An isoxazoline compound of Formula wherein R 1 is halogen, CF 3, OCF 3, CN, n is an integer from 0 up to and including 3, preferably 1, 2 or 3, R 2 is C 1 -C 3 -haloalkyl, preferably CF 3 or CF 2 Cl, T is a 5 to 12 membered mono or bicyclic ring system, which is optionally substituted by one or more radicals Y, Y is methyl, halomethyl, halogen, CN, NO 2, NH 2 -C=S, or two adjacent radicals Y form together a chain, especially a three or four-membered chain; Q is X-NR 3 R 4, NR 5 -NR 6 -X-R 3, X-R3 or a 5-membered N-heteroaryl ring, which is optionally substituted by one or more radicals; X is CH 2, CH(CH 3), CH, CO, CS, R 3 is hydrogen, methyl, haloethyl, halopropyl, halobutyl, methoxymethyl, methoxyethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, N-phenyl-N-methyl-amino, haloethylaminocarbonylmethyl, haloethylaminocarbonylethyl, tetrahydrofuryl, methylaminocarbonylmethyl, (N,N-dimethylamino)-carbonylmethyl, propylaminocarbonylmethyl, cyclopropylaminocarbonylmethyl, propenylaminocarbonylmethyl, halo-ethylaminocarbonylcyclopropyl, alkylsulfanyl, alkylsufinalkyl, alkylsulfonalkyl, cycloalkyl wherein Z A is hydrogen, halogen, cyano, halomethyl, preferably CF 3; R 4 is hydrogen, ethyl, methoxymethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, methylcarbonyl, ethylcarbonyl, propylcarbonyl, cyclopropylcarbonyl, methoxycarbonyl, methoxymethylcarbonyl, aminocarbonyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, haloethylaminocarbonylmethyl, cyanomethylaminocarbonylmethyl, or haloethylaminocarbonylethyl; R 5 is hydrogen, alkyl or haloalkyl; R 6 is hydrogen, alkyl or haloalkyl; or R 3 and R 4 together form a substituent selected from the group consisting of: or a salt or solvate thereof for use in the treatment and/or protection of sheep from Bovicola ovis chewing lice infestation after a single subcutaneous administration of a composition comprising an effective amount of at least one isoxazoline compound of Formula, wherein the composition is administered as solution or suspension to sheep once > 6 weeks after shearing R 1 is halogen, CF 3, OCF 3, CN, n is an integer from 0 up to and including 3, preferably 1, 2 or 3, R 2 is C 1 -C 3 -haloalkyl, preferably CF 3 or CF 2 Cl, T is a 5 to 12 membered mono or bicyclic ring system, which is optionally substituted by one or more radicals Y, Y is methyl, halomethyl, halogen, CN, NO 2, NH 2 -C=S, or two adjacent radicals Y form together a chain, especially a three or four-membered chain; Q is X-NR 3 R 4, NR 5 -NR 6 -X-R 3, X-R3 or a 5-membered N-heteroaryl ring, which is optionally substituted by one or more radicals; X is CH 2, CH(CH 3), CH, CO, CS, R 3 is hydrogen, methyl, haloethyl, halopropyl, halobutyl, methoxymethyl, methoxyethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, N-phenyl-N-methyl-amino, haloethylaminocarbonylmethyl, haloethylaminocarbonylethyl, tetrahydrofuryl, methylaminocarbonylmethyl, (N,N-dimethylamino)-carbonylmethyl, propylaminocarbonylmethyl, cyclopropylaminocarbonylmethyl, propenylaminocarbonylmethyl, halo-ethylaminocarbonylcyclopropyl, alkylsulfanyl, alkylsufinalkyl, alkylsulfonalkyl, cycloalkyl wherein Z A is hydrogen, halogen, cyano, halomethyl, preferably CF 3; R 4 is hydrogen, ethyl, methoxymethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, methylcarbonyl, ethylcarbonyl, propylcarbonyl, cyclopropylcarbonyl, methoxycarbonyl, methoxymethylcarbonyl, aminocarbonyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, haloethylaminocarbonylmethyl, cyanomethylaminocarbonylmethyl, or haloethylaminocarbonylethyl; R 5 is hydrogen, alkyl or haloalkyl; R 6 is hydrogen, alkyl or haloalkyl; or R 3 and R 4 together form a substituent selected from the group consisting of: or a salt or solvate thereof for use in the treatment and/or protection of sheep from Bovicola ovis chewing lice infestation after a single subcutaneous administration of a composition comprising an effective amount of at least one isoxazoline compound of Formula, wherein the composition is administered as solution or suspension to sheep once > 6 weeks after shearing