Cutaneous Filariasis in an American Traveler

A fertilized female in the subcutaneous tissue releases microfilariae that may remain in the skin or travel to the eyes of the host.³ The host may demonstrate signs of infection within 3 to 15 months.² Most commonly, patients report localized or generalized pruritus, and one extremity develops swelling, papules, lymphadenopathy, and alterations of skin pigment (hypopigmentation or hyperpigmentation).^5-8 Our patient developed a pruritic eczematous eruption that only affected her right arm with an inflamed firm nodule overlying the elbow, a suspected onchocercoma. Onchocercomas are the direct result of adult worms coiled in the dermis, subcutaneous tissue, and deep fascia. These commonly are found in close proximity to bony prominences with the specific location pending the geographic area of infection.⁸ For example, onchocercomas more commonly are found over bony prominences in the head and upper body region in patients who acquired the disease from Central or South America, whereas individuals infected in Africa more commonly develop onchocercomas near the femoral, coccyx, or sacral regions.²

The immune response mounted by the infected host is responsible for the ocular signs and symptoms.² Specifically, the inflammatory reaction may impact the patient’s cornea, anterior uveal tract, chorioretinal zone, or optic nerve. In fact, onchocerciasis, or river blindness, is the leading cause of blindness in the world.² The host immune response also is responsible for the dermatologic manifestations of this disease. In addition to the dermatologic manifestations already mentioned, others include epidermal atrophy, ulcerations, femoral or inguinal lymphadenitis, lymphedema, and/or general wasting in more severe long-standing infections. Additionally, patients may experience systemic signs resulting from an underlying O volvulus infection.⁸ Our patient demonstrated a subjectively remarkable systemic response manifested by shortness of breath, dyspnea, cough, and palpitations, likely the result of her existing filarial infection.

Diagnosis of onchocerciasis is made by identification of microfilariae or adult worms in skin snips or punch biopsies. Histopathologic analysis of onchocerciasis has been described as several adult worms in the subcutaneous tissue surrounded by a granulomatous, fibrotic, calcified, or sometimes ossified inflammatory reaction.⁸ Microfilariae may migrate to the upper dermis and typically are surrounded by lymphocytes, histiocytes, plasma cells, and eosinophils with an absence of neutrophils,^5,8 which directly causes the overlying epidermis to undergo reactive changes. Measurement of filarial nematodes often helps differentiate species. For example, O volvulus typically measures 230 to 500 mm in length for females and 16 to 42 mm in length for males.⁸ The thickness of cuticles typically measures 4 to 8 µm for females and 3 to 5 µm for males. Microfilariae of O volvulus also have been identified in patient’s sputum, urine, blood, and spinal fluid.⁸ An alternative diagnostic method described by Stingl et al⁹ is a diethylcarbamazine (DEC) patch test that was 92% accurate in onchocerciasis cases diagnosed by skin snip analysis.⁹ Therefore, this test may be a practical alternative when skin specimens are inconclusive.

Management of onchocerciasis should include excision of subcutaneous nodules to remove adult worms. In the past, DEC with suramin was prescribed and kills both microfilariae and adult worms.⁸ However, DEC may induce pruritus, chorioretinal damage, and optic neuritis and suramin is nephrotoxic.² Therefore, oral ivermectin (0.15–0.20 mg/kg one-time dose, may be repeated in 3–12 months) is supported to be a less harmful option. Patients treated with ivermectin have a decreased risk for transmitting infection to the blackfly vector for up to 6 months after treatment, and it is a more effective microfilaricidal agent than DEC.^2,3 Oral doxycycline (100 mg/d for 6 weeks) commonly is added as adjuvant therapy because it kills Wolbachia species, a bacterium that is needed for O volvulus reproduction.³

Although rare in the United States, cutaneous filariasis has become a prevalent public health concern, especially in tropical countries. Individuals with chronic cutaneous filarial infections are at increased risk for debilitating complications that negatively affect their quality of life and productivity. Although the World Health Organization has attempted to eradicate cutaneous filarial infections by mass drug administration, transmission of these diseases remains a challenge. Further research on treatment and methods to prevent transmission by controlling arthropod vectors is required to avoid short-term and long-term health consequences caused by cutaneous filariasis.

Parasitic infections should always be a diagnostic consideration in individuals who present with a pruritic eruption and a history of travel to foreign countries located in Africa, Central America, and South America. Dermatologists in the United States should increase familiarity with these infections because of increased travel, economic globalization, and the impact of global climate change on the geographic distribution of vector arthropods. To control these infections, research efforts should focus on improved sanitation; drug treatment; transmission prevention; and improved education of their clinical manifestations, especially mucocutaneous signs.