Clinical Presentation

Calabar Swellings and Worm Migration

Periodic Calabar swellings are one of the main symptoms of this disease. They are localized subcutaneous edema and are thought to be a type allergic reaction to dead worms or their metabolic byproducts. They can appear anywhere on the body, be up to several inches in diameter, and are often preceded by itching and localized pain. The swellings last from days to weeks and subside slowly.

The migration of the worms causes the hallmark of this disease: worms moving across the conjunctiva of the eye. When adult worms migrate across this subcutaneous tissue, and the nose as well, it causes some pain. Otherwise, the migrations are not noticed.


Eosinophilia is another symptom that can be characteristic of Loa loa, although it is by no means exclusively resultant from it. Eosinophilia is an "abnormal increase in the number of eosinophils in the blood that is characteristic of allergic states and various parasitic infections", an eosinophil being "a white blood cell or other granulocyte with cytoplasmic inclusions readily stained by eosin" ( From www.m-w.com). "Eosinophilia of 50 to 70% is frequently noted in individuals infected with Loa loa", especially when Calabar swellings are present (Markell, et al., pg 323).

Other indicators are elevated levels of serum IgE, elevated levels of antifilarial antibody, but infected individuals are sometimes asymptomatic. Microfilaremia is not always present.

Other Symptoms

Other, less common, symptoms may manifest themselves during the course of the disease. Hydrocele, "an accumulation of serous fluid in a sacculated cavity (as the scrotum)", and orchitis, "inflammation of one or both testes, characterized by pain and swelling", may occur if adult Loa are in the tunica vaginalis or spermatic cord ( From www.m-w.com and www.hyperdictionary.com). Colonic lesion, membranous glomerulonephritis, fibroblastic endocarditis, retinopathy, arthritis, and peripheral neuropathy have also been described, but are rare in people native to endemic areas. In fact, the disease may manifest itself differently in people that are not native to endemic areas, with a much higher likelihood of not being asymptomatic, just like lymphatic filariasis.

Lymphadenitis is also seen at times, and it is of a specific type. It is marked by "distension of the subcapsular and medullary sinuses by histiocytes and eosinophils and by atrophy of lymphoid follicles" and "may also represent a local reaction to dead microfilariae" (Markell, et al., pg 323).

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