A dangerous parasite, the cattle screwworm, is creeping northward towards the US after being detected in Mexico, prompting concerns for the livestock industry and agriculture across North America. The larvae of this parasite, which feed on living flesh, have caused significant disruptions in livestock populations across Central America. Now, with reports of infections in Mexico and warnings from experts, efforts are underway to prevent a full-scale outbreak.

The Return of a Forgotten Threat

The screwworm, a flesh-eating parasite that feeds on cattle, has been absent from North America since the end of the 19th century. However, recent findings in southern Mexico have caused alarm, triggering the US to temporarily halt cattle imports from the country. The parasite, Cochliomyia hominivorax, thrives by feeding on open wounds in mammals, with cattle being its primary target. The larvae can cause severe, sometimes fatal, infestations. The larvae are known to burrow into the animal’s flesh, feeding on it until they mature into flies.

 A Growing Problem in Central America

This parasite has reemerged in Central America, with Costa Rica, Nicaragua, Honduras, and Guatemala all reporting outbreaks since 2023. Experts attribute much of the spread to the illegal movement of cattle through these countries. According to environmental crime coordinator Kurt Duchez of the Wildlife Conservation Society, illegal cattle trade is accelerating the parasite’s spread, with livestock often moved across borders by road and boat, bypassing official checks.

 Economic and Environmental Concerns

The reappearance of the screwworm in Mexico and its potential spread northward is a serious concern for the US livestock industry. Mexico’s cattle exports to the US are worth billions annually, and if the parasite becomes established in the region, it could devastate the industry. Control measures such as inspection stations and deworming programs are already in place, but experts warn that closing the border to illegal cattle trade is the only way to prevent further spread.

Protecting the Livestock Industry

Screwworm outbreaks lead to weakened cattle, which stop gaining weight and producing milk, resulting in additional costs for farmers. Recovery from infestations can take weeks, impacting productivity and profitability. Countries in Central America and Mexico are increasing surveillance, training workers to detect and treat infestations, and deploying dogs to sniff out worms in cattle. However, with the parasite’s rapid movement, more stringent measures are required to protect the region’s cattle industry from this growing threat.