Loa Loa “African Eye worm” [pic] [pic] Loa Loa By Amanda Green Microbiology 210 Loa Loa is a parasite known more commonly as the “African Eye Worm”. This may be one of the most feared of the parasites. They are classified as filarial worms, meaning they thrive in human tissues. Before the 1920’s , Loa Loa infections occurred more frequently in the United States now it is more commonly found in West Africa and equatorial Sudan. It prefers areas with hot, wet climates, like swamps and rainforests. They are cylindrical and have a cuticle with three main outer layers.
This protects the nematodes (larvae) so they can invade the digestive tracts of animals. The outer layers are non cellular. The adult Loa Loa is a thin small worms ranging in length from 20 – 70 mm long and 350 – 430 mm wide. Males are smaller than the females. Loa Loa was first described in 1770 by a French surgeon, Mongin. He was the first surgeon to try to remove a worm from the eye of a woman in Santa Domingo. He was unsuccessful. Another observation came form a French ships surgeon, who observed an eye worm in slaves being taken to the West Indies from Africa in 1778.
The first person to identify the microfilaria of Loa Loa in 1890 was Dr. Patrick Mason when he was invited to examine blood smears with Dr. Stephen Mackenzie. This person was thought to have “sleeping sickness of the Congo. ” To reproduce the female produces a pheromone to attract males. After mating the female produces large numbers of active embryos called microfilaria. These microfilaria find their way to the blood stream where they can be transmitted through a bite to the next host. Loa Loa is an obligate endoparasite that feeds on fluids in the tissues of humans.
The parasite contains pharyngeal glands and intestinal epithelium that produce digestive enzymes that enable them to feed on the hosts’ body fluids. Extracellular digestion begins within the lumen and is finished intracellularly. The adult parasite has been known to live up to 15 years. A human infected by Loa loa is termed Loiasis. People become infected by the transmission by deerflies. Once the deerfly lands on the host and bites, the larvae then drops into the opening of the skin and burrows into the subcutaneous tissues.
The larvae then migrate through the body, commonly to the eye. They congregate in the lungs at night. Damage can be done to the eyes as it crawls through the cornea and conjunctive tissues. It can easily be seen and felt in the eye up to an hour. When they are deeper into the body they can cause encephalitis, if they reach the brain, which can lead to death. Joint pain can occur from swelling if the parasite stays near a joint for a period of time. The larva can remain unnoticed for months or years before becoming an adult, mating, and producing offspring.
They continuously travel through deep and connective tissues, often even without the person feeling any sensation other than occasional itching. A person may feel the greatest discomfort when the worm slows or reaches a sensitive spot. It is then that the immune reaction starts, with localized redness and swelling called Calabar. This type of reaction is thought to be caused by a type of allergic reaction to dead worms and their byproducts. Skin eruptions and muscle pain may be evident. Once the worm dies the surrounding tissues may abscess. An accumulation of serous fluid in a sacculated cavity called hydrocele is a less common symptom.
Colonic lesions, fibroblastic endocarditis, membranous glomerulonephritis, retinopathy, arthritis, and peripheral neuropathy can occur but are less common in people native to endemic areas. To diagnose Loasis, physicians look for Calabar swelling and the presence of worms in the conjunctiva. Those are the main tests used to diagnose an infestation. Some laboratory tests can help with the diagnosing including, C – reactive protein, elevated eosinophils (called eosinophilia), and IgE quantification. Identification of microfilariae by microscopic examination is the most practical diagnostic test.
The collection of the blood specimen is extremely important with the known periodicity of the microfilariae. The smear is stained with Giemsa or hematoxylin and eosin. Concentration techniques can be used for increased sensitivity, including centrifugation of the blood sample hemolyzed in 2% formalin. Checking for microfilaria in the blood on a newly suspected case is not recommended because it can take may years for them appear. Loa Loa is endemic only to parts of West Africa. A study done by S. Wanji at the University of Boea in Cameroon found that in 16 rural villages in southern Cameroon 2. 2% to 19. 23% of people were infected. It also showed that males are almost twice as likely to become infested as females. The level of infection increases from the ages of 15 to 65 years old and then drops. The treatment’s side effects for Loa Loa are more life-threatening than the actual infestation. Two of the most common treatments are diethylcarbamazine and ivermectin. Both of these treatments can cause encephalitis, coma, or death in people with high microfilaria loads. These drugs kill the microfilaria but not the adult worms. Other treatments include chemotherapy and surgical removal.