Lymphatic filariasis — known commonly as just filariasis or elephantiasis — is the target of elimination attempts in India, with a deadline set for 2021. Is it likely that India will meet this goal?
Currently, at least one million people in India are estimated to be infected by the disease. Even after the infection has subsided, the disease can leave lasting disability: this is believed to affect more than 23 million according to the Indian Council of Medical Research (ICMR). The disease is known to be present in at least 160 districts, making the condition both widespread and relatively common given the infection numbers.
The primary vector by which the disease is spread — mosquitoes — also makes it difficult to clamp down on. Much like other conditions such as malaria and dengue fever, disease numbers can be reduced, but eliminating the disease entirely is reliant on being able to control mosquito populations that are capable of creating breeding populations in many parts of the country.
In December 2018, India launched the World Health Organization (WHO)-recommended triple drug therapy (TDT) consisting of Ivermectin, diethylcarbamazine (DEC) and Albendazole (IDA) across five states: Bihar, Jharkhand, Karnataka, Maharashtra, and Uttar Pradesh.. The triple therapy improved upon a previous double therapy by reducing the time taken to interrupt transmission of the disease. Union Health Minister Dr Harsh Vardhan earlier said of the launch of the WHO-recommended TDT regimen in India that “rapid implementation of the TDT policy made us the first country in the South-East region to introduce this new preventive drug regimen.”
Three parasites – Wuchereria bancrofti, Brugia malayi, and Brugia timori – are responsible for causing lymphatic filariasis. The parasites affect the lymphatic system. Their removal and elimination from the lymph system is an extensive process. The former treatment option using two medications had an average of five years of treatment before the interruption of the transmission of the disease. Even with the new course of three medications, this period is still around two to three years.
As such, those who are being given treatment now may still be able to transmit the disease back into mosquito populations — and thus to other people. This offers an impediment to India realising the deadline of 2021. The extensive treatment duration is another aspect which makes this disease so hard to eliminate. Some may not adhere to treatment programmes should symptoms clear up. Others remain asymptomatic and so are never treated in the first place.
An estimated 650 million Indians across 21 states and union territories are at risk of lymphatic filariasis. Though India is following WHO-recommended treatment regimens, the deadline for elimination of 2021 may simply be far too optimistic. Progress has been made, as has been the case with many other infectious diseases, but much like the numerous other deadlines India has set in the past, lymphatic filariasis is likely to take far longer than the deadlines aspire to.