N-phenylpyrazole-based antiparasitic external device for cattle, in particular ear-rings

Process for the elimination of Haematobia irritans from cattle, in which one attaches to the cattle an external device formed of a matrix including from 1 to 15% by weight, relative to the device, of an active substance which is at least one compound of formula (I) below:

• ##STR3## in which:
• R.sub.1 is CN or methyl or a halogen atom;
• R.sub.2 is S(O).sub.n R.sub.3 or 4,5-dicyanoimidazol-2-yl or haloalkyl;
• R.sub.3 is alkyl or haloalkyl;
• R.sub.4 represents a hydrogen or halogen atom;
• or a radical NR.sub.5 R.sub.6, S(O).sub.m R.sub.7, C(O)R.sub.7, C(O)O--R.sub.7, alkyl, haloalkyl or OR.sub.8 or a radical --N.dbd.C(R.sub.9)(R.sub.10);
• R.sub.5 and R.sub.6 independently represent a hydrogen atom or an alkyl, haloalkyl, C(O)alkyl, alkoxycarbonyl or S(O).sub.r CF.sub.3 radical;
• or R.sub.5 and R.sub.6 may together form a divalent alkylene radical which may be interrupted by one or two divalent hetero atoms;
• R.sub.7 represents an alkyl or haloalkyl radical;
• R.sub.8 represents an alkyl or haloalkyl radical or a hydrogen atom;
• R.sub.9 represents an alkyl radical or a hydrogen atom;
• R.sub.10 represents a phenyl or heteroaryl group optionally substituted with one or more halogen atoms or groups such as OH, --O-alkyl, --S-alkyl, cyano or alkyl;
• R.sub.11 and R.sub.12 represent, independently of each other, a hydrogen or halogen atom or optionally CN or N.sub.02;
• R.sub.13 represents a halogen atom or a haloalkyl, haloalkoxy, S(O).sub.q CF.sub.3 or SF.sub.5 group;
• m, n, q and r represent, independently of each other, an integer equal to 0, 1 or 2;
• X represents a trivalent nitrogen atom or a radical C--R.sub.12, the other three valency positions of the carbon atom forming part of the aromatic ring;
• with the proviso that when R.sub.1 is methyl, either R.sub.3 is haloalkyl, R.sub.4 is NH.sub.2, R.sub.11 is Cl, R.sub.13 is CF.sub.3 and X is N, or R.sub.2 is 4,5-dicyanoimidazol-2-yl, R.sub.4 is Cl, R.sub.11 is Cl, R.sub.13 is CF.sub.3 and X is .dbd.C--Cl ;
• in order to ensure the elimination of Haemotobia irritans over a period exceeding 30 weeks.