Varroasis (Varroa Jacobsoni) is a parasitosis that affects bees, more precisely an acariosis. The damage caused by this parasitosis is serious because, without suitable protective measures, the infected colonies die.

The products presently available on the market contain active ingredients of synthetic origin which have the draw-back of causing drug resistance phenomena and of leaving in any case harmful residues in the beehive products.

The present invention relates to a pharmaceutical composition containing natural active ingredients that are not harmful to the bees, do not leave toxic residues in the honey and in the other edible products of the beehive.

The pharmaceutical composition according to the invention comprises : 45% to 90% of thymol crystals, 2.5% to 10% of menthol crystals, and optionally a pharmaceutically acceptable carrier,

on a solid absorbent support, said percentages being calculated with reference to the total weight of the composition, including the solid support.

The pharmaceutical composition according to the present invention may further comprise 5% to 20% of eucalyptol and/or 2.5% to 10% of camphor crystals.

The pharmaceutical composition according to the present invention preferably comprises: 65% to 75% of thymol crystals, 3% to 4% of menthol crystals, 10% to 20% of eucalyptol, 3% to 4% of camphor crystals.

By"a solid absorbent support"is meant any material capable of absorbing the components of the composition by immersing it into the admixture of the components in the molten state. Said solid support may be vermiculite, cardboard, felt, natural or synthetic sponges, wood, cork, or silicas and the like.

The solid support is preferably in the form of tablets.

The components of the composition can be absorbed into the material and/or crystallized on its surface.

The composition according to the invention is useful in the treatment of varroasis and other beehive

acarioses, such as the tracheal acariosis'" (Acaropis Woody Rennie).

BY"treatment"it is meant the prophylaxis or control or elimination of the parasitical infestation.

The compositions according to the invention are inserted into the beehive in any suitable place in order to produce the anti-parasitical effect by evaporation of the components from the solid support, yet in such a way as not to disturb the brooding, preferably above the honeycomb bearing frames at the four corners of the beehive.

The honey produced in the beehives, treated with the compositions according to the invention, contains residues of the products employed in very low amounts.

Anyway, any possible residue of the product is not harmful or toxic, and consequently does not pollute the honey and the other edible products of the honeycomb. Tolerance or resistance phenomena, or other secondary phenomena have not been observed.

The compositions according to the invention are prepared by a process comprising the following steps of: a) mixing the required quantites of thymol crystals, menthol crystals, and optionally camphor crystals, and/or the essential oil of eucalyptol and the optional carrier,

b) heating under stirring the mixture thus obtained at a temperature of from 40°C to 60°C for 2 to 8 hours, c) immersing the support into the thus obtained molten mixture for a period of time ranging from 0.5 to 10 seconds, d) weighing the tablet, optionally bringing it to the desired weight by dropping more molten solution onto its surface, e) introducing it into a suitable closed container, f) allowing the components to crystallize on the support, inside the closed container.

The starting materials are of pharmaceutical grade, as per specification of the major pharmacopoeias, such as the Farmacopea Ufficiale Italiana, the European Pharmacopoeia, USP, BP, DAB.

The temperature for step b) is preferably of from 45°C to 55°C, and the time is preferably in a range of from 4 to 5 hours. More preferably, the temperature is 50 °C and the time is 5 hours.

The immersion time for step c) is preferably 0.5 to 1.5 seconds. More preferably the immersion time is one second.

The weight of the tablet is preferably in the range of from 5 g to 25 g. More preferably the weight of the tablet is 10.5 g to 11.5 g.

The closed container may be any container that does not allow the composition to evaporate out. Preferably it is a plastics bag of suitable dimensions, in particular it is a coextruded two-layer bag, of which the first layer is a polyester film and the second one is a paper-polyethylene- aluminium-polyethylene layer.

EXAMPLE Thymol crystals 74.08 g Eucalyptol e. o. 16.00 g Camphor crystals 3.70 g Menthol crystals 3.70 g Vermiculite support q. s. to 100g.

Half the quantity of thymol and then sequentially the whole amounts of menthol, camphor and eucalyptol, and finally the remaining portion of thymol are introduced in a mixer. The temperature is raised to 50 °C and the mixture is continuously stirred for 4 to 5 hours, until the crystals are completely molten. The vermiculite tablets, the size of which is 7.5 x 5.0 x 0.5 cm. , are immersed into the molten mixture for 0.5-1 secs. The tablets are then taken out and allowed to drip over the immersion bath for 1-2 secs. Tablets having a

weight of 10.5 to 11.5 g are obtained. If necessary, the weight is corrected by dropping into the surface further molten mixture. Each tablet is immediately introduced into a bag of a coextruded double-layered material, the first layer being a polyester film and the second layer being a paper- polyethylene-aluminium-polyethylene film. The bags are allowed to rest until the components on the support are crystallized.