THE SERUM IMMUNE-RESPONSE OF YOUNG LAMBS TO A PRIMARY INFECTION WITH NEMATODIRUS-BATTUS

Young lambs (6-8 weeks of age) were infected with 50000 infective stag e larvae of the trichostrongyle nematode Nematodirus battus. Initial m ean adult worm burdens of 23884+/-1678 (S.E.M.) at day 14 post-infecti on (p.i.) were reduced significantly (P <0.01) to a mean burden of 538 3+/-1397 by day 21 p.i. Blood samples were taken and serum analysed us ing ELISA and Western blotting techniques for IgG antibodies specific for N. battus. Pre-infection serum from young naive animals showed IgG recognition of adult and larval N. battus whole worm homogenate. Reco gnition of adult antigens became reduced during the first 14 days afte r infection, followed by a subsequent increase beginning between days 14 and 18 p.i. and peaking at day 28 p.i. IgM recognition of N. battus antigens showed a single response peak, starting between days 14 and 18 p.i., without the pre-infection elevated titre as observed with IgG . These results show that young lambs can mount a significant serum re sponse to a primary infection with N. battus during rejection of adult worms and that lambs receive from their dams IgG antibodies that are capable of recognizing adult and larval N. battus during the first few weeks of life.