Filariasis and its importance in humans
Aqsa 0684
Introduction
• Filariasis is a group of diseases produced by parasitic worms
called filariae. These parasites are microscopic roundworms
(nematodes) that inhabit the blood, the lymphatics and
other tissues of humans (Cohn, 2015).
• Caused by blood feeding mosquitoes, blackfly and biting
midges.
• The most important filarial diseases infecting human beings
are lymphatic filariasis.
Causative Vectors Disease Distribution
agent
Wuchereria Aedes, Culex, Bancroftian Old and New
bancrofti Mansonia and filariasis World Tropics
Anopheles
Brugia malayi Brugian filariasis Southeastern Asia
mosquitos
Brugia timori Timorian filariasis Southern islands of
Indonesia.
Onchocercia Fly (Simulium River blindness Tropical areas and
Volvulus sp). Sub Sahara
Loa Loa Fly Loiasis West and central
Africa
Lymphatic filariasis
• Lymphatic filariasis, commonly known as elephantiasis, is a painful
and profoundly disfiguring disease. It is caused by infection with
parasites classified as nematodes (roundworms) of the family
Filarioidea that are transmitted through the bites of infected
mosquitos.
Lymphatic filariasis
Parasite
• Among eight filarial nematodes two species are much important for
lymphatic filariasis.
• W. bancrofti (90%)
• Brugia malayi and Brugia timori (10%) (Taylor et al., 2010)
• Live 5-7 years
• Block lymphatic system
• Edema
Lymphatic filariasis
Vectors
• Mosquitoes of the genera Aedes, Anopheles, Culex and Mansonia are
the vectors for lymphatic filariasis.
Host
• Humans are the definitive hosts.
Epidemiology
• African regions; parts of Northeastern South America; Brazil,
Dominican Republic, Southern and Eastern India, Southeastern Asia,
Eastern China, and Southern Japan, Indonesia, The Philippines, New
Guinea; and many island groups of the South Pacific Ocean.
• There are an estimated 905 million people at risk of contracting
lymphatic filariasis, and some 128 million active infections. Of these,
about 115 million are caused by W. bancrofti.
• Another 13 million cases are caused by B. malayi.
• About 43 million people have chronic symptoms of elephantiasis,
hydrocele, or lymphedema (Cano et al., 2014).
Mode of transmission
• Mosquitoes are infected with microfilariae by ingesting blood when
biting an infected host.
• Microfilariae mature into infective larvae within the mosquito.
• When infected mosquitoes bite people, mature parasite larvae are
deposited on the skin from where they can enter the body.
• The larvae then migrate to the lymphatic vessels where they develop
into adult worms, thus continuing a cycle of transmission (WHO,
2021).
Life cycle
Clinical manifestations
Symptoms
Asymptomatic Acute Chronic
(Carriers) symptoms symptoms
Fever, Lymphoedema
Swelling, Elephantiasis
Adenolymphangitis Hydrocele
, Pain Chyluria
Chronic filariasis
In case of W. bancrofti chronic manifestation are
• Lymphedema
Swelling and enlargement of limb, breast, vulva, scrotum due to
accumulation of lymphatic fluid.
• Hydrocele
Swelling of scrotum
• Elephantiasis
• Chyluria
Appearance of lymphatic fluid in urine (White appearence)
Diagnosis
• Identification of microfilariae in the blood smear by microscopic
examination.
• Mostly at night .
• Patients with active filarial infection typically have elevated levels of
antifilarial IgG4 in the blood and these can be detected using routine
assays.
• ELISA
• Examination of chylous fluid with Giemsa stain.
Treatment
• The main goal of treatment of an infected person is to kill the adult
worm
• Diethylcarbamazine citrate is both microfilaricidal and active against
the adult worm.
• Ivermectin is effective against the microfilariae of W. bancrofti, but
has no effect on the adult parasite.
• Albendazole is also used.
• Some studies have shown adult worm killing with treatment with
doxycycline.
• Vector Control.
Importance in humans
• Lymphatic filariasis has important social implications in communities
where it is endemic (Mullen, 2009). Following are some effects.
• Economic loss
• Effect on lifestyle
• Disgrace in society
• Rejection by Society
• Effects on Women and Men
• Impact on children.
References
• Cano, J., Rebollo, M. P., Golding, N., Pullan, R. L., Crellen, T., Soler, A., et al.
(2014). The global distribution and transmission limits of lymphatic
filariasis: Past and present. Parasites & Vectors, 7(1), 466.
• WHO, 2021: Lymphatic filariasis https://www.who.int/news-room/fact-
sheets/detail/lymphatic-filariasis
• Mullen, G. R., & Durden, L. A. (Eds.). (2009). Medical and veterinary
entomology. Academic press.
• Cohn, J. A. (2015). Imported Infectious Diseases: The Impact in Developed
Countries.
• Taylor, M. J., Hoerauf, A., & Bockarie, M. (2010). Lymphatic filariasis and
onchocerciasis. The Lancet, 376(9747), 1175-1185.
