Filarial infections are caused by parasitic worms and spread by biting insects. Filiasis is a group of parasitic diseases consisting of Uncherieria bancrofti (bancroftian filariasis), Onchocerciasis volvulus (Onchocerciasis), and Loa Loa.

Mosquitoes in urban and rural areas transmit Bancroftian type.

Classic elephantitis occurs in legs and genitals after heavy worm load over many years, which affects lymph drainage.

Acute infections may develop 3 months after exposure with fever, lymphadenopathy, cellulites, Lymphangitis, epididymo-orchitis and edema.

Fever may be on and off.

Suspicion, peripheral eosinophilia, filiaviral antibodies and micrfilaria on blood film confirm diagnosis.

Some people with uncheriria bancofti infection will exhibit cough, wheeze and transient pulmonary infiltrates.

General Filariasis Internet resources
Filarasis.net http://filariasis.net/
Pan American Health (English and Spanish) http://www.paho.org/Project.asp?SEL=TP&LNG=SPA&CD1=BDISPRVCT&CD=FILAR

World Health Organization WHO (elimination program)
http://www.who.int/health_topics/filariasis/en/ http://www.cdc.gov/ncidod/dpd/parasites/lymphaticfilariasis/

Onchocerciasis Filariasis
Onchocerciasis (River Blindness, Robie's Disease, Volvalosis, Mal Morado).

This is mostly found in Africa but some in Central and South America and Arabic Peninsula.

Is caused by worm transmitted by black fly found near fast-flowing water.

The larval are deposited by the black fly and mature inside the host.
After 1 year the worm matures and reproduces as small microfilariae that migrate through the body.

Symptoms include: widespread itchy rash (caused by large numbers of the microfilariae).

Nodules or 'boney bumps' occur where the adult worm is.

The microfilariae also cause fever, headache, lymphatic swelling, and fatigue.

While migrating they may lodge in the eyes causing irritation, redness and possible blindness.
Diagnosis is either by the clinical pattern or microfilariae seen on a tissue biopsy.

Treatment with the drug ivermectin once yearly kills the microfilariae but not the adult worm, which can live for 20 years!
Onchocerciasis is rare in travelers staying less than 3 months even if they are in high-risk areas.

River blindness occurs to people living long term with heavy infection.

Onchocerciasis is a leading cause of blindness, and is also known as river blindness.

It is acquired through simulium (black) flies that breed near fast flowing rivers.

The most common symptoms are itchiness and blurred visions.

Repeated exposure and high worm loads may lead to blindness.
Signs of infections will show minor skin changes and nodules (skin snips are biopsied from shoulder, buttocks, and thigh areas), and corneal inflammation.

No vaccination exists but anti-parasitic medication exists.

Highly suspicious cases may need serologic screening, checking skin biopsies and peripheral eosinophilia in complete blood count.
Onchocerca volvulus occurs mostly in West Africa but is found in many sub-Saharan countries.

Onchocerciasis links
World Health Organization WHO http://www.who.int/tdr/diseases/oncho/

CDC http://www2.ncid.cdc.gov/travel/yb/utils/ybGet.asp?section=dis&obj=oncho.htm

Journal of Community Eye Health http://www.jceh.co.uk/journal/38_2.asp NIAD     http://www2.niaid.nih.gov/newsroom/focuson/bugborne01/onchoc.htm

Medical Journal of Australia http://www.mja.com.au/public/issues/179_11_011203/tay10553_fm.html

World Bank http://www.worldbank.org/afr/findings/english/find174.htm

Filarial Lymphangitis
Filarial Lymphangitis occurs by transmission of worms by mosquitoes.

Present in Sub-Sahara Africa, Egypt, Southern Asia, Western Pacific Islands, Central and tropical South America, and Caribbean.

The adult worms live in lymph tissue and produce microfilariae, which the mosquitoes irrigate while feeding.

The mosquitoes deposit their new larval to the next victim.

Symptoms appear 5-18 months after being bitten.

Local inflammation of the lymphatic network occurs, with later scarring. Lymph may block leading to swelling; which in its extreme turn becomes elephantitis (which is permanent).

Other complications include fever, rashes, blindness, and tropical pulmonary eosinophilia (an inflammation of the lung causing coughing and wheezing).
A blood test confirms infection and a drug treatment will eradicate infection.

Bancroftian filariasis is a remote risk for travelers, but more so in back packers.

There is no vaccine available and general mosquito avoidance should be practiced.

Filarial Lymphangitis links:

Vector Control Research Centre, Medical Complex (India) http://www.pon.nic.in/fil-free/chronic.html
WHO http://www.who.int/ctd/filariasis/diseases/index.html
Filariasis.org http://www.filariasis.org/

Loasis (Loa Loa)
Loasis (Loa Loa) occurs in Western and Central Africa in forested areas such as Sudan and Cameroon.

The Loa worm transmitted by the daytime biting Chryops fly .

The eggs take 1 year to mature after deposited and as adults migrate freely under the skin. They can be up to 6cm 1mg and .5mm diameter. The female worm release more microfilarial which tabarid flies take up. The risk of infection to travelers is low (although not routinely given a weekly dose of the drug directly carbamazine 300mg will prevent disease).
Loasis rarely is serious and worms are first noticed crossing the bridge of the nose or under the conjunctiva. People can actually even see the worm more across their eye. Some people develop painless skin swellings 'Calabar swelling' near joints during hot weather, which is probably caused by a toxin released by the worm as it passes along. Loa Loa is acquired by the bite of the day feeding Chryops flies. Infection is mostly asymptomatic but the worm can migrate under the conjuctiva.
Other symptoms include tender swellings over pressure points (called Calabar swellings) and joint effusion. The Chryops flies are found in the rain forest areas of West and Central Africa and are attracted to dark colours Diagnosis can be confirmed with a blood test and treated with medication. If a worm is observed at the eye or bridge of the nose, a skilled doctor with local anesthesia can remove it.

Loa Loa links:
Microbiology and Immunology Online http://www.med.sc.edu:85/parasitology/nematodes.htm
Disease database
Disease reference.com