Seroepidemiology of human leptospirosis in the Dominican Republic: A multistage cluster survey, 2021

Abstract

Little is known about the epidemiology of leptospirosis in the Dominican Republic, the second most populous country in the Caribbean. We report on findings from a multi-stage household survey across two regions in the country that reveals a previously under-estimated burden of human Leptospira infection. Our findings, based on the reference-standard microscopic agglutination test, indicate a complex picture of serogroup diversity, spatial heterogeneity in infection and risk, and a marked discrepancy between reported cases and serologically estimated infections. Given an overall seroprevalence of 11.3% (95% CI: 10.8-13.0%) and a lower estimated force of infection (0.30% per year [0.27%-0.35%]) the number of infections may exceed national reported case data by 145-fold or more. Icterohaemorrhagiae, associated with severe Weil's disease, was the most commonly identified serogroup with a serogroup-specific prevalence of 4.4%. Consistent with other settings, risk factors including age, male sex, and rat exposure were associated with higher seroprevalence. Our study highlights the need for targeted public health interventions informed by serogroup-specific dynamics, detailed spatial analyses, knowledge of local animal reservoirs, and strengthened laboratory surveillance to effectively control this pathogen.

Fig 1. Distribution of Leptospira serogroups by highest titer, age and study setting, Dominican Republic, 2021.

(A) Bar plot indicates the number of participants stratified by the highest MAT titer and serogroup. (B) Ridge plot shows the distribution of MAT titers for each serogroup. (C) Stacked bar plot indicates the distribution of serogroups by age group. (D) Distribution of serogroups stratified by urban vs rural setting and Northwest (Espaillat) vs Southeast (San Pedro de Macoris) regions. Serogroup is defined as the serogroup that registered the highest MAT titer for each seropositive study participant. Individuals that registered the same highest titer to two or more serogroups are categorized as ‘Mixed.’ N = 237 for all plots. Serogroups aggregated as ‘Other’ are those with counts less than 10, with details listed in S1 Table.

Fig 2. Risk factors for Leptospira seropositivity by microscopic agglutination test in the Dominican Republic, 2021.

Multivariable logistic regression with all modeled covariates shown. Serogroups Australis and Canicola not presented given limited number of seropositive individuals (N = 38 and 25 respectively). Full model outputs including univariable odds ratios and model metrics shown in S4 and S5 Tables. SPM, San Pedro de Macoris (Southeast study region). Espaillat (Northwest study region).

Fig 3. Age-stratified seroprevalence by region, gender and urban vs. rural setting.

Individual plots show seroprevalence point estimates (black dots) and 95% confidence intervals (black vertical lines) by five-year age group. A smoothed line is fitted to the data using generalized additive models with a cubic spline and weighted for number of observations. Colored ribbons represent the 95% CI. Number of observations per plot listed in Table 1. Southeast study region (San Pedro de Macoris province). Northwest study region (Espaillat province). Additional plots showing age stratified seroprevalence by both gender and study region are presented in S2 Fig.