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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 tabarid fly causes
it.
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
http://www.diseasesdatabase.com/ddb7576.htm
DPDx
http://www.dpd.cdc.gov/dpdx/HTML/Filariasis.htm
Disease reference.com
http://www.disease-reference.com/Loiasis.htm
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