Wuchereria bancrofti is the causative agent of lymphatic Filariasis which in turn causes elephantiasis. It is a filarial roundworm parasite that lives in some species of mosquitoes and transmits the infection to man when the infected mosquito bites a human and injects the larvae into the skin where they then migrate to the lymph nodes, causing blockages.
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Wuchereria bancrofti Epidemiology
Wuchereria bancrofti infection is endemic to the Pacific Islands and also occurs much in tropical areas of Africa, Asia, and Latin America, affecting about 200 to 300 million people worldwide and about 1 billion people in developing countries are at risk of being infected. The mosquito species that act as vectors vary from area to area. Another filarial worm named Brugia malayi is endemic to the Malay Peninsula (where it got its name) and is also seen in much of South-east Asia
Life cycle of Wuchereria bancrofti
Wuchereria bancrofti Life cycle (Filarial worm life cycle)
- Culex fatigans mosquito ingests microfilariae when biting humans
- Ingested microfilariae pass through mosquito gut into hemocoel and eventually develop into infective juveniles
- Infected mosquito then transmits the infective juveniles to another host
- The juveniles then migrate via lymphatics to regional lymph nodes
- The adult filarial worms then develop into mature filarial worms in afferent lymphatic vessels and in the lymph nodes of the genitals and lower extremities. The adult worms mate and the female worms give birth to millions of microfilariae (offspring) in the afferent lymphatic vessels.
- The microfilariae then migrate from the lymphatics to the blood stream in the night where another mosquito ingests it and the cycle starts again
Characteristics and Morphology of Wuchereria bancrofti
Adult female worms measuring about 5 – 10cm long, live in the lymphatics while releasing large numbers of microfilariae into the blood in the night. Adult worms live for a long time about 10 to 15 years and reinfection is very common especially in endemic areas, so that disease tends to be chronic and progressive.
Wuchereria bancrofti seen under a microscope (filarial worm seen in blood smear)
Laboratory Diagnosis of Wuchereria bancrofti infection
Wuchereria bancrofti diagnosis is made using a microscope by identifying microfilariae in blood. The blood for the test is taken at night because that is the time that most of the microfilariae live the lymphatic tissue into the blood; very few microfilariae organisms circulate during day time this behavior of microfilariae being found in the blood only in the night is termed Nocturnal periodicity. Serologic tests such as immunofluorescence can as be done by identifying positive antibody titers.
Wuchereria bancrofti treatment
Drug treatment exist only against microfilariae worms (before the gross deformities of elephantiasis have developed) using diethylcarbamazine as there is currently no drug therapy for adult worms.
Prevention of Wuchereria bancrofti infection
- Prevention involves mosquito control with insecticides
- Use of protective clothing to prevent mosquito bites
- Use of mosquito netting for sleeping and on windows of houses
- Use of mosquito repellent cream
- Clearing of bushes around residential houses and clearing of drainages to ensure there is no breeding place for mosquitoes