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Climate-Driven Infectious Diseases
Context:
Globally, research on climate and environmentally driven infectious diseases has largely concentrated on vector-borne diseases like malaria and dengue. However, melioidosis caused by Burkholderia pseudomallei, presents a unique and significant health challenge that has long eluded widespread attention.
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- This disease, primarily contracted through soil and water exposure, is heavily influenced by environmental factors such as rainfall, temperature, and humidity.
- Despite being described over a century ago, melioidosis continues to perplex the medical community due to its varied clinical manifestations and diagnostic challenges.
Global and Regional Disease Burden
- A 2016 study published in The Lancet predicted approximately 165,000 global melioidosis cases annually.
- South Asia, including India, accounts for 44% of the global burden.
- The study increased awareness within India’s medical community, driving further research and investigation.
Understanding Melioidosis
- Melioidosis is a bacterial infection that can range from mild skin infections to severe pneumonia and sepsis, with fatality rates reaching 50% in septic cases.
- Melioidosis is typically transmitted through: Inhalation of dust or water droplets contaminated with B. pseudomallei. Contact with contaminated soil or water, particularly through breaks in the skin (e.g., cuts or scrapes).
- Many animals can also contract melioidosis, including: Sheep, goats, pigs, boar, horses, cats, dogs, cows. While animals can carry the bacteria, human-to-human transmission is not common.
- The complexity of diagnosing and treating melioidosis lies in several factors:
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- Clinical Manifestations: B. pseudomallei can cause a wide spectrum of clinical symptoms, making it difficult to diagnose. The disease can mimic other infections, leading to misdiagnoses and delays in treatment.
- Diagnostic Challenges: The bacteria require prolonged incubation conditions and are often misidentified as common pathogens, such as Pseudomonas aeruginosa, in routine microbiology laboratories.
- Treatment Complexity: Unlike many other infectious diseases, melioidosis demands an initial intravenous therapy followed by a prolonged eradication phase lasting 12-20 weeks, which underscores the importance of accurate diagnosis for effective treatment and prevention of recurrence.
Focus of Research in India
- Indian research has primarily explored host factors, including comorbidities (diabetes, renal diseases) and occupational factors (farming, alcoholism).
- Odisha has emerged as a key region with increasing case reports, particularly at AIIMS Bhubaneswar.
Collaborative Research Initiative
- AIIMS Bhubaneswar and IIT Bhubaneswar collaborated to study environmental conditions contributing to melioidosis occurrence.
- The study tracked 144 cases from 2015-2023, analysing meteorological parameters like rainfall, temperature, humidity, and solar radiation across 3,024 days.
- Disease mapping was conducted using 10 km grid sizes across Odisha.
Key Findings of the Study
- The study, published in the Current Research in Microbial Sciences, revealed a clear seasonal pattern to melioidosis incidence, with infections peaking during and after the monsoon season.
- The data also highlighted several key environmental conditions that correlate with increased risk of disease transmission:
- Temperature and Rainfall: Both factors significantly influenced the survival and transmission of B. pseudomallei, with optimal conditions occurring during the monsoon season when rainfall is high.
- Solar Radiation and Cloud Cover: These meteorological factors also played a role in determining bacterial survival and infection rates.
- High-Risk Regions: The study identified districts such as Cuttack, Balasore, Khordha, and Jajpur as high-risk areas for melioidosis, which also happen to be among the most densely populated regions in Odisha.
- Interestingly, the study also pointed out that land use changes, soil composition, and rapid urbanisation, which were not included in the analysis due to data limitations, may also contribute to the disease’s dynamics.
- Poor sanitation and increased human exposure to contaminated soil and water could exacerbate the spread of melioidosis, especially in urbanising areas.
Public Health Implications and Recommendations
- The study underlines the potential of climate-driven disease modelling for other environmentally influenced diseases.
- Integrating climate data into public health planning can improve outbreak predictions and mitigate health risks.
- Odisha’s approach could serve as a model for other regions, emphasising the need for interdisciplinary collaboration between climate scientists and medical researchers.
