Screwworm infestations resurface near US borders as cattle smuggling escalates

In summer 2023, Panama reported an increase in screwworm infestations affecting livestock near its northern border with Costa Rica, raising alarms about the potential spread of this dangerous parasite. This resurgence follows nearly two decades of successful eradication efforts that had kept the screwworm out of North America since 1966. Notably, chickens and horses were among the species found infested, with Honduras confirming outbreaks after inspections of illegally imported animals near its borders. This public health concern has been linked to illegal cattle smuggling routes utilized by traffickers who exploit weaknesses in border controls between Central America and Mexico. The screwworm, scientifically known as Cochliomyia hominivorax, poses a severe threat to livestock, as its larvae can burrow into the flesh of animals, feeding on their living tissue. Cattle smuggling across Mexico has impeded effective containment strategies, drawing attention from agricultural and health authorities in the region. The National Confederation of Livestock Organizations in Mexico has called for stricter measures against this illegal trade, as unchecked imports could enable the insect to spread deeper into Mexican territory. Efforts to curb the parasite's advance include a sterile insect technique, where irradiated male flies are bred to mate with females, without producing offspring. Although this method has been effective in controlling local populations, experts warn that failing to address illegal cattle movement could undermine these control efforts. Mexico, in anticipation of the parasite reaching his territory, is expected to take action in areas already experiencing high volumes of cattle traffic. Still, there are concerns that waiting until the screwworm establishes itself further north will come at a significant cost to local ranchers and the broader agricultural economy. The biological barrier constructed in Panama, costing around $15 million annually, has proven cost-effective, with the USDA estimating a benefit of over $900 million annually for the U.S. cattle industry from the prevention programs. As the sterile insect program continues to play a critical role in safeguarding animals from this parasite, the threat looms larger with the emergence of fertile flies in Central America. The potential involvement of cattle smugglers exploiting these routes indicates that regional cooperation and strict enforcement of customs regulations are more urgent than ever to prevent the serious consequences of a potential new outbreak on North American soil.