Wuchereria bancrofti & Brugia malayi

Benjamin S. Harris

EpidemiologyWuchereria Bancrofti

Found predominantly in regions close to the equator. Africa, South America, and tropical and sub-tropical

areas.Responsible for ~90% of lymphatic filariasis

and 120 million cases worldwide.Brugia malayi

Restricted to South and South EastResponsible for ~10% of lymphatic filariasis

and 13 million cases worldwide.Considered neglected tropical disease.http://www.cdc.gov/parasites/lymphaticfilariasis/epi.html

HostsDefinitive Host: (Both)

Prefers Humans

Intermediate: (Both)Mosquito acts as vector.

Both species prefer humans as their sole definitive hosts and have become highly adapted to our physiology.

Lifecycle (Both)Mosquito carrying third-stage filarial larvae

(L3) bites human host, parasite penetrates through skin infecting host.

Larvae move to the lymph nodes (Wuchereria bancroft) and/or blood channels (Brugia malayi) and mature into adults over the course of a year.

Mature adults reproduce sexually and females (Brugia malayi) produce on average 10,000 eggs (microfilaria).

Mosquito ingests microfilariae in blood meal and lose sheaths as they migrate through the cardiac region and into thoracic muscles.

CDC hyperlink

Lifecycle (Both) continuedOnce in the thoracic muscles, the

microfilariae develop into the first-stage larvae (L1) and eventually into third stage larvae (L3) where they will move to the mosquito proboscis and await infection opportunity.

http://www.cdc.gov/parasites/lymphaticfilariasis/epi.html

Brugia malayi

Morphology Brugia malayi Female adults measure between 43-55 mm in

length by 130-170 μm in width. Males measure between 13-23 mm in length and by 70-80 μm in width.

Microfilariae, measuring 177-230 μm in length and 5-7 μm in width, which are sheathed (diagnostic).

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Wuchereria bancrofti

Morphology Wuchereria bancroftiFemale adults measure between 80-100 mm

in length and 0.24-0.30 mm in diameter. Males measure between 40-0.1 mm.

Microfilariae measure between 244-296 μm in length and by 7.5-10 μm in width and sheathed (diagnostic). Text Hyperlink

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Transmission (Both)Insect bites

MosquitoBlood borne

Blood Transfusion of recipient receiving blood of contaminated donor (only that of L3 stage).

Class Questions:1.) Why would microfilariae be found in peak

levels of peripheral blood between 10:00 PM and 2:00 AM?

2.) With our knowledge of parasite detection, what diagnostic procedures would you think are effective?

Quick Answers1.) Increased chance of infection of mosquito with

microfilariae circulating in peripheral blood.

2.) - Blood SmearPolymerase chain reaction test (filarial DNA)

Sometimes must also test for adult antigen if microfilariae are absent.

Calcified worms may be detected by X-Ray examinations

Ultrasonography can detect movement of adult worm movement.

Symptoms (Both)Asymptomatic Phase: Upon initial infection

no symptoms may be present as microfilariae mature.

Lymphadenitis: Causes swelling of the lymph nodes that may occur prior to maturation.

Lymphangitis: Inflammation of the lymphatic vessels usually after maturation.Abscess formation and ulceration of lymph

nodes may also occur (more common in Brugia malayi)

Secondary bacteria infections (lymph node failure caused by extended overstimulation).

http://www.cdc.gov/parasites/lymphaticfilariasis/epi.html

Symptoms (Both) continuedLymphedema (elephantiasis): Enlargement of the

limbs, late onset condition caused by repeated inflammation of lymphatic vessels. Consistent irritation of lymphatic vessels leading to blockages caused by dead adult worms, inflammatory fibrosis, or granulomatous reactions. Leads to scar formation of affected tissues.Brugia malayi: typically affect distal portions of the

body such as arms and legs. Wuchereria bancroft: typically affects arms, legs,

and scrotum of men. Affects arms, legs, and breasts of women.

http://www.cdc.gov/parasites/lymphaticfilariasis/epi.html

He’s got the biggest balls of them all Wuchereria bancroft.

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Treatment (Both)Mass Treatment: Diethylcarbamazine (DEC)

effective at eliminating microfilariae, in countries such as India DEC-medicated salt is commonly consumed in an effort to stop spread to vectors and preventing new host infections or 6 mg/kg weekly for 6 weeks.Only available from CDC in United States.

No vaccine yet developed however, development is targeted for parasite elimination by the year 2020 by the World Health Organization,

Tetracyclines used secondary bacteria infections after lymph node damage.

http://www.cdc.gov/parasites/lymphaticfilariasis/epi.html

PreventionMosquito bed netting.Insect repellents/mosquito control

(environmental treatment DDT).Diethylcarbamazine therapy would be

considered as “preventative option).Cover exposed skin by loose clothing.

“The Elephant Man”http://www.youtube.com/watch?

v=kADJgoxdvE8Interesting fact: Joseph

Merrick originally misdiagnosed with Wuchereria bancroft turned out that he had actually suffered from neurofibromatosis. The two share the common symptom of elephantiasis and was nicknamed “The Elephant Man” after the first diagnosis.

Referenceshttp://www.dpd.cdc.gov/dpdx/html/frames/a-f/

filariasis/body_Filariasis_w_bancrofti.htmhttp://bioweb.uwlax.edu/bio203/s2008/krout_

bria/default.htmhttp://www.ncbi.nlm.nih.gov/pubmed/184396

91http://www.cdc.gov/parasites/lymphaticfilaria

sis/prevent.html