Loiasis: Causes, Symptoms and Treatment

Loiasis, commonly known as the African eye worm, is a parasitic infection caused by the Loa loa worm.

This disease primarily affects people living in or travelling to West Africa and Central Africa. It spreads when infected Chrysops flies (deer flies or mango flies) bite a person and pass the parasite into the skin.

If left untreated, loiasis disease can result in permanent skin damage, eye irritation, and other general discomforts. Blood tests and clinical observation make a diagnosis. Though drugs exist to treat outbreaks, treatment requires close monitoring, particularly in cases of severe infection.

Cause of Loiasis

Loiasis Causes stems from a parasitic infection triggered by the worm Loa loa, transmitted through insect bites. This infection occurs mainly in Central and West Africa, where the parasite’s carrier, the Chrysops fly, thrives in humid forests and swampy areas.

When these infected flies, also known as deer flies or mango flies, bite a human, they inject Loa loa larvae into the skin. Over time, these larvae mature into adult worms that move through subcutaneous tissues, causing visible swellings known as Calabar swellings.

Key causes of Loiasis include:

Bites from infected Chrysops flies found in rainforest regions.
Exposure to fly habitats during outdoor activities like farming, logging, or travelling in forested areas.
Poor insect protection, such as not using repellents or protective clothing.
Environmental conditions that support large fly populations, such as high humidity and dense vegetation.
Lack of awareness about loiasis transmission in endemic areas.

The Life Cycle of Loiasis

The causative agent of loiasis, the Loa loa worm, undergoes a complex life cycle involving the human host and the Chrysops fly. The adult worms reside in subcutaneous tissues, producing microfilariae that circulate in the bloodstream.

When a fly takes a blood meal from an infected individual, it ingests microfilariae, which then mature within the fly into infective larvae. These larvae are transmitted to a new host when the fly feeds again, continuing the infection cycle.

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Loiasis Symptoms

Loiasis symptoms can vary widely from person to person, but some signs are considered classic for this Loa loa infection. This disease, caused by the Loa loa worm, is known for affecting the skin, eyes, and general health of individuals exposed to infected Chrysops flies.

Common Loiasis Symptoms

Calabar swellings: These are temporary, itchy swellings caused by the movement of adult worms under the skin. They can appear on the arms, legs, or face and are often painful.
Eye worm migration: One of the most distinctive Loiasis symptoms is seeing the Loa loa worm moving across the eye. This can cause redness, itching, and discomfort.
Skin itching: Persistent skin itching (pruritus) is a frequent symptom due to the body reacting to the parasite.

Other Symptoms

Fatigue and body aches: Many people with Loa loa infection feel tired or unwell.
Joint pain: Some patients report joint stiffness or pain.
Headache and fever: Though less common, these symptoms can occur, especially if the infection triggers an immune response.

Diagnosing Loiasis

Accurate diagnosis of loiasis is imperative for effective treatment. The diagnosis typically involves a combination of clinical evaluation and laboratory testing.

Laboratory Testing

Blood Smear Examination: A standard diagnostic method involves microscopic examination of a blood smear to detect the presence of microfilariae. Blood samples are best collected during the day when microfilariae are most active in the peripheral blood.
Serological Tests: These tests can detect antibodies against Loa loa, though they may not distinguish between active and past infections.

Clinical Evaluation

Observation of Eye Worm Migration: Direct observation of the worm in the eye can be a definitive diagnostic indicator.
Patient History and Symptoms: A comprehensive assessment of the patient’s travel history, exposure risk, and symptomatology is critical in guiding the diagnosis.

Loiasis Treatment

Loiasis treatment focuses on eliminating the Loa loa parasite from the body and managing symptoms caused by the infection.

The primary treatment options for loiasis involve medications targeting adult worms and microfilariae (immature worms in the bloodstream).

Diethylcarbamazine (DEC): This is the first-line treatment for loiasis. DEC works by killing both adult worms and microfilariae. However, it must be used with caution in patients with a very high parasite count to avoid severe side effects, such as brain inflammation (encephalopathy).
Albendazole: This medication can lower the number of microfilariae before starting DEC treatment. It is often recommended for patients with high parasite loads to reduce the risk of severe reactions.
Symptom Management: Antihistamines and anti-inflammatory drugs may help relieve itching, swelling, and allergic responses caused by the migrating worms.
Hospital Monitoring: In severe cases, mainly if the parasite load is high, treatment should be done under close medical supervision to manage potential complications.

Preventing Loiasis

Preventing loiasis primarily involves reducing exposure to the Chrysops flies that transmit the parasite.

Use insect repellents: Apply repellents containing DEET or permethrin on exposed skin and clothing. This can repel the Chrysops fly and lower the chance of Loa loa infection.
Wear protective clothing: Long-sleeved shirts, pants, and closed shoes reduce skin exposure, protecting you from Loiasis transmission.
Avoid fly habitats: Stay away from forested or swampy areas where Chrysops flies are abundant, especially during the daytime when they are most active.
Sleep under insecticide-treated nets: Although Chrysops flies bite during the day, using protective nets can provide extra safety when resting outdoors.
Community awareness: Learn about Loiasis prevention and share this information with others in at-risk areas. Education helps reduce the spread of Loa loa infection.

You can protect yourself from this parasitic disease by following these Loiasis prevention tips. Travellers, healthcare workers, and residents should stay informed and adopt these preventive strategies to stay safe from Loa loa infection.

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Loiasis Risk Factors

Travellers to West/Central Africa, especially those visiting rural or forested areas, are at risk due to exposure to the infected Chrysops flies that spread the parasite.

Long-term residents in endemic areas face a higher risk of infection, particularly if they live near forested or humid environments where these flies are common. The longer someone stays in such areas, the greater their chance of exposure to repeated fly bites.
Outdoor workers (farmers, loggers, researchers) are also at considerable risk because their jobs often require prolonged outdoor activities in fly-infested zones. People with frequent forest exposure, including those involved in field research, agriculture, or logging, may encounter Chrysops flies daily, increasing the risk of Loa loa transmission.

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