Cochliomyia hominivorax, the New World screwworm fly, or simply screwworm or screw-worm, is a species of parasitic fly that is well known for the way in which its larvae (maggots) eat the living tissue of warm-blooded animals. It is present in the New World tropics. There are five species of Cochliomyia but only one species of screwworm fly in the genus is parasitic; there is also a single Old World species in a different genus (Chrysomya bezziana). Infestation of a live vertebrate animal by a maggot is technically called myiasis. While the maggots of many fly species eat dead flesh, and may occasionally infest an old and putrid wound, screwworm maggots are unusual because they attack healthy tissue.
The New World screwworm fly was the first species on which the sterile insect technique was tested and then applied in a natural environment, resulting in the control and systematic eradication of this species from North and Central America as well as parts of the Caribbean since the 1950s. [1] It is still widespread in tropical and subtropical parts of the Caribbean and South America, and import of infected animals from endemic areas risks re-introducing the fly to areas where it has been eradicated. [2]
Screwworm females lay 250–500 eggs in the exposed flesh of warm-blooded animals, including humans, such as in wounds and the navels of newborn animals. The larvae hatch and burrow into the surrounding tissue as they feed. Should the wound be disturbed during this time, the larvae burrow or "screw" deeper into the flesh, hence the larva's common name. The maggots are capable of causing severe tissue damage or even death to the host. About three to seven days after hatching, the larvae fall to the ground to pupate. The pupae reach the adult stage about seven days later. Female screwworm flies mate four to five days after hatching. The entire lifecycle is around 20 days. A female can lay up to 3,000 eggs and fly up to 200km (100miles) during her life.
The United States officially eradicated the screwworm in 1982 using the sterile insect technique, although an isolated outbreak occurred in the Florida Keys, Monroe County, Florida in autumn of 2016.[3] The Floridian government instituted control measures including mandatory inspections of all animals leaving the area; the outbreak was declared as neutralized in March 2017.[4] The screwworm was eradicated in Guatemala and Belize in 1994, El Salvador in 1995, and Honduras in 1996. Campaigns against the flies continue in Mexico, Nicaragua, Costa Rica, Panama, and Jamaica with financial assistance from the United States Department of Agriculture, which is trying to push the parasite south of the narrow Isthmus of Panama.[5]
From the Greek kochlias (snail with a spiral shell) + myia (fly) and the Latin hominis (man) + vorax (consuming), Cochliomyia hominivorax, or the New World screwworm fly (formerly Callitroga (Greek kallos, (beautiful), + trogein, (to gnaw), Americana), was first described by French entomologist Charles Coquerel in 1858.[6]