Pest Infestation Spurs Doubts Over Standards in Mexico

COWBOYS are not a squeamish lot. But the reappearance of the dreaded "screwworm" is giving United States cattle ranchers the willies.

The tiny fly larvae infestation will not make the North American free trade negotiations (NAFTA) any easier either.

Last week, a screwworm infestationn was detected among Mexican cattle in southern Tamaulipas, about 200 miles from the Texas border. To date, only two cases have been detected.

What concerns Mexican and US officials is that the pest suddenly jumped from a quarantined area 300 miles further south.

"It's logical to assume that if the infestation moves north, US border state ranchers could suffer severe economic losses. Their costs would rise, putting them at a competitive disadvantage with other US cattle producers," says Gary Wilson of the Washington D.C. office of the National Cattlemen's Association.

Cattle must be sprayed and dipped in pesticides to eradicate the flesh eating larvae, which weaken cows, destroy the hide, and often kill newborn calves.

"We've spent a lot of time and money to get rid of the thing and we absolutely don't want it back," says Darrell Wilkes, at the Cattlemen's Association headquarters in Englewood, Colo.

Indeed, over the last four decades, about $400 million has been spent in on US-Mexican programs to wipe out the pest. In Febru-ary 1991, Mexico was declared free of screwworms. But in January, a new outbreak was discovered in southern Mexico. The reinfestation occurred, officials here say, when inspectors failed to stop or treat a large herd of cows imported from Central America in November.

The reappearance of screwworm highlights US ranchers' concerns about differences in health and safety enforcement standards at a time when trade between the two nations is growing. Mexican and US officials give assurances that the free trade negotiations will not water down health standards.

The cattle industry does not oppose free trade. "We welcome the more open trade we have had in recent years and will soon get with the NAFTA agreement. But we sure don't want to reintroduce these kinds of problems," says Mr. Wilkes of the cattlemen's association.

Last year, Mexican ranchers shipped 1.2 million head of cattle north to be fattened (at lower cost) on the US side of the border. Many were then brought back to Mexico to be slaughtered and consumed as beef. But this growing trade could be stunted by the screwworm outbreak.

"We realize the situation is grave," says Dr. Marco Antonio Mendez of the US-Mexico Exotic Animal Disease Commission. "We have an emergency operation under way now."

Teams of inspectors are checking cattle on ranches near Aldama, Tamaulipas. A crash program is under way to release about 20 million sterile flies a week over the infested area.

The US is also supporting programs to eradicate screwworm from Guatemala, Honduras, and El Salvador. But if the Mexican infestation is not contained quickly, resources from the Central American program may be siphoned off to support the Mexican campaign.

"We're doing everything we can to stop this now. Tamaulipas has a lot of low-lying pasture land, and the rainy season is fast approaching. The conditions are perfect for the infestation to spread," says Dan Sheesley of the Animal and Plant Health Inspection Service branch of the US Agriculture Department in Mexico City.