Myiasis is an infection caused by the infestation of fly larvae, such as the screw-worm fly or the human botfly. It can lead to symptoms like red nodules on the skin, open wounds, pus, and a foul odor.

The larvae usually enter the body through skin wounds or natural openings, and the condition is more common in tropical regions with poor hygiene.

Treatment for human myiasis must be done by a doctor and often involves manually removing the larvae with tweezers. In some cases, oral ivermectin, pain relievers, or surgery may also be recommended.

Main symptoms

The main symptoms of myiasis include:

Red nodule on the skin
Boil-like lesions
Zig-zag red lines on the skin
Painful skin wounds
Pus and foul odor from the wound
Stinging, pinching, or movement sensation in the lesion
Fever and chills
Swollen lymph nodes

Depending on the location of the myiasis, other symptoms may occur, such as painful urination, nosebleeds, headaches, facial pain, diarrhea, abdominal pain, tearing, eyelid swelling, and general discomfort.

How to confirm the diagnosis

A dermatologist or general practitioner can diagnose myiasis by examining the lesion and evaluating the symptoms. Additional tests may include dermatoscopy, skin biopsy, or ultrasound.

Immersing the lesion in water may also help confirm the diagnosis, as live larvae release bubbles when submerged.

Types of myiasis

1. Auricular myiasis

Auricular myiasis is rare in adults but more common in children. It occurs when flies deposit larvae in the ear, often associated with conditions such as ear infections, tumors, skin lesions, poor living conditions, or poor hygiene. Symptoms include severe ear pain and the sensation of movement inside the ear.

2. Cutaneous myiasis

Cutaneous myiasis occurs when flies lay eggs on the skin. It can present in different ways:

Furuncular cutaneous myiasis, usually caused by the human botfly (Dermatobia hominis) or the tumbu fly (Cordylobia anthropophaga), which leads to boil-like lesions anywhere on the body
Migratory or subcutaneous myiasis, often caused by the tumbu fly or the screw-worm fly (Cochliomyia hominivorax), in which the larvae move under the skin and feed on fat or muscle tissue

Another form is wound myiasis, which happens when larvae infest open wounds. The mouth, nose, ears, eyes, and genitals can also be affected.

3. Oral myiasis

Oral myiasis is rare but may occur in periodontal pockets, tooth extraction wounds, or other open sores in the mouth. Poor oral hygiene is usually the main cause. Symptoms include pain in the jaw or facial muscles, fever, foul odor, swelling, redness, and difficulty eating or speaking.

4. Ophthalmic myiasis

Ophthalmic myiasis happens when larvae infest the eye. This is a rare condition, usually caused by direct contact with flies or contaminated hands. Symptoms include eye pain, itching, redness, eyelid swelling, sensation of movement in the eye, and bleeding with or without mucus.

5. Nasal myiasis

Nasal myiasis is rare and typically affects people with poor hygiene or chronic nasal conditions. Symptoms may include nosebleeds, local irritation and itching, sneezing, headaches, foul odor, and a sensation of a foreign body inside the nose.

If untreated, nasal myiasis can spread and lead to complications such as meningitis, orbital cellulitis, facial cellulitis, and even death.

6. Urogenital myiasis

Urogenital myiasis is very rare and may affect the vagina, penis, urethra, or bladder. It can cause pain in the side of the abdomen (between the ribs and hip), painful urination, frequent urination, itching, and lesions.

Risk factors include poor sanitation, inadequate hygiene, limited mobility, poor mental or physical health, the presence of stents, and sexually transmitted infections.

7. Intestinal myiasis

Intestinal myiasis develops when contaminated food containing fly eggs or larvae is ingested. Symptoms include vomiting, abdominal pain, and diarrhea.

Possible causes

Myiasis occurs when fly larvae are deposited on or near wounds, or in openings such as the nose, mouth, or ears. Flies can also lay eggs on the ground, clothing, or bedding. When in contact with these items, a person may become infected.

Larvae may also be transmitted by mosquitoes or ticks. When these insects bite, they can deposit fly larvae into the skin.

Myiasis does not spread from person to person.

Treatment for myiasis

Treatment for myiasis may involve:

Applying petroleum jelly, lidocaine, or another cream over the lesion to suffocate the larvae, making removal with tweezers easier for the doctor
Using oral or topical ivermectin to eliminate remaining larvae and reduce the risk of infection
Surgery to remove larvae or reconstruct damaged skin if needed
Pain relievers such as ibuprofen or diclofenac sodium, prescribed by the doctor
Chlorhexidine 0.2% mouth rinses for one to two weeks in cases of oral myiasis, to maintain hygiene and prevent infection

How to prevent myiasis

Prevention measures include:

Bathing daily with soap and water
Wearing clean clothes and ironing them with heat before use
Keeping wounds and scratches clean, disinfected, and covered
Changing dressings daily
Avoiding exposure to flies and mosquitoes by using repellents, insecticides, mosquito nets, and proper waste disposal

Myiasis: Symptoms, Types, Causes, Treatment & Prevention