Loa Loa (Loiasis)

Loiasis is a parasitic infectious disease caused by specific roundworms, the Loa loa filariae, and primarily manifests itself as inflammatory, allergy-related swelling reactions. An estimated 3 to 30 percent of the population is infected with Loa loa worms in the distribution areas (West and Central Africa).

Loa Loa (Loiasis)

What is loa loa?

According to Deluxesurveillance, loiasis is an infection with the nematode (roundworm) Loa loa, which is transmitted by diurnal horseflies of the genus Chrysops and is primarily found in the tropical rainforest of West and Central Africa (Congo Basin).

About two to twelve months after infection with the Loa loa, the parasite circulates in the subcutaneous tissue and connective tissue and occasionally in the subconjunctival tissue (eye connective tissue).

Allergic reactions to the Loa loa worm result in sudden, itchy swellings of the skin (called calabar rashes), particularly on the face and legs, which may persist for several days and may recur (return) at irregular intervals. If the larynx is invaded by the Loa loa parasite, life-threatening glottic edema (acute swelling of the larynx) can manifest itself.


Loa loa is a parasitic nematode (filaria) transmitted by infected diurnal horseflies of the genus Chrysops. The microfilariae (larvae of the Loa loa worm) transmitted by the horsefly mature within the incubation period (2-9 months) in the infected human body into sexually mature, adult filariae that live in the subcutaneous tissue and connective tissue of the skin, mucous membranes and possibly the eyes and inside of these structures can migrate (so-called “migratory filariae”).

The adult (full-grown) filariae also produce a large number of infectious microfilariae in the connective tissue, which enter the bloodstream via the lymphatic system and circulate there during the day. Due to allergies, the inflammatory reactions and swellings characteristic of loiasis are caused by the spread of adult filariae and microfilariae.

If an infected person is bitten by a diurnal horsefly at this stage of the disease, the horsefly becomes infected and can transmit the infectious Loa loa microfilariae to other humans or great apes. However, direct transmission of the Loa loa worm from person to person can be ruled out.

Symptoms, Ailments & Signs

Loa Loa or Loiasis is a worm infection found in West Africa, which mainly causes severe itchy skin swelling. The swellings are soft and can produce bumps up to four inches in size. However, the bumps usually disappear after two to three days, only to reappear elsewhere.

Usually only one arm or one foot is affected. The swellings represent an allergic reaction of the body to the nematode. The migration of the nematode also causes the swellings or bumps (Cameroon bumps or Calabar swellings) to migrate over the body. The disease is usually harmless.

Often, however, there is also a chronic course of more than ten years because the roundworm is very long-lived. During this time, however, other organs such as the heart or kidneys can also be affected. Heart valve defects, renal insufficiency or even meningitis can occur as long-term effects.

In rare cases, the crawling worm is also seen. This is especially true when it travels through the eye. Because of this property, Loa Loa is also known as the eyeworm. Although the disease is very protracted, it usually heals well after the worm has died. The worm can be removed surgically or killed medically with diethylcarbamazine.

Diagnosis & History

Infection with Loa loa parasites can usually be diagnosed based on the characteristic symptoms. The diagnosis of loiasis is confirmed by the detection of Loa loa microfilariae in the blood.

The blood should be taken during the day to prove that the microfilariae have adapted to the diurnal brake as an intermediate host and only circulate in the bloodstream at this time.

In addition, an immunofluorescence test to detect the infection antibodies and diethylcarbamazine (DEC), which triggers itching after a single dose and represents indirect evidence of the microfilariae, can be used.

In the majority of cases, infection with Loa loa is easily treatable and has a good prognosis. In rare cases, long-lasting loiasis can lead to late complications such as endocarditis, meningoencephalitis or kidney damage.


Loa loa causes various symptoms and complications that can appear anywhere on the patient’s body. In most cases, this leads to an allergic reaction of the body, so that those affected suffer from reddened skin or itching on the skin. Scratching usually only makes the itch worse.

Especially on the face, the itching and redness can be very uncomfortable for those affected and lead to reduced self-esteem. Not infrequently, the eyes also water and it comes to eye pain. Complications from Loa loa usually only occur if treatment is not provided or if treatment is initiated very late.

The patients can also suffer damage to the kidneys, so that in the worst case it can lead to kidney failure. The patient is then dependent on dialysis or a kidney transplant. Loa loa treatment is carried out with the help of medicines. There are no complications. Those affected often appear tired and exhausted as a result of the disease and can no longer actively participate in life. In most cases, however, there is a positive course of the disease.

When should you go to the doctor?

Swelling of the skin and itching are signs of an existing disease. If the symptoms persist for several days or weeks, a doctor should be consulted. If the itching causes open wounds, the affected person needs sterile wound care. If this cannot be adequately guaranteed, a doctor should be consulted. If pus forms or the affected parts of the body hurt, a doctor’s visit is necessary. The person concerned is threatened with blood poisoning, which without medical care can lead to a life-threatening situation. If you notice the formation of bumps, which recede on their own after a few days and then appear again on another part of the body, the observations should be discussed with a doctor.

In most cases, the diseased regions are located on the patient’s arms or feet. If left untreated, kidney function will be impaired in the long term. Therefore, a doctor should be consulted if there are functional disorders of the kidneys, problems with urination or changes in the urine. If there are abnormalities in heart activity, changes in blood pressure or heart rhythm, the affected person needs a doctor. If you feel generally ill, feel unwell, have an inner weakness or lose your usual ability to perform, you should also see a doctor.

Treatment & Therapy

Loiasis is generally treated medicinally with diethylcarbamazine, an anthelmintic or vermifuge, which kills the Loa loa microfilariae and some of the adult filariae by interfering with the metabolism of the pathogen.

A lower dosage that is gradually increased is recommended initially, since the very high number of dying Loa loa parasites releases toxic substances that can cause pronounced allergic reactions such as rashes, asthmatic attacks, fever and fatigue in the human organism (so-called Mazzotti -Reaction). Antihistamines or corticosteroids should be taken at the same time to inhibit or weaken such allergic reactions and to reduce itching and inflammatory reactions.

In some cases, other anthelmintics such as ivermectin or albendazole are used prior to the diethylcarbamazine therapy. Diethylcarbamazine is contraindicated in the presence of pregnancy and the simultaneous presence of other parasitic infectious diseases such as Dirofilaria immitis or onchocerciasis due to the allergic reactions triggered by the toxins released.

The proteinuria (excretion of proteins in the urine) that sometimes accompanies diethylcarbamazine therapy is usually transient in loiasis. If loa loa parasites are visible in the conjunctiva of the eye, they can be surgically removed under local anesthesia (numbness).

Outlook & Forecast

The prognosis of the Loa loa depends on the time of diagnosis and treatment, but also on the basic course of the disease. In many cases, the pathogen has already been in the organism for a few months before health problems become more apparent. Because of this, by the time the worm is detected, it can spread and already cause internal damage.

If the disease is discovered at an early stage, drug treatment can be initiated. This usually leads to an alleviation of the symptoms within a short time and a subsequent freedom from symptoms. If the course of the disease is unfavorable, the first internal organ damage has already developed.

In severe cases, renal insufficiency can occur. This poses a potential threat to human life. A donor organ is often required in order to have a chance of recovery. Transplantation is complex and associated with numerous side effects. The donor organ is not always well received by the organism. It can lead to reactions of rejection and thus to a further deterioration in the general state of health. The prognosis is also worse if the disease becomes chronic. Despite the administration of medication, there is a possibility that the pathogen will not be completely killed. Therefore, it is not uncommon for therapy to have to be carried out for up to ten years.


Since there is no vaccine against Loa loa to date, preventive measures are limited to exposure prophylaxis. These include wearing light-colored clothing that covers the skin, and using repellents (sprays, creams, lotions to repel insects) and mosquito nets to protect against bites from horseflies infected with Loiasis.

You can do that yourself

If you suspect a loasis, you should first consult a doctor. A doctor must clarify the disease and, if necessary, initiate treatment. Some self-help measures and various household and natural resources support the healing process.

Drug therapy can be supported by an active and healthy lifestyle. While rest and bed rest still apply in the first few days after the illness, light sport can be practiced after the acute phase. Exercise in the fresh air strengthens the immune system and relieves symptoms such as fatigue and asthma. If serious complications occur, the doctor must be informed. Although Loa Loa is easily treatable, close medical monitoring is still required. Otherwise, complications can develop.

The drug treatment can also be supported by a complaint diary. The patient should record any side effects and interactions as well as the effects of the preparation on skin rashes and other typical symptoms. With the help of these notes, the doctor can optimally adjust the medication and ensure rapid healing. Alongside this, reinfection must be avoided by taking the necessary precautionary measures.