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Why is it difficult to prevent the poor from contracting leptospirosis?

Leptospirosis has become a global epidemic in impoverished urban communities


It is important to identify possible barriers that limit prevention practices and continue to expose residents to leptospirosis

Leptospirosis is a major public health concern due to its high morbidity and mortality rates. It is estimated that 1.03 million new cases occur annually worldwide, with approximately 60 thousand deaths, mainly among young male adults. Underprivileged communities, especially large urban centers, have a higher incidence of infectious diseases than other communities do. Underprivileged neighborhoods with precarious environmental conditions and inadequate infrastructure, including untreated garbage, open sewage, and stagnant water, also contribute to the proliferation of pathogens and their hosts, increasing the exposure and risk of contracting diseases, such as leptospirosis, which is acquired through direct contact with water and soil contaminated with the urine of infected animals.

In urban centers, sewage rats are the main reservoirs and disseminators of Leptospira bacteria in the environment. More than 10,000 serious cases are registered in Brazil annually. The disease is characterized by high fever, headaches, and body aches and can be confused with dengue, influenza, and other viruses. In severe cases, the affected experience jaundice (eyes and skin turn yellow), kidney failure (reduced urine volume), and bleeding. Approximately 10% of the hospitalized patients with severe leptospirosis die, with the risk of death being 50% higher in patients with pulmonary bleeding.

Diagnosing this disease and recognizing it early is challenging because of its initial nonspecific appearance that resembles those of other bacterial and viral infections. Additionally, there is a lack of a standard testing technique to check for infection at all stages. Furthermore, some endemic areas lack adequate laboratory resources, infrastructure, and well-trained personnel.

A cross-sectional study titled “Why is leptospirosis hard to avoid for the impoverished? Deconstructing leptospirosis transmission risk and the drivers of knowledge, attitudes, and practices in a disadvantaged community in Salvador, Brazil” was conducted using Knowledge, Attitudes and Practices (KAP) methodology in a disadvantaged urban community in Salvador (BA); and environmental and epidemiological data on the transmission of leptospirosis was simultaneously collected. To learn more about this subject, the press office of the Brazilian Society of Tropical Medicine (SBMT) interviewed Dr. Federico Costa, one of the authors of this article. Details of the interview are provided below.

SBMT: Could you tell us about the study and the aspects you wish to highlight?

Dr. Federico Costa: This study was part of a larger research project titled “Optimization of Control Measures for Zoonoses in Brazilian Communities,” which was financed by the Medical Research Council (MRC) agency and conducted from 2017 to 2019 in four vulnerable communities in Salvador, located in the Railway Suburb of the city.

The KAP study related to leptospirosis, called KAPL, aimed to understand how the combination of demographic, socioeconomic, and environmental factors determined the KAP of residents and risk of infection. The research was conducted in Marechal Rondon, located in the Subúrbio Ferroviário of Salvador, which is considered a low-income community with poor socio-environmental and sanitation conditions and a high concentration of families in situations of social vulnerability. Social environments such as those of Marechal Rondon, which are affected by profound social inequalities, have historically exposed impoverished population segments to a wide range of zoonotic diseases, such as leptospirosis. According to data from a larger research project, the seroprevalence of Leptospira in Marechal Rondon was 12%, which was considered high compared with the results identified in other communities with similar characteristics, in which seroprevalences of 9 and 10% were observed.

SBMT: What are the main findings and importance of this study?

Dr. Federico Costa: In this study, we identified that residents’ knowledge of leptospirosis influenced both their attitudes and prevention practices, which consequently influenced the reduction of the risk of infection with Leptospira. Another relevant finding that has barely been explored in previous studies is the influence of socioeconomic and environmental factors on CAP. Regarding the population that was the focus in our study, most people had heard about leptospirosis, with mass media channels such as television and radio being the main sources of information. Most study participants perceived leptospirosis as a serious disease, showed concerns about being infected by bacteria that could cause leptospirosis, and avoided contact with sources that could spread the disease. Despite having such knowledge, some people reported that they did not use gloves and boots when in contact with sewage water, which could be attributed to their socioeconomic conditions, and that they used illegal poisons to control rat infestations in their homes.

It is also noteworthy that residents’ knowledge of the disease influenced their attitudes and, consequently, their prevention practices. Regarding CAP variables, they were significantly influenced by socioeconomic and environmental factors, and individuals with higher knowledge and practice scores had a reduced risk of exposure to Leptospira. Males and those with lower socioeconomic status were at a higher risk, but when we controlled for KAP variables, we noted that neither the male sex nor low socioeconomic status were direct drivers of seropositivity. Employment levels were linked to improved knowledge and less contaminated environments and logically, a lower risk. However, interestingly, being employed was associated with a higher risk of leptospirosis transmission, suggesting that working was a high-risk activity for people residing in areas with infrastructural deficiencies.

SBMT: Why did Black residents have better attitudes toward leptospirosis?

Dr. Federico Costa: In our study, self-declared Black residents had better attitudes towards leptospirosis than self-declared non-Black residents did. We also noticed no differences between these two groups in knowledge, practices, or seropositivity, contrary to previous studies that showed self-declared Black residents having a higher risk of leptospirosis. Thus, our findings suggested that self-declared black residents, which form the majority of the population in the context of extreme social vulnerability and exposure to risk factors that can cause leptospirosis, recognized the disease as a potentially serious health problem and that they were at a higher risk. The similar (higher in previous studies) leptospirosis rates of these residents compared to those of non-black residents may also be related to historical life experiences in contexts of socio-environmental deficiencies.

Our findings were in line with those reported for other diseases in different contexts. Historically, marginalized ethnic groups in the US have been most likely to perceive COVID-19 as a major threat to society, with COVID-19 disproportionately affecting marginalized ethnic minorities. Hospitalizations for infectious diseases are generally higher in Indigenous ethnic communities, especially in disadvantaged groups. In our study, although better attitudes were observed among self-declared Black people, socioeconomic and environmental inequalities, manifested by types of employment, living conditions, and sociodemographic and environmental factors, still remained in ethnic groups that lived on the margins of society and were at a disproportionate risk of being affected by infectious diseases.

SBMT: Does poverty increase the risk of contracting leptospirosis?

Dr. Federico Costa: Unfortunately, in the current century, poverty still remains an important determinant of health and contributes not only to increasing the risk of contracting diseases such as leptospirosis but also maintaining the exposure of the most vulnerable population segments to a set of risk factors and risks of other communicable diseases. Additionally, diseases such as leptospirosis remain on the list of neglected diseases. Such diseases mainly affect impoverished populations, and there are only scarce investments in healthcare toward the treatment, prevention, and effective and permanent control of these diseases.

Large urban centers like Salvador are subject to conditions with profound social inequalities and have populations living with poor sanitation and without sanitary sewage disposal facilities. These populations have been affected by episodes of frequent flooding in periods of heavy rain and live in precarious housing with poor urban infrastructure, a lack of proper paving, and inadequate garbage collection facilities. Such centers clearly show that poverty is real and still exists. Additionally, populations living under conditions such as these will be permanently exposed to the risk of developing not only leptospirosis but also other zoonotic and transmissible diseases.

SBMT: Why is it difficult to prevent leptospirosis among the poor?

Dr. Federico Costa: Leptospirosis is a zoonotic disease related to a set of socioenvironmental factors and living conditions. Additionally, public policies toward improving these factors and conditions have not been prioritized.

Therefore, if we remain in a scenario where effective intersectoral policies and intervention actions are not implemented to improve the living conditions of historically vulnerable population segments, it will continue to be difficult to prevent leptospirosis among the impoverished. In contexts with serious socioenvironmental deficiencies, where low-income populations reside, health-related messages and interventions should consider these complexities, prioritize interventions that can limit residents’ exposure, and support more effective leptospirosis prevention practices.

SBMT: The world’s population of slum dwellers has increased exponentially. Can studies on disease transmission in these communities guide environmental interventions for controlling leptospirosis?

Dr. Federico Costa: Yes. Epidemiological studies on disease transmission, such as the Canadian COVID-19 Antibody and Health Survey (CAPL) study, are population studies that aim to describe the health conditions of populations; investigate and assess the factors that determine the transmission of diseases; and propose, guide, and evaluate interventions. Additionally, these studies should be referenced by managers and health professionals when building actions aimed at interventions in environmental problems, which can contribute to the control and prevention of leptospirosis and other transmissible zoonotic diseases that disproportionately affect these populations.

SBMT: Would you like to add anything else?

Dr. Federico Costa: Thank you. In conclusion, I would like to say that to build effective solutions aimed at effective interventions in complex problems such as leptospirosis, all community residents, universities, health professionals, and managers need to participate effectively.