Got the Travel Bug? A Review of Common Infections, Infestations, Bites, and Stings Among Returning Travelers

Matthew P. Vasievich; Jose Dario Martinez Villarreal; Kenneth J. Tomecki

Disclosures

Am J Clin Dermatol. 2016;17(5):451-462. 

In This Article

Myiasis

Pathophysiology

Myiasis has three forms: follicular/furuncular myiasis, wound myiasis, and migratory myiasis. Follicular or furuncular myiasis is caused by one of four different types of flies: the human botfly Dermatobia hominis; the Tumbu fly Cordylobia anthropophaga; Cuterebra species, known as rabbit or rodent bot flies; and Wohlfahrtia vigil and W. opaca.[18,19] In furuncular myiasis, the female fly lays eggs on foliage or deposits them on a blood-sucking insect with a quick-drying glue-like substance. When the insect lands on a host for a blood meal, or the host brushes against the foliage, the eggs hatch and the larvae quickly burrow under the skin of the host, where they mature and feed on the host blood for 5–10 weeks. Once the larva matures, it emerges, drops to the ground, and continues development to a mature fly in the soil.[20]

Wound myiasis follows fly infestation of open wounds, mucous membranes, and body cavities. Flies that cause wound myiasis worldwide are Cochliomyia hominivorax, Chrysomya bezziana, and Wohlfahrtia magnifica. The female fly lays eggs around the edges of wounds or on mucous membranes, particularly the nose and orbit. Eggs hatch in 1–2 days, and larvae feed on tissue for approximately 1 week, which can increase the size of the wound. The spines on the body of the larvae serve as an anchor to the wound base, which can make removal of the larvae difficult. Infestation of the wound produces a characteristic odor that attracts more flies to lay eggs. After maturing, the larvae fall to the ground to complete maturation to an adult fly. The entire life cycle is approximately 24 days.[18,19]

Migratory or creeping myiasis is caused by the flies Gasterophilus intestinalis and Hypoderma ovis and lineatum. The female fly lays eggs on the leg hairs of the distal extremities of horse or cattle. The eggs remain dormant until the animal bites or licks the areas where the eggs are laid. The larvae subsequently hatch and burrow into the oral mucosa; from there, they are ultimately swallowed and remain in the gut for 8–11 months until they pass through the feces to the ground where they pupate. Humans are an accidental host in migratory myiasis and acquire the eggs by contact with the horse's coat or by accidental deposition of eggs by the fly onto human skin. On hatching, the larvae burrow into the epidermis and migrate 1–30 cm per day; however, they ultimately die as they are unable to pupate.[18,21,22]

Epidemiology

Myiasis is commonly seen in travelers returning from sub-Saharan Africa, Latin America, and the Caribbean, less so from northeast Asia, and represents 1–5 % of illness in returning travelers from these regions. However, cases of furuncular and migratory myiasis have also been reported across North America and Southern Europe.[3,18,19]

Clinical Presentation and Diagnosis

Furuncular myiasis (Figs. 4, 5) typically exhibits one or more erythematous papule or nodule, ranging in size from 0.2 to 2 cm with a central pore or punctum, which is the caudal spiracle of the larva through which it breathes and expels waste—a spontaneous serosanguinous drainage from the site. Favored sites are the head and neck, upper shoulders, and chest. Symptoms may include itching, nocturnal lancinating pain at the sites, a sense of movement from within the nodule, fevers, and chills. The disease may also be associated with local adenopathy. Diagnosis is primarily clinical and often strengthened by the travel history. If the furuncle is closely observed, movement can often be appreciated around the punctum, and the spiracle can be appreciated on dermoscopy. If imaging is necessary, ultrasound or magnetic resonance imaging (MRI) may be used. Differential diagnosis includes an inflamed cyst, abscess, folliculitis, or other arthropod bite. If the nodules are submerged in water and the organism is alive, air bubbles may appear at the punctum.[23,24]

Figure 4.

Furuncular myiasis

Figure 5.

Botfly larva

Migratory myiasis is characterized by pruritic serpiginous linear tracts that form as the larva burrows through the skin. The tracts may resemble the helminthic infection cutaneous larva migrans, with a similar differential diagnosis, though migratory myiasis travels more slowly and can persist in the skin for months, unlike the helminthic infestation. Fly larvae are also larger and can be visualized with mineral oil and dermoscopy.[18]

Wound myiasis is characterized by the presence of larvae in an open wound or mucous membranes. In severe cases, fever, chills, pain, superinfection of the site, and peripheral neutrophilia or eosinophilia may occur.[25]

Treatment

Furuncular myiasis is treated with occlusion of the punctum with vaseline for 24 h, thus suffocating the organism, causing it to emerge from the skin. An eccentrically placed cruciform incision can be helpful in removal, as incision directly over the punctum can result in transection of the larva and incomplete removal/[23,24,26] Migratory myiasis can be treated surgically with removal of the larva from the leading edge of the tract using a sterile needle or local anesthetic followed by incision and removal of the larva.[19] Irrigation and debridement is necessary for wound myiasis. For large wounds, general anesthesia may be necessary.[18]

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