New World screwworm: The deadly flesh-eating parasite spreading throughout Central America

By zoeysky // 2025-01-02

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A flesh-eating parasite, the New World screwworm (Cochliomyia hominivorax), is spreading across Central America, posing a growing threat to both livestock and human health.
The screwworm primarily targets livestock but also infects humans, causing a condition called myiasis. The larvae burrow into open wounds, feeding on living tissue, causing excruciating pain, infection and, in severe cases, death.
Vulnerable groups include rural residents working with livestock, outdoor workers and travelers to affected regions. Open wounds, cuts, insect bites or conditions like skin cancer or sinus infections can attract the flies.
Prevention measures include keeping wounds clean and covered, using insect repellents and taking precautions like wearing protective clothing and sleeping in screened areas.
The U.S. Department of Agriculture (USDA) has imposed restrictions on livestock imports from Mexico to prevent the parasite from entering the United States.

A terrifying flesh-eating parasite is on the rise in Central America, and it’s not just livestock that's at risk. The New World screwworm, a relentless and invasive fly species, is spreading its larvae into the wounds of both animals and humans, causing a condition known as myiasis that can be deadly if left untreated. While the parasite has long been a scourge for farmers and their herds, recent outbreaks suggest it’s now a growing threat to human health as well. The New World screwworm (Cochliomyia hominivorax) is no ordinary pest. It thrives in open wounds, laying hundreds of eggs that hatch into ravenous larvae. These larvae burrow into the flesh, feeding on living tissue and causing excruciating pain, infection and, in severe cases, even death. For decades, the parasite was thought to be under control, but recent data shows a troubling resurgence across Central America, with cases spreading north from Panama to Mexico. The New World screwworm has a long and destructive history. In the 1930s and 1950s, it wreaked havoc on livestock in the southern U.S., costing farmers an estimated $100 million annually. The parasite was so devastating that it prompted a massive eradication effort, culminating in the mid-1960s in the creation of a barrier zone along the U.S.-Mexico border to prevent its spread. By 1986, the parasite had been largely eradicated in Mexico, and for years, it seemed that the dangerous threat was contained to South America and the Caribbean. But in 2023, the screwworm began to show signs of a comeback. U.S. officials now warn that the parasite is spreading north, with cases reported in Panama, Costa Rica, Nicaragua, Honduras, Guatemala and most recently, Mexico. The situation has become so dire that the U.S. Department of Agriculture (USDA) has imposed restrictions on the import of livestock from Mexico, fearing the parasite could cross into America.

A growing threat to human health

While the screwworm primarily targets livestock, it’s also known to infect humans. The condition, called New World screwworm myiasis, is not only painful but also potentially fatal. There is no known treatment for the infection in humans, leaving victims with only one option: physically removing the larvae from the infected tissue. This gruesome process often requires surgery and leaves victims vulnerable to further complications, including secondary infections. (Related: Merritt Medical Hour: PARASITES and TOXINS are often the root cause of disease – Brighteon.TV.) In Costa Rica, the resurgence of the screwworm has already claimed at least one human life early in 2024. The victim, whose case was confirmed by the U.S. Embassy in Costa Rica, highlights the parasite’s ability to leap from animals to humans, especially in rural areas where people work closely with livestock. The screwworm’s life cycle is both fascinating and horrifying. Adult female flies are drawn to the smell of blood and open wounds, laying up to 300 eggs at a time. Over the course of their 10- to 30-day lifespan, these flies can deposit thousands of eggs in wounds as small as a tick bite. Once the eggs hatch, the larvae waste no time burrowing into the flesh, where they feed on living tissue with their sharp, hooked mouths. The larvae’s feeding causes the wound to grow deeper and larger, leaving the host in excruciating pain. Over time, the larvae drop to the ground, burrow into the soil and emerge as adult flies to continue the cycle. The entire process is not only gruesome but also highly efficient, allowing the parasite to spread rapidly. Anyone with an open wound is at risk of screwworm infestation, but certain individuals are particularly vulnerable. People living in rural areas, especially those who work with livestock or spend time outdoors, are at the highest risk. Open wounds from cuts, insect bites or recent surgeries can all attract the flies, as can conditions that cause bleeding or open sores, such as skin cancer or sinus infections. Even travelers to affected regions are not immune. Those who visit South America, the Caribbean or Central America and spend time outdoors with open wounds are at risk of contracting the parasite. The Centers for Disease Control and Prevention (CDC) warns that sleeping outdoors or in areas without proper screening can increase the likelihood of exposure.

The painful reality of myiasis

Screwworm infestations are not just a medical emergency — they’re a nightmare. The larvae’s feeding causes intense pain, and the wounds they create are often deep and difficult to heal. Symptoms of myiasis include:

Bleeding
A foul odor emanating from the infected area
Unexplained skin lesions
Worsening sores

In some cases, the larvae can infest areas like the nose, mouth or eyes, causing additional complications. Secondary bacterial infections are common, leading to fever, chills and other systemic symptoms. Without prompt treatment, the condition can be fatal. Given the lack of a specific treatment for screwworm myiasis, prevention is the best defense. The CDC recommends keeping open wounds clean and covered, especially when in contact with livestock or wild animals. Using insect repellents registered with the Environmental Protection Agency (EPA) can also help reduce the risk of infestation. For those traveling to affected regions, taking extra precautions is essential. Wearing long sleeves, pants and socks can limit exposed skin, while treating clothing with insect repellents can provide additional protection. Sleeping indoors or in screened areas can also reduce the risk of exposure. The resurgence of the New World screwworm has prompted a coordinated response from governments and international organizations. The USDA’s Animal and Plant Health Inspection Service (APHIS) is working to prevent the parasite from crossing into the U.S., while agencies in Central America are stepping up surveillance and control efforts. In Panama, where the outbreak has been particularly severe, the Panama and United States Commission for the Eradication and Prevention of Livestock Screwworm (COPEG) has reported a staggering increase in cases, from an average of 25 per year before 2023 to over 22,000 as of December 2024. The scale of the outbreak underscores the urgent need for action. Outbreak.news has more stories like this. Watch the video below to learn about other common signs and symptoms that you have parasites. This video is from the Sun Fruit Dan channel on Brighteon.com.

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