Myiasis is an infection from an open wound or sore that is infected with fly larvae, where the invaders feed on the host’s living or dead tissue. While uncommon in the United States, it does occur in [tropical and subtropical countries and the impact varies depending on the type and extent of the infection. It is the fourth most common skin disease related to travel.
Myiasis typically occurs when flies lay eggs in an open wound or sore. When these eggs hatch, the larvae burrow into the skin, causing an infection. Another method for contraction is when flies attach eggs to biting pest,s such as ticks or mosquitoes. The eggs are then released onto the skin of the tick’s victim, and the larvae use the bite spots as an entrance to the body.
Signs and Symptoms
The most common sign of myiasis is a growing lump or boil under the skin. This is caused by the growing larvae. The lump may also move as the larvae do. Other symptoms include itching, pain, or a prickly heath sensation. Symptoms of myiasis tend to occur within two days of the infestation.
If you think you have contracted myiasis, contact your doctor immediately for diagnosis and treatment. To treat myiasis, the larvae need to be surgically removed and the area cleaned daily. On occasion, patients will be instructed to take medication to prevent ongoing or secondary infection. Treatments vary depending on the type of larvae.
One specific type of myiasis, chrysomya bezziana (caused by the old world screw-worm fly), has been a focus for research due to the impact it has on morbidity rates in animals and people, as well as the economic losses, in countries such as Africa, the Indian subcontinent, and East and Southeast Asia. Research shows that patients tend to be from poor socio-economic regions without sufficient access to clean water and other hygiene products or have age-related diseases.
With prompt medical treatment, myiasis should clear completely without leaving scarring or marks. On occasion, minor scars or pigmentation remains after surgical treatment, but this is rare. Recovery time depends on the type of infection and how deeply burrowed the larvae were. It can range from one to two months in typical cases.
There are several subtypes of myiasis based on the location of the infection and the host/insect relationship. These include
- Cutaneous (skin)
- Nasopharyngeal (nose, sinus, pharynx)
- Opthalmomyiasis (eyes)
- Intestinal, gastric, or rectal (digestive system)
- Urogenital (urinary tract, genitals)
- Auricular (ears)
- Hematophagus (lesions on face)
Relationship-based myiasis includes:
- Obligatory (parasite requires a living host to complete life cycle)
- Facultative, incidental, or accidental (parasite accidentally invades host)
While myiasis is highly treatable, there are some potential complications of an infection These include allergic reactions in addition to the infection, meningitis (inflammation of fluid surrounding the brain), erosion of infected organs, a secondary pus infection, and death if treatment is delayed. The best way to avoid these complications is to have suspicious bites or wounds checked by a physician as soon as possible.
The most common risk factor for myiasis is travel to a tropical area. Other possible factors include
- Advanced age
- Poor hygiene or unhygienic living conditions
- Vascular disease
- Travel during rainy seasons (increased mosquito presence)
- Open wounds or sores
Because myiasis is considered a travel-related disease, it is important to take extra precautions when visiting infection hotspots. If you are traveling to a tropical country, be sure to cover your skin to reduce the risk of bites, and use insect repellent regularly. At night, use a mosquito net and ensure window screens are in place. When hanging clothes to dry, iron with high heat to eliminate potential predators.
Luckily, myiasis is not contagious. Because it travels strictly via bugs and flies, it can’t be transferred from person to person.