Lymphatic filariasis (LF)

• lymphatic filariasis (LF)
  • LF is (after malaria) the second most common mosquito-borne disease globally
  • caused by three species of nematode parasites - these nematodes can be spread by a wide range of mosquito species
  • estimates from the World Health Organization (WHO) suggest the global burden of infection to be 120 million with 1 billion people at risk of infection
    • LF has a widespread geographical distribution
      • affects mainly the tropical regions of the world, especially the Indian sub-continent, tropical Africa, South and Central America, Southeast Asia and the Pacific Island countries

There are three forms of lymphatic filariasis caused by the following nematodes:

• Wuchereria bancrofti - the most common causative agent and accounts for around 90% of cases
• Brugia malayi - confined to east and Southeast Asia
• Brugia timori - found only in Timor and nearby islands

In this group of filiarial diseases it is the adult worms lodging in lymphatics which cause the characteristic lymphoedema of the limbs, breasts or genitalia.

LF has also been described in travellers, military expeditionary forces and other expatriates

• LF should be considered in the differential diagnosis of travellers returning from endemic areas, and experiencing acute episodes of fever, pain and swelling of the limbs or external genitalia, or lymphatic system

Notes:

• LF was previously thought to occur only sporadically in children. However the introduction of highly sensitive diagnostic tests (antigen detection, ultrasound examination) now reveal, however, that LF is first acquired in childhood, often with as many as one-third of children infected before age 5
  • initial damage to the lymphatic system by the parasites generally remains subclinical for years or gives rise only to non-specific presentations of adenitis/adenopathy; however, especially after puberty the characteristic clinical features of the adult disease syndromes (lymphoedema, hydrocele) manifest themselves

Reference:

1. World Health Organization. Lymphatic filariasis fact sheet. March 2022.