Wormwood first detected in Arizona during outbreak

(Bloomberg) — A New World hookworm first found in Arizona has been found in a dog as cases of the deadly parasite accelerate.

Late Wednesday, the U.S. Department of Agriculture confirmed the infection in a dog in Cochise County, Arizona.

The spread of the parasitic fly, whose larvae burrow into animal wounds, has remained relatively contained since the pest was first detected in the US in June. Most of the early cases were confined to Texas. But the pace of infections has picked up this month, especially in New Mexico.

According to the USDA, there have been a total of 71 cases of helix in the U.S. since the outbreak began. Eighteen are still active, 10 of which are located in New Mexico.

The increase in October comes after a roundworm, which can be fatal to livestock if left untreated, was discovered in the wild for the first time last week. Spread among wildlife is a major concern for cattle ranchers because the animals travel over the same terrain that their herds graze on.

The expansion also comes as the USDA reopened ports in Arizona and New Mexico to shipments of cattle from Mexico. The US halted cattle shipments from the country and largely maintained the ban until late August, when it began a phased reopening of ports.

The US had previously eradicated the helix, pushing the pests south of Panama. But the fly began to spread northward again after the pandemic, arriving in Mexico in late 2024.

While the helix is the main threat to U.S. cattle herds, the parasite has also infected animals from goats to horses. The last five cases involved four dogs and one cat.

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