GB2110092A - Parasiticidal compositions - Google Patents

Abstract

A composition for topical application to animals to control ectoparasites comprising a mixture of a synthetic pyrethroid in a carrier comprising particular combinations of an alcohol solvent with an ester co-solvent.

Description

SPECIFICATION Parasiticidal compositions This invention relates to compositions for topical application of chemicals to animals for the control of parasites. In particular it relates to compositions comprising the synthetic pyrethroid, cyhalothrin, for the control of ectoparasites.

Topical application of parasiticides for the control of ectoparasites is well known and usually takes the form of spraying or dipping animals with suitable formulations of parasiticides. Recently attempts have been made to develop pour-on formulations, that is, formulations that are fully effective against parasites when a suitable amount of the formulation is applied to a particular area of the animal's surface, typically along the spinal region. A pour-on approach has inherent advantages over spraying or dipping techniques in that complete coverage of the animal is not necessary and the storage and loss of expensive chemicals in dip baths is avoided. The range of parasiticides which are effective in this technique is limited and the prior art compositions. have associated tissue reactions caused by the solvent systems used for preparing these compositions.These tissue reactions lead to considerable discomfort for the treated animals and in addition lead to severe damage to the hides and skins of the animals with consequent economic loss to the grazier. This is a particular problem with sheep in Australia where the major sheep breed is the Merino or Merino-cross, since this breed has been found to be very sensitive even to those solvent systems which have been tolerated to some degree by other breeds.

It is an object of the present invention to provide effective and non-toxic solvent systems that are tolerated by animals with a wide range of type and degree of sensitivity.

In the case of pour-on application to sheep, immediately after shearing is potentially a good time to treat sheep for parasitic control by topical application since the sheep are already mustered and the wool is relatively short. However the wool cover is still a significant barrier to the topically applied compositions particularly in the case of Merinos because the individual fibers are fine and closely packed. In addition there is a layer of wool grease covering the skin which provides a further barrier to penetration of the medication. This layer of wool grease can reach a very high level in Merinos. It is a further object of our invention to provide compositions which are effective in penetrating these wool and wool grease barriers while maintaining the freedom from adverse skin and tissue reactions.

Degreasing solvents such as for example, paraffins, isoparaffins, cycloparaffins and aromatics such as the xylenes, are well known, However these solvents, which effectively penetrate the wool grease cover, produce severe tissue reactions such as pain, swelling, dryness and cracking of the skin.

This in turn leads to wool loss and permanent hide damage.

Other solvents, such as alcohols and alcohol ethoxylates, do not produce tissue reactions but are relatively ineffective at penetrating the wool or wool grease cover.

We have now found certain compositions which are effective for the topical application to animals of the group of ectoparasiticides commonly referred to as the synthetic pyrethroids, and which are free from adverse tissue reaction even when applied to sensitive breeds of animals. A further advantage of these compositions is that organo-metallic materials may be readily incorporated to counteract specific mineral deficiencies in the animals.

Accordingly we provide compositions for topical application to animals for the control of endoparasites and ectoparasites which compositions comprise a synthetic pyrethroid carrier comprising a first solvent selected from the group consisting of C3 to C4 alcohols alkoxylated with from one to three moles of ethylene oxide per mole of alcohol, and C, to C4 alcohols alkoxylated with from one to three moles of propylene oxide per mole of alcohol and mixtures thereof; and a co-solvent selected from di(C1 to C6 alkyl) esters of C2 to C6 dicarboxylic acids, di(C, to C6 alkyl) esters of C2 to C6 dihydric alcohols, and C2 to C6 carboxylic esters of alcohol alkoxylates prepared by reacting one mole of an alkylene oxide selected from ethylene oxide and propylene oxide, and mixtures thereof.

The preferred C2 to C6 dicarboxylic acids are adipic acid and sebacic acid, and the preferred esters of these acids are dimethyl adipate, diethyl adipate, dimethyl sebacate, and diethyl sebacate. The preferred C2 to C6 dihydric alcohols are ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol.

The preferred synthetic pyrethroid is cyhalothrin.

Cyhalothrin is the name commonly given to the synthetic pyrethroid ( + )-a-cyano-3-phenoxybenzyl( j )-cis,trans-3-(2-chloro-3, 3, 3-trifl- uoroprop-1 -en-yl)-2,2-dimethylcyclopropane carboxylate. Reference to cyhalothrin includes reference to geometric and optical isomers thereof, and mixtures thereof.

Other synthetic pyrethroids may also be used in the composition, in particular the compounds 3-phenoxybenzyl ( + )-cis,trans-3-(2, 2-dichloro- vinyl)-2,2-dimethyl-cyclopropane carboxylate commonly known as permethrin, a-cyano-3-phenoxybenzyl (i )-cis,trans-3-(2,2dichlorovinyl)-2, 2-dimethylcyclopropane car boxylate commonly known as cypermethrin, and a-cyano-3-phenoxybenzyl ( + )-cis,trans-3-(2,2- dibromovinyl)-2, 2-dimethylcyclopropane carboxylate commonly known as deltamethrin, and geometric and optical isomers thereof, and mixtures thereof.

A particular feature of our compositions is that even when the pour-on composition is applied to a limited surface area of the host animal, both blood-sucking parasites such as ticks, and non-blood-sucking parasites such as lice and flies, are effectively controlled at sites on the animal remote from the application area even though the pyrethroids are not generally considered to operate systematically in animals.

The preferred first solvents are 2-propoxyethanol, 2-butoxyethanol, 1-methyl-2-propanol and 1-ethoxy-2-propanol, and mixtures thereof. The preferred co-solvents are ethylene glycol diacetate, 2-propoxyethyl acetate, 2butoxyethyl acetate and 1-methoxypropyl-2 acetate, and mixtures thereof. The most preferred carrier comprises 2-butoxyethanol and ethylene glycol diacetate.

These particular carriers provide rapid wetting of the wool or hair of the animal permitting movement to the skin level with minimal run-off and loss of formulation, and have the required solubility for the ectoparasiticide.

Preferably the weight/weight ratio of the first solvent to the co-solvent is in the range from 9:1 to 1:1.

The concentration of the synthetic pyrethroid is in the range from 0.2 to 5% weight/volume. The particular concentration can be readily chosen by those skilled in the art so that when a selected quantity of the solution of the ectoparasiticides is applied topically to the animal then the parasiticide will be present in an effective amount to control the particular parasitic infestations in the animal.

The effective dose range is dependent on the particular synthetic pyrethroid as well as the prevailing ectoparasite, but such dose ranges are readily determined by those skilled in the art. The synthetic pyrethroid, cyhalothrin, for example is used at a rate of approximately 2 mg/kg of animal bodyweight for good control of body lice, Damalinia ovis.

The species of parasites controlled by the various synthetic pyrethroids have been welldocumented in the prior art. It is a particular feature of our compositions that the synthetic pyrethroid is fully effective in topical applications in the compositions of our invention at the same time dose rates that are employed by conventional methods of applications such as spraying, dusting or dipping.

Thus, for example, a composition containing 1% w/v of cyhalothrin applied at the rate of 0.2 ml/kg of animal bodyweight gives effective control of body lice.

While the compositions are particularly effective for control of ectoparasites in cattle and sheep thay may also be used for pigs and domestic animals such as dogs and cats.

The compositions may additionally contain other ingredients such as, for example, preservatives and stabilizers. A particularly useful stabilizer is an antioxidant such as for example 4-butyl-2,5-dimethylphenol. Other antioxidants known to those skilled in the art may be used and the selected antioxidant or mixture of antioxidants is typically added to provide a concentration in the range of from 0.1 to 1.0% w/v, preferably 0.5 to 1.0% w/v, in the final composition.

In a further embodiment of our invention we provide compositions which additionally comprise a non-fast dye so that animals treated with the pour-on compositions may be readily recognized and thus unnecessary and undesirable duplicate treatment may be avoided. Suitable non-fast dyes soluble in the compositions will be readily selected by those skilled in the art so that the dyed area of skin or wool will fade in sunlight within a suitable period of exposure and without deleterious effect on the skin or wool. A particularly useful dye is rhodamine which is typically used in an amount to give a concentration range from 0.01 to 0.05% w/v in the final composition.

In a further embodiment of our invention we provide a process of treating animals which process comprises applying to the surface of the animals the composition of our invention comprising a synthetic pyrethroid in a first solvent as hereinbefore defined and a co-solvent as hereinbefore defined.

The compositions of our invention are applied in a line along the back of the animal from the withers to the rump. The compositions spontaneously "wet" and penetrate the wool or hair and migrate rapidly down the skin level. The compositions may be applied by brushing or rolling-on but more conveniently are simply poured on to the back of the animal.

This invention is now illustrated by but not limited to the following examples in which all parts and percentages are by weight unless otherwise specified.

Example 1 A formulation is prepared with the following composition: Rhodamine 0.1% w/v Cyhalothrin 1% w/v Ethylene glycol diacetate 25% v/v 2-Butoxyethanol to 100 vols Example 2 A formulation is prepared with the following composition: Rhodamine 0.1% w/v Cyhalothrin 1% w/v Ethylene glycol diacetate 25% w/v 1-Methoxy-2-propanol to 100 vols Example 3 A formulation is prepared with the composition of Example 2 except that the 1-methoxy-2-propanol is replaced with 1-ethoxy-2- propanol.

Example 4 Lice-infested merino sheep were sheared and the undiluted formulation of Example 1 applied along the spine as a strip 30-40 cm long at the rate of 2 my/ 10 kg bodyweight to provide an effective dose rate of 2 mg/kg of cyhalothrin. The presence of lice was assessed by parting the fleece at 30 sites on both sides of each sheep and counting the number of lice in each parted area. Some lice were detected two weeks after treatment but the sheep were completely lice-free at the six- and twelve-week inspection.

Example 5 The procedure of Example 4 was repeated with 10 merino cross breed lambs after five weeks the sheep were completely lice free.

Example 6 The procedure of Example 5 was repeated with 382 merino cross-breed sheep. Thirteen sheep were selected at random and were found to be completely free of lice after 4 weeks.

Comparative Example 1 A formulation was prepared with the composition of Example 1 except that the ethylene glycol diacetate was omitted. When this formulation was applied to three sheep by the procedure of Example 4 at an application dose of 4 ml tissue hardening on the animal was noted after six days.

Claims (11)

1. Pour-on composition for controlling or eradicating ectoparasite infestations in animals comprising an ectoparasiticidal amount of a synthetic pyrethroid in a carrier comprising a first solvent selected from the group consisting of C2 to C4 alcohols alkoxylated with from one to three moles of ethylene oxide per mole of alcohol, and C, to C4 alcohols alkoxylated with from one to three moles of propylene oxide per mole of alcohol and mixtures thereof, and a co-solvent selected from di(C, to C6 alkyl)esters of C2 to C6 dicarboxylic acids, di(C, to C6 alkyl) esters of C2 to C6 dihydric alcohols, and C2 to C6 carboxylate esters of alcohol alkoxylates prepared by reacting one mole of a C3 to C6 alcohol with from one to three moles of an alkylene oxide selected from ethylene oxide and propylene oxide, and mixtures thereof.

2. A pour-on composition according to claim 1 wherein the synthetic pyrethroid is selected from the group constituting of cyhalothrin, permethrin, cypermethrin and deltamethrin and geometric and optical isomers thereof, and mixtures thereof.

3. A pour-on composition according to claim 1 wherein the synthetic pyrethroid is cyhalothrin.

4. A pour-on composition according to claim 3 wherein the animals comprise sheep.

5. A pour-on composition according to claim 2 or claim 4 wherein the C2 to C6 dicarboxylic acids are adipic acid and sebacic acid and the C2 to C6 dihydric alcohols are ethylene glycol, propylene glycol, diethylene glycol and triethylene glycol.

6. A pour-on composition according to claim 5 wherein the concentration of the cyhalothrin is in the range of from 0.2 to 5% w/v.

7. A pour-on composition according to claim 6 wherein the carrier forms 95 to 99.8% w/v of the composition and the weight/weight ratio of the first solvent to the co-solvent is in the range from 9:1 to 1:1.

8. A pour-on composition according to any one of claims 5 to 7 wherein the first solvent is selected from the group consisting of 2-propoxyethanol, 2-butoxyethanol, 1-methoxy-2-propanol and 1-ethoxy-2-propanol, and mixtures thereof.

9. A pour-on composition according to any one of claims 5 to 7 wherein the cosolvent is selected from the group consisting of ethylene glycol diacetate, 2-propoxyethyl acetate, 2-butoxylethyl acetate and 1-methox- ypropyl-2-acetate, and mixtures thereof.

10. A pour-on composition according to claim 6 or claim 7 wherein the carrier comprises 2-butoxy-ethanol and ethylene glycol diacetate.

11. A method of controlling or eradicating ectoparasitic infestations in animals which method comprises applying to a portion of said animal a composition as claimed in any one of claims 1 to 10.

1 2. Pour-on compositions substantially as described herein and with reference to the examples.