الفهرس 
INTRODUCTION
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Abstract
An investigation was conducted with the aim to illucidate the presence of specific antibodies to L. monocytogenes in apparently healthy animals. 250 serum samples were collected from two age groups of cows and buffaloes in Assiut province. The sera were subkected to the somatic and flagellar agglutination test, precipitation test, complement fixation test and immobilization test, using different antigens prepared from 5serotypes of L. monocytogenes.
The number of positive reactors of the quantitative tests decreased with the increase of the serum dilutions and a marked difference was noted between the number of positive reactors at a dilution of 1/10 or 1/20 and that at a dilution of 1/160. The percentage of positive reactors is higher in animals over 3 months old than of younger animals. The increased percentage at low dilutions was explained as due to the presence of small amounts of natural non-specific antibodies in normal animals and the presence of shared a antigen (s) between L. monocytogenesb and other organisms.
This explanation would also account for larger number of positive reactors to the somatic agglutination test rather than the other serological tests. Accordingly, the somatic agglutination test appears to be more sensitive.