Get prevention, detection, and treatment tips for endemic regions.
Health officials in the United States have confirmed the first case of screwworm infestation to be observed in the country.
The U.S. Centers for Disease Control (CDC), in conjunction with the Maryland Department of Health, confirmed the case in early August in a patient who had recently returned from El Salvador. A CDC spokesperson characterized the risk to public health in the United States as very low. Maryland health officials have noted that the patient—a Maryland resident—has since recovered.
Officials also noted that the screwworm is a flesh-eating parasite infestation, rather than a virus or bacteria, so controlling cases is relatively easy, but screwworm infestations that are left unchecked can grow large and ultimately be fatal.
The screwworm infestation comes from a female fly that lays its eggs in an open wound of a live human or other warm-blooded animal. Wounds as small as a tick wound, or other bodily openings such as nasal or eye openings, healing umbilical scars of newborns, genitalia, or other open wounds can attract the female flies, which can lay up to 3,000 eggs.
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People most at risk are those who work near or with livestock, and vulnerable populations such as the elderly, immunocompromised, or malnourished.
The CDC advises doctors to inform patients to beware when traveling to endemic regions for screwworms, which currently includes parts of Central and South America and the Caribbean. Travelers bound for those regions should be careful not to sleep outside in rural areas where livestock are housed. The risk to travelers bound for outbreak areas, but visiting or staying near cities, beaches, or resort areas well-removed from farms, is not currently a significant risk for screwworm.
Travelers who will be visiting or staying in remote areas should be careful to cover open wounds, wear loose-fitting and long-sleeved shorts, long-sleeved pants, and socks. The CDC also notes that the infestations are very painful, and that travelers who suspect they may have been infected should seek medical care immediately.
Treatments can be time-consuming and involve physically removing all the larvae from the open wound, depositing them into an ethanol solution, which will kill and preserve them so they can be tested to confirm their identity. The CDC advises doctors with patients who present with a screwworm infestation to notify their state health regulators.
There is no medication or vaccine that can prevent a screwworm infestation—the CDC notes that preventing and speedy treatment are key to keeping infestations from spreading.
Travelers bound for destinations with outbreaks or infestations can review the risks and current threat levels at the CDC website. The site also includes information about which countries or destinations have specific vaccination recommendations or entry requirements (which are generally enforced by local health authorities). The CDC also publishes a list of travel health notices, outlining which precautions travelers should take for a number of countries around the world.
There are four levels of Travel Health Notice. The CDC currently ranks no destination higher than the second level of health notice, meaning that there are no destinations abroad to which the agency recommends reconsidering or avoiding travel on the basis of a health-related threat.
Domestic travelers in the United States can largely visit farms or interact with livestock without fear of contracting screwworm, as the parasite is not considered endemic in U.S. livestock populations.