A twelve-year study of leptospirosis on Barbados

Abstract

Between November 1979 and December 1991, 398 cases of severe leptospirosis were confirmed on Barbados (range for 1980–1991 23–56; mean 32.7; incidence 13.3/100,000/year). For the six-year periods 1980–1985 and 1986–1991 there was no significant change in incidence with time. Incidence is unlikely to change significantly in the next decade. Monthly average case numbers ranged from 1.4 (July) to 4.3 (November). The average (2.8) for June to December (the 7 wetter months) was not significantly higher than that (2.5) for January to May (the 5 drier months). The age range was 7–86. There were three times as many male cases (302) as female (96), and nearly 10 times as many in those Leptospira were isolated and identified from 117 (29.4%) of the 398 sick patients. The infecting organisms werebim (serogroup Autumnalis — 75),copenhageni (Icterohaemorrhagiae — 26),arborea (Ballum — 14) andbajan (Australis — 2). These infecting serovars could not be distinguished clinically, but infection was milder in children than in adults. Despite its predominance in surveyed children, serogroup Panama was virtually absent in this study. Rainfall is the major factor affecting the distribution of cases; not surprisingly, sanitation workers and agricultural workers appear to be the groups at highest risk. The general lack of clear-cut risk factors reflects the ubiquity of leptospires in the environment and the fact that the disease is not entirely occupational.