Loa Loa

Many have the fear to have a parasite living inside their body.
An unwelcome guest crawling inside their body.



What would you think about a worm living inside...the human eye.





Loa loa is a thread-like worm that lives under the skin in the subcutaneous fat causing loiasis.
Because it is often spotted migrating in the eye, it is known as the eye worm.
Loiasis is endemic to 11 countries and 12 million Africans are infected.
The disease is also known as subcutaneous filariasis, Calabar swellings, African eye worm infection, Loa loa filariasis and Fugitive swelling.






Loiasis is carried by day-biting deer and mango flies (Chrysops silacea and Chrysops dimidiata). They both live in rain forests and warm swamps in central and western Africa. Deer fly's bite is very painful because it has to rip skin apart in order to drink blood. It does not have a narrow sophisticated feeding tube like that of a mosquito. A deer fly is about 5–20 mm in length.






The life cycle of Loa loa starts, when a Loa loa female gives birth to living microfilariae (prelarval eggs) inside the skin of an infected human. The microfilariae travel in peripheral blood during daytime, but during the night (noncirculation phase) they reside in the lungs. When a noninfected deer fly takes a blood meal from an infected human, it ingests microfilariae. The microfilariae lose their sheaths, migrate from the fly's midgut to the hemocoel and eventually to the thoracic muscles. There they develop into first stage and eventually into third stage (infective) filarial larvae. The development inside the fly takes up to two weeks. They migrate to the fly's proboscis (the snout) and invade another human during the next blood meal. The third stage larvae are transferred from the deer fly's mouth parts to the skin. They burrow into the bite wound and enter the subcutaneous layer where they mature into adults in one year. The cycle is completed, when male and female mate and release microfilariae into the bloodstream. Loa loa adults live up to 17 years.

Adult Loa loa male is about 30–34 mm long and 0.35–0.42 mm thick; Loa loa female about 40–70 mm long and 0.5 mm thick. Loa loa migrates in the subcutaneous layer.
When it stops moving, the surrounding tissue develops Calabar swelling. This often occurs in joints, which are its usual stopping points.
If an adult Loa loa is killed, its body becomes waste, which causes abscesses and pus.
The waste products need to be eliminated to make sure that the surrounding tissue and cells are not disturbed.
If the body cannot get rid of the waste, it restricts it by fibrosis.




Loiasis can be asymptomatic.
Native people are more likely to have symptoms than tourists. Adult worms (both living and dead) and their metabolic byproducts (waste) can cause localized subcutaneous itching and allergic reactions. The inflammation may cause red skin eruptions and swelling in the deeper layers of the skin which can last many weeks. Migrating adults can cause instant pain, when moving in sensitive areas, for example, across the surface of the eye. Loiasis is often the cause of eosinophilia (large quantities of eosinophil granulocytes, white cells, that use antigens and special proteins to fight against foreign organisms such as parasites.).


Other symptoms that may occur:

• arthritis (joint pain)
• colonic lesion (damaged large intestine)
• inflammation, swelling and accumulation of fluid in testicles
• lymphadenitis (infection of the lymph glands)
• membranous glomerulonephritis (kidney disease)
• peripheral neuropathy (damaged peripheral nervous system)
• retinopathy (damaged retina (thin layer on the back wall of the eye)).

But don`t worry, it can be treated.


Aldo the treatment is not innocent!



Loiasis is usually treated with diethylcarbamazine (DEC) or sometimes with ivermectin. Both drugs have severe side effects which include death. DEC is effective against microfilariae and less effective against adult worms.
Treatment with DEC is not advised for patients with high quantities of microfilariae because those patiens can develop encephalopathy (brain disease).
When side effects need to be minimized, albendazole can be used instead.




Sometimes eye worms can be removed surgically, although the time frame during which the removal must be done is very short. After the surgery, DEC therapy should follow to manage other adult worms and microfilariae.



What is the truth?

Yes this creature does exist!

And for the true horror;

An Indian doctor did a strange and unappetizing discovery when an older man with pain and swelling in his eye came into his practice. A worm of 13 cm nested in his eye.

The 75-year-old man underwent emergency surgery to prevent damage to his eye. The doctor did so through a small opening in the conjunctiva to remove the parasite.



Can you imagine, a 13cm worm crawling inside your eye.


Now go check your eyes in the mirror... you never know.