It is labeled for roundworms, but only for the mature ones. It sounds like you did good. You got them killed.
INDICATIONS: Consult your veterinarian for assistance in the diagnosis, treatment, and control of parasitism. HORSE HEALTH Equine Ivermectin Paste provides effective treatment and control of the following parasites in horses.
Large Strongyles (adults) - Strongylus vulgaris (also early forms in blood vessels), S. Edentatus (also tissue stages), S. Equinus, Triodontophorus spp. Including T. Brevicauda and T. Serratus, and Craterostomum acuticaudatum; Small Strongyles (adults, including those resistant to some benzimidazole class compounds) - Coronocyclus spp. Including C. Coronatus, C. Labiatus and C. Labratus; Cyathostomum spp. Including C. Catinatum and C. Pateratum; Cylicocyclus spp. Including C. Insigne, C. Leptostomum, C. Nassatus and C. Brevicapsulatus; Cylicodontophorus spp.; Cylicostephanus spp. Including C. Calicatus, C. Goldi, C. Longibursatus and C. Minutus, and Petrovinema poculatum; Small Strongyles - Fourth-stage larvae; Pinworms (adults and fourth-stage larvae) - Oxyuris equi; Ascarids (adults and third- and fourth-stage
larvae) - Parascaris equorum
; Hairworms (adults) - Trichostrongylus axei; Large-mouth Stomach Worms (adults) - Habronema muscae; Bots (oral and gastric stages) - Gasterophilus spp. Including G. Intestinalis and G. Nasalis; Lungworms (adults and fourth-stage larvae) - Dictyocaulus arnfieldi; Intestinal Threadworms (adults) - Strongyloides westeri; Summer Sores caused by Habronema and Draschia spp. Cutaneous third-stage larvae; Dermatitis caused by neck threadworm microfilariae, Onchocerca sp. http://www.valleyvet.com/ct_detail.h...6-2d4f8c7006f0