Retarded growth of Lucilia cuprina larvae on sheep and their sera following production of an immune response.

Attempts were made to immunize sheep against larvae of the sheep blowfly Lucilia cuprina using supernatant and pellet prepared by centrifuging (100,000 g max) homogenates from whole second instar larvae of L. cuprina or their excised guts. Injection of supernatant from whole larvae and from two fractions of this supernatant, prepared by ammonium sulphate precipitation, significantly reduced (by 24-58%) the final weight of larvae grown in vivo (i.e. on immunized sheep) for 20 or 44 h. Serum from animals vaccinated with supernatant from whole larvae reduced larval weights by 12% after growth for 20 h in vitro (i.e. on diet containing serum from treated animals). Pellet material from whole larvae or guts, when injected into sheep, stimulated an immune response which reduced the weight of larvae by 20-23% after 20 or 48 h in vitro. Larvae grown on these animals were not reduced in weight. Immunoglobulin (Ig) isolated from serum of a sheep vaccinated with gut material strongly retarded growth of larvae in vitro, the effect increasing with Ig concentration. These results indicate that an immune response in sheep, induced by injecting extracts of L. cuprina larvae, substantially reduces growth of this parasite.