Myiasis

Myiasis

Chris Schach

Author Bio -

 

Key Points
*Insect infestation which may occur on any area of the skin
*Caused by an infestation of the larvae of flies
*Presentation varies depending on the type of larvae present

Myiasis is a infestation of fly larvae which may occur on any area of the skin. Presentation of the condition varies depending on the type of larvae present. The condition is divided into 3 subtypes based on this information, furuncular, migratory, and wound Myiasis.

Furuncular myiasis is associated with several species of fly. Typically found in South and Central America, cutaneous symptoms of dermatobia hominis infestation consist of a small red bump at the site of infestation, which develops a boil-like appearance as the larvae burrows deeper. This will be accompanied by severe itching, pain, sensations of movement in the affected area. Larvae exit the skin after maturing, leaving little scarring. Cordylobia infestation (found in Africa) typically occurs when infested persons come in contact with articles contaminated with waste. Within 2 days of infection, symptoms emerge consisting of a hot, prickly sensation in the affected area to severe pain. Affected persons may be agitated or have trouble sleeping. In cases where multiple lesions are present, fever and swollen glands may accompany the lesions, in addition to discharge which is thin and bloody or yellow in color. Cuterebra infestation is rare, but occurs in North America in late summer/early fall. Infestation typically occurs through mucosal surfaces, and consists of small red papules which may be accompanied by discharge, itching and pain. Wohlfarhrtia infestations also occur in parts of North America, and typically only affects young hosts. It is most common during summer.

Migratory myiasis is typically associated with one of two species, gaserophilus intestinalis and hypoderma bovis/H. lineatum. G. intestinalis is the most common culprit, and migratory myiasis occurs worldwide. Infestation occurs when in direct contact with eggs, typically through contact with horses. Initial presentation is similar in appearance to furuncular myiasis, but develops into red, linear lesions which are slightly elevated. Hypoderma infestations are extremely rare, and is typically mild and self-resolving, though some cases may be accompanied by fever, malaise, joint and muscle pain, swelling and fluid buildup in internal organs.

Wound myiasis develops when larvae are introduced directly into open Wounds, though mucosal surfaces may also be affected. This may be accompanied by a variety of symptoms, including fever, chills, bleeding, pain, infection, and in severe cases tissue and/or organ destruction, bone and sinus erosion, and death.

Differential Diagnosis (Other conditions with similar appearance)
Abscess
Lymphadenopathy
Cellulitis
Onchocerciasis (River Blindness)
Exaggerated arthropod reaction
Ruptured epidermoid Cyst
Foreign body reaction
Tungiasis
Furunculosis

Diagnosis
Key Points
*Diagnosis based on characteristic appearance of lesions
*Dermoscopy, ultrasound, and submersion testing may be performed to confirm diagnosis and rule out other conditions

Myiasis is typically diagnosed based on the characteristic appearance of lesions in clinical examination. Dermoscopy, ultrasound, and submersion testing of affected areas may be performed to confirm the diagnosis and to rule out similar appearing conditions.

Treatment
*Treatment of lesions may be accomplished by a variety of methods
*Occlusion, removal, and destruction of larva are the most commonly used therapies
*Proper wound care is important in preventing wound Myiasis

Treatment of myiasis may be accomplished by a variety of methods. Occlusion, the prevention of larva from receiving oxygen can destroy larva or induce them to exit the skin, easing manual removal. Manual removal of larvae is also a commonly used therapy, and typically consists of removing larvae via small surgical excision, though this may be difficult with some species. Additionally, larvicides such as Ivermectin may be prescribed to destroy larvae or encourage them to exit the skin.

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