United States Confirms First Human Case of New World Screwworm Infection

Health officials in the United States have confirmed the country’s first human case of infection by the New World screwworm, a parasitic insect whose larvae feed on living tissue. This rare occurrence in a human has drawn attention because the screwworm was eradicated from the U.S. decades ago. The individual reportedly contracted the infection during recent travel outside the country.

Understanding the New World Screwworm

The New World screwworm, scientifically named Cochliomyia hominivorax, is a fly whose maggots, or larvae, are obligate parasites. This means they must feed on the living flesh of warm-blooded animals to develop. While they commonly infest livestock such as cattle, goats, and sheep, they can, in unusual circumstances, infect humans. The larvae typically enter an animal or person through an open wound or a natural body opening, leading to a condition known as myiasis.

The parasitic larvae burrow into the tissue, causing significant damage as they feed. The name “screwworm” is derived from their segmented bodies, which give them a screw-like appearance. This parasite is known for its ability to cause severe economic losses in agriculture due to its impact on animal health.

A Significant Eradication Success and Re-emergence Concerns

The United States, along with Mexico and Central American countries, successfully eradicated the New World screwworm in the 1960s using a highly effective technique involving the release of sterile male flies. This method disrupted the parasite’s reproductive cycle, leading to its elimination from these regions. This achievement was a major public health and agricultural victory, safeguarding livestock and reducing disease risks.

Because of this historical eradication, any cases detected within the U.S. are considered imported, meaning the infection originated elsewhere. The current human case serves as a reminder of how international travel can introduce exotic diseases and parasites into areas where they are no longer endemic, necessitating ongoing vigilance from public health authorities and healthcare providers.

Travel-Related Infection and Symptoms

Reports indicate that the individual who contracted the infection had recently traveled to El Salvador, a country where the New World screwworm is still present. This connection highlights the importance of travel health precautions. Travelers visiting regions where such parasites are common are often advised to be mindful of open wounds and to seek medical advice for any unusual symptoms upon returning home.

Symptoms of a screwworm infection in humans can include a noticeable, painful lesion, swelling, and a discharge from the affected area. The larvae themselves might be visible within the wound. If left untreated, the infection can cause substantial tissue destruction and, in severe cases, may lead to more serious health complications. Prompt medical attention and the careful removal of the larvae by a healthcare professional are essential for effective treatment and recovery.

What happens next

U.S. health agencies are expected to continue monitoring the patient’s recovery and investigate the precise circumstances surrounding the infection to prevent potential further spread. Given that the New World screwworm is not endemic in the United States, this isolated human case is unlikely to pose a widespread public health threat. However, it will likely prompt renewed advisories for healthcare providers to consider rare parasitic infections when diagnosing illnesses in patients with a history of international travel. Public health information campaigns may also reinforce general recommendations for travelers to protect themselves from insect bites and to report any concerning symptoms after returning from affected regions.