Characterisation of rickettsial diseases in a hospital-based population in Malta

Abstract

Objective: The aim of the study was to characterise the causative agents of rickettsial disease in Malta. A secondary objective was to study the epidemiology of cases of rickettsial disease.

Methods: Cases admitted to St Luke's Hospital between June 2002 and May 2003 presenting with complaints of fever, headache, rash and/or an eschar were considered possible cases of rickettsial disease. A patient interview was conducted within 24h of admission. Paired sera were taken for serology and blood samples sent for rickettsial PCR and culture. Whenever an eschar was present, biopsies were taken for culture and immunohistochemical analysis.

Results: Thirty-three cases of possible rickettsial disease were identified. Although serological tests showed cross reactivities between different species of rickettsiae, one was diagnostic for Rickettsia conorii. None of the sera showed any cross-reactivity with Rickettsia typhi. There was one positive biopsy for R. conorii when tested by PCR and another was positive for spotted fever group Rickettsia by immunohistochemistry.

Conclusion: Spotted fever rickettsiosis is endemic in Malta. Contrary to previous belief, none of the cases were due to murine typhus. The predominant causative agent of rickettsial disease in Malta is likely to be R. conorii, although the animal reservoir has still not been definitely identified.