What are the other Names for this Condition? (Also known as/Synonyms)

• Myiasis of the Skin
• Skin Myiasis

What is Cutaneous Myiasis? (Definition/Background Information)

• Myiasis is primarily a skin disease caused by several species of parasitic fly larva (of taxonomic order Diptera). The fly larvae (maggots) cause disease in humans and other vertebrate animals by feeding on the tissues. The infection is usually characterized by a painful, itchy, boil-like skin lesion that contains the parasite within it
• Cutaneous Myiasis is the most common form of myiasis that is observed among children and adults worldwide, particularly in the tropical and sub-tropical regions. Depending on the type of infesting larvae, the skin form of myiasis is grouped into the following three types:
  • Furuncular Myiasis: The condition occurs when the parasitic larvae bury into skin and present a pus-filled inflamed (furuncular) skin lesion with a central pore, due to infection in the hair follicles
  • Wound Myiasis: It is a serious form that develops when open wounds are infested by parasitic fly larvae; the condition typically favors wounds that are filled with pus, bleeding, and/or decomposing (necrotic) tissue. It is the most common form of Cutaneous Myiasis
  • Migratory Myiasis: It develops when the maggots buried beneath the skin, starts to move randomly through skin burrows, leaving behind a visible trail of wavy or zigzag pattern skin lesions
• Depending on the type, Cutaneous Myiasis can cause mild to extensive tissue destruction and serious complications deepening on the body region involved. The preferred treatment is a minor surgical excision to remove the larva. In many cases, the condition may be self-limiting without treatment (adult larva breaks out and leaves the skin), although medical intervention is important

Who gets Cutaneous Myiasis? (Age and Sex Distribution)

• Cutaneous Myiasis may be observed in individuals of any age group; both children and adults are affected
• Both males and females are affected, and no gender preference is noted
• Worldwide, individuals of all racial and ethnic groups may be affected

The global prevalence of Cutaneous Myiasis is based on the geographical region of the offending parasite. However, a majority of the cases are observed in the continents of Africa, Asia, and South America.

What are the Risk Factors for Cutaneous Myiasis? (Predisposing Factors)

The following are the common risk factors for Cutaneous Myiasis: (mainly in the endemic regions)

• Living in or traveling to the endemic regions
• Contact with infected animals in the endemic regions
• Living in poverty and overcrowded unclean surroundings
• Individuals who work outdoors, including farmers, forest personnel, and tourists
• Poor personal hygiene
• Lack of quality healthcare in the endemic regions
• Elderly adults, especially those with certain neurodegenerative conditions
• Poor mental health
• Bedridden patients who cannot care for themselves
• Alcoholics and drug addicts
• Uncontrolled diabetes

The specific risk factors for furuncular myiasis include:

• Wearing wet clothes
• Using contaminated clothes (washed and dried outside) without ironing

The specific risk factors for wound myiasis include:

• Having an open suppurating wound
• Presence of other skin diseases or malignancies

The specific risk factors for migratory myiasis include:

• Handling horses and other animals that are infected by botflies
• Handling infected cattle, such as by farmers and farmhands, children who interact with farm animals

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Cutaneous Myiasis? (Etiology)

The causative parasite of Cutaneous Myiasis depends on the specific subtype.

• Furunculous Myiasis is mostly caused by the African tumbu fly and human botfly. The transmission occurs during contact with human skin; the larva penetrate the skin and resides and feeds on subcutaneous tissues
• Wound Myiasis is mostly caused by screw-worms and flesh flies. The parasitic insects either lay eggs or deposit their larvae near open wounds
• Migratory Myiasis is predominantly caused by the horse bot fly and cattle bot fly. Humans are accidental hosts for these flies

What are the Signs and Symptoms of Cutaneous Myiasis?

The signs and symptoms of Cutaneous Myiasis may vary from one individual to another and is based on the specific form of Cutaneous Myiasis and the offending agent (larva species).

The signs and symptoms of furunculous myiasis may generally include:

• Presence of swelling and red skin with appearance of an enlarging lesion
• Abscess formation with a central pore; oozing of pus and blood
• Most of the lesions appear on the face, scalp, or arms and legs

The signs and symptoms of wound myiasis may generally include:

• Open wound/ulcer that is aggravating and increasing in size
• Increased redness, swelling, and bleeding
• Pungent or foul-smelling discharge may be observed

The signs and symptoms of migratory myiasis may generally include:

• After invasion into the subcutaneous layers, the larva causes a very itchy inflammatory skin lesion
• The larva starts to move in a random direction tracing a path of migration
• The path may present redness and swelling and pus-filled blisters and nodules

Additionally, systemic signs and symptoms, such as high-grade fever, chills, and muscle and joint pain may be noted.

How is Cutaneous Myiasis Diagnosed?

Cutaneous Myiasis is diagnosed on the basis of the following information. The diagnostic techniques used may vary based on the specific type of causative parasite.

• Complete physical examination and a thorough medical history evaluation, with emphasis on recent travel and/or handling of animals which may be infected
• Assessment of signs and symptoms, including a visual examination of the lesion
• Laboratory tests: Blood tests, such as complete blood count and peripheral blood smear
• Imaging studies, as necessary: Ultrasound scan of the affected region to localize the larva and extent of involvement. This can help enable the surgeon to remove the larva without damaging the surrounding tissues

A differential diagnosis to eliminate other similar skin conditions may be needed before arriving at a definitive diagnosis.

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Cutaneous Myiasis?

The complications of Cutaneous Myiasis may generally include:

• Severe emotional stress
• Severe pain and discomfort
• Secondary infection of the abscess; rupture of the abscess
• Cellulitis: Skin infection that involves the deeper skin tissues
• Wound myiasis may result in severe complications if treatment is delayed
• Migratory myiasis may present complications based on their migration path; this may involve the eye, brain, or lung, among other organs 
• Hypereosinophilia and leukocytosis (increased white blood cells)
• Severe inflammatory response to dead larvae or parts of larvae, especially during its removal
• Sepsis, which can be life-threatening

How is Cutaneous Myiasis Treated?

The treatment for Cutaneous Myiasis may involve the following measures:

• Occlusion of larvae using suitable agents, such as petroleum jelly, oil, paraffin, etc., to move the parasite towards skin surface
• Manual removal or surgical extraction (through a minor procedure) of the larva from affected skin region
• Surgical debridement of dead or necrotic tissue, if necessary
• Dressing and wound care, as required
• A course of prescription oral medications if surgery is not feasible
• Administration of broad-spectrum antibiotics

Examination and identification of the larva following removal from skin tissues may be undertaken.

How can Cutaneous Myiasis be Prevented?

Cutaneous Myiasis may be prevented by considering the following measures:

• Maintaining basic personal and community hygiene and proper sanitation is highly important, particularly in the endemic zones
• Ensure that wounds and skin ulcers are properly treated and dressed/covered
• Washing hands after handling farm animals, especially horses and cattle
• Extra care should be taken while travelling to the endemic regions
• Try to cover all portions of the skin using long-sleeved shirts, full trousers, and socks to protect the body and skin from insect bites
• Dry clothes in direct sunlight; iron clothes to kill the eggs that may have been laid on damp clothes
• Use insect repellents to prevent the insects from entering residences
• Seek medical attention for any changes in skin; especially, after visiting known endemic regions
• The growth of adult flies must be effectively controlled and methods for eradication followed on a regular basis

What is the Prognosis of Cutaneous Myiasis? (Outcomes/Resolutions)

The prognosis of Cutaneous Myiasis is good with early treatment.

• Extensive tissue destruction and delayed/inadequate treatment may result in severe complications that may even be fatal in wound myiasis
• In many individuals, migratory myiasis may be self-limited, although it can cause severe complications as the larva migrates that may even be fatal
• In some individuals, rupture of an abscess containing the larva may lead to a severe inflammatory response
• Additionally, life-threatening sepsis may occur due to secondary infections

Additional and Relevant Useful Information for Cutaneous Myiasis:

The following DoveMed website link is a useful resource for additional information:

https://www.dovemed.com/healthy-living/skin-disorders/