What Is Myiasis?

Medically Reviewed by Stephanie S. Gardner, MD on June 09, 2024
5 min read

Parasites are organisms that live on other creatures and depend on the host organism for survival. Humans can become hosts to many parasitic creatures, including insect larvae. The resulting infections are uncomfortable and unpleasant. 

Myiasis is an infection with fly larvae. There are some species of flies that need living tissue to develop from eggs to fully grown insects. These flies lay eggs on mammals, including humans. The result is an infestation of maggots on the person.

This type of parasitic infection is not common in the United States. It happens more frequently in tropical areas such as Central America, South America, Africa, and the Caribbean Islands. Americans who travel to those areas, though, sometimes become infected while they are there.

Occasionally, there are incidents of people developing myiasis in the United States. It can happen when you have an open wound and don’t get proper care for it. Indigent people are often at risk for this type of infection.

Myiasis occurs when fly eggs hatch on a person and the larvae grow in their body. People cannot spread myiasis to other humans. If you have myiasis, there is no need to worry that you’ll cause other people in your household to develop a parasitic infection.

The symptoms of myiasis vary depending on the type of infection you have. 

Furuncular Myiasis

Some flies don’t lay eggs directly on humans. They lay them on other insects, including ticks and mosquitoes, or on objects like fabrics or furniture. When mosquitoes bite humans, or people touch infested objects, the eggs transfer to people’s skin.

The eggs hatch into larvae, which burrow under the skin and begin to mature. The result is a red bump or furuncle that looks like a bug bite or pimple. As the fly larvae get larger, the spot might itch or hurt. You might feel like there’s something moving under the skin. There will be an opening on top of the bump for the larvae to breathe. Eventually, the larvae use the opening to burrow back out and leave the host body.

Wound Myiasis 

People who have unprotected open wounds may be vulnerable to myiasis. Some fly species, such as green or black blowflies, lay eggs on dead or dying tissue, and they are attracted to open wounds. The larvae will move to healthy tissue as well and might infest eyes, ears, or mucosal membranes such as the nostrils.

People who are indigent or unable to care for themselves are vulnerable to this type of infection. If you have a wound, but you can’t clean and cover it, the injury can become infected or attract parasites.

Migratory Myiasis

Migratory myiasis is most common in animals like horses and cattle. The subtypes of fly that cause migratory myiasis don’t lay their eggs on humans. Instead, humans get infected through contact with infected animals.

The larvae from these flies burrow deep under the skin and create tunnels in the lower levels of the epidermis. They move around under the skin, leading to areas of irritation that are long and serpentine. They are usually very itchy and occasionally painful.

Intestinal Myiasis

In rare cases, you might eat something with fly eggs on it. If the eggs survive in the intestine, the larvae can mature. You might have symptoms including abdominal pain, vomiting, and diarrhea. You may be able to see the larvae in your stool after you defecate.

If you have furuncular or migratory myiasis, you should talk to your doctor. You will need to seek myiasis removal to clear the larvae from your skin. A doctor can use a topical anesthetic to numb the area and make a small incision where the larvae are. They may also prescribe an anti-parasitic drug such as ivermectin to clear the infestation.

To treat wound myiasis, doctors clean the wound carefully to remove any larvae. They may also remove any dead tissue to prevent infection or more tissue damage.

Intestinal myiasis may go away on its own or your doctor may prescribe anti-parasitic medicine.

After the removal of any type of fly larvae, your doctor will tell you how to keep the wound clean. Proper cleaning will prevent infection and recurrence of the myiasis.

If you are in an area where myiasis is common, you should take steps to prevent getting infected. 

Since biting insects can transfer fly eggs to humans, avoiding insect bites is important. Covering your skin with clothing will protect it from insect bites. Wear well-fitting socks when hiking outdoors to keep bugs away from your feet and ankles. Use insect repellant to discourage bugs from landing on you.

Use window screens and mosquito nets to protect yourself from insects that fly indoors. Using fans to keep air circulating may also help. Some studies find that mosquitos can’t fly well when they’re caught in a breeze, so fans help keep them away from people.

If you hang fabrics out to dry, iron them before using them. The heat from the iron can kill off any fly eggs on the fabric.

If you have an open wound, keep it clean and cover it with fresh dressings regularly. Your doctor can tell you how to avoid insects that might lay eggs in a wound.

There are times when fly larvae are beneficial. Doctors have found that “ maggot therapy” is an effective way of cleaning or debriding a wound. Larvae can cleanse wounds much more rapidly than conventional methods, which improves healing times and reduces the risk of certain infections.

If you have a wound with dead tissue that needs careful removal, your doctor might apply larvae to the site. They are often contained in a sealed bag, so you don’t see the process. The larvae feed on dead tissue and bacteria in the wound. The dressing will stay on for several days.

Maggot therapy is safe and effective. The type of larvae that doctors use won’t feed on healthy tissue, so there is no risk of damage to uninjured skin. Most people don’t experience any significant discomfort during the process.

If you suspect that you have myiasis, you should call your doctor. They can help you get rid of the infection and prevent any recurrence.