Prevalence of rickettsial infections in acute coronary syndromes in Sri Lanka: A case control study

Abstract

BACKGROUND: Interest in the relationship between infection and atherosclerosis induced coronary heart disease has recently increased. Rickettsiae are a group of obligate intracellular pathogens who invade endothelial cells and cause vasculopathy. In a longitudinal nation wide study conducted in Thaiwan, the incidence of acute coronary syndromes (ACS) in patients with scrub typhus was found to be higher than a comparison cohort (3.10 vs 1.92 per 1000 person-years). A 37% increased risk in subsequesnt development of ACS has been demonstrated compared to general population after adjusting for age, sex and other indipendant risk factors; hypertension, diabetes, hyperlipidaemia, chronic obstructive pulmonary disease and coronary artery disease. The prominent effect of scrub typhus on subsequent ACS development has appeared within 1 year after infection. AIMS: To assess the prevalence of Rickettsial infections in patients with ACS who live in the Western province, Sri Lanka. METHODS & MATERIALS: Patients admitted with ACS to the Professorial Medical Unit, Colombo North Hospital, Ragama, Sri Lanka from April to December 2011 were studied for the serological prevalence of rickettsial infections and were compared with a matched control group; who had no fever or ACS and admitted during the same period. 2 ml serum samples were obtained at enrolment and 2 weeks after, to assess exposure to rickettseal infections by IFA-IgG antibody titres against Orientia Tsutsugamushi (OT) and Spotted fever group (SFG) rickettsioses. An IgG titre ›1:128 or a rising/declining titre were considered positive for acute rickettsioses. A static titre was considered previous exposure to Rickettsioses. RESULTS: 46 ACS [males n(23.9%), mean age (SD) 61.1(13.1) y] and 52 controls (males n (50%), mean age(SD) 56.0(13.6) y] were studied. None had evidence of acute rickettsiel infection. Sero-prevalence of IgG (OT) was 6.4% and IgG-SFG was 15.2% among ACS patients while that of control group were 3.8% and 11.5% respectively. There was no significant difference in sero-prevalence of OT [OR =0.74 (CI, 0.28-10.93), p=0.66] or SFG [OR=1.376 (CI, 0.43-4.44), p=0.59] in patients with ACS compared to controls. CONCLUSION: We observed no significant difference in sero-prevalence of rickettsioses in patients with acute coronary syndromes compared to controls in this study.