Wuchereria Bancrofti

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Wuchereria Bancrofti

• Peter Bertrán

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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

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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.

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Wuchereria Bancrofti Life Cycle
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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.

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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.

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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.

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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