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Loa loa is the filarialnematode (roundworm) species that
causes Loa loa filariasis(subcutaneous
filariasis) or loiasis.It is commonly
known as the
"eye worm.Its geographic
distribution includes
Africa and India.
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As of 2009, loiasis is endemic to 11 countries,
all in western or central Africa, and an estimated
12-13 million people have the disease. The highestincidence is seen in the following countries:
Cameroon, Republic of the Congo,
Democratic Republic of Congo, Central African RepubliNigeria, Gabon, Equatorial Guinea
The rates ofLoa loa infection are lower but it is
still present in and Angola, Benin, Chad and Uganda.
The disease was once endemic to the western
African countries of Ghana, Guinea, Guinea Bissau,
Cte d'Ivoire and Mali but has since disappeared.
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Morphology
Loa loa worms have a simple body including
a head, body, and tail.Males range from 20mm to 34mm long
and 350m to 430m wide.
Females range from 20mm to 70mm longand are about 425m wide.
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Primary Reservoir:Humans
Others:Horses
Hippopotamus
primates
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Vector
The young larvae develop
in horseflies of the genus Chrysops
which infect humans by biting them
Yellow fly Deer fly
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Three species involved in the life cycle
include the parasite Loa loa, the fly vector,
and the human host:
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Loa loa parasites infect human hosts by
travelling through subcutaneous tissues
These parasites cause inflammation in the skin
wherever they travel. If a parasite stops in one
place for a short period of time, the human hostwill suffer from local inflammation known as
Calabar swellings.
These often occur in the wrist and ankle joints
but disappear as soon as the parasite begins to
move again
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Parasites can also travel through and infect
the eye, causing the swelling of the eye.Common symptoms include itching,
joint pain, fatigue, and death.
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Reproduction
Like all roundworms, Loa loa is sexual so amale and female worm must be present in the
Same host for a full infection to ensue.
Upon reproduction the female worm produces
sheathed eggs called microfilariae which
circulate in the blood stream.
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The main methods of diagnosis include the
presence of microfilariae in the blood, the
presence of a worm in the eye, and thepresence of
skin swellings.
Surgical
removal
of the worm
Can easily
be
performed.
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The common treatment for the disease is a
use of one of two drugs:
diethylcarbamazine (DEC) or Ivermectin.
Ivermectin (22,23-dihydroavermectin B1a +
22,23-dihydroavermectin B1b) is a broad-
spectrum antiparasitic avermectin medicine.
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Diethylcarbamazine (DEC) is an anthelmintic
drug that does not resemble other
antiparasitic compounds. It is a syntheticorganic compound which is highly specific for
several parasites and does not contain
any toxic metallic elements.
Anthelminticsor antihelminthics are drugs
that expel parasitic worms from the body, by
either stunning or killing them.
They may also be called vermifuges (stunning)
or vermicides (killing).