On the basis of this experience, we recommend the following when faced with possible filariasis in an expatriate from Western Central Africa: (1) Attempt a clinical differentiation between L loa and other filarial infections present in West Africa. It is important to suspect loiasis because this is the only filarial infection that is readily curable; (2) ophthalmologic assessment to diagnose onchocerciasis; (3) if L loa is suspected, thick blood smears should be obtained from midmorning to midafternoon and stained with Giemsa or hematoxylin stains, after a concentration technique is used. Nighttime blood specimens should be obtained if the patient has been in an area where W. bancrofti is prevalent; (4) skin snip biopsies prepared as follows: Bilateral symmetrical skin snips should be taken. In the case of suspected West African filariasis, the pelvic girdle, iliac crest, and back of scapula are thought to have the highest yield. One snip from each of six different sites should be obtained. Each skin snip should be approximately 2 to 3 mm (a cornealoscleral biopsy forceps can be used). Each skin snip is placed in 100 µL (approximately one drop) of normal saline in a flat-bottomed microtiter plate. The plate is incubated at room temperature and checked periodically for 24 hours under a dissecting microscope (x20 to x40). If present, the small worms will be seen wiggling and squirming in the drop of saline; (5) serologic diagnostic methods are most efficient if human filarial antigens are used; (6) if treatment is with diethylcarbamazine, the initial dose should be small. During treatment with diethylcarbamazine, WBCs, differentials, and renal function must be monitored.

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