India aims to eliminate lymphatic filariasis – a painful, disfiguring disease commonly referred to as elephantiasis – by 2027 and join several other countries which successfully eradicated it as a public health issue. Complicating India’s plans, though, a new WHO study says climate change may lead to new behaviour patterns, and could trigger the disease spread through new vectors.
Lymphatic filariasis is characterised by the World Health Organisation (WHO) as one of many neglected tropical diseases. It is caused by parasitic worms passed through mosquito bites and affects millions of people in tropical and subtropical areas. India accounts for 40% of the global human lymphatic filariasis burden, with 31 million people infected, and over 450 million are at risk. Unfortunately, a paucity of data on what is happening limits how effectively it can be eradicated.
Martin Walker, assistant professor of epidemiology at the Royal Veterinary College said that as “a neglected tropical disease, [lymphatic filariasis] lacks adequate attention. Creating a disease repository is crucial to deepen our knowledge of lymphatic filariasis and support research efforts.” A disease repository, such as the Infectious Diseases Data Observatory, allows researchers to pool together data and explore new challenges, as well as come up with solutions together.
A long campaign, and a new risk
The principal strategy adopted in India to fight the disease has been mass drug awareness campaigns at the rural and local level. Akhila Sivadas, executive director at Centre for Advocacy and Research, said individuals who do not have lymphatic filariasis were uncertain about the importance and safety of taking medication when approached by Accredited Social Health Activists – community health workers employed by the Ministry of Health and Family Welfare.
“We started a campaign which led us to come up with the concept of involving the community directly in the mass drug administration programme, with patients taking the lead,” she said.
Data from the National Vector Borne Disease Control Programme showed that in the states of Uttar Pradesh and Bihar, over 14,177 LF patients have joined the Filaria Patient Network, with women comprising 7,821 patients compared to 6,356 men. This collective effort is underway across 21 districts in UP and Bihar, and is set to expand to 17 additional districts in both states.
Vector borne diseases have a strong link with climatic factors like rainfall, temperature, and humidityRoxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology
This success is now being challenged by both climate change, and a lack of knowledge of how the disease is spreading.
21-year-old Rupa Saha (name changed) from Falakata in West Bengal was diagnosed with lymphatic filariasis during a night sample test. Species that cause lymphatic filariasis have microfilarial levels that tend to peak at night, so it is recommended to collect samples between 10:00 pm and 2:00 am. Saha had never heard about lymphatic filariasis before and had no idea how she got it.
“This is the first time our village has submitted blood samples for a test. I have never heard of filaria in Falakata. It only started in September 2023,” she said.
Climate change and the link with disease spread
As temperatures increase and rainfall patterns become unpredictable, areas inhabited by transmitting vectors, such as mosquitoes, broaden and shift. The expansion allows the infection to survive in such areas, thus increasing the spread of disease from one area to another. Moreover, as temperature and humidity levels are affected, the mosquito breeding rate can increase, expanding the number of transmitting cycles.
Syed Iftiqar Ahmed, a tropical medicine expert in Guwahati, Assam, said “The Wuchereria bancrofti [carrier worm of lymphatic filariasis] multiplies in different climatic environments. It has the ability to spread in different geographical locations. If West Bengal has cases, then it’s possible for states like Assam and other northeastern states to get it, as migration and climate change have a huge impact in these regions. A repository might help [to gather data] from different epicentres of the country where lymphatic filariasis is prominent to study its progress in the adjoining geographical areas.” He added that an observatory could help epidemiologists access trends during future spreads.
“Vector borne diseases have a strong link with climatic factors like rainfall, temperature, and humidity,” said Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology. “Our ongoing research on dengue dynamics in Pune shows a strong seasonality associated with the rainfall and temperature patterns. Understanding these climate-health links can help in preparing early warning systems that can warn of potential disease outbreak two or three months in advance,” he added.
The problem, though, was that health data was not as easily available as climatic data. “While meteorological data is available readily at daily timescales, health data is not shared, even for research purposes,” Koll said. “This is hurting our advancement in terms of preparing disease predictions and advancing our health care system.”
Sivadas, of Centre for Advocacy and Research, said, that “it is clear that unless we tackle the problem on a war footing with the active involvement of community and people, we are likely to lose the war not only against filaria but [also] against the ever-growing threat of climate change and its potential to influence the spread of the disease.”
She added, “In filaria endemic areas, it’s crucial to emphasise the need for a unified response to both filaria and climate change risks. Similar to COVID-19, piecemeal efforts won’t suffice.”
Reporting for this story was supported by the MSF-DNDi Grant on Neglected Tropical Diseases as part of the Without Borders Media Fellowship. The fellowship encourages independent, impartial and neutral reporting on health and humanitarian crises.
