Acute symptoms of the disease include:
In travelers (those that do not live in the endemic areas) – the exposure is usually insufficient to filariasis to develop chronic complications. However, these persons may manifest hypersensitivity reactions to the developing larvae: eosoinophilic infiltrate with lymphangitis and lymphadenitis, urticarial and rash.
Chronic symptoms include :
Diagnosis can be made with a blood smear. The microfilariae that cause lymphatic filariasis circulate in the blood at night; therefore blood draw should be performed at night. The smear is stained with Giemsa or hematoxylin and eosin and microscopically evaluated for the worm.
Blood tests that detect antigens for the parasites are also available as a diagnostic tool. Circulating antigen detection assay (CFA assay) has been developed for diagnosis of W. bancrofti infections. This test detect antigens released by adult worms, in addition to microfilariae, and therefore can be performed at any time of the day.
There are two commercially CFA tests available for detection of W. bancrofti: Og4C3 ELISA assay which gives an actual count (quantative measure) of adult worms in the body; and TropBio ELISA test that gives only a positive or negative (qualitative) result .
Imaging: Ultrasound can be used to detect presence of adult worms in lymphatic vessels. A scan that is positive for the disease shows as a “filarial dance sign” indicating movements of the worms in blood .
Persons currently infected with the parasite are treated with diethylcarbamazine (DEC) 6 mg/kg for 12 days irrespective of clinical symptoms . DEC kills the adult worms and therefore ultimately decreases the microfilarial burden. DEC should be avoided in pregnancy and lactation .
Doxycycline is sometimes given in addition to DEC (200 mg/d for 4 to 6 weeks) as it has demonstrated macro filaricidal activity and reduces pathology in mild and moderate diseases .
DEC is contraindicated in patients as it can worsen onchocercal eye disease. In patients with loiasis, DEC can cause serious adverse reactions such as encephalopathy and death. In such patients doxycycline should be used .
Treatment of symptoms (while being treated medically, with DEC or doxycycline) include: lymphedema and acute inflammatory episodes can be relieved using hygiene care, skin care, exercise and most importantly, elevation of the limb affected. Surgery can provide relief from hydrocele.
Over nine months, the larvae develop into mature adult worms. The adults male and female worms mate and produce sheathed microfilariae. The microfilariae migrate into lymph and enter the blood stream. When a mosquito bites an infected individual, it ingests the microfilariae and transmits to another human when it bites him/her.
There are three different filarial species that can cause lymphatic filariasis in humans:
Geographic distribution: Most of the infections in the world are caused by the species: Wuchereria bancrofti. Brugia malayi and Brugia tmori are seen primarily in Asia. It is estimated that more than 120 million people worldwide, in 73 countries are infected.
More than 90% of the infections are caused by W. bancrofti species. In the United States (US), Charleston South Carolina was the last known place with lymphatic filariasis episode. The infection has been eradicated in the US .
Age: Lymphatic filariasis is most likely first acquired in childhood, but a third of children remain asymptomatic until 5 years of age. The prevalence of this disease in endemic communities increases with age. In endemic areas, most people have been exposed by 40 years of age.
The pathogenesis of the disease is impacted by several factors such as the extent and duration of exposure to infective insect bites, the quantity of accumulating adult worm antigen in the lymphatic system and the host immune response.
Clinical presentation in exposed persons also depends on a number of host and parasite factors, such as: timing of the first exposure to the parasite, the species of filarial pathogen involved, the intensity of exposure to infected mosquitoes, prenatal sensitization . Genetics may also influence clinical presentation (lymphedema tends to occur in families).
Later in infection, immune responses to parasite antigens are down regulated with suppression of T-lymphocyte proliferation (which results in impaired production of Th1 and Th2, and thus cytokines), therefore contributing to this infection becoming a chronic infection.
Filariasis is a parasitic disease that is caused by nematodes (round worms) that inhibit the lymphatic system and subcutaneous tissues of humans and animals. These are thread-like worms that live in the human lymph system. The infection is transmitted human to human by mosquitos. Lymphatic filariasis is a major cause of disfigurement and disability in endemic areas. For example, people with the disease can have lymphedema and elephantiasis and in men scrotum swelling.
Filariasis is a parasitic disease that is caused by nematodes (round worms). These are thread-like worms that live in the human lymphatic system. Some types of filariasis can be transmitted to both animals and humans by mosquitoes. However the most common type (Wuchereria bancrofti) is transmitted only to humans by mosquitos.
Who is at risk?
People who live in tropical and subtropical areas in the world (e.g. Asia, Africa, the Western Pacific, and parts of the Caribbean and South America) are at risk. Most of the infections are caused by the species Wuchereria bancrofti. It is estimated that more than 120 million people worldwide, in 73 countries are infected . W. bancrofti species can only infect humans (unlike the other 2 species which can affect both humans and animals).
There are currently no cases of this disease in the United States.
Both men and women are affected equally. The rate of infection increases with age (in particular during childhood and teenage years).
How is the disease transmitted?
A mosquito bites an infected person and then transmits the disease when it bites another person. When the mosquito bites an infected person, the mosquito becomes infected with microfilariae (larvae, or baby worms).
Then when the mosquito bites another person, the microfilariae are deposited on the skin and enter the human’s body. The microfilariae travel to the lymphatic vessels, where they develop into adult worms. Adult worms mate and produce more microfilariae. The cycle repeats until a person is treated.
What are the symptoms of Filariasis?
Some infected people have no symptoms. They are called “carriers”. The infection can be detected using blood smears (drop of blood is placed on a slide, stained with a special dye and looked at using a microscope).
For those who have symptoms:
What tests can be done to check for the disease?
Blood tests can be performed to check for infection: blood smears, immunological tests that are designed to check for chemicals in your body that are specific to filariasis.
Urinalysis can be performed to check for chyluria and for the microfilariae (under a microscope).
Ultrasound test can also be used to look at certain lympatic areas to detect adult worms.
How can filariasis be treated?
Your doctor can prescribe medications to treat this disease. Common medications used are diethylcarbamazine (DEC) and doxycycline. Symptoms can be alleviated by maintaining good hygiene and keeping the affected body part elevated. A hydrocele can be alleviated by surgery.