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Wuchereria bancrofti & Brugia malayi
Ashley Skellie & Karissa Jensen
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Background Lymphatic filariasis and elephantiasis
Leading cause of permanent disability worldwide 120 million people affected More than 30% have severe cases One billion people are at risk in over 80 countries
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Background Elephatiasis WWII soldiers feared the disease
Was confused with leprosy Nonsense word WWII soldiers feared the disease Wuchereria bancrofti Responsible for 90% of lymphatic filariasis. Likely brought to New World by slave trade Lingered near Charleston, NC until 1920s Brugia malayi Microfilariae first discovered in 1927 In 1940, adult form discovered
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Hosts Definitive Host: Intermediate Host: Humans Mosquito 77 species
Anopheles, Aedes, Culex, and Mansonia
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Geographical Range Wuchereria bancrofti Asia Africa The Pacific
Subtropical and tropical Mostly India Africa The Pacific Americas Brazil Haiti Guyana Dominican Republic Brugia malayi Asia South and South East South China Indonesia Thailand Vietnam Malaysia Philippines South Korea
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Geographical Range
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Morphology Microfilariae Larvae Adults
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Microfilariae Considered advanced embryos Retain egg membrane sheath
When stained, can see nuclei and organs Nuclei are diagnostic Maximum number in peripheral blood occurs between 10pm and 2am During the day, found in tissues How do the microfilariae know when to come out of the tissues and into the peripheral blood? Periodicity of microfilariae in the peripheral blood- happens at certain times of day. Maximal numbers of microfilariae occur at night, between 10pm and 2 am. Because of this, mostly night feeding mosquitoes are primary vectors. During the day, microfilariae are concentrated in blood vessels of deep tissues, primarily pulmonary capillaries. Arterial oxygen tension and body temperature are two of the most likely reasons for the periodicity. It isn’t clinically important, but has significant diagnostic and epidemiological implications.
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Larvae Stage found in mosquito
Microfilariae ingested and turns into L1 for 8 days Molts into L2 Short Sausage-shaped Lack anus 2 to 4 days later, molt to L3 Become elongated, gut development completed Juveniles 1.4 to 2.0 mm
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Adults Brugia malayi Wuchereria bancrofti Females Females Males Males
mm Vuvla is near the level of the middle of their esophagus Males mm Tail Curved ventrally Bears 3 to 4 pairs of both adanal and postanal papillae. Spicules are unequal and dissimilar Left papillae more complex Nuclei in end of tail Wuchereria bancrofti Females 6-10 cm Vuvla is near the level of the middle of their esophagus Ovoviviparous, producing thousands of microfilariae Males 40 mm Finger-like tail No nuclei in end of tail
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Adults Long and slender Smooth cuticle and bluntly rounded ends
Head is slightly swollen and bears two circles of papillae Mouth is small, buccal capsule is lacking Live in lymphatic ducts Afferent lymph channels near major lymph glands of lower body Take 6 to 12 months to mature
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Life Cycle
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Symptoms Lymphatic filariasis
Asymptomatic Phase, Inflammatory Phase, Obstructive Phase IgE mediated allergic response which brings on asthma-like symptoms Elephantiasis Swelling in legs, arms, genitalia, breasts Thickening of skin and underlying tissues Elephantiasis is more common with Wuchereria bancrofti infections Asymptomatic phase- have high microfilaremias, lack of symptoms, but worm antigen can still be detected in the blood. Inflammatory/ acute phase- inflammation due to antigens from adult female worms, adults in lymph channels cause dilation and interfere with lymph flow resulting in lymphedema Obstructive Phase- lymph ducts become obstructed IgE mediated allergic response due to microfilariae in lungs and blood.
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Diagnosis Blood Sample Finger-prick Polymerase Chain Reaction (PCR)
Nighttime draw to ensure microfilariae in sample Presence of antibodies Antifilarial IgG4 Finger-prick Detects antigens Taken anytime during the day Polymerase Chain Reaction (PCR) Molecular level Detects as little as 1 picogram of microfilariae DNA to determine which species is present X-ray and ultrasonography Vigorous movements of adults can be detected by ultrasonography- pattern of noises called “filaria dance sign” X-Ray examinations can detect dead, calcified worms
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Treatment Diethylcarbamazine (DEC) Ivermectin
Many side effects Kills microfilariae and usually adults with careful administration Ivermectin Only kills microfilariae Best when combined with DEC or albendazole Clean infected areas daily Prevents bacterial infections Exercise or use pressure bandages Allows movement of bodily fluids No vaccines are available Side effects of DEC have been so disliked that it is hard to persuade patients to return for repeated treatments. Side effects include dizziness, nausea, fever, headache, and muscle and joint pain
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Wolbachia Wolbachia bacteria in symbiosis with Wuchereria bancrofti
Bacteria lives inside worm Antibiotics used to kill bacteria, and kill the W. bancrofti at the same time
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Control Mosquito control and preventative measures
Repellant applied to skin and bed nets Wear pants and long sleeves near reservoirs and vectors, especially at night Mass treatments to entire communities Education Mosquitoes at night and swampy areas Education programs- WHO trying to erradicate by do you think that this is possible and why?
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Review What are the definitive and intermediate hosts?
What are the 3 morphological forms? Name one difference between Wuchereria bancrofti and Brugia malayi. What is the infective stage in the life cycle? Is elephantiasis more common in Wuchereria bancrofti or Brugia malayi? Name two treatments.
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