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Dissertation/Thesis Abstract

A Retrospective Study of the Urban and Rural Epidemiological Patterns and the Occupational Risk Groups of Leptospirosis in Brazil
by Galan, Deise Iagalo, Dr.P.H., The George Washington University, 2021, 122; 28414272
Abstract (Summary)

Leptospirosis is considered one of the most widespread zoonotic diseases causing 1.03 million cases and over 58,000 deaths worldwide each year. However, it still remains a neglected disease that affects the most vulnerable populations, especially those living and working in unsanitary environments that facilitate the transmission of the disease. Brazil reports the highest number of leptospirosis cases in Latin America and since 2000 has had a robust national surveillance system in place to monitor the disease. There is a lack of comprehensive information about the urban and rural patterns of the disease and a gap in our understanding of occupational exposures of leptospirosis in Brazil.

The objective of this doctoral dissertation is to assess the urban and rural epidemiological patterns and occupational risk groups of leptospirosis in Brazil using surveillance data collected by the Brazilian Ministry of Health since the establishment of the leptospirosis national surveillance system in 2000. In our first study, we describe the geographic distribution, the demographic characteristics, and the presumptive exposure factors of urban and rural cases of leptospirosis, and we identify the spatial clusters of the disease in urban and rural areas of Brazil from 2000 to 2015.

In our second study, we identify the occupational groups with a higher risk of leptospirosis in Brazil from 2010 to 2015 among those who were 14 years of age and older. In our first study, leptospirosis cases were described by age, sex, and race, and exposure factors were characterized in urban and rural areas. A spatial autocorrelation analysis was conducted using local Moran’s I to identify urban and rural clusters of disease. From 2000 to 2015, approximately 4,000 leptospirosis cases were reported annually in Brazil with higher numbers in urban areas. Although the mean annual incidence rate in both urban and rural areas was 1.9 cases per 100,000 population, noteworthy regional differences were observed. Urban incidence rates were higher in the North and Northeast regions, while rural incidence rates were higher in the Southeast and South. The main exposure factors reported in urban and rural areas were exposure to places with signs of rodents, exposure to flood in urban areas, and agriculture and animal farming in rural areas. Clusters of leptospirosis were identified in densely populated urban areas of the North, Southeast, and South regions, while rural clusters were concentrated in the Southern region with large agriculture and animal farming practices.

In our second study, a multivariate analysis was performed to identify occupational groups at a higher risk for leptospirosis. Analysis was restricted to laboratory confirmed cases (20,193) and non-cases (59,034), 14 years of age and older, classified into 12 occupational groups. Cases were predominantly male (79.4%), between 25-59 years of age (68.3%), white (53.4%), illiterate or with incomplete primary education (51.1%), and participating in agricultural work (19.9%). Five occupational groups were identified with higher risk for leptospirosis compared to retired and unemployed individuals after controlling for age, sex, race and area of residency: garbage and recycling collectors (AOR[Adjusted Odds Ratio] = 4.10; 95% CI = 3.36-4.99); agricultural, forestry and fishery workers (AOR = 1.65; 95% CI = 1.49-1.84); prisoners (AOR = 1.56; 95% CI = 1.04-2.35); building workers (AOR = 1.36; 95% CI = 1.22-1.51); cleaners and mining workers (AOR = 1.25; 95% CI = 1.07-1.45).

The results of this dissertation highlight that leptospirosis is a poverty-related disease, affecting populations with poor working conditions and low educational levels. To our knowledge, this is the first study conducted at a national level describing the urban and rural patterns of leptospirosis and the high-risk occupational groups in Brazil. Leptospirosis is a multifactorial disease that requires a combination of prevention and control strategies at the national, community, and individual level, coupled with actions to improve the living and working conditions of the most affected populations. Although Brazil has made progress to prevent, detect and control the disease, knowledge gaps still exist regarding disease transmission, exposure risk factors, and effective prevention strategies in high-risk occupational groups. Leptospirosis remains an important public health problem worldwide and until practical tools are developed to detect, prevent and control it, this neglected disease will continue to affect the most vulnerable populations in developing countries.

Indexing (document details)
Advisor: Roess, Amira A.
Commitee: Gray, George, Schneider, Maria Cristina
School: The George Washington University
Department: Environmental & Occupational Health
School Location: United States -- District of Columbia
Source: DAI-B 82/10(E), Dissertation Abstracts International
Subjects: Epidemiology, Public health
Keywords: Brazil, Epidemiology, Leptospirosis, Neglected disease, Surveillance, Zoonotic disease
Publication Number: 28414272
ISBN: 9798597098487
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