Loiasis, commonly called African eye worm, is a parasitic infection caused by the filarial nematode *Loa loa*. This parasite is transmitted to humans through the bite of infected deer flies (genus *Chrysops*), which are found mainly in the rainforests and swampy areas of West and Central Africa. The disease is named after one of its most distinctive features: the adult worm’s migration across the surface of the eye.
The signs and symptoms of loiasis can vary widely among individuals, ranging from mild or unnoticed to more obvious and uncomfortable manifestations. Understanding these signs helps in recognizing this tropical disease early.
One hallmark sign is **the visible migration of an adult worm across the white part of the eye (the conjunctiva)**. This phenomenon often causes alarm because people can actually see a thin, white or cream-colored worm moving slowly just beneath their eyelid or over their eyeball. This movement may last from minutes to hours before disappearing back into subcutaneous tissues. Although it looks alarming, this migration usually does not cause permanent damage to vision but can be very disturbing.
Another common symptom linked with loiasis is **transient localized swellings called Calabar swellings**. These are itchy, raised areas on parts of the body such as arms or legs that appear suddenly and then disappear within days or weeks. They result from allergic reactions to migrating larvae under the skin rather than direct tissue damage by worms themselves.
People infected with *Loa loa* often experience **itching (pruritus)** without any rash initially; this itching may be generalized or localized around sites where worms migrate beneath skin layers.
In some cases, individuals report nonspecific symptoms like:
– Fatigue
– Joint pain
– Headaches
These symptoms reflect systemic immune responses but are less specific for diagnosis compared to visible worms or Calabar swellings.
Because adult worms live in subcutaneous tissues for years—sometimes up to 17 years—the infection can persist chronically without dramatic illness but with repeated episodes of swelling and discomfort over time.
Eye-related symptoms beyond seeing a moving worm include mild irritation, redness (conjunctivitis), tearing, and sometimes pain during migration episodes when worms pass near sensitive ocular structures.
In rare instances where many microfilariae circulate in blood at high levels—a condition known as hypermicrofilaremia—patients might develop complications such as kidney problems due to immune complex deposition or neurological issues if microfilariae invade central nervous system vessels during treatment reactions; however these severe outcomes are uncommon without therapy triggering them.
Diagnosis typically relies on clinical observation combined with laboratory tests detecting microfilariae circulating in peripheral blood during daytime hours since *Loa loa* exhibits diurnal periodicity—it appears mostly between 10 AM and 2 PM when flies bite most actively.
To summarize key signs:
– Visible crawling adult worm across eye surface
– Recurrent Calabar swellings—itchy localized skin lumps
– Generalized itching without rash
– Mild ocular irritation accompanying worm passage
– Occasional systemic complaints like fatigue
Recognizing these features especially among travelers returning from endemic regions or residents living there helps prompt appropriate medical evaluation for loiasis before complications arise due to treatment challenges associated with high parasite loads.
