The prevalence of severe leptospirosis among humans on Barbados

Abstract

Leptospirosis was confirmed by the Leptospira Laboratory in 138 hospital patients on Barbados between early November 1979 and the end of 1982 (annual average 43·6 cases). These were the great majority of severe cases occurring on the island during that time. The crude incidence rate ranged between 15 and 23 per 100,000 population per year (average 17·6). 26 of the patients died (15 males, 11 females), giving an over-all case fatality rate of 18·8%, and an average of 8·2 deaths per year. 68% of all cases were in males. The highest percentages of cases were in males aged 20 to 24 and females aged 55 to 59, but the incidence of the disease in both sexes increased with age up to 60 years. Previous figures recorded on the island by the Ministry of Health for 1975–1979 were considerably lower, with a mean of 23·6 cases per year and a crude annual incidence of 9·5 per 100,000. 15 of the patients died (13 males, 2 females), giving an over-all case fatality rate of 12·7% and an average of 3 deaths per year. 74% of all cases were in males. The highest percentages of cases were in the 20 to 29 and 50 to 59 year age groups for males and females, respectively, i.e., similar to those in the present series. In both sexes the incidence of leptospirosis increased with age up to 60 years. 11 of 14 strains isolated from patients' blood, urine or dialysate fluid were subsequently identified as follows: Serogroup Autumnalis, eight (one belonged to serovar bulgarica and seven to a new serovar within that group); Serogroup Icterohaemorrhagiae, serovar copenhageni, two; Serogroup Canicola, serovar canicola, one. Serological tests on patients' sera resulted in predominantly single serogroup reactions in 97 of the 138 cases and indicated that 72% of the 97 infections were due to strains of Autumnalis, while 20% were of Icterohaemorrhagiae, 6% Ballum, 1% Canicola and 1% Grippotyphosa serogroups.