Two new cases of deadly screwworm parasite detected in U.S.

Cattle in a stable in Hamilton, Texas. Three of the four cases of New World screwworm found in the U.S. were identified in Texas cattle. Photo by Brandon Bell /Photographer: Brandon Bell/Getty

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The U.S. Department of Agriculture confirmed an additional two cases of New World screwworm, bringing the total number of detections in the U.S. to four and raising concerns over a broader spread of the parasite.

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The fly was detected in a calf in La Salle County, Texas, and a dog in New Mexico, the agency said in a Monday release. That comes after two cases were confirmed last week in calves in Zavala County in South Texas, marking the first U.S. detection of the fly in over a decade, and the first in cattle in about five decades.

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The latest detection in La Salle County is close to Zavala, where the past two cattle cases were confirmed. But the confirmation of screwworm in the dog places the pest far outside that region and across state lines. The animal had initially been linked to Andrews County in Texas because it was reported by a veterinarian in the state, but the dog’s home is in Lea County, New Mexico, the USDA clarified later Monday.

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While that is “believed to be an isolated case,” the USDA and state partners are inspecting additional animals in the dog’s home and increasing outreach in the area “because the dog’s recent travel and exposure history remain unknown,” the agency said. The USDA said earlier that the dog was believed to be in Mexico recently.

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Agriculture Secretary Brooke Rollins, speaking on CNBC on Monday, said the U.S. is “going to do everything we can, investing over US$1 billion” to push the New World screwworm out of the country.

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The spread risks more cautionary measures to limit cattle movement. Georgia’s Agriculture Department said last Friday that it would restrict the movement of both livestock and pets into the state from a dozen Texas counties, while Canada is blocking the transit of livestock that has been in Texas within a three-week window.

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That adds more worries for a U.S. beef industry already struggling with supply tightness as the domestic herd has dwindled to a 75-year low.

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The detection of screwworm is probably going to further delay any efforts to expand the U.S. herd, said Glynn Tonsor, a professor of agricultural economics at Kansas State University. Tonsor said he was “pretty vocal” late last year that more ranchers would start the process of expansion this summer, but increased dryness — and now screwworm — are creating more uncertainty, he added.

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Tighter cattle supplies, even if limited to Texas alone, would also continue to pressure beef processing plants that have already been operating at losses due to the cattle shortage. Companies including Tyson Foods Inc. and JBS NV have resorted to closing plants amid high cattle prices.

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Feeder cattle futures in Chicago are up about two per cent since last Wednesday, when the first Texas case was reported but not yet confirmed. Tyson shares were down as much as 2.3 per cent on Monday, while JBS slumped as much as 6.1 per cent to the lowest price since U.S. trading began a little over a year ago.