NTDs: Lymphatic filariasis – mosquitoes plus parasites equal elephantiasis

This post is the 11th in a series highlighting the WHO’s list of 17 Neglected Tropical Diseases (now technically 18 as mycetoma was added to the list at the 69th World Health Assembly in May 2016). To read the previous posts in this series click here.

A man suffering from lymphatic filariasis in his left lower leg and foot. Courtesy WHO/Kalapathar Orissa.

Lymphatic filariasis (LF), also known as elephantiasis, is another one of the so-called Neglected Tropical Diseases (NTDs) that affects millions of people living in rural, lower-income communities. This disease is caused by filarial parasites (classified as roundworms) that are transmitted by various mosquitoes species. The thing to know about LF is that it isn’t the cause of death for lots of folks, but is a serious cause of disability, disfigurement and the subsequent increase in poverty as people are unable to continue working due to their disability and disfigurement. That’s not to mention the stigma and shame that accompany suffers of LF.

An estimated 40 million people suffer from clinically significant LF disfigurements. More than 556 million people received treatment for LF in 2015, resulting in more than 6.2 billion treatments delivered since 2000 which have prevented or cured 97 million cases of LF. While progress is being made to get treatment out to the people who need it, more than 97 million people in 54 countries are currently at risk of LF and need treatment to prevent the spread of infection. About 80% of those 97 million people at risk live in Angola, Cameroon, Cote d’Ivoire, Democratic Republic of the Congo, India, Indonesia, Mozambique, Myanmar, Nigeria and Tanzania.  Seventy three countries are considered endemic for LF but six of those 73 countries (Cambodia, The Cook Islands, Maldives, Niue, Sri Lanka, Vanuatu) have successfully eliminated it.

Map of lymphatic filariasis, 2014. Courtesy WHO.

Lymphatic filariasis causes various versions of disfigurement, depending on which area of the lymphatic system was damaged. Globally, over 25 million men suffer from genital disease (swollen male genitalia) while over 15 million people suffer from lymphodema (swelling of the arms/legs).

We can eliminate LF through the use of drug treatment. Giving everyone in the at-risk geographic areas a single dose of medication annually can result in an interruption to the LF transmission cycle. The drugs work to decrease to load of immature parasites in the body, reducing the parasite burden in the affected patient and also making it harder for mosquitoes to transmit LF because there are fewer parasites in the blood stream. When conducting this preventive chemotherapy for 4-6 years, transmission of LF can be successfully interrupted. However, one drawback of this program is that is does not help people who have adult parasites or who already have physical signs of LF.

The WHO started the Global Programme to End Lymphatic Filariasis (GPELF) in 2000 and since then more than 97 million cases have been treated or cured, preventing more than US$100 billion in economic losses due to people being unable to work because of having LF. Beyond just the WHO working to end LF, the Carter Center also has a LF elimination program where they are helping Ministries of Health implement elimination programs.

While lymphatic filariasis is one of the more well-known NTDs, due to the characteristic symptoms displayed by people suffering from the disease, transmission is still occurring in many countries which means many people are still at risk.

 

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