Myiasis

What is Myiasis?

Myiasis is the invasion of the skin by fly larvae. The larvae feed on the human beings and other vertebrae tissues causing myiasis. This disease is characterized by skin lesions, which are painful and itchy and has organisms inside1, 2.

Myiasis

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Myiasis occurs in hot and humid places especially in the tropics and subtropics regions. It also affects all people irrespective of age.

Types of Myiasis

Myiasis is classified basing on the place the fly larva has infested and how the parasite and host relate.5

Myiasis classified according to the place infestation includes the following:

Cutaneous Myiasis

This is a type of myiasis affecting the skin. There are various types of cutaneous myiasis caused by different species of fly larvae. They include:

Furuncular Myiasis

This disease occurs mostly in sub-Saharan Africa. It is caused by Cordylobia anthropophagi (tumbu fly). This fly likes shade and is active in the morning and afternoon. It is attracted to the odor of urine and feces. The female fly lay eggs on dump clothes hang outside to dry and on dry sand. These eggs hatch and the larvae can penetrate your skin when you wear clothes hanged outside to dry.

Wound myiasis

People get this type of myiasis when they are resting outside as wind disperses flies which get attached to your body. You can also get wound myiasis from trauma or injury on your body.

Nosopharyngeal Myiasis – It affects the sinuses, pharynx and nose.

Opthalmomyiasis – It affects the eyes, periorbital tissues and orbit.

Intestinal myiasis– This type of myiasis occurs in the digestive tract.

Auricular Myiasis– it affects the ears.

Hematophagus Myiasis– it is uncommon type myiasis which affects infants less than nine months.

Myiasis is also classified basing on how the parasite and host relate. They include:

Facultative or accidental myiasis– This type of myiasis occurs when you accidentally swallow food with larvae and eggs.

Causes of Myiasis

Myiasis in human beings is caused by human botfly and tumbu fly. The larvae can go inside the host body through the following ways:

  • The larva can go inside the body through wounds or lesions on the skin.
  • The larva can be swallowed with food and reach the intestine and stomach and cause Intestinal myiasis or Gastric.
  • The larvae can enter the body through the nose and ears.
  • The eggs of the fly can affix on the clothes left outside and then penetrate your body when you wear them or use the towel.
  • The eggs can also append on the body of the female mosquito and penetrate your body when the mosquito feeds on your blood.

Risk factors of Myiasis

There are several factors that may trigger myiasis. They include:1, 2, 5

  • Children who live near or swim in stagnant water are at risk of getting this disease.
  • Myiasis attack occurs during summer and spring.
  • Those people who like traveling to subtropical and tropical regions such as Africa, South America, and Central America are vulnerable to myiasis.
  • Those who look after animals (goats, cattle) are vulnerable to myiasis because these animals carry flies that cause this disease.
  • People living in paces with poor sanitation and hygiene are susceptible to myiasis.
  • Those who are diabetic and take alcohol are also at risk of myiasis
  • Those who are elderly are at risk of myiasis.
  • Those people who leave their wound untreated for a long time and open are vulnerable to wound myiasis.

Symptoms of Myiasis

The symptoms of myiasis depend on the place of the infestation on the body. These symptoms include:3

  • Symptoms of Cutaneous Myiasis include: You develop boils and sores on your skin which may last for a long time. You also have ulcers that develop slowly in your body but not painful.
  • For nasal myiasis: Your face may swell, a condition known as facial edema. You may develop fever and feel irritation in your nose. In some cases, your nose is congested and gets blocked.
  • Symptoms of Opthalmomyiasis myiasis include your eyes may become red and swollen and also experience painful irritation.
  • For Aural Myiasis, symptoms include having difficulties in hearing. You may experience swarming sensation in affected area and buzzing noises.

Diagnosis of Myiasis

Several clinical methods can be used to diagnose Myiasis. They include:1

Physical exam

Your doctor evaluates your health history and also finds out whether you have recently visited tropical and subtropical regions. Your doctor would also check your levels of hygiene and sanitation so as to have information to help in conducting further tests.

Blood tests

Your doctor would take a sample of your blood and analyze it to determine components in your blood. If the test results show an increase or decrease in cell count, it may indicate that you have infection and your doctor would perform further evaluation to determine the type of infection.

Ultrasound

Your doctor can use ultrasound technique to determine the extent of the larva in the affected area and help the doctor to eliminate the larva safely.

Magnetic Resonance Imaging (MRI) scan

If your doctor suspects that larva have reached your brain, an MRI scan would be performed to locate the larva in the brain cells.

Biopsy

Your doctor will perform a biopsy by removing a sample of the tissue from your wound and analyzed in the laboratory.

Complications of Myiasis

Myiasis may cause undesirable effects such as2

  • Allergies. You may have allergies when larvae are not detached properly from the body.
  • Meningitis. When the larva reaches the brain, it attacks the meninges in the brain causing inflammation which leads to meningitis.
  • The larva obtains its food on the mucous membrane and as a result it can result in erosion of your eyes, face and nose.
  • It can also lead to pus infection in the affected areas.
  • It may also lead to death if not treated early.

Treatment of Myiasis

Myiasis can be managed through the following treatment options:2, 5

Occlusive and Suffocation methods

In these techniques, your doctor applies liquid paraffin or petroleum jelly on the affected area on your skin. This prevents oxygen from reaching the larva and as a result, the larva would get out of the body by itself.

Surgery

Your doctor may also opt for surgery intervention to remove the fly larvae from the affected area.

Medication

Your doctor may prescribe specific medication depending the form of myiasis. The drugs recommended include drug ivermectin to treat orbital and oral myiasis.

Prevention of Myiasis

Myiasis can be prevented when through the following:4

  • Use insect repellent to prevent insects from moving inside the house.
  • Spray around the affected area using insecticides that has organophosphorus to destroy larvae.
  • Use mosquito nets and wind screens to prevent insect from moving inside the house.
  • If you have a wound, always cover it with a bandage to protect yourself from infection.
  • Iron clothing that are hanged outside before putting them on to kill any insect affixed on them
  • Maintain high levels of hygiene: wash clothes regularly and wash hands properly before you eat and after you have finished eating; dry clothes under the direct sun.

Pictures

buccal myiasis

Buccal or oral Myiasis

Cutaneous Myiasis

Cutaneous Myiasis

Nasal Myiasis

Nasal Myiasis

Ocular myiasis

Ocular Myiasis with Conjunctivitis, Ocular Discharge

Ocular myiasis 2

Occular Myiasis

nasocomial myiasis 2

Nasocomial Myiasis

Reference List

  1. Myiasis. http://emedicine.medscape.com/article/1491170-overview#a4
  2. Myiasis. http://www.dovemed.com/diseases-conditions/myiasis/
  3. Cutaneous myiasis. https://www.dermnetnz.org/topics/cutaneous-myiasis
  4. Myiasis. https://web.stanford.edu/group/parasites/ParaSites2001/myiasisBLOCKED/Anna%20West’s%20Myiasis%20Page.htm
  5. Myiasis. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3255963/

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