• Kingdom: Animalia,

  • Phylum: Nematoda

  • Class:

  • Order:

  • Infraorder:

  • Superfamily: Filarioidea


  • Filarial worms that infect blood and tissues of man and other animals

  • Adults can live for up to 15 years in the human host

  • Larval stages known as microfilariae (what see in clinical specimens)

  • Immune response can lead to symptoms

Species with microfilariae in the blood

Species with microfilariae in the skin

Diagnosis of LF and Loa loa:

  • Find mfs in the blood

  • Periodicity

  • Thick blood films

  • Nuceopore filtration


Filariasis is a parasitic disease caused by an infection with roundworms of the Filarioidea type. These are spread by blood-feeding insects such as black flies and mosquitoes. They belong to the group of diseases called helminthiases.

These parasites exist in the wild in subtropical parts of southern Asia, Africa, the South Pacific, and parts of South America. One does not acquire them in the Northern Hemisphere like Europe or the US.[2]

Eight known filarial worms have humans as a definitive host. These are divided into three groups according to the part of the body they affect:

The adult worms, which usually stay in one tissue, release early larval forms known as microfilariae into the person's blood. These circulating microfilariae can be taken up during a blood meal by an insect vector; in the vector, they develop into infective larvae that can be spread to another person.

Individuals infected by filarial worms may be described as either "microfilaraemic" or "amicrofilaraemic", depending on whether microfilariae can be found in their peripheral blood. Filariasis is diagnosed in microfilaraemic cases primarily through direct observation of microfilariae in the peripheral blood. Occult filariasis is diagnosed in amicrofilaraemic cases based on clinical observations and, in some cases, by finding a circulating antigen in the blood.