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

• Traumatic Myiasis
• Wound Infestation by Fly Larvae

What is Wound 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
• Wound Myiasis or Traumatic Myiasis is a serious form of cutaneous myiasis 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. Wound Myiasis constitutes one of the most common clinical subtypes of myiasis; it may also involve the mucous membranes and cavitary openings
• The parasites frequently causing the condition include screw-worms (Cochliomyia hominivorax and Wohlfahrtia magnifica) and blow-flies (Calliphoridae sp.). The contributory factors for these flies to deposit their eggs/larvae on the wounds or ulcers include poor personal hygiene, squalid conditions, patients with poor mental health, and inadequate healthcare, among other factors
• Wound Myiasis can cause severe and extensive tissue destruction and serious complications, if not immediately addressed. Management of the condition involves removal of all larvae followed by surgical debridement of infected tissue. Nevertheless, the prognosis of Wound Myiasis depends on its severity; tissue destruction on a large scale may lead to mortalities

Who gets Wound Myiasis? (Age and Sex Distribution)

• Wound Myiasis may be observed in individuals of any age group, although most cases are seen in very young children and elderly adults
• Both males and females are affected, and no gender preference is noted
• Worldwide, individuals of all racial and ethnic groups may be affected

The screw-worm flies are found across the world, in the continents of Asia, Africa, and South America (including central America); while, the blow-flies are found across Africa and Southern Europe.

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

Having an open suppurating wound is the primary risk factor for Wound Myiasis. The following skin conditions are known to predispose individuals to Wound Myiasis:

• Basal cell carcinoma of skin
• Cancrum oris
• Condyloma acuminatum
• Cutaneous B-cell lymphoma
• Filarial lymphedema
• Hemorrhoids
• Herpes zoster virus infection
• Impetigo
• Leprosy
• Lipedema
• Neuropathic ulcer
• Onychomycosis
• Pediculosis
• Psoriasis
• Seborrheic keratosis
• Vascular insufficiency ulcer

The other main risk factors for Wound Myiasis include: (mainly in the endemic regions)

• Living in or traveling to the endemic regions
• Living in poverty and overcrowded unclean surroundings
• Poor personal and oral hygiene
• Natural calamities such as floods
• War or civil strife that cause injuries and poor access to medical care
• 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
• Uncontrolled diabetes

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 Wound Myiasis? (Etiology)

Wound Myiasis is a parasitic infection caused by any of the following species of insect larvae. In general, the screw-worm flies are the most common cause of this condition.

• New World screw-worm fly (Cochliomyia hominivorax)
• Old World screw-worm fly (Chrysomya bezziana)
• Black blow fly (Phormia regina)
• Filth flies (Sarcophagidae sp.)
• Green bottle blow fly (Lucilia sericata)
• House flies and stable flies (Muscidae sp.)
• Spotted flesh fly or screwworm fly (Wohlfahrtia magnifica)

The parasitic insects either lay eggs or deposit their larvae in or near open wounds. An increased incidence is noted during the summer months.

Screwworms can lay up to 500 eggs around open wounds. When eggs hatch to larva, they bury into the skin and feed on the wound tissue from beneath causing severe parasitic infestation. The local invasion and tissue damage/destruction can soon become extensive. The invasion may attract even more flies to the now severe wound.

What are the Signs and Symptoms of Wound Myiasis?

The signs and symptoms of Wound Myiasis may vary from one individual to another and is based on the type of larva species. In many individuals, the following may be noted:

• Open wound/ulcer that is aggravating and slowly increasing in size
• Increased redness, swelling, and bleeding is noted
• Pungent or foul-smelling discharge may be observed
• Individuals can sense movement of the larva within the wound
• The lesions may be large and deep, termed cavernous
• Pain may be severe
• Formation of fistula

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

How is Wound Myiasis Diagnosed?

Wound 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. Wound Myiasis may be visually diagnosed through wound inspection and pungent smell of the wound (pus)
• 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

Imaging studies and biopsy studies are not generally necessary to diagnose the condition.

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 Wound Myiasis?

The complications of Wound Myiasis can be significant and may 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
• Hypereosinophilia and leukocytosis (increased white blood cells)
• Amputation of the limb or body part; extensive surgery requirement
• Severe inflammatory response to dead larvae or parts of larvae, especially during its removal
• Sepsis, which can be life-threatening

How is Wound Myiasis Treated?

The treatment for Wound Myiasis may involve the following measures:

• Surgical debridement of dead or necrotic tissue after removal of larvae that is easily visible; often, multiple sessions may be needed to extract all larvae
• The larvae may be immobilized through oil and chloroform and then extracted
• Deep lesions may be irrigated with antiseptic solutions
• Regular dressing changes and wound care, as needed
• Use of ivermectin topical applications
• Prescription oral medications (usually ivermectin), based on healthcare provider’s evaluation

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

How can Wound Myiasis be Prevented?

Wound Myiasis may be prevented by considering the following measures:

• Ensure that wounds and skin ulcers are properly treated and dressed/covered
• Medical centers should provide fly screens on patient area doors, windows, and ventilators
• Pantry areas and food canteens must be separated from patient ward areas to minimize flies in patient areas
• Maintaining basic personal and community hygiene and proper sanitation is highly important, particularly in the endemic zones
• Use insect repellents to prevent the insects from entering residences
• The growth of adult flies must be effectively controlled and methods for eradication followed on a regular basis

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

The prognosis of Wound Myiasis may vary from one individual to another depending on its severity.

• The prognosis can be good for mild cases and localized wounds with adequate treatment
• Extensive tissue destruction and delayed/inadequate treatment may result in severe complications that may even be fatal
• In some individuals, rupture of an abscess containing the larva may lead to a severe inflammatory response

Additional and Relevant Useful Information for Wound Myiasis:

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

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