First Human Case of Screw-Worm Infection Found in Mexico’s Yucatan Peninsula

Mexico has reported its first human case of New World screwworm infestation (NWS), also known as myiasis, involving the larvae of the Cochliomyia hominivorax fly. This case was identified in a woman from Campeche, a state bordering Yucatán. The initial detection of NWS in livestock occurred in the southern state of Chiapas, near the Guatemalan border, in November 2024 and authorities have been on high alert since then.

Primary Areas of Concern:

The rapid northward spread of NWS has raised significant concerns across several regions:​

• Southern Mexico: States such as Chiapas, Campeche, and Yucatán are at heightened risk due to recent detections in both livestock and humans.​
• Central America: Countries including Costa Rica, Nicaragua, Honduras, Guatemala, Belize, and El Salvador have reported NWS cases, indicating a broad regional spread. ​
• United States: There is an increased vigilance in the U.S., particularly in border states like Texas, to prevent potential incursions of NWS. ​

Facts About the Disease:

NWS is caused by the larvae of the Cochliomyia hominivorax fly, which infest living tissue of warm-blooded animals, including humans. Unlike typical maggots that feed on dead tissue, NWS larvae consume healthy flesh, leading to severe tissue damage and potentially fatal outcomes if untreated. The female fly lays eggs in open wounds or mucous membranes; upon hatching, the larvae burrow deeper into the flesh, exacerbating the wound and causing significant tissue damage. ​

Detection and Treatment:

Early detection is crucial. Signs include:​

• In Animals: Discomfort, irritated behavior, head shaking, isolation from other animals, and visible larvae in wounds.​
• In Humans: Pain, discomfort, and visible larvae in the affected area.​

Treatment involves the physical removal of larvae from the infested tissue, followed by thorough cleaning and application of appropriate medications to prevent secondary infections. Prompt medical or veterinary attention is essential to manage the infestation effectively. ​

Preventive Measures:

In response to the recent detections, Mexican authorities, in collaboration with international partners, have implemented several measures:​

• Public Awareness: Educating the public, livestock owners, and veterinarians about the importance of monitoring and promptly treating any wounds in humans or animals to prevent NWS infestation.​
• Surveillance and Reporting: Enhanced surveillance systems have been established to detect new cases quickly. Authorities are urging the immediate reporting of suspicious wounds or infestations to contain potential outbreaks.​
• Sterile Insect Technique (SIT): Mexico is collaborating with international partners to implement the SIT, which involves releasing sterile male flies to disrupt the breeding cycle of the NWS population, thereby reducing their numbers over time. ​

These proactive measures aim to control the spread of NWS and protect both public health and the livestock industry from this parasitic threat.