Antiparasitic use of isoxazoline compounds

1. A Method of preventing re-infestation of animals by fleas comprising administering to an flea infested animal a sub-insecticidal dose of an isoxazoline compound of formula (I)

wherein

R 1 =halogen, CF 3 , OCF 3 , CN,

n=integer from 0 to 3

R 2 =C 1 -C 3 -haloalkyl,

T=5- or 6-membered ring, which is optionally substituted by one or more radicals Y,

Y=methyl, halomethyl, halogen, CN, NO 2 , NH 2 —C═S, or two adjacent radicals Y form together a chain;

Q=X—NR 3 R 4 or a 5-membered N-heteroaryl ring, which is optionally substituted by one or more radicals;

X=CH 2 , CH(CH 3 ), CH(CN), CO, CS,

R 3 =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, haloethylaminocarbonylcyclopropyl,

wherein Z A =hydrogen, halogen, cyano, halomethyl,

R 4 =hydrogen, ethyl, methoxymethyl, halomethoxymethyl, ethoxymethyl, haloethoxymethyl, propoxymethyl, methylcarbonyl, ethylcarbonyl, propylcarbonyl, cyclopropylcarbonyl, methoxycarbonyl, methoxymethylcarbonyl, aminocarbonyl, ethylaminocarbonylmethyl, ethylaminocarbonylethyl, dimethoxyethyl, propynylaminocarbonylmethyl, haloethylaminocarbonylmethyl, cyanomethylaminocarbonylmethyl, or haloethylaminocarbonylethyl,

Or R 3 and R 4 together form a substituent selected from the group consisting of:

sufficient to inhibit the development of the offspring of such fleas into adult stages and to reach blood plasma concentrations between 1.5 and 25 ng/ml, wherein the administration is topical administration or parenteral administration.

2. The method of claim 1 , wherein the administration is parenteral administration.

3. The method of claim 1 , wherein n is 1, 2 or 3.

4. The method of claim 1 , wherein R 2 is CF 3 or CF 2 Cl.

5. The method of claim 1 , wherein two adjacent radicals Y form together a three or four membered chain.

6. The method according to claim 2 wherein the isoxazoline compound is fluralaner.

7. The method according to claim 2 , wherein the animal is a dog or a cat.

8. The method of claim 1 , wherein the administration is topical administration.

9. The method according to claim 8 wherein the isoxazoline compound is fluralaner.

10. The method of claim 8 , wherein the animal is a dog or a cat.

11. The method of claim 1 , wherein Z A is CF 3 .