Lymphatic filariasis, commonly known as elephantiasis, is a disease that is usually acquired in childhood. Infection occurs when filarial parasites are transmitted to humans through mosquitoes. — Wikimedia Commons
World Neglected Tropical Diseases Day, observed annually on Jan 30, was officially recognised by the World Health Assembly in 2021 to bring long-overdue attention to diseases that affect the poorest and most marginalised communities worldwide.
The date commemorates key global commitments to control and eliminate neglected tropical diseases, including international pledges by governments, donors and health organisations.
Its purpose is not only to raise awareness, but to sustain political commitment, encourage public participation in prevention programmes, and remind countries that progress against neglected tropical diseases can easily be reversed if attention fades.
What are they?
The larval stage of filarial parasites are seen here via light microscopy circulating in a patient’s peripheral blood, a key feature of lymphatic filariasis. — Dr VINOTH KUMARASAMY
Neglected tropical diseases are a group of infections caused by parasites, bacteria and viruses that thrive in conditions of poverty, inadequate sanitation and limited access to healthcare.
They include lymphatic filariasis, dengue, soil-transmitted helminth infections and schistosomiasis, among others, which continue to affect millions of people worldwide.
While some of these conditions are familiar by name, they are rarely discussed as part of a broader public health challenge.
In Malaysia, neglected tropical diseases are often perceived as problems of the past or issues confined to other countries.
Dengue, for example, is widely recognised, yet it is rarely framed within the wider context of neglected diseases driven by environmental, social and structural factors.
Other infections, particularly parasitic diseases, remain largely invisible because they tend to cause chronic illness rather than sudden death.
This invisibility has consequences.
Chronic anaemia, impaired child growth, reduced cognitive development and long-term disability quietly affect education outcomes and economic productivity.
These impacts rarely make headlines, but they shape lives, particularly among rural communities, indigenous populations, migrant workers and the urban poor.
In Malaysia, significant efforts have been undertaken by the Health Ministry against these diseases.
Efforts include mass drug administration programmes, vector control activities, surveillance systems and public health outreach, particularly for priority diseases such as lymphatic filariasis and dengue.
These initiatives have contributed to substantial progress in reducing transmission.
Climate change increases risk
Soil-transmitted helminth infections are caused by a number of worms, including this hookworm Ancylostoma caninum, seen here attached to a patient’s intestinal mucosa. — US CDC
Unfortunately, climate change has further increased the relevance of neglected tropical diseases in Malaysia.
Rising temperatures, heavier rainfall and flooding create conditions favourable for disease transmission.
Changes in vector habitats mean that infections once considered geographically limited can spread to new areas, including urban and peri-urban settings.
As extreme weather events become more frequent, disruptions to sanitation and displacement of communities heighten disease risks.
In this context, neglected tropical diseases are no longer remote or theoretical concerns, they are directly linked to climate resilience and public health preparedness.
Still working on elimination
The best way to prevent rabies in both humans and animals is by vaccinating pet and stray dogs and cats, especially in areas with known cases. — Filepic
Malaysia has made notable progress in controlling lymphatic filariasis through long-term public health interventions.
Under the National Lymphatic Filariasis Elimination Programme, implemented since 2002, infection prevalence has been reduced to below 2% in 125 endemic sub-districts across eight states, i.e. Kedah, Perak, Johor, Pahang, Terengganu, Kelantan, Sabah and Sarawak.
This milestone reflects sustained efforts such as mass drug administration, active surveillance and vector control.
Nevertheless, elimination remains a work in progress.
A small number of sub-districts in Sarawak and Sabah have yet to meet the target antibody prevalence threshold, and active screening continues to detect positive cases, indicating low-level transmission.
Surveillance data have shown several hundred antibody-positive individuals identified over recent years, highlighting the importance of maintaining control measures even as overall prevalence declines.
While no new cases of severe elephantiasis have been reported for many years, individuals living with chronic complications remain a reminder of the long-term impact of this preventable disease.
Lymphatic filariasis develops when microscopic parasitic worms are transmitted through repeated mosquito bites.
Once inside the human body, the larvae migrate to the lymphatic system, where they mature into adult worms and can survive for several years.
These worms interfere with normal lymph flow, gradually damaging lymph vessels and surrounding tissues.
Over time, this can lead to persistent swelling of the limbs, thickening of the skin, and in some cases, hydrocele (a painless swelling in the scrotum due to fluid build-up).
The disease often progresses silently in its early stages, with infected individuals showing no symptoms while transmission continues within the community.
This long asymptomatic phase makes early detection and sustained prevention efforts especially important.
Other neglected diseases
Beyond lymphatic filariasis, Malaysia continues to face several other neglected tropical diseases that receive less public attention despite their health impact.
Rabies remains a serious concern, particularly in Sarawak, where human deaths still occur following exposure to infected animals, highlighting the importance of vaccination and prompt treatment after bites.
Soil-transmitted helminth infections persist among vulnerable groups, especially in rural and indigenous communities, where poor sanitation and unsafe water facilitate ongoing transmission.
Re-emerging infections such as scrub typhus and melioidosis also pose growing risks, particularly among agricultural workers and individuals with underlying conditions like diabetes.
These diseases are often underdiagnosed because their early symptoms resemble common fevers, delaying treatment and increasing the risk of severe outcomes.
Dr Vinoth Kumarasamy is a parasitologist and lecturer at Universiti Kebangsaan Malaysia. For more information, email starhealth@thestar.com.my. The information provided is for educational and communication purposes only, and should not be considered as medical advice. The Star does not give any warranty on accuracy, completeness, functionality, usefulness or other assurances as to the content appearing in this article. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.
