Lymphatic filariasis

Lymphatic filariasis is a human disease caused by parasitic worms known as filarial worms.^[2][3] Usually acquired in childhood, it is a leading cause of permanent disability worldwide, impacting over a hundred million people and manifesting itself in a variety of severe clinical pathologies^[6][7] While most cases have no symptoms, some people develop a syndrome called elephantiasis, which is marked by severe swelling in the arms, legs, breasts, or genitals. The skin may become thicker as well, and the condition may become painful.^[2] Affected people are often unable to work and are often shunned or rejected by others because of their disfigurement and disability.^[7]

It is the first mosquito-borne disease directly linked to mosquitoes.^[8] The worms are spread by the bites of infected mosquitoes.^[2] Three types of worms are known to cause the disease: Wuchereria bancrofti, Brugia malayi, and Brugia timori, with Wuchereria bancrofti being the most common.^[2] These worms damage the lymphatic system by nesting within the lymphatic vessels and disrupting the system's normal function. Worms can survive within the human body for up to 8 years, all while reproducing millions of larvae which circulate through the blood.^[9] The disease is diagnosed by microscopic examination of blood collected during the night. The blood is typically examined as a smear after being stained with Giemsa stain. Testing the blood for antibodies against the disease may also permit diagnosis.^[4] Other roundworms from the same family are responsible for river blindness.^[10]

Prevention can be achieved by treating entire groups affected by the disease, known as mass deworming.^[2] This is done every year for about six years, to rid a population of the disease entirely.^[2] Medications usually include a combination of two or more anthelmintic agents: albendazole, ivermectin, and diethylcarbamazine.^[11] Efforts to prevent mosquito bites are also recommended, including reducing the number of mosquitoes and promoting the use of bed nets.^[2]

As of 2022, about 40 million people were infected, and about 863 million people were at risk of the disease in 47 countries.^[5] It is most common in tropical Africa and Asia.^[2] Lymphatic filariasis is classified as a neglected tropical disease and one of the four main worm infections.^[10] The impact of the disease results in economic losses of billions of US dollars a year.^[2]