The present invention relates to the use of 6-halogeno-[1,2,4]-triazolo[1,5-a]-pyrimidine compounds of the general formula I wherein A, R1, R2, R3 and R4 are as defined in the specification; and/or an enantiomer, diastereomer, tautomer, solvate, crystalline form or veterinarily acceptable salt thereof alone or in combination with an additional anti-parasiticidal agent for combating parasites in and on animals.