Sustained release bolus effective for the prolonged prevention, treatment or control of nematode, acarid and endo- and ectoparasitic infestations of ruminants

A sustained release bolus composition, containing a prophylactically effective amount of a compound selected from LL-F28249 alpha , 23-(O-methyloxime)-LL-F28249 alpha and derivatives thereof provides a method for protecting ruminant animals for a prolonged period of time against infestation by nematodes, acarids and endoand ectoparasitic insects, and which over time can also eliminate the initial population of parasites present at treatment. The invention also relates to a method for the systemic control of ectoparasitic insect infestations of ruminant animals by orally administering to said animals a sustained release bolus containing an insecticidally effective amount of LL-F28249 alpha , 23-(O-methyloxime) LL-F-28249 alpha or derivative thereof, which continuously releases into the rumen of the treated animal a systemically effective amount of LL-F28249 alpha , 23-(O-methyloxime)LL-F28249 alpha or derivative thereof.