Malaria and Environmental Determinants in Bangladesh: Implications for Occupational Health and Disease Control

1. Introduction

Malaria, a vector-borne disease caused by Plasmodium species and transmitted by Anopheles mosquitoes, continues to pose significant public health challenges globally. As a persistent global public health issue, malaria accounted for an estimated 247 million cases and 619,000 deaths in 2022, with the majority of these occurring in low- and middle-income countries (Organization, 2023). Although the national malaria control program has achieved remarkable progress in reducing morbidity and mortality, environmental factors continue to play a pivotal role in sustaining transmission cycles (Organization, 2015).

The ecology of malaria in Bangladesh is deeply intertwined with environmental determinants such as temperature, rainfall, land use patterns, and deforestation. These factors influence the distribution and breeding habitats of mosquito vectors, ultimately impacting transmission dynamics (Emeto et al., 2020).For instance, the monsoon season, characterized by heavy rainfall and high humidity, provides ideal conditions for mosquito proliferation, thereby increasing the risk of outbreaks (Reid et al., 2012). Furthermore, anthropogenic activities such as agricultural expansion and urbanization have significantly altered the landscape, leading to the creation of vector-friendly habitats (Haque et al., 2011).

From an occupational health perspective, specific worker groups, including forest workers, farmers, and construction laborers, are disproportionately exposed to malaria due to their prolonged outdoor activities in high-risk areas. Such exposures not only increase the risk of infection but also impose economic and social burdens, particularly on marginalized communities (Sinha et al., 2020). Understanding the interplay between occupational exposure and environmental determinants is critical for designing targeted interventions.

This review aims to comprehensively examine the environmental determinants of malaria in Bangladesh and their implications for occupational health and disease control strategies. By synthesizing current evidence, this paper seeks to identify gaps in knowledge and provide recommendations for strengthening malaria control programs in the context of environmental and occupational health challenges.

2. Environmental Determinants of Malaria in Bangladesh

2.1. Climatic Factors

• Temperature and Humidity: Malaria transmission is highly sensitive to temperature and humidity. Bangladesh’s tropical climate, characterized by monsoons, creates optimal conditions for mosquito breeding and parasite development [7].
• Rainfall Patterns: Heavy rainfall increases mosquito breeding sites, particularly in stagnant water bodies [8]. These stagnant water bodies provide an ideal environment for mosquitoes to lay their eggs and develop rapidly. As the water accumulates, it becomes a breeding ground for vector species such as Aedes, Anopheles, and Culex mosquitoes, which are responsible for diseases like dengue, malaria, and chikungunya [9].
• Seasonal Variations: Malaria incidence peaks during the monsoon season when vector populations thrive [10]. High humidity and warm temperatures during the monsoon season create optimal conditions for mosquito survival and reproduction. The increased vector population, coupled with frequent human-vector contact, significantly amplifies malaria transmission [11,12].

2.2. Land Use and Urbanization

• Deforestation: Conversion of forests for agriculture or settlement has altered ecosystems, increasing human-vector contact in regions [13]. This deforestation disrupts natural habitats, forcing vectors such as mosquitoes to adapt to human settlements as their primary environment [14]. The reduction in biodiversity also eliminates natural predators of these vectors, further escalating their population. As a result, the frequency of vector-borne diseases like malaria, dengue, and leishmaniasis has surged in these regions, posing significant public health challenges [15].
• Agriculture and Irrigation: Stagnant water from irrigation projects provides breeding sites for mosquitoes [16]. These artificial water bodies, created for agricultural purposes, often remain undisturbed for long periods, allowing mosquito larvae to mature without interruption. Improperly managed irrigation systems can inadvertently contribute to the proliferation of vector species, increasing the risk of diseases such as malaria and lymphatic filariasis in surrounding communities [17].
• Urbanization: Poorly managed urban infrastructure, such as blocked drainage systems, creates breeding sites in peri-urban areas [18,19].

3. Occupational Health and Malaria: High Risk Gorup

• Agricultural Workers: Field workers often face prolonged exposure to mosquito bites, especially during early mornings and evenings [20]. Prolonged exposure to mosquito bites compromises their health and can lead to increased absenteeism, impacting productivity. Additionally, the lack of protective measures or inadequate use of repellents further heightens the risk of disease transmission in these vulnerable workers [21,22].
• Forest Workers: Those involved in logging or forest-related activities in malaria-endemic regions are at high risk due to proximity to vector habitats [23]. Their work in forested areas, often close to stagnant water sources, increases exposure to mosquito bites, making them more susceptible to malaria transmission [22].
• Construction Workers: Construction laborers are often exposed to unsafe living conditions near stagnant water sources [24].
• Migrant Labor: Movement of workers between endemic and non-endemic regions can introduce malaria to previously unaffected areas, complicating control efforts [25].

4. Strategies for Malaria Control in Bangladesh

4.1. Environmental Management

• Vector Control: Regular cleaning of stagnant water sources, such as drains, ponds, and ditches, along with the introduction of natural predators like fish, can reduce mosquito breeding sites. Promoting environmentally friendly insecticides ensures effective vector control while minimizing harm to non-target species and the environment [26]. Additionally, community-based programs can encourage individuals to remove standing water around their homes, further reducing the risk of mosquito proliferation.
• Land Use Policies: Incorporating health considerations in agricultural and urban planning involves designing areas with proper drainage systems to prevent water accumulation and reduce mosquito breeding [27]. Zoning regulations can ensure that settlements are built away from known vector habitats. Moreover, integrating green spaces and promoting sustainable agricultural practices can help balance human development with ecosystem preservation, reducing the risk of vector-borne diseases in growing populations [28].

4.2. Occupational Health Interventions

• Protective Equipment: The distribution of insecticide-treated bed nets and clothing to high-risk workers can significantly reduce mosquito exposure, particularly in areas with high transmission rates of malaria [29]. Such interventions are effective in both preventing bites during rest and while working in the field. Personal protective measures, like the use of repellents and treated clothing, have been shown to lower the incidence of vector-borne diseases in high-risk occupations [30].
• Awareness Campaigns: Educating occupational groups, such as agricultural workers, construction laborers, and forest workers, about malaria risks and prevention is vital to reducing disease transmission[31]. Community-based awareness programs focusing on proper use of bed nets, repellents, and the importance of regular health checks can empower individuals to protect themselves and their families. Studies have shown that targeted health education increases the adoption of preventive measures, thereby decreasing the incidence of malaria in at-risk populations[32].
• Targeted Health Services: The establishment of mobile clinics and workplace health checks for high-risk populations provides essential healthcare services directly to workers in remote or underserved areas [33]. Regular health checks allow for early detection and treatment of malaria and other vector-borne diseases, reducing the impact on workers' productivity[34]. Research has indicated that mobile health units significantly improve access to healthcare in rural and agricultural settings, contributing to lower disease transmission rates [35].

5. Discussion

The reviewed literature highlights the profound impact of environmental determinants and occupational exposure on malaria transmission in Bangladesh. Climatic factors such as temperature, humidity, and rainfall significantly shape the dynamics of malaria vectors, particularly during the monsoon season, when stagnant water bodies provide breeding grounds for Anopheles mosquitoes [8,11]. Similarly, anthropogenic activities, including deforestation, agricultural expansion, and urbanization, amplify human-vector interactions, sustaining the transmission cycle [36,37]. These findings underscore the multifaceted nature of malaria risk and the necessity of a comprehensive approach to disease control.

From an environmental and occupational health perspective, the evidence reveals significant disparities in malaria risk, with vulnerable groups such as agricultural workers, construction laborers, and forest workers disproportionately affected. This finds align with previous studies conducted in other countries [38,39]. Prolonged exposure to vector-rich environments, coupled with inadequate access to healthcare, places these populations at heightened risk. This occupational health burden not only affects individual well-being but also perpetuates socio-economic inequities, as malaria impacts productivity, income, and quality of life in affected communities [40].

Interpretation of these findings within the broader public health context underscores the interconnectedness of environmental and occupational determinants. Malaria control efforts that focus solely on clinical interventions are unlikely to yield sustained reductions in transmission without addressing these upstream drivers. For instance, mitigating the environmental risks associated with unplanned urbanization and poorly managed drainage systems can reduce mosquito breeding sites in peri-urban areas. Similarly, promoting awareness and distributing protective measures such as insecticide-treated nets among high-risk occupational groups can significantly reduce exposure.

Policy implications of this analysis are far-reaching. First, integrating health considerations into urban planning and land use policies can help address the root causes of malaria proliferation. Strategies such as promoting eco-friendly agricultural practices, implementing sustainable irrigation systems, and reforestation could mitigate the environmental factors that foster mosquito breeding. Second, targeted occupational health interventions, including mobile health services and workplace malaria prevention programs, should be prioritized to protect vulnerable populations. Policymakers must also strengthen disease surveillance systems to monitor and respond to the spread of malaria, particularly in the context of labor migration.

6. Conclusion

Malaria in Bangladesh is deeply influenced by environmental factors and occupational health dynamics. Addressing this dual challenge requires an integrated approach that incorporates vector control, environmental management, and occupational health interventions. By focusing on high-risk groups and regions, policymakers can develop targeted strategies to reduce malaria transmission and improve public health outcomes..