Household Transmission of Leptospira Infection in Urban Slum Communities

Abstract

BackgroundLeptospirosis, a spirochaetal zoonotic disease, is the cause of epidemics associated with high mortality in urban slum communities. Infection with pathogenic Leptospira occurs during environmental exposures and is traditionally associated with occupational risk activities. However, slum inhabitants reside in close proximity to environmental sources of contamination, suggesting that transmission during urban epidemics occurs in the household environment.Methods and FindingsA survey was performed to determine whether Leptospira infection clustered within households located in slum communities in the city of Salvador, Brazil. Hospital-based surveillance identified 89 confirmed cases of leptospirosis during an outbreak. Serum samples were obtained from members of 22 households with index cases of leptospirosis and 52 control households located in the same slum communities. The presence of anti-Leptospira agglutinating antibodies was used as a marker for previous infection. In households with index cases, 22 (30%) of 74 members had anti-Leptospira antibodies, whereas 16 (8%) of 195 members from control households had anti-Leptospira antibodies. Highest titres were directed against L. interrogans serovars of the Icterohaemorrhagiae serogroup in 95% and 100% of the subjects with agglutinating antibodies from case and control households, respectively. Residence in a household with an index case of leptospirosis was associated with increased risk (OR 5.29, 95% CI 2.13–13.12) of having had a Leptospira infection. Increased infection risk was found for all age groups who resided in a household with an index case, including children <15 years of age (P = 0.008).ConclusionsThis study identified significant household clustering of Leptospira infection in slum communities where recurrent epidemics of leptospirosis occur. The findings support the hypothesis that the household environment is an important transmission determinant in the urban slum setting. Prevention therefore needs to target sources of contamination and risk activities which occur in the places where slum inhabitants reside.

Seroprevalence and factors associated with Leptospira infection in an urban district of Cali, Colombia

“…These findings are likely explained by the study sampling and large improvement of the public services in recent years in some areas of District 18, but there are several SES-1 areas without access to public services or with flooding areas. Many studies on leptospirosis patients have widely documented that the disease is particularly prevalent in communities with inadequate sanitation 3,16,20,36,37,38,39 .…”

“…Several SES-1 areas of District 18 present open sewers, temporary accumulation of garbage piles, unpaved streets, and rainwater puddles; all of which are environmental conditions that increase proliferation of rodents and wandering of stray animals, and could ultimately explain a higher risk for Leptospira infection. Although the socioeconomic stratification systems (if available or existing) could vary among countries, leptospirosis-endemic urban areas are characterized by environmental conditions as the aforementioned 3,9,10,16,20,22,36,38,39 . Being uninsured was directly associated with Leptospira infection, but it was marginally associated after multivariate analysis (aOR = 2.94; 95%CI: 1.01-8.59; p = 0.05), therefore confounding is possible.…”

Human leptospirosis in the Federal District, Brazil, 2011-2015: eco-epidemiological characterization

“…This observation contradicts the common-sense explanation that the occurrence of the disease is associated with low-income populations and poor sanitary environmental conditions, such as those found in the outskirts of large cities and metropolitan areas 2,8,9,17 . In the FD, there exists an environment not yet characterized for human infection which does not match the socioeconomic profi le of the areas usually associated with this disease 2 .…”

“…There are specifi c places along its shoreline used for fi shing and other leisure activities such as swimming, diving, or sports that may increase the risk for infection 19 . Dumping points for rainwater, sewage, and garbage treatment plants close to Lake Paranoá deserve attention for environmental monitoring 9,17 . The availability of water, food, and shelter create conditions for the development and maintenance of synanthropic rodents 18,22 .…”

Decrease in antithrombin III and prothrombin serum levels contribute to coagulation disorders during leptospirosis

“…Host infection by pathogenic Leptospira causes an assorted array of clinical symptoms, varying from subclinical to jaundice, renal failure, bleeding and pulmonary haemorrhage, acknowledged as a major -often lethal -clinical sign of leptospirosis (Nicodemo et al, 1997;Marotto et al, 1999;Segura et al, 2005;Maciel et al, 2008). …”