Loa loa
| Loa loa | |
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Loa loa microfilaria in thin blood smear (Giemsa stain) |
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| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Nematoda |
| Class: | Chromadorea |
| Order: | Spirurida |
| Superfamily: | Filarioidea |
| Family: | Onchocercidae |
| Genus: | Loa |
| Species: | L. loa |
| Binomial name | |
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Loa loa (Cobbold, 1864) |
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| Synonyms | |
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Filaria loa Cobbold, 1864 |
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Filaria loa Cobbold, 1864
Loa loa is the filarial nematode (roundworm) species that causes Loa loa filariasis. It is commonly known as the "eye worm". Loa Loa is commonly found in Africa and India. It mainly inhabits rain forests in West Africa and has native origins in Ethiopia.
L. loa is one of three parasitic filarial nematodes that cause subcutaneous filariasis in humans. The other two are and Onchocerca volvulus (causes river blindness).
Maturing larvae and adults of the "eye worm" occupy the subcutaneous layer of the skin – the fat layer – of humans, causing disease. The young larvae develop in horseflies of the genus Chrysops (deer flies, yellow flies), including the species C. dimidiata and C. silacea, which infect humans by biting them.
Loa loa worms have a simple body consisting of a head, body, and tail. Males range from 20mm to 34mm long and 350μm to 430μm wide. Females range from 20mm to 70mm long and can be about 425μm wide. They vary in color.
The human remains the definitive host where the parasitic worm attains sexual maturity and the fly species serve as intermediate hosts needed for the morphological development of the worm and microfilariae production.
Two species of Chrysops deerflies, C. silacea and C. dimidiata are the two vectors for Loa loa filariasis disease.
Loa loa parasites infect human hosts by travelling from the entry site through subcutaneous tissues and causing inflammation in the skin wherever they travel. If a parasite stops in one place for a short period of time, the human host will suffer from local inflammation known as Calabar swellings. These are localized, tense, inflammatory pruritic subcutaneous edema seen in joints of extremities, lasting for 1–3 days. They represent areas of angioedema resulting from a host response to allergens released by the maturating worm and its metabolic products. Calabar swellings often occur in the wrist and ankle joints but disappear as soon as the parasite begins to move again. Parasites can also travel through and infect the eye, causing the swelling of the eye. Common symptoms include itching, joint pain, and fatigue.
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Wikipedia