Use of pooled serum or milk samples for the epidemiological surveillance of bovine hypodermosis

Abstract

An enzyme-linked immunosorbent assay (ELISA) was used on pooled serum and milk samples to determine whether hypodermosis could be detected where a larger sero-epidemiological survey was required. This study was undertaken to assess the potential of this assay for testing sera on milk samples, pooled from 10 cows, and determining the period of the year when detection was optimal. The sensitivity of the assay was determined by increasingly diluting a positive serum with pooled negative sera, from 1 : 10 to 1 : 100. The diagnostic lower limit of the assay requires at least two serological reactors within a herd of 100. The kinetic development and depletion of anti- Hypoderma antibody of individual and pooled sera or milk from 30 cows was evaluated from November to July. Anti- Hypoderma antibody levels of two groups of 8 calves, one control and one treated with ivermectin (Ivomec), were tested from October to June. These preliminary results indicate that an ELISA assay on serum or milk samples pooled from 10 cows can be used between February and April to evaluate the prevalence of hypodermosis within cattle herds in France, demonstrating the feasibility of using pooled serum already collected for bovine leucosis testing.