Presentation on theme: "Benjamin S. Harris. Epidemiology Wuchereria Bancrofti Found predominantly in regions close to the equator. Africa, South America, and tropical and sub-tropical."— Presentation transcript:
Benjamin S. Harris
Epidemiology Wuchereria 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 East Responsible for ~10% of lymphatic filariasis and 13 million cases worldwide. Considered neglected tropical disease.
Hosts Definitive 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) continued Once 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.
Morphology Brugia malayi Female adults measure between mm in length by μm in width. Males measure between mm in length and by μm in width. Microfilariae, measuring μm in length and 5-7 μm in width, which are sheathed (diagnostic). Hyperlink Text Hyperlink
Morphology Wuchereria bancrofti Female adults measure between mm in length and mm in diameter. Males measure between mm. Microfilariae measure between μm in length and by μm in width and sheathed (diagnostic). Text Hyperlink Picture Hyperlink
Transmission (Both) Insect bites Mosquito Blood 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 Answers 1.) Increased chance of infection of mosquito with microfilariae circulating in peripheral blood. 2.) - Blood Smear Polymerase 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).
Symptoms (Both) continued Lymphedema (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.
He’s got the biggest balls of them all Wuchereria bancroft. Picture hyperlink
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.
Prevention Mosquito 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” DJgoxdvE8 DJgoxdvE8 Interesting 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.