Advanced System for Worldwide Surveillance of Rickettsial Disease Antibodies

Members of the genera Rickettsia and Ehrlichia are obligately intercellular, arthropod-borne bacteria which are distributed either worldwide or in defined geographic areas. Several are human pathogens; the severity of infection ranges from inapparent to fatal. Initiation of preventive measures and appropriate treatment depend on awareness of the infectious agent's prevalence within a given region. Assessment of disease incidence would benefit greatly from commercial availability of a simple, standardized,l and economical diagnostic test suitable for use in unsophisticated settings. A dipstick (DS) test meeting these criteria, produced by Integrated Diagnostics, is being used in several countries for detection of antibodies to pathogenic rickettsiae. We propose to develop a similar test for recognizing ehrlichia infections, whose importance is only now being appreciated. Phase I comprises (1) developing methods for bulk cultivation of 2 ehrlichia species (e. sennetsu, E. chaffeensis) and purification of these plus human granulocytic ehrlichia and (2) antigen validation studies to determine the ehrlichia DS suitability for further testing. Phase II will encompass distribution of ehrlichia and rickettsia DS in a regionally appropriate manner for extensive field testing of their sensitivity and specificity. Accumulation of data in Phase II will permit refinement and tailing of the DS to meet the specific needs of a geographic area.