The Loa loa is a nematode, found only in the rainforests and swamps of Central and West Africa , and causes causes a disease known as loiasis. The filarial adult worm migrates to the lymphatics  and subcutaneous tissues (the third layer of the skin); it may also migrate to the eye under the conjunctiva . Humans become infected when bitten by Chrysops silacea and Chrysops dimidiate (two species of Mango fly) .
The definitive host of the worm is humans, whom receive the parasite via its vectors Chrysops silacea and C. dimidiate. Infected mango flies pass on their infected larvae to humans. In turn, a healthy mango fly becomes infected from an infected human . A more detailed description of the process of human infection, and Loa loa life cycle is given below.
When the Mango Fly bites a human to take a meal Mango Fly larvae are left on the skin and enter through bite.Once inside the body the infective larvae wonder through the subcutaneous tissue while they develop into a mature adults. Adults produce microfilariae measuring 250 to 300 μm by 6 to 8 μm, which are sheathed and have diurnal periodicity (circadian rhythms). Microfilariae have been recovered from spinal fluids, urine, and sputum. During the day they are found in peripheral blood, but during the night, they are found in the lungs.
When another fly ingests microfilariae during a blood meal, the microfilariae lose their sheaths and migrate from the fly's midgut through the hemocoel to the thoracic muscles. It is here that the microfilariae develop into infective larvae. The infective larvae migrate to the fly's proboscis where they can infect another human when the fly takes in a meal.
Worms often go unnoticed as they travel through subcutaneous tissues but can be painful as they pass over the eyeball or bridge of the nose. Swelling of the conjunctiva and eye lid are other characteristics of infection.Patients may describe literaly seeing something crawl across their eye . While in the subcutaneous tissues, the worms trigger immune responses that result in swelling of specific areas often a hand or foot. When they remain in one spot for a short time, localized Calabar swellings, especially in the wrist and ankles, appear, which disappear when the worm moves on. There may also be intense itching, joint pain and fatigue . Other symptoms may include: lymphadenitis (infection of the lymph glands),kidney disease, peripheral neuropathy (damaged peripheral nervous), and retina damage 
The Loa loa worm is a prime example of a parasite that is increasing its "encounter" filter, enabling it to infect a new host. Emergence rhythms allow for maximizations of encountering a host .Because humans are greatly dispersed and always on the move, the worms must develop strategies to make the most of their energy. By only coming to the surface of the skin during the day when the flies are feeding, the worms increase their protection by retreating back within the body where they are less likely to be removed.
6.Combes, C.(2005).The Art of Being A Parasite. University of Chicago.