Lymphatic filariasis (LF) is a parasitic disease caused by microscopic, threadlike nematode worms.

The adult worm of this parasitic nematode only live in the human lymph system and people with this disease suffer from lymphadema (swelling that generally occur in one arm or legs) and elephantiasis (An enlargement and hardening of limbs or body parts due to tissue swelling). Men experience swelling of the scrotum, called hydrocele (swelling of the scrotum).

Lymphatic filariasis (LF) has been considered globally as a neglected tropical disease (NTDs). It is a leading cause of permanent disability worldwide. It is mostly found among poor and vulnerable populations, often in remote communities that lack access to basic health care and in countries where this disease is endemic it has both social and economic impact.

Brief history of lymphatic filariasis (LF)

The first reference of lymphatic filariasis(LF) was in ancient Greek literature, where scholars differentiated the often similar symptoms of lymphatic filariasis (LF) from those of leprosy, they described leprosy as elephantiasis graecorum and lymphatic filariasis (LF) as elephantiasis arabum.

Lymphatic filariasis (LF) is said to have affected humans for about 4000 years. Possible elephantiasis symptoms were shown by Artifacts from ancient Egypt (2000 BC) and the Nok civilization in West Africa (500 BC). The first documentation of symptoms of lymphatic filariasis (LF) occurred in the 16th century, when Jan Huyghen van Linschoten wrote about the disease during the exploration of Goa. Some similar symptoms were also reported by subsequent explorers in areas of Asia and Africa, though an understanding of the disease did not begin to develop until centuries later.

 Timothy Lewis, building on the work of Jean Nicolas Demarquay and Otto Henry Wucherer in 1866, made the connection between microfilariae and elephantiasis, establishing the course of research that would ultimately explain the disease. In 1876, Joseph Bancroft discovered the adult form of the worm. The life cycle involving an arthropod vector was theorized by Patrick Manson In 1877, who later proceeded to demonstrate the presence of the worms in mosquitoes. Manson incorrectly hypothesized that the disease was transmitted through skin contact with water in which the mosquitoes had laid eggs.  George Carmichael Low determined the actual transmission method in 1900 by discovering the presence of the worm in the proboscis of the mosquito vector.

What are the cause of filariasis (LF)?

Lymphatic filariais is caused by three species of threadlike nematode worms know as wuchereria bancrofti, brugia malayi and brugia timori.

Geographical distribution of lymphatic filariasis (LF)

Approximately over 120 million people are infected with lymphatic filariasis (LF) in 72 countries throughout the tropics and sub-tropics of Asia, the Western Pacific, Africa, and parts of the Caribbean and South America.

A wide range of mosquitoes can transmit the parasite, depending on its geographic area. In Africa, the common vector is Anopheles and in the Americas, it is Culex quinquefasciatus. Aedes and Mansonia can transmit the infection in the Pacific and in Asia.

How do you get lymphatic filariasis(LF)?

Lymphatic filariasis (LF) spreads from one person to another person through mosquito bites. When a mosquito bites someone who has lymphatic filariasis (LF), the microscopic worms circulating in the person’s blood enter and infect the mosquito. When the infected mosquito bites another person, the microscopic worms pass from the mosquito through the skin, and travel to the lymph vessels. In the lymph vessels they grow into adults. An adult worm lives for about 5–7 years. The adult worms of this parasite mate and release millions of microscopic worms, called microfilariae, into the blood.  People with the infection can serve as a host for the continuous spread of the disease.

Sign and symptoms of lymphatic filariasis (LF)

Majority of lymphatic filariasis (LF) infections are asymptomatic (i.e showing no external signs of infection while contributing to transmission of the parasite).

Although  asymptomatic infection of lymphatic filariasis (LF) still cause damage to the lymphatic system and the kidneys, and alter the  immune system over a long period of time without signs of illness. Severe infections of lymphatic filariasis (LF), which may not show up for years, causes swelling in the genitals, breasts, arms and legs may progress to lung disease.

Diagnosis

Lymphatic filariasis (LF) can be examined and  diagnosed through the examination of blood under the microscope to identify the microscopic worms, called microfilariae. This is not always feasible because in most parts of the world, microfilariae are nocturnally periodic, which means that they only circulate in the blood at night. For this particular reason, collection of blood has to be done at night to coincide with the appearance of the microfilariae in the blood.

Serologic techniques provide an alternative to microscopic detection of microfilariae for the diagnosis of lymphatic filariasis (LF). Because lymphedema may develop many years after infection, lab tests are often negative with such patients.

Treatment

Treatment of lymphatic filariasis (LF) includes the use of anti-helmintic drugs but differ depending on the geographical location of the area of the world in which the disease was acquired.

How can I prevent and control lymphatic filariasis (LF)?

Avoiding mosquito bites is the best form of prevention. The mosquito that carries the microscopic worms usually bites between the hours of dusk and dawn. If you live in or travel to an area with lymphatic filariasis (LF) you should do the following:

Sleep under an insecticide treated net.

Wear long sleeved shirt and trouser.

By using mosquito repellent on exposed skin between dusk and dawn.

Reviewed on 10/4/2020

REFERENCES
https://www.who.int/news-room/fact-sheets/detail/lymphatic-filariasis

https://www.cdc.gov/parasites/lymphaticfilariasis/gen_info/faqs.html

“Lymphatic Filariasis Discovery”Archived from the original on 2008-12-10. Retrieved 2008-11-21.

Grove, David I (1990). A history of human helminthology. Wallingford: CAB International. p. 1–848. ISBN 0-85198-689-7.

Grove, David I (2014). Tapeworms, lice and prions: a compendium of unpleasant infections. Oxford: Oxford University Press. p. 1–602. ISBN 978-0-19-964102-4.