The parasitic roundworms belong to the family of Filarioidea and Phylum Nematoda. Parasitic disease is caused by threadlike parasitic roundworms and the resultant larvae. These species are known by the name filarial worms or filariae and the infection caused by them as filariasis.



Filariasis a parasitic disease transmitted by black flies and mosquitoes. These parasites are thin, round and worm-like structures and has white in color appearance. The life span of filariae would be around 5 to 7 years. During their lifespan, they produce millions of larvae which are creamy in color. The size of female larvae ranges from 2-50cm and the size of male larvae is twice that of the size of female larvae.

How is Filariasis transmitted? 

This disease is transmitted mainly by mosquitoes. Firstly, a mosquito bites an infected individual with larvae. This mosquito bite injects the larvae into a healthy person. The injected larva of a parasite enters the bloodstream of a healthy host and consume the resources required for the larva to grow. The complete stage of larva to adult filarial worms is carried out within the lymphatic system. The matured and adult filarial worm starts to release smaller worms called microfilariae. The newly generated microfilariae again enter into the mosquito along with the host’s blood and the cycle repeats itself. This parasitic disease is categorized into the below groups and on the basis of which body part is infected:

  1. Lymphatic filariasis: In this case, the circulatory system is infected by the worms.
  1. Subcutaneous filariasis: In this case, the bottom layer of the skin and white part of the eyes are infected by the worms.
  1. Serous cavity filariasis: In the case of this disorder, the serous cavity of the abdomen is infected by the worms.

There are more than hundred species of filarial. Among them, only 8 to 9 are categorized as filarial parasites, which causes infections in human beings.

Filariasis Cycle

Filariasis Cycle

Symptoms of filariasis. 

 The general symptoms of filariasis during its early stages include:

  • Fever.
  • Chills.
  • Headache.
  • Skin lesions are observed in the beginning stage .i.e. between three months to nine months after the insect bite.

These symptoms are seen in the later stage:

  • Blockage in the lymphatic system which leads to edema.
  • Swelling, redness, and pain in the arms and legs.
  • Accumulation of pus in cells.

The formation of pus in a cell due to the dying worms or a secondary bacterial infection results in:

  • Skin rashes.
  • Abdominal pain
  • Damage to the cornea, choroid, retina and optic nerve finally resulting in loss of vision.
  • The hyper or hypopigmented skin on face, arms, feet, and other parts of the body.
  • If these symptoms are left neglected, the final stage of this disease would result in gross enlargement of the limbs and genitalia in a condition called elephantiasis.

Diagnosis of filariasis.

It is quite difficult to diagnose this disease as the symptoms vary from one type to another type and the symptoms diagnosed in the early stage are similar to normal viral and bacterial infections.

There are few diagnosis processes carried out by performing body analysis, physical examination, body fluid test including a blood test and urine test. Apart from these tests, few blood tests are carried out during the night time as the larvae are found active at night because of the mosquito (disease carrier) spread the infection between 7 pm to 11 pm. This test is called as finger prick test.

In finger prick test, blood is drawn from a larger vein and a thick smear is formed on the glass slide. The slide is examined under the electron microscope to check the presence of parasitic roundworms. The presence of Filariasis is examined with the help of Giemsa stain. The other diagnosis for subcutaneous filariasis is performed with skin snip test.

Treatment for filariasis.

Currently, there is no vaccine available for filariasis. Scientists are still working on developing a cure for filariasis.

Prevention is better than cure.

As we all know, this disease is caused by the bite of mosquitoes, it is better to prevent the cause of this disease by:

  1. Wearing long sleeves and pants to prevent the bite of mosquitoes.
  2. Avoid perfumes and colognes during night times.
  3. Apply DEET insect repellents like odomos and so on.
  4. Remove the stagnant water near your windows and doors.
  5. Practice making use of mosquito mats, coils, nets and maintain hygiene around your home.
  6. Avoid using dark-colored clothing, mattress, cushions, and curtains as they attract mosquitoes.

These filarial worms live for about 5 to 7 years in the body of the host. Once they enter the host’s body, they start to develop, grow, mature and die by producing millions of offsprings in the lymphatic system of the host’s body.

Practise This Question

Which of the following can be present in a female unisexual flower?

I: Filament

II: Anther

III: Stigma

IV: Ovary