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Wuchereria bancrofti presentation

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					Wuchereria bancrofti

Christopher Hofich Nicole Napier Chelsea Wradislavsky

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One of three organisms to cause lymphatic filariasis Responsible for up to 90% of cases. Commonly called Bancroftian filariasis. The parasites reside in the lymphatic vessels, more commonly in the lower extremities. An estimated 1.1 billion people live in known endemic areas, with over 120 million infected. More than 40 million are incapacitated or disfigured due to this disease.

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Definitive host – humans. Intermediate host – mosquito  Aedes  Culex  Anopheles  Mansonia

An adult W. brancrofti

Geographical distribution – Tropical and subtropical areas. Africa, the Nile Delta, Turkey, India, Southeast Asia, East Indies, Philippine and Oceanic islands, Australia and parts of South America.

Morphology
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Adults – Long, white and slender with a smooth cuticle and bluntly rounded ends – Two circles of well defined papillae and lacks a buccal capsule. – Males are 40 mm long, 100 um wide. – Females are 6 – 10 cm long, 2 – 3um wide.
Adults in a cross section of a lymphatic vessel

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Microfilariae – 250 – 300 um long, 7 – 9 um wide. – Embryonic sack containing thousands of juveniles – Contain an egg membrane, a sheath – Exhibit nocturnal periodicity

Life Cycle
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Adults live in the major lymphatic ducts of humans tightly coiled into nodular masses.
– Majority are found in lymph glands of the lower half of the body. – Female produces thousand of microfilariae (first stage larvae) which are present in the blood circulation.

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The mosquito ingests microfilariae when taking a blood meal. Microfilariae shed sheaths, penetrate mosquito’s midgut, and migrate to the thoratic muscles where they molt into L3 larvae (filariform juveniles)

Life Cycle (con’t)
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Filariform juveniles escape from mosquito’s proboscis when the insect is feeding and penetrate skin of definitive host. Adult worms develop to sexual maturity in afferent lymphatic vessels of human (predominantly in the legs and genital region) Adult worms mate, female gives birth to microfilariae, and migrate to bloodstream. Life cycle repeats!

Pathogenesis
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The onset of symptoms is slow
– Incubation period of 3- 12 months in which there is no symptoms

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Acute symptomatic stage—some swelling of the extremities may occur and this may be accompanied by pain, weakness of arms and legs, headache, and insomnia Other early symptoms include recurrent filarial fever, lymphadenitis, and retrograde lymphangitis

Pathogenesis
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Chronic signs include:
– Hydrocele (collection of fluid in the scrotal sac) most common clinical condition – Chyluria (chyle in urine—milky appearance) – Elephantiasis of the limbs, breast and genitalia

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Those with tropical pulmonary eosinophilia syndrome, manifested by nocturnal asthma, chronic interstitial lung disease, recurrent low-grade fever

Pathogenesis
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During the initial inflammatory stage, a host can exhibit swelling, granulation lesions, and impaired circulation—this known as lymphatic filariasis which is caused by the presence of filariae in the lymphatic vessels

– Lymph nodes become enlarged and dilated. They also 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.

Pathogenesis
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Without the proper drainage of fluids, the affected tissue will expand
– Elephantiasis, a gross expansion of body, will result – Sometimes followed by death

Elephantiasis

Legs

Genitals

Mortality/Morbidity
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Rarely Fatal WHO – second leading cause of permanent and long-term disability in the world. Morbidity is due mainly to the host reaction to microfilariae or developing adult worms in areas of the body.

Diagnosis
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Diagnosed by finding microfilaria in peripheral blood Antigen detecting techniques: – Detect DNA of microfilaria (commercial kits are available) – ICT: Immuno Chromatographic Test Urine examination and microscopy: – Chyluria and concentrated for microfilariae  (when lymphatic filariasis suspected) CBC: Eosinophilia Serum immunoglobulins: Elevated IgE and immunoglobulin G4

Diagnosis Cont….
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Vigorous movements of adult worms can be seen using ultrasonography
– ―filaria dance sign‖

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X-rays can detect dead, calcified worms

Microfilaria of Wuchereria bancrofti in a peripheral blood smear

ICT: in vitro immnodiagnositc test for W bancrofti antigen in whole blood

Treatment
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Drug of choice: Ivermectin Albendazole Diethylcarbamazine (DEC) (Hetrazan) – Eliminates microfilariae from the blood and also can kill adults. Use of single-dose regimens of all three reduce W bancrofti microfilaremia, antigenemia, and clinical manifestations

Management
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Antibiotics
– Prevent secondary infections

Pressure bandages
– Reduce swelling

Surgically removing tissues
– Improve lymph flow

Chemotherapy
– Kills circulating microfilaria

Vector control

Control
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Protect yourself from mosquito bites in endemic areas
– Use insect repellent – Mosquito nets

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Educate people in endemic areas


				
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