Lymphatic Filariasis
Lymphatic filariasis is caused by Wuchereria bancrofti and Brugia malayi; thread like nematode worms that live in the lymphatic vessels. It is estimated that up to 120 million people in 83 countries worldwide are affected by some form of filariasis. Lymphatic filar
iasis is also known as elephantiasis – this is because people suffering with lymphatic filariasis can develop swollen limbs and thickened skin which resembles the legs of elephants.
Lymphatic filariasis is transmitted by mosquitoes. When an infected mosquito bites and takes a blood feed, infective larvae transfer from the mosquito onto the skin. After they have entered the skin they migrate to the lymphatic system – the system in the body which regulates the balance of fluids and fights infection. It will take the larvae 6 months to 1 year to develop into adult worms; the males will grow to approximately 2-4 cm long and the females to between 4-10 cm. After mating, the females will release thousands of microfilariae into the lymphatic system. The microfilariae then migrate into the blood stream and when the host is bitten again, the microfilariae will transfer back into the mosquito. Once inside the mosquito, the microfilariae migrate to the mosquito stomach where they shed their sheaths before entering the body cavity and moving into the flight muscles. After 10 to 14 days the larvae migrate into the mouth-parts of the mosquito and the cycle is completed when the mosquito bites again.
The symptoms of lymphatic filariasis depend on the how advanced the disease is. Hydrocoeles formed from lymph fluid filling the scrotal sac is the most common pathological feature. The next most common is lymphoedema or 'elephantiasis'. Usually people suffer from swollen legs but arms, breast tissue and groin areas can also become affected. Skin
thickens and folds and lesions and knobs can grow to give the skintexture a blistered appearance. Victims of the disease suffer reduced mobility, poor quality of life and social exclusion. To view the stages of lymphatic filariasis development, download our guide to grading the symptoms of lymphatic filariasis.
Links
Liverpool School of Tropical Medicine
Centre for Neglected Tropical Diseases
The Bill & Melinda Gates Foundation
GAELF – The Global Alliance to Eliminate Lymphatic Filariasis
Centres for Disease Control and Prevention
The Special Programme for Research and Training in Tropical Diseases (TDR)