The infection can be treated with drugs. However, chronic conditions may not be curable by anti-filarial drugs and require other measures, eg. surgery for hydrocele, care of the skin and exercise to increase lymphatic drainage in lymphoedema.
Annual treatment of all individuals at risk (individuals living in endemic areas) with recommended anti-filarial drugs combination of either diethyl-carbamazine citrate (DEC) and albendazole, or ivermectin and albendazole; or the regular use of DEC fortified salt can prevent occurrence of new infection and disease.
The disease
Lymphatic filariasis, commonly known as elephantiasis, is a neglected tropical disease. Infection occurs when filarial parasites are transmitted to humans through mosquitoes. Infection is usually acquired in childhood causing hidden damage to the lymphatic system.
The painful and profoundly disfiguring visible manifestations of the disease, lymphoedema, elephantiasis and scrotal swelling occur later in life and lead to permanent disability. These patients are not only physically disabled, but suffer mental, social and financial losses contributing to stigma and poverty.
Currently, more than 1.4 billion people in 73 countries are living in areas where lymphatic filariasis is transmitted and are at risk of being infected. Approximately 80% of these people are living in the following 10 countries: Bangladesh, Democratic Republic of Congo, Ethiopia, India, Indonesia, Myanmar, Nigeria, Nepal, Philippines and the United Republic of Tanzania.
Globally, an estimated 25 million men suffer with genital disease and over 15 million people are afflicted with lymphoedema. Eliminating lymphatic filariasis can prevent unnecessary suffering and contribute to the reduction of poverty.
Cause and transmission
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| Wuchereria bancrofti |
- Wuchereria bancrofti, which is responsible for 90% of the cases
- Brugia malayi, which causes most of the remainder of the cases
- B. timori, which also causes the diseases.
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| Female culex mosquito |
Mosquitoes are infected with microfilariae by ingesting blood when biting an infected host. Microfilariae mature into infective larvae within the mosquito. When infected mosquitoes bite people, mature parasite larvae are deposited on the skin from where they can enter the body. The larvae then migrate to the lymphatic vessels where they develop into adult worms, thus continuing a cycle of transmission.
Lymphatic filariasis is transmitted by different types of mosquitoes for example by the Culex mosquito, widespread across urban and semi-urban areas; Anopheles mainly in rural areas, and Aedes, mainly in endemic islands in the Pacific.
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| Life cycle of Wuchereria bancrofti |
Symptoms
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| Elephantiasis |
Acute episodes of local inflammation involving skin, lymph nodes and lymphatic vessels often accompany the chronic lymphoedema or elephantiasis. Some of these episodes are caused by the body's immune response to the parasite. However most are the result of bacterial skin infection where normal defences have been partially lost due to underlying lymphatic damage.
When lymphatic filariasis develops into chronic conditions, it leads to lymphoedema (tissue swelling) or elephantiasis (skin/tissue thickening) of limbs and hydrocele (scrotal swelling). Involvement of breasts and genital organs is common. Such body deformities lead to social stigma, as well as financial hardship from loss of income and increased medical expenses. The socioeconomic burdens of isolation and poverty are immense
How does LF affect children?
In children, the infection from LF is usually symptomless and not clinically detectable. The damage caused by adult worms in the lymphatic system develops slowly, and it is generally not apparent until children are four or five years of age. However, swollen lymph glands may be observed as early as two years of age. At about seven years, about 30% of infected children will start to show ultrasound-detectable, irregular ballooning of the tiny walled lymphatic ducts and some will have noticeably swollen lymph glands.
By about 13 years, girls may start to show clinically visible signs of infection of the lymph vessels in the leg. Further cumulative damage to the lymphatic drainage system predisposes them to lymphoedema (an abnormal accumulation of lymph fluid in the tissues causing swelling of a limb). This may progress to elephantiasis (painful and disfiguring swelling of the leg, arm, breast or genitals, up to several times their normal size, with thickening of the skin) in adulthood.
By about 11 years, boys may start to show detectable ballooning of the lymphatic vessels in their scrotum. By about 13 years, they may start to develop hydrocele - a fluid-filled, balloon-like enlargement of the sacs around the testes. Scrotal nodules often develop in adulthood and further bacterial infection can lead to massive enlargement of the scrotum and gross deformation of the penis.
Less commonly, boys may also develop lymphoedema and elephantiasis of the extremities, similar to girls. However, the parasites in males seem to prefer the lymphatics of the scrotum over those of the extremities. Thus, genital disease is more common in males, and is the most common of all clinical manifestations of LF.
Treatments
Prevention of lymphatic filariasis is possible by stopping the spread of the infection. Large-scale treatment involves a single dose of 2 medicines given annually to an entire at-risk population in the following way: albendazole (400 mg) together with ivermectin (150-200 mcg/kg) or with diethylcarbamazine citrate (DEC) (6 mg/kg).
These preventive chemotherapy medicines have a limited effect on adult parasites but effectively clear microfilariae from the bloodstream and prevent the spread of parasites to mosquitoes. Large-scale treatment conducted annually for 4-6 years, treating all persons living in areas where the infection is present can interrupt the transmission cycle.
By 2012, 56 countries had started implementing large-scale treatment through mass drug administration (MDA). Of the 56 countries that had implemented MDA, 13 countries have moved to the post-MDA surveillance phase.
From 2000 to 2012, more than 4.4 billion treatments were delivered to a targeted population of about 984 million individuals in 56 countries, considerably reducing transmission in many places.
Some studies have shown adult worm killing with treatment with doxycycline (200mg/day for 4–6 weeks). (Source: CDC )
Sources: CDC / WHO / Department of Parasitology, University of Peradeniya / Global Alliance