The New World Screwworm threatens livestock in Sonora

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A screwworm larva grasps the flesh in a wound with its mouth's tusklike protrusions and screws itself in.

The United States’ suspension of live cattle imports from Mexico hit at the worst possible time for rancher Martín Ibarra Vargas, who, after two years of severe drought, had hoped to put his family on a better footing by selling his calves across the northern border.

Like his father and grandfather before him, Ibarra Vargas has raised cattle on the parched soil of Sonora, the state in northwestern Mexico that shares a long border with the United States, particularly Arizona. His family has faced punishing droughts before, but has never before had to contend with the economic hit of a new scourge: the New World Screwworm, a flesh-eating parasite.

U.S. agriculture officials halted live cattle crossing the border in July – the third suspension of the past eight months — due to concerns about the flesh-eating maggot, which has been found in southern Mexico and is creeping north.

The screwworm is a larva of the Cochliomyia hominivorax fly that can invade the tissues of any warm-blooded animal, including humans. The parasite enters animals’ skin, causing severe damage and lesions that can be fatal. Infected animals are a serious threat to herds.

The U.S. Department of Agriculture calls it a “devastating pest” and said in June that it poses a threat to “our livestock industry, our economy, and our food supply chain.” It has embarked on other steps to keep it out of the United States, which eradicated it decades ago.

As part of its strategy, the U.S. is preparing to breed billions of sterile flies and release them in Mexico and southern Texas. The aim is for the sterile males to mate with females in the wild who then produce no offspring.

The U.S. ban on live cattle also applies to horses and bison imports. It hit a ranching sector already weakened by drought, and specifically a cattle export business that generated $1.2 billion for Mexico last year. This year, Mexican ranchers have exported fewer than 200,000 head of cattle, which is less than half what they historically send in the same period.

For Ibarra Vargas, considered a comparatively small rancher by Sonora’s beef-centric standards, the inability to send his calves across the border has made him rethink everything.

The repeated bans on Mexican cows by U.S. authorities have pushed his family to branch into beekeeping, raising sheep and selling cow’s milk. What he earns is just a fraction of what he earned by exporting live cattle, but he is trying to hold on through the lean times.

“Tiempos de vacas flacas” — times of the lean cows — as he calls them.

“At least it lets us continue ranching, the 57-year-old said with a white cowboy hat perched on his head.

Click here to read the complete, original article by Fernando Llano and Fabiola Sánchez on AP

The Sonora Post