Humans are not the only creatures living on this earth. The fact that humans live with many other creatures including small organisms or known as microorganisms mean there is a possibility for humans to get affected by these small living things. It is worth noting that not all microorganisms pose harm to humans but certain species may actually lead to serious medical conditions. In this DoctorOnCall’s article, we will be learning about one of the many diseases that is caused by microorganisms known as loiasis.
Loiasis, also known as African eye worm, is caused by parasitic worm Loa loa. This parasite is transmitted by deer flies or also known as mango flies/ mangrove flies, specifically of the genus Chrysops. The flies breed in certain rain forest of West and Central Africa. Infections with the parasite can also cause repeated itchy swellings of the body known as Calabar swellings.
A person is infected by this parasite when he or she has been bitten by an infected deer fly of the Chrysops. Deer flies become infected when they eat blood from an infected person. Deer flies usually bite during the day and are more common during the rainy season. These deer flies are attracted by movement of people and by smoke from wood fires. Many deer flies can be found in the rubber plantation areas.
More than 10 million people are affected by loiasis with 14 million people currently reside in high-risk areas. Travellers that have been in the endemic regions of where loiasis is prone to, are more likely to contract the infection if their duration of exposure is greater than 1 month. However, occasionally, travellers may get infected even if they are in the area for less than 30 days.
Many people do not develop any symptoms. Even if there are symptoms, it usually only shows up many months after the prior infection. A person with loasis may have itchy, non-painful swellings of the body that come and go. Swelling can be found anywhere on the body although it is more common to be found near joints. It may inhibit movement of the nearest joint. Loiasis may cause a person to develop an eye worm that crawls across the surface of the eye. This explains why Loa loa is referred to as “African Eye Worm”. Common symptoms of the eye problems are discomfort, foreign body sensation of the eyes, pain and light sensitivity (photophobia). Vision loss may occur. At times, the worm is visible with the naked eye and crawls under the skin. Less common symptoms include itching all over the body, muscle pain, joint pain and fatigue.
Blood tests typically show high counts of eosinophils (eosinophilia). Eosinophils are white blood cells that are associated with parasitic infections. Temporary residents and travellers who are infected by the parasite is frequently presented with “hyperresponsive syndrome”, characterised by eosinophilia, severe angioedema (swelling under the skin), elevated serum IgE, generalised pruritus (itchy skin) and antibody to filariae (parasite worms). This is the opposite in permanent residents of the endemic regions as most have mild to moderate eosinophilia, episodic angioedema, episodic eyeworm and microfilaremia (presence of microfilariae in blood).
Treatment depends on the symptoms. In case of eye worms, the worm can be surgically removed. This will provide immediate relief. However, removal of the worm does not cure the infection because infection is often found in other parts of the body. Hence, medication is the best way to eliminate the infection. Medication to kill the parasite may pose danger to humans. Hence, doctors may need to talk with experts in tropical medicine first before giving any medicine to treat loiasis. Diethylcarbamazine (DEC) is a common medication used to eliminate the parasite. Even so, this medication does have serious side effects but the risk is small. Hence, healthcare providers will run a few tests before medication is given to ensure the safety of the patient and the effectiveness of the medicine. Beside DEC, doctors may prescribe albendazole or ivermectin. At times, people may need to get special treatment before it is safe to give medication and sometimes treatment with medication is not recommended.
The best way to avoid loiasis is to take preventative measures. This includes wearing long pants and long-sleeved shirts to avoid insect bites and avoid being around the smoke of the wood fires. Those planning to stay in an area endemic to the Loa loa in West and Central Africa for a long period of time, taking DEC weekly can help reduce risk for loiasis. Best to consult with tropical medicine experts if DEC is the right medication to be used as preventive measures. Since obtaining DEC may be time consuming, those planning to get this should not wait until the last minute and meet the expert early way ahead before the trip to West and Central Africa. It is important to use medication as prescribed by the doctor by following the right dose and frequency as according to the doctor’s instruction.