Hundreds of millions of flies dropping from planes in the sky might sound like a horrible nightmare, but experts say such a swarm could be the livestock industry’s best defense against a flesh-eating threat poised to invade the southwestern border of the United States.
An outbreak of New World screwworms — the larval form of a type of fly that’s known to nest in the wounds of warm-blooded animals and slowly eat them alive — has been spreading across Central America since early 2023, with infestations recorded in Panama, Costa Rica, Nicaragua, Honduras, Guatemala, Belize and El Salvador. Most Central American countries hadn’t seen an outbreak in 20 years.
The fly reached southern Mexico in November, sparking concern among U.S. agricultural industry officials and triggering the closure of several border-area cattle, horse and bison trading ports.
The U.S. mostly eradicated the New World screwworm populations in the 1960s and 1970s by breeding sterilized males of the species and dispersing them from planes to mate with wild, female flies.
The strategy slowly degraded the insects’ populations by preventing them from laying more eggs. Now, as the insects continue to spread north, officials are hoping the approach could work again.
However, today only one facility in Panama breeds sterilized New World screwworms for dispersal, and hundreds of millions more sterile flies are needed to slow the outbreak.
The U.S. Department of Agriculture has announced plans to open a new “fly factory” in a yet to be determined town near the Texas-Mexico border.
New World screwworms are the parasitic larva of a metallic blue blow fly species called Cochliomyia hominivorax. It feeds on the flesh of living animals, rather than dead ones, said Dr. Phillip Kaufman, a professor at Texas A&M University.
The flesh-eating maggots go for most warm-blooded animals, including horses and cows. They have also been known to infect domestic pets and even humans in rare cases, Kaufman said.
“After mating, the female fly finds a living host, lands on its wound, and will lay up to 200 to 300 eggs,” Kaufman explained. “After 12 to 24 hours, those eggs all hatch, and they immediately start burrowing and feeding on the tissue of that animal, causing very large wounds to form.”
After the larvae feed on the tissue with their sharp mouth hooks for several days, they drop from the animal and burrow into the ground to emerge later as fully grown adult flies.
In a sterile fly production facility, the pupae are subjected to high-energy gamma rays that break down the DNA of the males, damaging their sex chromosomes. The result: impotent adult flies that cause female mates to lay unfertilized eggs. The amount of radiation the male flies are exposed to does not pose a danger to animals or humans. But since the female flies only mate once in their 20-day lifespan, once populations are exposed to sterile males, the populations die out over the course of months or years, depending on the size of the outbreak.(SD-Agencies) 數以億計的蒼蠅從飛機上傾瀉而下，聽起來像一場可怕的噩夢，但專家表示，這支“昆蟲軍團”或將成為美國畜牧行業抵御螺旋蠅入侵西南邊境的最強防線。自2023年初以來，新大陸螺旋蠅疫情（這種蠅類的幼蟲會在溫血動物的傷口寄生并蠶食活體）已席卷中美洲。巴拿馬、哥斯達黎加、尼加拉瓜、洪都拉斯、危地馬拉、伯利茲和薩爾瓦多均報告感染案例——其中多數國家已20年未爆發此類疫情。 2023年11月，螺旋蠅入侵墨西哥南部，引發美國農業官員高度警覺，隨即關閉多個邊境地區的牛馬交易口岸。美國曾在20世紀60-70年代通過培育絕育雄蠅、用飛機空投與野生雌蠅交配的方式，基本根除了新大陸螺旋蠅。這種策略通過阻斷繁殖渠道逐步消滅種群。如今隨著蟲害北擴，當局希望故技重施。 但當前全球僅剩巴拿馬一家絕育螺旋蠅培育基地，要遏制疫情還需增產數億只絕育蠅。美國農業部宣布將在美墨邊境城鎮新建“蒼蠅工廠”，選址待定。得州農工大學教授菲利普?考夫曼博士解釋，新大陸螺旋蠅幼蟲專食活體動物組織。這些食肉蛆蟲主要攻擊馬牛等溫血動物，偶見感染寵物甚至人類案例。 考夫曼說：“雌蠅交配后會尋找活體宿主，在傷口產下200-300枚卵。12-24小時后孵化，幼蟲立即鉆入動物組織啃食，形成巨大創面。”幼蟲用銳利口鉤蠶食宿主數日后鉆入土中化蛹，最終羽化為成蟲。在絕育蠅培育工廠中，蛹接受γ射線照射致使雄蠅DNA斷裂、性染色體受損，喪失生育能力。這種輻射量對動植物無害，由于雌蠅20天壽命中只交配一次，只要持續投放絕育雄蠅，種群將在數月到數年內滅絕——具體時長取決于疫情規模。 (Translated by DeepSeek) | 