Wuchereria bancrofti and Brugia malayi are filarial nematodes
Spread by several species of night - feeding mosquitoes
Causes lymphatic filariasis, also known as Elephantiasis
Commonly and incorrectly referred to as “Elephantitis”
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Humans are the definitive host for the worms that cause lymphatic filariasis
There are no known reservoirs for W.bancrofti .
B.malayi has been found in macaques, leaf monkeys, cats and civet cats
A Debilitating disease.
Abnormal accumulation of watery fluid in the tissues causing severe swelling.
Skin usually develops a thickened, pebbly appearance and may become ulcerated and darkened
W.bancrofti is transmitted by Culex, Aedes, and Anopheles species
B.malayi is transmitted by Anopheles and Mansonia species.
Anopheles Aedes Culex Mansonia
Lymphatic filariasis occurs in the tropics of India, Africa, Southern Asia, the Pacific, and Central and South America.
Terms to Know
Elephantiasis : is a disease that is characterized by the thickening of the skin and underlying tissues, especially in the legs and genitals.
Filariasis : is a parasitic disease caused by roundworms
Lymph Edema : Is a condition of localized fluid retention caused by a compromised lymphatic system.
Brugia malayi : a causative agent of human lymphatic filariasis leading to lymph edema and swelling of the legs
Genome : a complete DNA sequence of one set of chromosomes.
Lymphatic Filariasis by the numbers
Endemic in 83 countries
1.2 billion at risk
More than 120 million people infected
More than 25 million men suffer from genital symptoms
More than 15 million people suffer from lymphoedema or elephantiasis of the leg
Morphology - W.bancrofti
W.bancrofti is a sexually dimorphic species.
The adult male worm is long and slender, between four and five centimeters in length, a tenth of a centimeter in diameter, and has a curved tail.
The female is six to ten centimeters long, and three times larger in diameter than the male.
Microfilariae are sheathed, and approximately 245 to 300 µm in length.
Morphology - B.malayi
B.malayi microfilariae are slightly smaller than those of W.bancrofti.
Microfilariae are sheathed, and about 200 to 275 µm.
Not much is known about the adult worms, as they are not often recovered
One distinctive feature of B.malayi is that the microfilarial nuclei extends to the tip of the tail
Wuchereria Life Cycle
1. Asymptomatic: patients have hidden damage to the lymphatic system and kidneys.
2. Acute: attacks of ‘filarial fever’ (pain and inflammation of lymph nodes and ducts, often accompanied by fever, nausea and vomiting) increase with severity of chronic disease.
3. Chronic: may cause elephantiasis and hydrocoele (swelling of the scrotum) in males or enlarged breasts in females.
The standard method for diagnosing active infection is the identification of microfilariae by microscopic examination
However, microfilariae circulate nocturnally, making blood collection an issue
A “card test” for parasite antigens requring only a small amount of blood has been developed
Does not require laboratory equipment
Blood drawn by finger stick
The table below shows how the symptoms are graded by severity of the swelling – known as a lymphœdema. These swellings usually occur in the legs, breast tissue and groin.
As with malaria, the most effective method of controlling the spread of W.bancrofti and B.malayi is to avoid mosquito bites
The CDC recommends that anyone in at-risk areas:
Sleep under a bed net
Wear long sleeves and trousers
Wear insect repellent on exposed skin, especially at night
Covering water-storage containers and improving waste-water and solid-waste treatment systems can help by reducing the amount of standing water in which mosquitoes can lay eggs.
Killing eggs (oviciding) and killing or disrupting larva (larviciding) in bodies of stagnant water can further reduce mosquito populations.
Treatment of filariasis involves two components:
Getting rid of the microfilariae in people's blood
Maintaining careful hygiene in infected persons to reduce the incidence and severity of secondary (e.g., bacterial) infections.
Drugs, Drugs, Drugs!
Anti-filariasis medicines commonly used include:
reduces microfilariae concentrations
kills adult worms
kills adult worms
kills the microfilariae produced by adult worms
…And more drugs!
The disease is usually treated with single-dose regimens of a combination of two drugs, one targeting microfilariae and one targeting adult worms (i.e.,either diethylcarbamazine and albenadazole, or ivermectin and albendazole
In some areas, DEC laced table salt is used as a prophylactic
Treatment 2: Manchester United 0
If a high enough coverage of anti-filariasis drug treatment can be achieved (treating greater than 80% of the people in a community), the disease can be eradicated from an area.
Attempts to eliminate the disease are being helped considerably by Merck and Co., which is donating ivermectin to treatment efforts, and Smith Kline Beecham, which is donating albendazole.
The Gates Foundation has also donated millions towards eliminating lymphatic filariasis