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Frequently Asked Questions

What is lymphatic filariasis?
Lymphatic filariasis (LF) is the 4th leading cause of permanent disability worldwide1. Often known by the name elephantiasis, it results in clinical symptoms such as swollen limbs and breasts (lymphoedema) and genitals (hydrocele), or swollen limbs with dramatically thickened, hard, rough and issured skin (elephantiasis). Found mostly in tropical areas, LF is a parasitic disease caused by thread-like worms, or “filariae”. Each adult worm lives for about six years in the human lymphatic system, and female worms release millions of microfilariae (immature worms) that circulate in the blood and are then picked up by mosquitoes for transmission to another human.

How common is the disease?
In 2006, the World Health Organization estimated that over 1.25 billion people are at risk in 83 countries and territories. Approximately 120 million already have been infected with LF, and over 40 million2 are seriously incapacitated and disfigured by the disease3. In 2002, it was estimated that LF is responsible for the loss of 4.4 million disability adjusted life years (DALYs) in men and over 1.3 million DALYs in women4. This represents the loss of healthy, productive years of life due to disability caused by LF. One third of the people infected live in India, one third in Africa and the rest in South Asia, the Western Pacific and parts of Central and South America2. In tropical and sub-tropical areas where LF is well-established – notably Africa and the Indian subcontinent – the prevalence of infection is continuing to increase1. Reasons for this include the rapid and unplanned growth of cities which creates numerous breeding sites for the mosquitoes that transmit the disease, and the rise in poverty1.

What are the signs and symptoms?
The infection is usually acquired early in childhood, but the worst symptoms of the chronic disease do not generally appear until adulthood5. Many people with LF never develop clinical signs of their infections. However, studies show that people actually have hidden, internal damage to the kidneys and lymphatic system. In men and women with clinical signs, the damage to the lymphatic system usually causes fluid to collect and results in swelling in the arms, legs, breasts and genitals. This is called lymphoedema6. Often lymphoedema is accompanied by acute episodes of local inflammation involving skin, lymph nodes and lymphatic vessels due to bacterial infections. Such infections cause elephantiasis, a hardening and thickening of the skin7. Men also can suffer from hydrocele, a fluid-filled enlargement of the sacs around the testes.

How extensive is LF in Tanzania?
The estimated population at risk in mainland Tanzania exceeds 37 million – this is the whole of mainland Tanzania with the exception of Chunya and Babati districts. There are at least four million people with clinical manifestations of the disease.

Is lymphatic filariasis a new disease?
LF has been a scourge of civilization for thousands of years, being first depicted on the pharaonic murals of Egypt and in the ancient medical texts of China, India, Japan and Persia. Elephantiasis and hydrocele were first associated with parasitic filarial worms and their mosquito vectors in the late 19th century by French, English and Australian physicians working with patients from Cuba, Brazil, China and India.

How is the disease transmitted?
LF is transmitted from person to person by mosquitoes. Adult worms live in an infected human’s lymphatic vessels. The female worms release large numbers of very small worm larvae (called microfilariae), which circulate in an infected person’s bloodstream. When a human is bitten by a mosquito, the mosquito ingests the larvae. The larvae develop in the mosquito into an infective stage and are then spread to other people via mosquito bites. After a bite, the larvae pass through the skin, travel to the lymphatic vessels and develop into adult worms. These mosquitoes breed in dirty water, often found in remote areas and in neglected periurban and urban areas, and so LF is primarily a disease of the poor2. Inadequate sanitation, standing water, crowding, lack of screens on houses, and lack of bed nets all contribute to the transmission of the disease.

What is the social and economic impact of lymphatic filariasis?
LF causes several billion US dollars a year in productivity losses. It occurs primarily in poor communities, and exacerbates poverty by physically incapacitating people and thus preventing them from having a normal working life8. The fight against LF is also a fight against poverty. LF exerts a heavy social burden, particularly since chronic complications are considered shameful and are often hidden. For men, the genital damage is a severe handicap leading to physical limitations, poor self-image and social stigmatization. Persons affected by lymphoedema are sometimes considered undesirable, and are severely stigmatized. Marriage, usually an essential source of security, is often impossible for men and women with chronic complications5.

Can LF be prevented?
Yes, disease transmission can be stopped through a feasible, effective and inexpensive prevention strategy – the administration of two oral drugs to at-risk populations once a year. Ministry of Health programmes distribute albendazole plus either diethylcarbamazine (DEC) or Mectizan® to people in infected communities annually for at least five years. Alternatively,
table/cooking salt fortified with DEC can be given to a population for at least two years. These drugs kill the microfilariae in an infected person’s blood so that mosquitoes cannot transmit the disease to others.

What can be done for those already infected?
While giving drugs to those already infected will decrease infectivity to others, it will not cure them. This is because the drugs only kill the microfilariae but not the adult worms which cause damage to the lymphatic system. However, infected patients’ symptoms can be managed by reducing the frequency of acute attacks. Simple hygiene practices and exercise help reduce the frequency of acute attacks and keep lymphoedema from becoming more severe. In men, surgery can repair the damage caused by hydrocele.

Can LF be eliminated?
As of 1994, LF transmission was interrupted in China using both strategies: mass drug distribution and fortification of salt with DEC. There were 330 million people at risk of infection with LF before the control programme was implemented. Using lessons learned in China and in other endemic countries worldwide, strategies have been modified and tools have been developed to make the elimination of LF more effective and efficient. The goal is to eliminate LF as a public health problem globally by 2020.

Who is working on the elimination effort?
The Global Programme to Eliminate LF provides technical support to Ministry of Health-led programmes. It has two goals: to eliminate LF as a public health problem and to alleviate hardship in individuals with LF-induced disability. WHO established the Global Programme after the World Health Assembly resolved in 1997 to eliminate LF a public health problem and GlaxoSmithKline and Merck & Co., Inc. agreed to donated albendazole and Mectizan® for as long as necessary to achieve this goal. The Global Alliance to Eliminate LF, established in 2000, is a global public-private partnership of country Ministries of Health and over 40 other organizations in academia, private enterprise, government institutions, and others, all working together to eliminate LF. The Alliance mobilizes political, financial and technical resources to support the Global Programme to Eliminate LF.

How much does it cost to treat a person?
According to a major new international study of treatment costs9, the per-person cost of once yearly administration of the medicines to eliminate LF vary by region and country, ranging from just $0.06 to $1.96. In the first year of a country programme, costs have been as high as $2.23 but always decrease in subsequent years. Treatment is still surprisingly inexpensive and highly effective, thanks in part to the fact that two of the three drugs available for treatment – albendazole and Mectizan® - are donated by GlaxoSmithKline and Merck & Co., Inc. respectively.

How does the LF program integrate with other disease initiatives?
In order to ensure that LF elimination programmes use resources effectively, the Global Programme places great emphasis on integration with other public health programmes. Linkages are pursued with programmes that use similar strategies – such as bed nets for malaria control, and drugs for controlling intestinal parasites, schistosomiasis and river blindness

Have any countries eliminated LF yet?
In March 2006, at the fourth meeting of the Global Alliance to Eliminate LF, China announced that it has successfully eliminated the disease. This announcement followed a report published in The Lancet medical journal which confirmed that the strategy of mass drug administration is proving effective towards eliminating LF in Egypt. In addition to Egypt, Sri Lanka and several
Pacific island nations have completed at least five rounds of treatment and are conducting surveys to assess whether LF transmission has halted.

How many treatments have been administered since the start of the global elimination effort?


No of Treated Countries

Total No of Treatments (Millions)

Total Treatments to Children (Millions)









Eastern Med




Mekong Plus








South East Asia








How many people have benefited?
More than 496 million individuals have been treated for LF and approximately 44 million infections have been averted. During their lives, an estimated

• 9 million cases of hydrocele have been averted
• 5 million cases of lymphedema have been averted
• 29 million cases of subclinical lymphatic damage have been averted

What are the benefits to children?
Albendazole and Mectizan®* are very effective de-worming medications. As an additional benefit to the LF programme, 38 million children receiving these drugs were therefore also treated for intestinal parasites, resulting in improved growth and fitness, school attendance, and cognitive abilities.10,11,12 It is estimated that 25 million babies have been born with little or no risk of contracting LF (i.e., babies born into areas undergoing LF mass drug administration) with approximately 2.5 million LF infections therefore prevented.

During these children’s lives:
• Over a half million cases of hydrocele will be prevented
• More than 300,000 cases of lymphedema will be prevented
• Approximately 1.6 million cases of sub-clinical lymphatic damage will be

Are we on track to eliminating this disease by 2020?

Papers of relevance
1 WHO (1998) World Health Report. Geneva: World Health Organization

2 WHO (2004) Weekly Epidemiological Record #47, 79 pp 417-424

3 Ottesen EA, Duke BOL, Karam M, et al (1997) “Strategies and tools for the control/elimination of lymphatic filariasis” Bulletin of the World Health Organization, 75 (6):491-503.

4 WHO (2002) Global Burden of Disease.

5 Lymphatic filariasis website, WHO, www.who.int/mediacentre/factsheets/fs102/en/

6 Mortimer PS (1990) “Investigation and management of lymphoedema” Vas Med Rev 1:1-20.

7 Burri H, Loutan L, Kumaraswami V, et al (1996) “Skin changes in chronic lymphatic filariasis” Transactions of the Royal Society of Tropical Medicine & Hygiene 90:671-74.

8 Wegesa, et al. (1979) “Tanzania filariasis project: Survey methodology and clinical manifestations of Bancroftian filariasis” Acta Tropica 36 (4):369-77.

9 Goldman AS, Guisinger VH, et al. (2007) National Mass Drug Administration Costs for Lymphatic Filariasis Elimination. PLoS Negl Trop Dis 1(1): e67.

10 Stephenson, LS et al. (1993) Physical fitness, growth and appetite of Kenyan school boys with hookworm, Trichuris trichiura and Ascaris lumbricoides infections are improved four months after a single dose of albendazole. Journal of Nutrition, 123: pp. 1036-1046.

11 Adams, EJ et al (1994) Physical Activity and Growth of Kenyan School Children with Hookworm, Trichuris trichiura and Ascaris lumbricoides Infections are Improved after Treatment with Albendazole. Journal of Nutrition, 124: pp. 1199-1206.

12 Stephenson, et al (1993) Weight Gain of Kenyan School Children Infected with Hookworm, Trichuris trichiura and Ascaris lumbricoides is Improved Following Once- or Twice-yearly Treatment with Albendazole. Journal of Nutrition, 123: pp. 656-665.

* Mectizan® (ivermectin) has formal regulatory approval for lymphatic filariasis and onchocerciasis and is donated by Merck & Co., Inc. only for those indications.