美国农业部首次在境内发现这种野生螺旋蝇。这种寄生虫大约四个月前首次在美国的牲畜中被发现，这表明尽管总体感染病例数量较少，但该寄生虫仍有可能继续扩散。
By Ilena Peng The US Department of Agriculture has caught its first wild screwworm fly since the parasite was detected in the country’s livestock nearly four months ago, signaling the potential for continued spread even as overall cases have remained muted.
这种野生螺旋蝇于周五在德克萨斯州的布鲁斯特县被发现，它被捕获在美国边境沿线设置的100多个专门用于捕捉螺旋蝇的陷阱之一中。
The wild screwworm fly was detected in Brewster County, Texas, on Friday. It was caught in one of the USDA’s more than 100 screwworm-specific fly traps along the US border.
根据美国农业部的数据，这种寄生虫的传播范围一直相对有限：自6月以来，美国境内仅报告了50例感染病例。其中一例发生在与布鲁斯特县相邻的普雷西迪奥县的一匹马身上；另一例则发生在新墨西哥州的格兰特县。
The spread of the parasitic fly, whose larvae burrow into the wounds of animals, has remained relatively contained, with just 50 cases in the US since June, according to the USDA. A horse in Presidio County — which is adjacent to Brewster — is one of only two active screwworm cases in the US; the second is a horse in New Mexico’s Grant County.
目前尚不清楚这种害虫是如何在不同县之间传播的——因为在野生动物中尚未发现螺旋蝇的感染病例，而且这些野生苍蝇此前一直逃避了政府的监测。世界动物卫生组织的高级兽医流行病学家保罗·蒂扎尼（Paolo Tizzani）表示：“虽然检测到的病例数量较少，这令人鼓舞，但仅凭病例数量无法解释传播为何受到限制，也无法评估任何防控措施的实际效果。”他呼吁继续加强对野生动物和苍蝇的监测，并指出：“监测结果本身并不能证明传播已经完全停止。”
It has been unclear how the pest has spread across counties, as screwworm cases haven’t been found in wild animals, and wild flies have evaded government surveillance efforts until now. “The limited number of detected cases is encouraging, but case numbers alone cannot tell us why spread has been limited or quantify the effect of any intervention,” Paolo Tizzani, the World Organization for Animal Health’s senior veterinary epidemiologist, said Monday. He called for continued monitoring of wild animals and flies, noting that “surveillance results cannot by themselves establish that transmission has completely stopped.”
这次野生螺旋蝇的发现有助于美国农业部制定相应的防控策略——例如释放不育雄性苍蝇，让它们与野生雌性苍蝇交配以抑制害虫的繁殖。美国农业部在周六发布的声明中表示，他们会在受感染区域附近设置陷阱，以避免捕获不育苍蝇，并更准确地判断野生苍蝇的移动方向。虽然尚未在野生动物中发现螺旋蝇的感染病例，但动物健康专家认为，德克萨斯州即将到来的狩猎季节可能为进一步监测提供机会。
The detection of the wild fly could help inform the USDA’s dispersal of sterile male flies, which are meant to mate with wild female flies in order to curb the pest’s reproduction. The agency said in a Saturday post on X that it places traps “just outside of infested areas to avoid capturing sterile flies and better pinpoint where wild flies may be moving.”While no cases in wildlife have been confirmed, animal health experts say the upcoming hunting season in Texas could provide an opportunity for closer scrutiny.
尽管这种害虫的传播速度较慢，但仍缓解了牧场主的担忧；同时，美国也通过恢复从墨西哥进口牲畜来缓解国内牛只短缺的问题。
The slow spread has nonetheless alleviated concerns for ranchers, while also allowing the US to ease a domestic cattle shortage by resuming livestock imports from Mexico.
此前，美国已经成功根除了这种名为“螺旋蝇”的害虫，将其驱赶到了巴拿马以南地区。然而，在疫情结束后，这种害虫又开始向北扩散，并于2024年底传入了墨西哥。美国随即暂停了从墨西哥进口牲畜的贸易，并一直维持这一禁令，直到8月底才逐步重新开放边境口岸。
The US had previously eradicated screwworm, pushing the pest south of Panama. But the fly began spreading north again after the pandemic, reaching Mexico in late 2024. The US halted livestock shipments from Mexico, and largely maintained that ban until late August when it began a phased reopening of ports.
不过，要彻底根除这种害虫可能至少需要等到明年才能实现，因为这取决于位于德克萨斯州的一个大型无菌蝇生产设施——该设施预计要到2027年4月或5月才能投入使用。目前，美国主要依靠在巴拿马和墨西哥生产的无菌蝇来进行防治工作。
Still, a complete elimination of screwworm from the US likely won’t happen until at least next year, creating the potential for more bursts of cases. That’s as eradication will depend on a large sterile fly production facility in Texas that isn’t scheduled to open until April or May 2027. Currently, the US has been dispersing flies produced at smaller plants in Panama and Mexico.
“我们还没有完全摆脱这场危机，”美国农业部长布鲁克·罗林斯在本月早些时候的新闻发布会上表示，“我们仍在建设用于生产无菌蝇的设施，因为这是根除这种害虫的唯一可靠方法。不过，我们已经取得了令人瞩目的进展。”
“We are not out of the woods yet,” Agriculture Secretary Brooke Rollins said at a press conference earlier this month. “We’re still building the facilities for the the sterile flies, which we know is the one true way to eradicate. But we have made such amazing progress.”