There is provided a method of detecting in a sample the presence of an anti-M and/or anti-A and/or anti-C/Y antibody, the method comprising contacting the sample with a diagnostic conjugate provided according to the invention, comprising an oligosaccharide which comprises at least two units of 4,6-dideoxy-4-acylamido--pyranose and comprising at least one -(1-3)- link between adjacent 4,6-dideoxy-4-acylamido--pyranose units, in which the carbon at position 5 in the pyranose is linked to an R group, where R is independently selected from CH.sub.2OH, H or an alkyl group having at least one C atom, the oligosaccharide being covalently linked to a non-saccharide molecule or to a surface.

The present invention provides biomarkers, methods and kits for diagnosing a Brucellosis, Q-Fever, and/or Lyme Disease, methods and kits for monitoring the effectiveness of treatment for Brucellosis, Q-Fever, or Lyme Disease, as well as methods for identifying a compound that can treat Brucellosis, Q-Fever, and/or Lyme Disease reduce or inhibit the development of complications associated with the disease in a subject, and methods to treat a Brucellosis, Q-Fever, and/or Lyme Disease.

There is provided a method of detecting in a sample the presence of an anti-M and/or anti-A and/or anti-C/Y antibody, the method comprising contacting the sample with a diagnostic conjugate provided according to the invention, comprising an oligosaccharide which comprises at least two units of 4,6-dideoxy-4-acylamido--pyranose and comprising at least one -(1-3)- link between adjacent 4,6-dideoxy-4-acylamido--pyranose units, in which the carbon at position 5 in the pyranose is linked to an R group, where R is independently selected from CH.sub.2OH, H or an alkyl group having at least one C atom, the oligosaccharide being covalently linked to a non-saccharide molecule or to a surface.

A diagnostic kit for a confirmatory assay using the indirect ELISA method that measures the levels of anti-Native Hapten antibodies produced during a real infection, thereby preventing large financial losses to livestock farm, by discerning false positives that present anti-LPS antibodies due to cross-reactions with enterobacteria and post-vaccinal antibodies for the diagnosis of bovine brucellosis in blood serum and individual milk (per animal) and bulk milk (tank), characterised by using the crude Native Hapten antigen, extracted from B. melitensis 16M strain, with no purification treatment and an effective adherence capacity, which is used to antigenize plates at a known concentration (1 g per well), where using as reference positive and negative controls subjected to the lyophilisation (freeze drying) method to ensure their preservation, thereby avoiding the contamination and degradation of the antibodies present and ensuring the stability of the optical densities in said controls for a correct results interpretation of an indirect ELISA, are taken as reference. The lyophilisation method for controls that may be used in other diagnostic methods is also presented.