SERUM ANTIBODY-RESPONSE IN LAMBS NATURALLY AND EXPERIMENTALLY INFECTED WITH CRYPTOSPORIDIUM-PARVUM

The immunoglobulin (IgG), IgM and IgA responses in Castellana-Manchega cross-bred colostrum-deprived and colostrum-fed lambs infected neonat ally with Cryptosporidium parvum were measured using an enzyme-linked immunosorbent assay. A comparison of oocyst shedding and anti-C parvum serum IgG levels in lambs suffering either natural or experimental in fection was undertaken. Effects on the oocyst shedding and IgG levels of C parvum rechallenge at 30 and 120 days of age in neonatally infect ed lambs were also evaluated. Anti-C parvum immunoglobulin levels in c olostrum-deprived animals peaked on Day 30 of life for IgG and on Day 15 for IgM and IgA. Lambs that received maternal colostrum showed elev ated antiC. parvum IgG, IgM and IgA levels at 3 days old indicating a transfer of colostral immunoglobulins. Experimentally infected lambs s howed a IgG response similar to naturally infected lambs, suggesting t hat the serum IgG response is independent of the infective dose. Final ly, lambs rechallenged at 30 and 120 days old did not show either appr eciable oocyst shedding or any increase in their anti-C parvum IgG lev els when compared with prechallenged animals.