet-itch to a more normal
response to midge bites. This also corrects problems with the
subsequent tissue-healing process. One of our difficulties has
been to work out the optimal schedule for use of the treatment.
We began with injections alone and have moved on to a set of three
priming injections that have to be given by the vet before the
midge season starts. This is followed by treatment with capsules
that can be given by mouth throughout the season. We started with
capsules being given at monthly intervals, but now think it is
better for them to be given fortnightly. The treatment is extremely
safe with few reports of even minor side effects.
In 2006 four trials were carried out:-
1. A large open trial in which nearly 300 horses participated.
2. A blinded, randomised, placebo-controlled trial of 10 injections.
3. A blinded, randomised, placebo-controlled trial of 3 injections
followed by up to seven monthly capsules.
4. A small open trial for horses entering in the middle of the
season.
We have the results of the large open 2006 trial, based on reports
from 217 owners. The treatment showed success in 151 horses, but
made little difference in 66 horses. Thus 70% of owners considered
the treatment successful and 30% thought that it was not.
Nine horses showed no signs of sweet-itch throughout the season,
22% of owners thought that the sweet-itch was the same as in 2005,
69% thought that it was better and 8% thought that it was worse.
We are very pleased with these results.
This year (2007) we are using the best treatment schedule worked
out so far. As before, there were three injections given by a
vet, and then 20 capsules, one to be given every 2 weeks by owners.
It is hoped that this trial will show an even greater level of
improvement than previous years.
Professor J L Stanford, Chief Scientific Officer, BioEos Ltd.
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