A significant rise in cases of flesh-eating screwworm has been reported in Mexico, with the country’s government data indicating a 53% increase in the past month.
The parasite, which primarily affects cattle and other animals, has been spreading northwards towards the United States border, posing a substantial threat to the livestock industry and the economy.
According to the Mexican government, there were 5,086 cases of screwworm reported as of August 17, including 649 active cases.
The screwworm infestation has already disrupted Mexican cattle exports, with losses valued at $1.3 billion over the past year, according to the Mexican National Agricultural Council.
The US Department of Agriculture (USDA) has warned that if left unchecked, screwworm threatens $100 billion in economic activity linked to the cattle and livestock industries.
“The risk to human health in the United States remains very low, but the potential future threat to animal populations and the food supply chain requires proactive action,” the US Department of Health and Human Services (HHS) said.
Screwworm infestations begin with parasitic flies laying their eggs in warm-blooded animals. The eggs hatch into larvae, which burrow into the flesh of their host, killing them if left untreated.
Infections are challenging to treat, and preventing future outbreaks is also difficult. To combat the spread of screwworm, the Mexican and US governments are building “sterile fly” production facilities in the states of Chiapas and Texas.
These facilities will produce a large number of male flies, sterilize them, and release them to mate with females in the wild, reducing the wild population over time.
The two facilities, along with another in Panama, will need to produce about 500 million sterile flies a week to push screw flies back to South America, where the parasite is endemic, according to the USDA.
HHS has also approved emergency veterinary drugs to prevent the parasite from spreading. These include “animal drug products that may be approved for other purposes, or available in other countries, but not formally approved” for the screwworm.
The screwworm parasite has been found primarily in cattle, as well as in horses, sheep, and dogs. There have also been dozens of human infections reported, with 41 cases confirmed in Mexico over the past year, primarily in the state of Chiapas.
The first human case was confirmed in the US state of Maryland on August 4 in a patient who had traveled to El Salvador. Mexico and the US had previously eradicated screwworm decades ago, but the parasite returned around 2023 after moving northward from Central America.
The Mexican government has been working to contain the outbreak, but the situation remains concerning. The US has closed its ports of entry to Mexican cattle for fear of the parasitic, flesh-eating worm spreading north. Mexico’s President Claudia Sheinbaum has criticized the US response as “exaggerated.”
However, the US government has taken steps to prevent the spread of the parasite, including approving emergency veterinary drugs and building sterile fly production facilities.
The screwworm infestation highlights the need for continued cooperation between Mexico and the US to address the issue. The two countries have a significant economic relationship, and the spread of the parasite could have substantial implications for trade and the economy.
As the situation continues to evolve, it remains to be seen how the governments of Mexico and the US will work together to contain the outbreak and prevent further spread of the parasite.