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The main purpose of this experiment was to test the effect of Insol® Dermatophyton (ID) by employing a placebo controlled blind study, testing 51 horses suffering from summer eczema. The animals were vaccinated three times every two weeks in February of the year the experiment took place using ID (n=27) or placebo (n=24). Furthermore, the testing encompassed showing whether immunomodulatory effects could be detected when having used ID. For this purpose, each time the horses were tested – 5 times in total – blood samples of serum were taken in order to evaluate specific cytokines (IL-1, IL-4, IL-10, IFNγ, TNFα). As a third aim, both in-vitro allergy tests – “Funktioneller in-vitro Test” (FIT) and “Cellular Antigen Stimulation Test” (CAST) – were conducted and the results compared. Changes of the clinical results (alteration of skin, itching) were assessed by a score especially developed for this purpose, before, during and after the insect period of the respective testing year. Following the generally well-known predilection sites, 12 body regions were specified, each of which was analysed for five symptoms (hair breakage, alopecia, bloody/purulent skin alteration, dandruff) and rated using points between 0 (not apparent) and 5 (extremely apparent). By adding and evaluating these points, for each animal and each point in time the clinical intensity of the summer eczema could be quantified.
The symptom most apparent was the hair brittleness, followed by thickening of the skin. All symptoms, except for dandruff, were most intense in the summer and had their lowest value in the winter. Regarding the symptom of dandruff, it was vice versa. The region most afflicted was the neck, followed by the tail and the lower abdomen. The most obvious characteristic of the medical condition could be observed in summer, whereas in winter the symptoms were least apparent. It is possible though to gather conclusions from the score of the first examination in winter regarding the intensity of medical condition throughout the season. Horses with a high score in the winter were also afflicted worse in summer than horses with a generally lower score.
After having used ID in a therapeutical or prophylactic placebo controlled blind study, it could not be established that there was a significantly positive effect on the symptomatology of skin affected by summer eczema. However, a positive trend could be observed in that the ID vaccinated animals in summer had a lower score than the ones which had been treated with a placebo. The score, nevertheless, was not statistically significant. This trend, however, could be confirmed by an owner-survey comparing the year of treatment with the year before. On this occasion the owners of the verum group evaluated the clinical appearance of the symptoms as significantly improved in the year of treatment compared with the year before. This effect could not be seen in the placebo group. Therefore in this group the owners declared that the average beginning of the symptoms was one month later (July) than the year before and lasted one month less (3 months), too. Both were statistically significant. Furthermore, the “young eczema” horses treated with ID (with symptoms of 2 years maximum) had a respectively lower score each time they were examined.
Having examined the cytokines, an immunomodulatory effect resulting from the therapy could be verified. For instance, the concentrations of IL-10, TNFα, and IFNγ in the verum group rose considerably and what is also statistically significant, they rose after the vaccination too. This means an immunomodulatory shift from Th2 (allergy) to Th1 (tolerance). However, this effect could only be shown in-vitro.
Comparing both allergy tests FIT and CAST, the results were as follows: both tests come to representative and similar results, also regarding off-insect periods. Nevertheless, FIT is the more sensitive and therefore more accurate test, having an obvious lower number of false-negative horses. This is mainly due to the cross-reacting insects, which are not primarily involved in the summer eczema complex. This suggested that there is a very wide allergen-spectrum responsible for the summer eczema disease. In both tests, however, in winter the manifestation of summer eczema disposition in the winter was more extreme; there were also not as many false-negative horses in winter. All of this leads to a more accurate and reliable result in winter.
As a final point, the intensity of worm attack was contrasted with the severity of summer eczema symptoms in the FIT test. It could be shown that the worm attack was not directly proportional to the score of FIT. On the contrary, the tendency could be observed that verminous horses had a significantly lower FIT than horses without any actual worm attack. A false-positive result of the allergy test, caused by a strong worm attack, is therefore impossible.
Further studies will have to establish if the immunomodulatory effect, shown in-vitro, can be intensified by changing of the ID formula, hence allowing statistical evidence in-vitro.