By Michelle Arnold
The New World screwworm (NWS, Cochliomyia hominivorax) is a blow fly that is native to the Western Hemisphere. Unlike most species of blow flies, adult female screwworms do not lay eggs on dead and decaying flesh. Instead, they lay eggs on living mammals at the borders of fresh wounds or at the edge of body orifices. Almost any wound is attractive to the female fly, whether the wound occurred naturally (for example, from fighting, predators, thorns, disease, tick or insect bites) or was man-made (from shearing, branding, castrating, dehorning, tail docking, and/or ear-tagging). The most commonly infested wounds are navels of newborn animals and the vulva and perineum of their dams, especially if there was any trauma when giving birth. The larvae (maggots) feed on the host’s living flesh, causing extensive damage by tearing at the host’s tissue with sharp mouth hooks. The term “myiasis” is used to refer to wound infestation by fly larvae/maggots. The wound will become larger and deeper as more eggs hatch and larvae feed on the living tissue, which may result in secondary infection and death if left untreated. New World screwworm is a pest that poses a significant agricultural, economic, and public health threat to livestock, wildlife, pets, and people. For updates on NWS, visit Screwworm.gov, the U.S. Government’s Unified NWS website.
Although the United States eradicated this fly in 1966 and eliminated a small outbreak in the Florida Keys in 2017, the fly is once again a concern as it continues its northward migration towards the Texas border (Figure 1). This steady migration has prompted the FDA’s Center for Veterinary Medicine (CVM) to quickly identify products to prevent and treat NWS myiasis if it reaches US livestock.
Source : osu.edu