Filarial Worm

Filarial Meaning

Filarial worm is any flock of parasitic worms that belongs to the family Filariidae (phylum Nematoda) which generally needs two hosts, a vertebrate (the primary host), an arthropod (the intermediate host) to complete the life cycle. The larval phase takes place within the body of a biting insect. The reproductive phase takes place in the body of an animal bitten by the insect.


The female worm forms large numbers of active, microscopic embryos known as microfilariae that pass into the bloodstream of the primary host. The microfilariae may then make way to the body of an insect as the insect munches into the infected animal. The microfilariae develop into larvae in the insect’s muscles and may then be transmitted to the principal host as the insect bites an animal. The larvae get to adulthood within the vertebrate host, and the cycle continues to repeat. In mammals, filarial worms induce a group of infectious disorders including elephantiasis, heartworm, and river blindness. These disorders are collectively called filariasis. Currently, over 200 million people are infected with filarial parasites.

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Filarial Worm Scientific Name

From the kingdom Animalia, Lymphatic filariasis, commonly called elephantiasis, is a neglected tropical disease. Filarial worm phylum is Nematoda with a class—chromadorea and order—rhabditida.

Diagnosis of Filarial Worm

Diagnosis is recommended clinically by lymphangitis and erratic fever; definite diagnosis depends on demonstrating microfilariae in thick blood besmirch.

Causes of Filarial Worm Infections

Filarial worm infections are brought about by specific roundworms and affect various parts of the body based upon the species of worm.


There are different species of filarial worms, but only some infect people. Species that infect people may subsist in the

  1. Lymph Tissues: Brugia malayi, Brugia timori, or Wuchereria bancrofti causes lymphatic filariasis

  2. Subcutaneous Tissues: (Tissues under the skin in the eye): Loa Loa (African eye worm), that induces loiasis, or Onchocerca volvulus, causes river blindness (onchocerciasis)

Most filarial infections take place in the tropical and subtropical areas.

Infection with the dog heartworm (Dirofilaria immitis) takes place across the globe, including in North America. This infection hardly ever induces symptoms, since the dog heartworm does not grow to maturity in people. Sometimes, an immature heartworm reaches the lungs and may give rise to chest pain and cough. Seldomly, larvae develop nodules in the brain, eyes, and/or testes.

Transmission of Filarial Worm Infections

Filarial Worm Infections are Transmitted as Given Below:

  • The infection is spread when an infected individual is bitten by a mosquito or fly, which consumes the microfilariae.

  • An infected fly (like a horsefly or deer fly) or mosquito bites an individual and deposits larvae of the worm in the skin.

  • The larvae mature into adult worms in lymph tissues or beneath the skin.

  • The adult worms’ yields offspring known as microfilariae that circulate in the bloodstream or reside in the skin.

  • Inside the insect, the microfilaria grows into larvae that can give rise to infection.

  • The insect then transfers these larvae when it bites another individual.

  • These infections are not spread directly from person to person.

Symptoms of Filarial Worm Infections

On the inside of the body, adult filarial worms can migrate and develop lumps in the lymph vessels or beneath the skin, depending on the kind of filarial worm inducing infection. Adult female worms produce immature kinds of the worm known as microfilariae. Much of the harm and many symptoms induced by filarial infections arise from the body's inflammatory reactions to the adult worms or microfilariae.


When lymphatic tissues (cells and organs which compose the lymphatic system) are involved, adult Wuchereria or Brugia worms and the inflammation that go along with them can obstruct lymph vessels, inducing areas of the arms, legs or genitals to become inflamed and swell. After many years, the arms, legs and genitals may become enlarged and impaired.


Circulating Brugia, or Microfilariae of Wuchereria can cause allergic reactions in the lungs leading to cough, breath shortness, and asthma-like symptoms. Adult Loa loa worms migrate beneath the skin inducing temporary nodules and sometimes cross the eye underneath the clear, outer membrane (conjunctiva). Adult Onchocerca reside in nodules beneath the skin and produce microfilariae that induce itching and injury to the skin. They also enter the eye and bring about scarring and inflammation that can lead to blindness after many years.

Filarial Worm Life Cycle

Adult female filarial parasites produce microfilariae. Feeding vector mosquitoes consume microfilariae from the bloodstream. In the mosquito the microfilariae mature to contagious larvae that migrate to the mosquito's mouth-parts, enter a new host through the vector's puncture wound, migrate to the lymphatics, mature, and mate.

Clinical Manifestations of Filarial Worm

Disease demonstrations include inflammation of lymph nodes, lymphedema and irregular fevers. Repeated, chronic infection may lead to elephantiasis.

Structure of Filarial Worm

Adults are elongate and threadlike. Microfilariae are 250 to 300 μm long, equal in diameter to a red blood cell, and sheathed.

Pathogenesis of Filarial Worm

Disease manifestations are due to lymphatic dysfunction resulting from the presence of living and dead worms, lymph thrombi, inflammation, and immune reactions to worms and worm products.

Host Defenses of Filarial Worm

Inflammatory responses result in cellular infiltration and fibrosis of lymphatics. Impairment to vessel walls lead to endothelial cell multiplication. It is still dubious as to what extent circulating antibodies to filariae are safeguarded.

Epidemiology of Filarial Worm

Lymphatic filariasis is widespread in many tropical and subtropical countries where the vector mosquitoes frequently occur.

Classification of Filarial Worm

Filariae are scientifically called nematodes (roundworms). They are vectored by arthropods; mature and mate in particular host tissues; and form microfilariae. The Brugia malayi and lymphatic filaria Wuchereria bancrofti live in lymphatics.

FAQs (Frequently Asked Questions)

Q1. What is Vector Control?

Answer: Mosquito control is a supplemental technique aided by WHO (World Health Organization). It is basically used to decrease transmission of mosquito-borne infections and lymphatic filariasis. Based upon the parasite-vector species, measures such as personal protection, insecticide-treated nets, and indoor residual spraying measures may support in protection of people from infection. The use of insecticide-treated nets at sites where Anopheles is the primary vector for filariasis augments the effect of transmission during and after MDA. Traditionally, vector control has been in environs due to the removal of lymphatic filariasis in the absence of large-scale preventive chemotherapy.

Q2. Who are the Affected Populations of Filarial Worms?

Answer: Filariasis is a common disorder in the tropical areas of the world. The organism called W. bancrofti is prevalent across Asia, Africa, China, and South America. B. malayi is commonly encountered in southern and Southeast Asia. Filariasis is highly rare in North America and takes place only when these organisms are imported from tropical areas. The infection is transferred by a few different kinds of tropical mosquitos that transmit the microfilariae from one host to another. Lymphatic filariasis affects approximately 120 million people around the world. Short-term travelers to regions where it is endemic are subjected to low risk for this infection. People who visit endemic regions for an elongated span of time, and particularly those who are in areas or settings in which they are extensively exposed to infected mosquitoes, can get infected. Most infections observed in the United States are in immigrants from endemic countries, as per the Centers for Disease Control and Prevention.

Q3. How Can I Prevent Filarial Worm Phylum Infection?

Answer: Avoiding mosquito bites is an excellent way of prevention and protection against the filarial worm induced infection. The mosquitoes that bear the microscopic worms generally bite between the hours of dusk and dawn. If you stay or travel to a region with lymphatic filariasis:

  • Make sure to sleep under a mosquito net.

  • Wear long sleeve shirts/tops and trousers.

  • Apply a mosquito repellent on revealed skin between dusk and dawn.