IE52108B1

IE52108B1 - A method of controlling lice on sheep

Info

Publication number: IE52108B1
Application number: IE2719/81A
Authority: IE
Original assignee: Wellcome Found
Priority date: 1980-11-21
Filing date: 1981-11-20
Publication date: 1987-06-24
Also published as: GB2150026B; FR2494561B1; GB2150025B; ZA818079B; GB8332684D0; GB2150026A; IE812719L; FR2494561A1; GB2088212B; ZA833066B; GB2088212A; GB2150025A; NZ199009A; GB8332685D0

Abstract

Sheep ectoparasites including keds, flies and mites are controlled by the localised application to the skin or fleece of the sheep of a pyrethroid in a solvent system containing a glycol. The treatment is effective even on long-woolled Merino sheep.

Description

The present invention relates to pour-on formulations for controlling lice ©n sheep. The invention has special application to the control of the sheep-biting louse (Damalinia ovis) particularly on merino sheep.

Traditionally, sheep have been treated for the control of ectoparasites by dipping or spraying the whole external surface of the sheep. However, this is an inconvenient and timeconsuming operation. Attempts have been made to treat infested sheep, particularly lice-infested sheep, with a large variety of known insecticides by various more convenient routes, including pour-on treatments, subcutaneous injection, and by oral dosage. Hitherto, none of the treatments has any significant effect on the control of the lice populations. In particular, merino sheep which have very dense wool have, not responded to such treatments.

Our copending Irish ApjilΐςδΙΐο'ηεΊίοϊ. , if disclose and claim a method for controlling keds, blowflies and mites on sheep by localised administration of a pvrethroid and formulations of pyrethroids in a solvent system containing diethyleiie' glycol mono-N-butyl ether respectively.

The present invention is based on the unexpected discovery that localised applications of pyrethroids are surprisingly effective in controlling and eradicating lice. It is particularly surprising that such localised application is effective even on longwoolled merino sheep.

Thus, the present invention provides a method of controlling lice on sheep which comprises the application onto a localised region of the skin or fleece of a sheep oi a pvrethroid of the formula: 53108 wherein M is - CO - CH - CH - CH = C ^C CH, CH, CO - CH- CH - CH - C^ \ / I |\ C *3 X4 CH CH, or - CO - CH - R, CH CH, CH, -3and wherein X± to Xft are independently selected from halo, CpC^ alkyl, halogen-substituted alkyl, and halogen-substituted phenyl; X5 is -H or halo; R^ is -H or cyano; and R^ is halogen-substituted phenyl, By localised application is meant that the pyrethroid is applied to a minor portion of the skin or fleece of the sheep, generally as a line or spot on the sheep's back. It has been surprisingly discovered that, notwithstanding the presence of a sometimes dense coating of wool, the pyrethroid appears to act over the entire surface of the sheep. It is believed as a hypothesis that the pyrethroid is transmitted over the surface of the sheep by diffusion through the wool grease.

The pyrethroid is generally applied as a liquid formulation, a paste or as a solid powder. Surprisingly, it has been found that it is not necessary that the pyrethroid be dissolved to be effective.

The localised application is preferably carried out as a pour-on treatment by pouring the formulation comprising the pyrethroid along the back of the sheep (i.e. a so called backline application). Surprisingly, it is not necessary to totally immerse the sheep in the formulation so that the treatment of large numbers of sheep is facilitated.

Alternatively, the application may be carried out by means of a localised spray or aerosol, usually along the sheep's back as it passes through a sheep race. The aerosol might comprise the pyrethroid dissolved in a liquid carbon dioxide propellant.

Without wishing to be limted by any theoretical mode of action, it is believed that the pyrethroid acts superficially and is not dermally and systemically absorbed. It is therefore surprising that protection over the entire sheep is attainable from a localised application.

The pyrethroid is preferably selected from the group of light stable pyrethroids.

Deltamethrin lalso known as decamethrin) is preferred and is a solid under normal conditions. Suitable pyrethroids are disclosed in Tables I to III. 53108 53108 -5lAELEJL M * - CO - CH- CH - CH - C - \ / C / \ CHj CH3 1 X3 *4 No.X1 x2X3X4X5R1 trivial name 9 Br Br Br Br H CN tralomethrin 10 Cl Cl Br Br H CN tralocythrin -6It is a particular advantage of the present method that only small volumes of pyrethroid or pyrethroid-containing formulation need to be applied. Depending on the size of the sheep, the volume applied will generally lie in the range 2 to 15 ml per sheep. For convenience, the pyrethroid will generally be applied in a liquid formulation.

Depending on the efficacy of the particular pyrethroid employed, the formulation generally contains from 0.1 to 500, preferably 1 to 250 mg/ml of the pyrethroid. Moreover, the pyrethroid is preferably applied to the sheep in an application of from 1 to 500, preferably 1.5 to 250 mg/kg body weight.

The formulation may be applied to full-woolled or sheared sheep. However, higher doses are required for full-woolled sheep. The pyrethroid is preferably applied in the form of a pour-on formulation. The formulation may comprise one or more organic solvents, such as xylene, toluene, cyclohexanone, and a glycol. One preferred solvent system comprises 30-70 wt % xylene, 20-40- wt % cyclohexanone and 5-25 wt % vegetable oil.

Suitable glycols include ethylene glycol and propylene glycol, polyethylene glycols and polypropylene glycols, ethylene glycol-propylene glycol copolymers, and alkyl ethers and alkyl ether esters of the general formula: R1 z I R O - tCHz - CHO) -CO-R n R1 = C. alkyl or hydrogen, 1 3 R = Cj-Ct, alkyl, hydrogen or -CO-R , Rj — Cj®I4yl, and n = J. - 40 ' Diethylene glycol mono-n-butyl ether has been found to be particularly useful. It 25 has been found to have minimal adverse effect on the skin in terms of a mild epidermal shedding seen with other solvents in some sheep. Alternatively, the formulation may be an aqueous formulation containing the pyrethroid in the form of a suspension or emulsion and comprising suitable surfactants to stabilise the suspension or emulsion, and prevent undue run-off from the back of the sheep.

Thus, it has been surprisingly found that the pyrethroid is effective even when in the undissolved state. -7Paraffin oils, vegetable oils, e.g. com oil, peanut oil, castor oil, olive oil, can be added as viscosity modifiers and co-solvents.

Alkylamides and esters of fatty acids are useful formulation adjuncts e.g. n-butyl oleate, Ν,Ν-dimethyl oleamide and isopropyl myristate (1PM).

It has been found that the inclusion of an antioxidant such as 2,6-ditert-butyl-4cresol (BHT) or 2-tert-butyl-4-methoxyphenol (BHA) has a useful stabilising effect on the active ingredients in formulations based on glycols, glycol ethers, glycol ether esters and cyclohexanone.

The present invention will now be illustrated with reference to comparative tests showing the lack of activity of a large number of conventional insecticides, and w)th reference to specific examples illustrating the present invention.

(I) COMPARATIVE TESTS The effectiveness of a number of known insecticides in controlling sheep lice using pour-on formulations was assessed. A summary of the active agents and dose rates is given in Table 1.

TABLE 1 Chemical Pour-on (mg/kg) chlorfenvinphos 100 maldison 250 carbaryl 100 dimethoate 100 dioxathion 100 ethion 100 fenitrothion 100 trichlorphon 100 famphur 50,100 ronnel 100 crotoxyphos 100 bendiocarb 100 bromophos ethyl 100 dichlofenthion 100 crufomate 100 naled 100 53108 -8AI1 the pour-on treatments were formulated in β solvent system containing xylene, cyclohexanone and corn oil· A total of It) groups of lice-infested merino sheep divided into control (1) and treatment groups (17) were selected and treated according to Table 1.

No pour-on treatment bed any significant effect on existing lice burdens.

(H) TREATMENT ACCORDING TO THE PRESENT INVENTION A variety of pyrethroids were evaluated in the control of lice on merino sheep, when applied by a liquid pour-on formulation.

Test 1 (xylene-cyclohexanone-corn oil solvent) Ιθ Forty-eight merino sheep, half carrying full-wool and half carrying one month's wool, with significant louse infestations, were allocated equally into four groups of six animals.

Treatments, with formulations comprising a xylene (55 wt %), cyclohexanone (30 wt %), com oil (15 wt %) solvent system were made as follows: Group 1 deltamethrin 10 mg/kg 10 mg/ml formulation Group 2 deltamethrin 50 mg/kg 50 mg/ml formulation Group 3 permethrin i00mg/kg lOOmg/ml formulation Group 4 permethrin 250mg/kg 250mg/ml formulation On full-woolled sheep, partings were made along the backline to place the formulation at skin level. After treatment the various groups, each with three full-woolled and three short-woolled sheep, were held in separate pens, remote from each other. 83108 -9Post-treatment lice examinations were made at 1, 3 end 7 weeks, to assess the effects of the various treatments on the louse populations.

At seven weeks, groups 1 and 2 were run with a mob of fifteen infestor sheep, carrying considerable lice infestations, to gauge the persistence of deltamethrin. Further examinations were made at 9 weeks but subsequent examinations were prevented by wet weather.

Results The results of the pre-treatment and post-treatment lice examinations are shown in Table 2 and are outlined below. full Infestations fell rapidly to extremely low levels GROUP 1 wool and persisted at these low levels throughout the trial. deltamethrin (10 mg/kg) short wool One light infestation was eradicated by Week i. Moderate to heavy infestations were eradicated by Week 7. GROUP 2 full wool At one week, two newly emerged lice were found in matted wool on one animal, only after an exhaustive search. No lice were seen on the other two animals. At week 3 an exhaustive search of each animal deltamethrin revealed one or two newly emerged lice. Nd lice were found at Week 7 or at Week 9, after a fourteen-day challenge period. short No lice were seen at any examination after wool treatment. full Infestations were markedly reduced but were permethrin (250 mg/kg) short wool wooimaintained at low levels throughout the trial. Infestations were reduced to extremely low levels but lice were still present at Week 7. -ιο- GROUP 4 permethrin full wool Infestations were greatly reduced on two out of three sheep but persisted at low levels until Week 7. Lice were eradicated on 5 the (250 mg/kg) third animal by Week 7. Light infestations were drastically short reduced at Week 1 and eradicated 10 at wool Week 3. In the following tables, the numbers represent the total number of lice detected in twenty partings of the wool of the eheep, and L = light infestation O = no lice present ί 5 Μ = moderate infestation + = lice present H = high infestation -11Test 2 The results of the evaluation of deltamethrin on recently sheared merino sheep using xylene and DGBE-based solvent systems are given in Tables 3 and 4. The results of the untreated control group are given in Table 5.

The xylene-based solvent system is the seme as that given in Test 1.

The DGBE-based solvent system had a composition as follows: diethylene glycol mono-n-butyl ether (DGBE) isopropyl myristate (IPM) 2,6-ditert-butyl-4-cresol (BHT) wt % 15 wt % 2.5 g/1. 53108 -3 2TABLE 2 (First Three Sheep per Group Carrying Full-Wool, Second Three Carrying One Month's Wool) Groigj Sheep No. Pre* Treatment Week 1 Week 3 Week 7 Week 9 Comment* B 34 H 13/20 24/20 16 A0 2/20 GROUP 1 B 882 H L-M L-M 2/20* 8/20* •One heavy deltamethrin 0 800 L 0 0 0 0 patch found (10 mg/kg) B 28 M-H 14/20 0 0 0 in neck fold y 749 M-H 3/20 1/20 • 0 0 B 883 M-H 0 5/20 0 0 GROUP 2 G 790 H 2/20*· 1/20 0 0 Ϊ 840 M-H 0 2/20 0 0 ♦•Found in deltamethrin B 44 M-H 0 0 0 0 matted wool (50 mgAg) y 830 L-M 0 0 0 0 y 738 M 0 0 0 O B 50 H L L L y 835 H M M-H M-H GROUP 3 y 833 H L L 19/20 perms thrin B 27 M-H 20/20 9/20 24/20 (100 mgAg) B 49 M 17/20 6/20 11/20 • Y 744 L-M 7/20 3/20 4/20 B 387 H 12/20 7/20 3/20 B 38 L-M 7/20 0 0 GROUP 4 B 42 H L-M L-M L perme thrin B 35 L 1/20 0 0 B 29 L 1/20 0 0 y 991 L 1/20 0 0 47 L-M M-H M L L 877 H H H H H 742 H H H m-h M-H CONTROLS 754 L L-M L-M L L-M 37 M M L L L-M 736 L-M M L-M died S2108 -13TABLE 3 Xylene-Based Solvent* Delta- Sheep No. Body- weight Dose (ml) Post- : Treatment Challenge Inspections methrin Group (g/D (kg) Inspections (Group I and Group 2) week week week week week 3 6 10 12 14 GROUP 1 (a) 51 50 6.3 0 0 0 0 1 8.0 1 mg/kg 90 46 5.8 0 0 0 0 2 1 ml/8 kg 106 44 5.5 0 0 0 0 0 GROUP 1 (b) 52 44 11.0 0 0 0 lambed 4.0 1 mg/kg 55 48 12.0 0 0 0 0 1 ml/4 kg 139 43 10.8 0 0 0 0 GROUP 2 (a) 54 50 6.3 0 0 0 0 2 16.0 2 mg/kg 112 44 5.5 0 0 0 0 1 1 ml/8 kg 127 46 5.8 0 0 0 0 1 GROUP 2 (b) 53 44 11.0 0 0 slaughtered (injury) 8.0 2 mg/kg 88 48 12.0 0 0 0 1 3 1 ml/4 kg 146 43 10.8 0 0 0 0 2 GROUP 3 (a) 76 50 6.3 0 0 20.0 2.5 mg/kg 126 44 5.5 0 0 1 ml/8 kg 134 46 5.8 0 0 GROUP 3 (b) 67 44 11.0 0 0 10.0 2.5 mg/kg 75 42 10.5 0 0 1 ml/4 kg 102 48 12.0 0 0 GROUP 4 (a) 113 50 6.3 0 0 24.0 3 mg/kg 131 44 5.5 0 0 1 ml/8 kg 137 46 5.8 0 0 -13aTABLE 3 (contd.) Xylene-Based Solvent* Delta- Sheep No. Body- weight (kg) Dose (ml) Post- Treatment Inspections Challenge Inspections (Group 1 and Group 2) methrin (g/1) Group week 3 week 6 week week week 10 12 14 GROUP 4 (b) 69 44 11.0 0 0 12.0 3 mg/kg 84 42 10.5 0 0 1 ml/4 kg 143 48 12.0 0 0 GROUP 5 (a) 61 49 6.1 0 0 32.0 4 mg/kg 141 44 5.5 0 0 1 ml/8 kg 147 46 5.8 0 0 GROUP 5 (b) 71 44 11.0 0 0 16.0 4 mg/kg 110 42 10.5 0 0 1 ml/4 kg 118 47 11.8 0 0 GROUP 6 (a) 58 45 5.6 0 0 40.0 5 mg/kg 68 49 6.1 0 0 1 ml/8 kg 83 43 5.4 0 0 GROUP 6 (b) 80 44 11.0 0 0 20.0 5 mg/kg 124 47 11.8 0 0 1 ml/4 kg 125 42 10.5 0 0 * Figures shown in week columns are the number of lice seen in twenty wool partings. -14TABLE 4 DGliE-Based Solvent* Delta- Sheep No. Body- weight (kg) Dose (ml) Poet- Treatment Inspections Challenge Inspections (Group 1 and Group 2) methrin (g/1) Group week 3 week 6 week week week 10 12 14 GROUP 1 (c) 60 45 5.6 0 0 0 1 1 8.0 1 mg/kg 73 49 6.1 0 0 0 3 0 1 ml/8 kg 85 43 5.4 0 0 0 1 1 GROUP 1(d) 78 41 10.3 <1/20 0 0 4 1 4.0 1 mg/kg 81 44 11.0 0 0 1 0 1 1 ml/4 kg 129 47 11.8 0 0 0 0 0 GROUP 2 (c) 62 45 5.6 0 0 0 3 2 16.0 2 mg/kg 74 49 6.1 0 0 0 1 1 1 ml/8 kg 96 43 5.4 0 0 slaughtered (injury) GROUP 2 (d) 18 41 10.3 0 0 0 1 0 8.0 2 mg/kg 89 44 11.0 0 0 0 1 1 1 ml/4 kg 132 47 11.8 0 0 0 1 2 GROUP 3 (c) 86 49 6.1 <1/20 0 20.0 2.5 mg/kg 107 45 5.6 0 0 1 ml/8 kg 114 43 5.4 0 0 GROUP 3 (d) 91 41 10.3 0 0 10.0 2.5 mg/kg 94 44 11.0 0 0 1 ml/4 kg 144 47 11.8 0 0 GROUP 4 (c) 108 45 5.6 0 0 24.0 3 mg/kg 117 43 5.4 0 0 1 ml/8 kg 120 49 6.1 0 0 -14aTABLE 4 (contd.) DGBE-Based Solvent* Delta- Sheep No. Body- Dose Post- Treatment Inspections Challenge Inspections (Group 1 and Group 2) methrin (g/1) Group weight (kg) (ml) week 3 week 6 week week week 10 12 14 GROUP 4 (d) 56 40 10.0 0 0 12.0 3 mg/kg 57 46 11.5 0 0 1 ml/4 kg 97 44 11.0 0 0 GROUP 5 (c) 119 43 5.4 0 0 32.0 4 mg/kg 128 49 6.1 0 0 1 ml/8 kg 135 45 5.6 0 0 GROUP 5 (d) 66 40 10.0 0 0 16.0 4 mg/kg 70 46 11.5 0 0 1 ml/4 kg 98 44 11.0 0 0 GROUP 6 (c) 133 43 5.4 0 0 40.0 5 mg/kg 136 49 6.1 0 0 1 ml/8 kg 145 45 5.6 0 0 GROUP 6 (d) 72 40 10.0 0 0 20.0 5 mg/kg 87 46 11.5 0 0 1 ml/4 kg 101 44 11.0 0 0 * Figures shown in week columns are the number of lice seen in twenty wool partings. 53108 15TABLE5 Results of Examinations of Shorn Untreated Control Group* Untreated Controls Sheep No. Body weight (kg) Week 3 Week 6 65 51 io· 10 77 56 9 8 10 79 52 17 15 82 38 24 31 95 54 18 29 104 28 37 35 105 52 20 8 15 111 29 24 23 116 44 10 16 122 39 22 18 123 36 19 18 130 35 18 17 20 *Figures show the number of lice seen in twenty wool partings.

Test 3 (varying solvent systems) Table 6 gives the results for formulations of deltamethrin in a variety of other solvent systems when applied to recently sheared merino sheep. -16a- -16b- -17Test 4 (varying pyrethroids) The efficacy of a variety of different pyrethroids applied as liquid pour-on formulations to merino sheep was determined. The results are given in Teble 7. A backline application was made within 24 hours of shearing. All formulations used the xylene-based solvent system given in Test 1, except flumethrin which was formulated as a miscible oil formulation but which was diluted with the xylene-based solvent to achieve the lower concentrations.

The results show all the pyrethroids tested to be effective, although at the dosages 1 0 used phenothrin and flumethrin did not give complete eradication. 18TABLE7 Control of the Sheep-Biting Louse by a Number of Pyrethroids Compound/Dose/F ormulation Sheep No. Result (No. of Lice) CYPERMETHRIN 5 mg/kg 782 0 (1 ml/5 kg - 25 g/1 formulation) 767 7 752 26 50 mg/kg 756 0 (1 ml/5 kg - 250 g/1 formulation) 746 0 733 0 (14/10-D) PHENOTHRIN 25 mg/kg 721 8 (1 ml/5 kg - 125 g/1 formulation) 765 23 727 3 400 mg/kg 724 β 14 ml/5 kg - 500 g/1 formulation) 779 6 753 18 FENVALERATE 10 mg/kg 744 9 (1 ml/5kg - 50 gi formulation) 740 3 769 2 (14/j.O-D) lOO mg/kg 766 0 (2 ml/5 kg - 250 g/1 formulation) 770 0 730 0 FLUMETHRIN 0.5 mg/kg 783 '21 ll ml/5 kg - 2.5 g/1 formulation) 725 10 7l9 1 12-16 mg/kg 722 0 (25 mI/30-40 kg - 20 g/i formulation) 755 5 748 7 741 64 CONTROLS 737 52 764 83 no treatment 754 53 758 121 723 55 D = died between 14/10 and 21/10 -19Test 5 Itime to take effect) The time for the pyrethroid to fully dear the merino sheep following backline application of the liquid formulation was investigated and the results are shown in Table 8. These demonstrate that the pyrethroid takes a finite period to completely clear the sheep of lice- However, the sheep are substantially cleared within 15 days. The effect is also demonstrated in certain of the preceding.Tables. -20Process of Reduction in Lice Numbers Following Pyrethroid Backline Treatment TABLE 8 Group Sheep - No. Lice Score 0 7 9 15 35 42 756 20 7 3 0 21 0 Cypermethrin 746 20 7 2 5 21 0 50 mg/kg 733 20 9 3 0 0 0 766 20 2 2 3 0 ' 0 Fenvalerate 770 20 6 1 0 0 0 100 mg/kg 730 20 2 2 2 11 0 722 20 10 8 41 0 Flumethrin 755 20 19 - 10 181 3T,2A 12-16 mg/kg 748 20 12 - 4 71,2 A 4I.3A 741 20 14 64 (18) 737 20 - - 15 - 52 (18) Controls 764 20 - - 16 - 83 (19) 754 20 - - 10 - 53 (.15) 758 20 - - 22 - 121 (19) 723 20 20 55 (13) I = immature lice A - adult lice -21(11) FORMULATIONS FOR USE ACCORDING TO THE PRESENT INVENTION Suitable formulations are presented in the following Examples. In general, a suitable system contains 0 to 100% by weight xylene, 0 to 100% by weight cyclohexanone, and up to 20% by weight corn oil.

Example 1 .1 g of technical deltamethrin (989 g active- per kg) was dissolved in a solvent consisting of: cyclohexanone Sudan Red IV (oil soluble dye) 50 ppm ] 0 and the volume adjusted to one litre to give a solution containing 10 g/1 deltamethrin.

Example 2 g of technical deltamethrin (989 g active constituent per kg) was dissolved in a solvent blend containing: xylene cyclohexanone corn oil Sudan Red IV 55% by weight 30% by weight 15% by weight 100 ppm and the volume adjusted to one litre with the same solvent blend to give a solution 20 containing 50 g/1 deltamethrin.

Example 3 .1 g of technical deltamethrin (989 g active per kg) was dissolved in a solvent blend, containing: xylene cyclohexanone corn oil Sudan Red IV 55% by weight 30% by weight 15% by weight 50 ppm and the volume adjusted to one litre with the same solvent blend, to give a solution containing 10 g/1 deltamethrin. -22" Example 4 · g of technical deltamethrin (989 g active per kg) was dissolved in the same solvent blend given in Example 3 and the volume adjusted to give a solution containing 50 g/1 deltamethrin.

Example 5 5 .1 g of technical deltamethrin (989 g active per kg) was dissolved in a solvent consisting of: diethylene glycol monobutyl ether BHT antioxidant 2500 ppm o Sudan Red IV 50 ppm and the volume adjusted to one litre with the same solvent to give a solution containing 10 g/1 deltamethrin.

Example 6 .1 g of technical deltamethrin (989 g active per kg) was dissolved in a solvent 15 blend containing: cyclohexanone 50% by weight diethylene glycol monobutyl ether 50% by weight BHT antioxidant 2500 ppm Solvent Blue No. 36 50 ppm and the volume adjusted with the same solvent blend to give a solution containing 10 g/1 deltamethrin.

Example 7 .1 g of technical deltamethrin (989 g active kg) was dissolved in a variety of solvent blends containing: -23diethylene glycol monobutyl ether or ethylene glycol monobutyl ether acetate isopropyl myristate BHT antioxidant Sudan Red IV 85-90% by weight -15% by weight 2500 ppm ppm and the volume adjusted with the respective solvent blend to give a solution containing 10 g/1 deltamethrin.

Example B 0 Amounts of 2.6, 10.5, 42.5 and 84.2 g of technical cypermethrin (950 g active per kg) were dissolved in a solvent blend containing: Xylene 55% by weight cyclohexanone 30% by weight corn oil 15% by weight and the volume adjusted to one litre with the same solvent blend to give solutions containing 2.5 g, 10 g, 40 g and 80 g per litre respectively of cypermethrin.

Example 9 103 g of technical permethrin (970 g active per kg) in which the cis:trans isomer (arising from the two asymmetric carbon atoms in the cyclopropane ring) ratio was 25:75 was dissolved in a solvent blend containing: xylene 55% by weight cyclohexanone 30% by weight corn oil 15% by weight and the volume adjusted to one litre with the same solvent blend to give a solution containing 100 g/1 permethrin. -24Example 10 An equeous suspension of deltamethrin was prepared by suspending 10.1 g of technical deltamethrin of average particle size 2 to 5 microns in an aqueous formulation containing: non-ionic wetting agent 1.5 g il mole nonylphenol condensed 1 with 15 moles of ethylene oxide/ fumed silicon dioxide 5.0 g xanthan gum 4.0 g propylene glycol 60.0 g formaldehyde 1.0 g silicone oil lantifoaming agent) 1.0 g water to one litre.

Various other deltamethrin suspensions in the range 1 to 500 g/1 deltamethrin were 15 also prepared.

Claims

1. A method of controlling lice on sheep which comprises the application onto localised region of the skin or fleece of a sheep of a pyrethroid of the formula. wherein CH - CH = C M is - CO - CH \ X C X, X \ 2 CH, CH, v - CO - CH -CH - CH - C I l\ / \ X 3 *4 x 2 CH, CH, - CO - CH - RCH, CH X \ CH, and wherein to X^ are independently selected from halo, C^-C^ alkyl, halogen substituted C^-C^ alkyl, and halogen-substituted phenyl; -26is -H or halo; R a is -H or cyano; and » R 2 ls halogen-substituted phenyl

2. A method according to claim 1 wherein the pyrethroid is selected from the group 5 of light stable pyrethroids.

3. A method according to claim 1 or 2 wherein the pyrethroid is selected from permethrin, phenothrin, cyfluthrin, cyphenothrin, tralomethrin, tralocythrin and fenvalerate tall as herein defined).

4. A method according to claim 1 or 2 wherein the pyrethroid is cypermethrin (as 1 o herein defined).

5. A method according to claim 1 or 2 wherein the pyrethroid is cyhalothrin (as herein defined).

6. A method according to claim 1 or 2 wherein the pyrethroid is flumethrin (as herein defined). T5 7. A method according to claim 1 or 2 wherein the pyrethroid is deltamethrin (as herein defined). B. A method according to any preceding claim wherein the pyrethoid is applied to a sheared sheep.

7. 9. A method according to any of preceding claims 1 to 7 wherein the pyrethroid is 20 applied to a substantially full-woo/lled sheep.

8. 10. A method according to any preceding claim wherein the sheep is a merino sheep.

9. 11. A method according to any preceding claim wherein the pyrethroid is applied at a rate of from 1 to 500 mg per kilogram sheep body weight. 25 12. A method according to any preceding claim wherein a pour-on application is made -27of from 2 to 15 ml of a liquid formulation comprising the pyrethroid.

10. 15. A method according to Bny preceding claim wherein from 2 to 15 ml of a liquid formulation is applied which comprises the pyrethroid dissolved in one or more organic solvents. 5 14. A method according to any preceding claim wherein a liquid formulation is applied which comprises the pyrethroid and one or more of toluene, xylene and a glycol. 15. A method according to any preceding claim wherein a liquid formulation is applied which comprises the pyrethroid in a solvent system containing a glycol. 10

11. 16. A method according to claim 15 wherein the glycol is selected from ethylene glycol, propylene glycol, polyethylene glycols, polypropylene glycols, and ethylene glycol - propylene glycol copolymers.

12. 17. A method according to any one of claims 1 to 13 wherein a liquid formulation is applied which comprises the pyrethroid in a solvent system containing an alkyl 1 5 ether of a glycol. IB. A method according to claim 17 wherein the alkyl ether of the glycol is an alkyl ether of a glycol selected from ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycols and ethylene glycol - propylene glycol copolymers. ±9. A method according to any one of claims 1 to 13 wherein a liquid formulation is 20 applied which comprises the pyrethroid in a solvent system containing a glycol alkyl ether ester of the general formula R 1 2 \ R X OICH,-CHO) -CO-R ζ π wherein R = C. . alkyl or hydrogen, 2 3 R = Cj-Cj alkyl,hydrogen or -CO-R , R 3 = C r C 12 ^y 1 ». and n = 1-40 -2820. A method according to any one of claims 1 to 12 wherein a liquid formulation is applied which comprises a suspension or emulsion of the pyrethroid in an aqueous liquid.

13. 21. A method according to any one of claims 13 to 20 wherein the liquid formulation also contains a paraffin oil or vegetable oil.

14. 22. A method according to any one of claims 13 to 21 wherein the liquid formulation also contains an alkylamide or an ester of a fatty acid.

15. 23. A method according to any one of claims 13 to 22 wherein the liquid formulation also contains an antioxidant.

16. 24. A method according to any of claims 1 to 14 wherein a liquid formulation is applied which comprises the pyrethroid dissolved in a solvent system comprising 30-70 wt % xylene, 20-40 wt % cyclohexanone and 5-25 wt % vegetable oil.

17. 25. A method according to any one of claims 1 to 14 wherein a liquid formulation is applied which comprises the pyrethroid dissolved in a solvent system comprising a major proportion of diethylene glycol mono-n-butyl ether.

18. 26. A method according to claim 25 wherein the solvent system further contains a minor proportion of isopropyl myristate.

19. 27. A method according to any one of claims 1 to ll wherein the pyrethroid is applied in the form of an aerosol. 2b. A method to claim 27 wherein the aerosol formulation comprises the pyrethroid dissolved in a liquid carbon dioxide propellant.

20. 29. A method according to ahy preceding claim wherein the pyrethroid is applied together with a dyestuff.

21. 30. A method of controlling lice on sheep which comprises the application of a formulation substantially as disclosed in any Example.

22. 31. A method substantially as hereinbefore described with reference to the Examples.