The US Department of Health and Human Services (HHS) confirmed the nation’s first human case of infection with the New World screwworm, a parasitic fly larva that consumes living tissue. The case was identified on August 14 in a patient who had recently returned to Maryland from a trip to El Salvador.
The parasite was detected following a joint investigation by the Maryland Department of Health and the US Centers for Disease Control and Prevention (CDC). This incident marks a significant and rare public health event within the continental United States.
Chronicle NG examines what to know about New World screwworm and the infection linked to the parasite.
WHAT IS THE NEW WORLD SCREWWORM?
New World screwworm, also known as Cochliomyia hominivorax, is a species of parasitic blowfly whose larvae (maggots) eat the living tissue of warm-blooded animals.
They infest a wide range of hosts, including livestock, pets, wildlife and, in rare cases, humans. According to the CDC, the species is typically found in South America and the Caribbean.
Screwworms cause a condition known as myiasis, which occurs when the larvae (maggots) invade the tissue or flesh of warm-blooded animals.
The CDC explains that screwworms are drawn to the smell of body fluids or natural openings such as the nose, umbilical cord of a newborn animal, or genitals. When a female screwworm locates a host, she typically lands on an open wound and deposits between 200 and 300 eggs.
When the eggs hatch, the maggots burrow deeper into the tissue, resulting in painful and often severe infestations.
SYMPTOMS OF INFECTION
New World Screwworm infestations are often extremely painful. Symptoms may include:
- Persistent skin lesions (wounds or sores) that fail to heal or worsen over time
- Painful open wounds
- Bleeding from affected areas
- A crawling sensation or movement of larvae within a wound, the nose, mouth, or eyes
- Visible maggots in or around open sores
- A foul-smelling discharge from the site of infestation
In some cases, fever may also develop due to secondary bacterial infection.
WHO IS AT RISK?
One might be at risk of screwworm infestation when:
- Travelling to areas where the flies are present
- Having an open wound from a scratch, insect bite, or surgery
- Living with a weakened immune system due to medications or conditions such as HIV or cancer treatment
- Sleeping outdoors
- Living or working near livestock or other warm-blooded animals in areas where the flies are present
- Having medical conditions that cause bleeding or open sores, such as skin or sinus cancer
PREVENTION
Preventing yourself from the screwworm is important to avoiding its infestation. To protect yourself from the infestation, ensure to:
- Prevent insect bites, especially when visiting tropical areas or spending time outdoors.
- Keep open wounds clean and properly covered.
- Wear loose-fitting, long-sleeved shirts, long pants, and socks to reduce skin exposure.
- Apply insect repellent to exposed skin.
- Treat clothing and gear with products containing 0.5% permethrin.
- Sleep indoors or in well-screened rooms.
TREATMENT
Screwworm myiasis can only be treated surgically, as there is no drug-only cure at the moment.
If you notice maggots in or on a wound or any other part of your body, it is important to seek medical attention immediately.
The usual treatment involves carefully removing the larvae through surgery, after which a pesticide or larvicide is applied to ensure no larvae remain. If the wound has become infected, antibiotics are also prescribed. The removed larvae are destroyed to prevent further spread of the infestation.
It is strongly advised not to attempt removing or disposing of the maggots yourself, whether in humans or animals, as doing so can worsen the condition and increase the risk of complications.
