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Sweet Itch Vaccine Trial: 2007


The 2007 Sweet-Itch Vaccine trial will probably be the final and most important one. Recruitment was carried out early this year, with over 500 horses and ponies participating. Once again three initial injections were given two weeks apart and administered by a Vet. Thereafter owners are feeding a small capsule to their horse every two weeks until the end of the Sweet Itch season.
Results from this trial will be known at the beginning of 2008 and will be published on this web site - so watch this space!
(Jennifer Greaves, The National Sweet Itch Centre)

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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