Wuchereria Bancrofti

1. Wuchereria Bancrofti Peter Bertrán

2. Wuchereria Bancrofti • Named for Otto Wucherer and Joseph Bancroft. • Affects over 120 million people, primarily in Africa, South America and other tropical and sub-tropical countries. • Taxonomy: • Eukarya; Animalia; Nematoda; Secernentea; Spirurida; Filarioidea; Wuchereria; Bancrofti • Filariasis is caused by nematodes (roundworms) that inhabit the lymphatics and subcutaneous tissues. • Eight main species infect humans, but only three of these are responsible for most of the morbidity due to filariasis. • Can result in Elephantiasis

3. Life Cycle • Transmitted through Mosquito vector. • Culcenine and Anopheline • Aedes Polynesiensis is specific to pacific • Once the microfilariae have entered an appropriate mosquito host through its blood meal they shed their sheaths and penetrate the insect's gut wall and move to the thoracic muscles where they mature (through two life stages) into third-stage infective larvae • Enter the blood of the definitive host through the wound made by the intermediate host mosquito • Migrate to the nearest lymph gland where they mature into the thread like adult worms about 3 months to 1 year later. Mature adults can survive for 5 to 10 years. • Once male and female nematodes mate the female viviparously produces microfilarae which enter the circulatory system and end up in the atrioles of the lungs. • At night, they migrate out where they can be picked up by another intermediate host mosquito.

4. Wuchereria Bancrofti Life Cycle

5. Distribution • Distributed throughout the tropical regions of Asia, Africa, China, the Pacific and isolated locations in the Americas. • Current estimates suggest that W.bancrofti and B.malayi infect some 128 million people, 
and about 43 million have symptoms. • Nocturnally periodic forms occur indigenously in almost every tropical and subtropical country and are very widespread. • However, they show focal and periodic distribution patterns which are dependent on their vector of transmission.

6. Pathogenic Effects of W. Bancrofti • Following infection with third stage larvae there is usually a period of vigorous immune response to the invading larvae. If the larvae are not cleared from the body during this period then the various pathologies associated with filarial infection can develop. • Conditions do not appear to arise from the effects of the nematodes themselves but from immune reactions to their presence. • Most pronounced of these is the damage to the lymphatic vessels which is mediated by the immune system's response to the adult worms living in them • Repeated episodes of lymphangitis lead to the formation of fibrous and calcified tissues in and around the lymphatic vessels.

7. Symptoms of W. Bancrofti infestation • The onset of symptoms is slow, but the effects are very apparent after several years. • During initial inflammatory stage, a host can exhibit swelling, granulation lesions, and impaired circulation. • Following, the lymph nodes are enlarged and dilated. They become hardened and clogged with fibrous tissue, and this prevents the lymphatic system from operating correctly. • The microfilariae also cause swelling, thickening, and discoloration of the skin. Without the proper drainage of fluids, the affected tissue will expand and elephantiasis will result, followed sometimes by death.

8. What Can Be Done… • The parasite's severe symptoms can be avoided by the use of therapeutic drugs. • Both diethylcarbamazine and sodium caparsolate are used to kill the worms and their microfilariae. • Diethylcarbamazine is most commonly used and is administered orally. • Protection is similar to that of other mosquito spread illnesses • Barriers and chemical sprays