Dr. Ajay Mohan (AIIMS)MBBS

June 28, 2017

March 06, 2020



Filariasis is a parasitic infection transmitted by mosquitoes that affect the lymphatic system and the tissues under the skin. It is caused by a parasite, namely Wuchereria bancrofti, Borgia malayi and Borgia timori. The diseases caused by the first two parasites is a major health issue in India. The disease can affect both the genders and individuals of any age group. The infection is transmitted through mosquitoes.

Filariasis is very common in tropical countries, especially Africa, South Asia, India, South America and China. More than two-thirds of the cases are reported in Asia. Even though the number of cases has drastically reduced due to effective mass drug administration, infection rates are still high in some areas. Many people may be asymptomatic throughout life, whereas others may experience fever, body aches with painful swelling in the lymph nodes and genitalia, in the acute phase. People with chronic symptoms show massive swelling due to oedema in the lower limbs known as elephantiasis, a condition caused due to the obstruction of the lymphatic channels. Anti-parasitic treatment is prescribed after diagnosis is confirmed on a blood smear.

What is Filariasis

Filariasis is a serious medical disorder caused by parasites. The parasites transmitting the infection are Wuchereria bancrofti, Brugia malayi, and Brugia timori. The parasite undergoes several stages in its life cycle, wherein, it rapidly multiplies within the human body to produce smaller parasitic forms known as microfilariae infecting the mosquitoes which are vectors of the infection. Female mosquitoes pick up the microfilariae, which circulate in the blood of an infected person while biting them. These microfilariae mature within the female mosquitoes and are then transferred by biting another healthy person.

The disease is mainly seen in the tropical and sub-tropical regions like India and Africa. An estimated 120 million people in 73 countries in Asia, Africa, South America, Pacific, and Caribbean nations are affected by filariasis. Of these, approximately 25 million men have been affected with a genital disease and 15 million women have developed elephantiasis in the leg. Filariasis is also one of the leading causes of disability worldwide.

In some untreated cases, body deformities can lead to financial loss due to lack of income and increased medical expenses. It is estimated that 36 million people are severely disfigured due to this infection globally. An Indian study has reported that people affected with filariasis lose almost 29 days of work in a year due to complications of filariasis. Some of these people are mentally and socially affected due to the abnormal appearance of their limbs.

Along with individual drug therapy, the governments of various tropical countries have implemented mass eradication programs, wherein medicines are administered to large masses to decrease the multiplication of the parasite and kill the larval forms. This is done to decrease the disease prevalence and also to reduce human-mosquito contact. Out of the population that needs mass treatment, 57% of people are from South Asian countries and 37% are from the continent of Africa. Use of other preventive measures like mosquito nets and coils also help in reducing the number of mosquito bites, thereby, decreasing the chances of transmission of the parasite.

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Filaria (filariasis) symptoms

The symptoms of filarial infections depend on the parasitic species that cause them. Usually, symptoms are not seen until the infected person reaches adulthood when the concentration of worms is highest. The symptoms are divided as follows:

In the majority of cases, affected persons may not produce any symptoms at all. Those with a high load of parasites in the blood may show the presence of inflammatory tissues known as granulomas that result from the destruction of the spleen. Some people may have a cloudy urine.

Acute phase
The acute phase of filariasis occurs immediately after infection due to the body’s immune response to the parasite. These attacks may debilitate a person to the extent that he/she may miss work. In the acute phase, the person may complain of:

  • Episodic fever.
  • Shaking chills.
  • Body aches.
  • Swollen and painful lymph nodes.
  • Excess collection of fluid called oedema, seen in the limbs and genitals as a result of blocking of the lymphatic vessels which gets better after the symptoms subside.
  • Inflammation of the genitalia, testes, sperm cord, and scrotum.
  • Pain in the groin or the testes.
  • Exfoliation of the skin.
  • Swelling of the limbs.
  • Chronic lymphedema.
    • Persistent swelling of the lymph nodes.
    • Accumulation of fluid in the scrotum known as hydrocele.
    • Presence of lymphatic fluid in the urine giving it a cloudy appearance.
    • Oedema of the genitals in men and women.
    • Oedema of the breasts, arms, and legs known as elephantiasis.
    • Oedema causes the skin to become thick and hardened.

Other symptoms of acute filariasis include:

  • Tropical pulmonary eosinophilia
    This is a hidden type of filarial infection. The symptoms are due to an inflammatory response to the infection. The symptoms include:
    • Dry cough at night
    • Wheezing
    • Breathlessness
    • Swelling of the liver (hepatomegaly)
    • Swelling of the lymph nodes
    • Weakness and weight loss
    • Abnormal findings on chest X-Ray
  • Onchocerciasis (also known as hanging groins or leopard skin)
    • Scab-like eruptions on the skin.
    • Skin nodules on bony prominences.
    • Sometimes, associated with epilepsy.
  • Loiasis
    Symptoms are seen due to local hypersensitivity to the parasite L Loa, found in Nigeria. These include:
    • Pain
    • Itching
    • Urticaria or hives
    • Swellings around joints.
    • Nerve involvement.

Filariasis causes and risk factors


Filariasis is caused by parasites. The infection is known to spread from person to person mosquitoes (Culex and Aedes egypti). There are several parasites that cause filariasis, but only 8 species can cause infection in humans. The most common ones affecting humans are Wuchereria bancrofti, Brugia malayi and Brugia timori. Of the three parasites, the infection is most frequently spread by W. bancrofti. There is a specific cycle that exists between the mosquito, the parasite, and the human. Microfilariae are picked up by a female mosquito during biting an infected person. The infected mosquitoes act as vectors and carry the small worms called microfilariae. When such infected mosquitoes bite another person, the worms are transmitted and these worms multiply within the person then. Mosquitoes that transmit the parasites depend on their geographical location. Several mosquito bites are required to get an infection. Tourists have a very small risk of developing filariasis.

Risk Factors

The following risk factors affect the prevalence of filarial infections:

  • Age
    The disease affects all age groups. The risks during childhood and reaches its peak by the age of 20 years.
  • Geographical location
    People living in the tropical and sub-tropical regions are at a very high risk of contracting the infection. Filariasis has also been reported in the South East Asian populations, especially in India.
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Prevention of filaria (filariasis)

  • Once the incidence of infected mosquitoes is controlled, the growth of the microfilariae can be controlled.
  • There are several eradication programs employed worldwide in which drug therapy is given to a large group of people. These medications help to reduce the growth of the parasites in humans, thereby, the parasite population, as well as, decreasing the chances of transmission of the infection to another person.
  • There is a global campaign to eradicate filariasis in the world. Several such campaigns have been used effectively in China and other nations.
  • In addition to drug therapy, avoiding mosquito bites is the best way one can prevent filariasis in areas with a high risk of filariasis infected mosquitoes.
  • Wearing full-length clothing covering the arms and legs during daytime and applying mosquito repellents to protect against mosquito bites.
  • Using bed nets at night is also helpful to keep mosquitoes away.

Diagnosis of filaria (filariasis)

Diagnosis is established by:

  • Physical examination
    To make an accurate diagnosis, the doctor will examine lymph nodes, ulcers, and abscesses. Assessment of fever, pulse, along with, examination of other organ systems is performed. Limbs and genitalia will be examined for elephantiasis, pigmentation and warts
  • Blood tests
    The most standard method to diagnose filarial infection is to detect the presence of the parasites in a blood smear. These small parasites circulate in the blood at night time, hence, a blood sample is collected at night when there is a peak concentration of the parasites in the blood. This can also be done using parasite detecting kits. These kits are useful for diagnosis as well as, for monitoring treatment. There are tests to detect antibodies as well. Other blood tests like parasite DNA assays can be carried out based on the doctor’s discretion.
  • Urinalysis
    The lymphatic fluid can give urine a cloudy appearance in filariasis. As such, the doctor may suggest a urine examination.
  • Imaging studies
    If there is a blockage in the scrotum or in the abdomen, it can be viewed on ultrasound. Ultrasound can also be used to detect worms in the scrotum.

Though the latest diagnostic tests are useful, they may not always be available. Hence, blood tests and immunological assays are the most reliable methods of detecting filarial infection.

Filaria (filariasis) treatment

The treatment protocol for filariasis is as follows:

  • Medications
    Acute symptoms of filariasis are often treated using anti-histamines, and painkillers. While these medicines merely treat the symptoms, the best way to remove parasitic infections from the blood is to administer a group of anti-parasitic drugs. These medicines help to eliminate the larval forms of these worms and stop the multiplication of the adult worm and even kill them. Even though these drugs are effective, they may produce side effects or bad reactions, which can be relieved with anti-inflammatory drugs. Care should be taken while taking these drugs as a collection of dead worms in lymph nodes or blood vessels can trigger an allergic reaction or produce abscesses.
  • Surgery
    In case of complications, surgery may be needed in people with an abnormal collection of fluid in the scrotum, calcifications in the lymph nodes, and to remove remains of larval form of worms.

Lifestyle management

  • Along with medications, the following measures should be adopted following an infection:
  • Clean the webs of hands and toes.
  • Pat dry and apply moisturizer thereafter.
  • Clip and clean nails.
  • Avoid injuries and infections.
  • Check for wounds regularly and apply medicated anti-fungal creams if needed.
  • Wash the limb daily to prevent fungal and bacterial infections.
  • Keep leg elevated or walk daily to keep swelling away.
  • Take ample rest.
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Filaria (filariasis) prognosis & complications


Filariasis is rarely fatal, but, infected people usually have poor health and are less productive at work leading to more leave days. The World Health Organization (WHO) has labelled filarial diseases as the second most common cause of permanent long-term disability.


Complications depend on the site and type of reaction to the infection in the body and include:

  • Chronic lymphedema which consists of swelling due to blockage in the lymphatic system preventing the flow of lymphatic fluid
  • Chronic filariasis.
  • Elephantiasis in which there is severe enlargement of the lower limbs, with hardening of the skin, massive accumulation of fluid in genitals and subcutaneous tissues due to obstruction of lymphatic fluid.
  • Accumulation of fluid in the scrotum (hydrocele).
  • Body deformities.
  • Disability.
  • Stigmatization from the unnatural appearance of limbs.


  1. S Sabesan, P Vanamail, KHK Raju, P Jambulingam. Lymphatic filariasis in India: Epidemiology and control measures. Journal of Postgraduate Medicine; Year : 2010 | Volume : 56 | Issue : 3 [Internet]
  2. Ichimori K, King JD, Engels D, Yajima A, Mikhailov A, Lammie P, Ottesen EA. Global programme to eliminate lymphatic filariasis: the processes underlying programme success. PLoS neglected tropical diseases. 2014 Dec 11;8(12):e3328. PMID: 25502758
  3. World Health Organization [Internet]. Geneva (SUI): World Health Organization; Lymphatic filariasis.
  4. National Organization for Rare Disorders [Internet], Filariasis
  5. Center for Disease Control and Prevention [internet], Atlanta (GA): US Department of Health and Human Services; Epidemiology & Risk Factors
  6. Stanford Health Care [Internet]. Stanford Medicine, Stanford University; Prevention and Treatment

Medicines for Filariasis

Medicines listed below are available for Filariasis. Please note that you should not take any medicines without doctor consultation. Taking any medicine without doctor's consultation can cause serious problems.

Lab Tests recommended for Filariasis

Number of tests are available for Filariasis. We have listed commonly prescribed tests below:

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