Second Screwworm Infection Found in Chiapas Patient

Chiapas, Mexico — The Mexican Ministry of Health has confirmed the second human case of myiasis caused by Cochliomyia hominivorax, commonly known as the New World screwworm fly, in the state of Chiapas. This new case follows the first reported between April 15 and 25, 2025, according to the Epidemiological Bulletin for Week 17.

Details of the Second Case

The second patient is a 50-year-old man from the municipality of Tuzantán. He developed symptoms after being bitten by a dog. The wound progressed to the point of larval emergence, accompanied by pain and fever, prompting medical attention on April 25.

The case was confirmed by the National Service for Agrifood Health, Safety, and Quality (Senasica), which identified the presence of C. hominivorax larvae. Samples were sent to the State Public Health Laboratory for taxonomic analysis. The patient was transferred to the General Hospital of Huixtla for surgical wound cleaning.

First Reported Case

The first confirmed case involved a 77-year-old woman from Acacoyagua, Chiapas. The patient had a history of untreated diabetes mellitus and lived with farm animals. According to the Ministry of Health, the animals she had contact with—a goat and a calf—had shown signs of screwworm infestation weeks earlier.

On April 13, a surgical cleaning was performed on a wound in her right parietal region, where larvae were found. Senasica confirmed the diagnosis on April 17. The patient was transferred to the “Ciudad Salud” Regional High Specialty Hospital, where she was reported in stable condition.

Understanding Screwworm Myiasis

Miasis is an infestation caused by fly larvae that affect living tissue. In the case of screwworm, C. hominivorax larvae feed on open wounds, causing progressive tissue damage. While more common in livestock such as cattle, pigs, and horses, it can also infect humans, particularly those with untreated wounds or compromised immune systems.

Health Authority Recommendations

The Ministry of Health has issued the following guidelines for suspected cases:

• Immediate identification and cleaning of infested wounds.
• Notification to health authorities within the first 24 hours.
• Collection of at least 10 larvae for analysis.
• Submission of samples to the Institute for Epidemiological Diagnosis and Reference (INDRE) under established protocols.

Suspected cases should be reported to: miasisgbg.humano@salud.gob.mx.

Current Situation in Mexico

These are the first confirmed human cases in Mexico for 2025. Senasica had previously warned of the pest’s presence in livestock in prior years. Entomological surveillance and prompt reporting remain critical to preventing further spread.