EVALUATION OF SEROLOGICAL METHODS (ELISA) FOR THE CONTROL OF SALMONELLAE-ENTERITIDIS IN LAYER FLOCKS

A commercially available ELISA kit (''CHEKIT S. ENTERITIDIS'') for the detection of antibodies against S. enteritidis in egg yolk and serum was evaluated. The question, how the occurence of antibodies in a herd of layer hens is correlated with the existence of the infectious agen t, was of particular interest. It could be shown that in cases, where S. enteritidis could easily be isolated from eggs, the proportion of s eropostive eggs in a sample was always high (47-100 %). In two herds, S. enteritidis was also found at low seroprevalences (10 and 30 %) but only in environmental swabs and not in eggs. In another herd with a s eroprevalence of 15 %, S. e. was isolated from samples of oviducts and ovaries but not from feces and eggs. Eggs from herds with a low preva lence of antibodies do not seem to be an important epidemiological ris k for humans. However, it must be taken into consideration that at a l ater time, favourized by particular conditions such as ageing of the h erd, horizontal spreading of the infectious agent could occur with sub sequent significant contamination of eggs. With regard to consumer pro tection, it is important that herds with an invasive activity of S. en teritidis are identified. For this purpose ''CHEKIT S. ENTERITIDIS'' E LISA is a suitable instrument. The confirmation of positive serologica l results with the bacterialogical analysis of eggs and organic sample s from hens seems to be only justified at seroprevalences of greater t han or equal to 10 %.