Necrosis 10 cm deep: should we be worried about this “man-eating” fly that is invading Costa Rica ?

Since February, Costa Rica has been facing a real fly epidemic. Their particularity, which also makes them dangerous, is to lay their eggs in living animals.

Commonly called the meat fly or Libyan fly, the screwworm is invading Costa Rica. A human case was detected last March. Since February 7, 2024, the country has declared a state of emergency, reports HuffPost.

Cochliomyia hominivorax, whose name literally means "devouring men", has habit of laying its eggs not in carrion but in living animals, including humans.

A hatching in just 12 hours

The slightest injury, even minimal, can attract the female fly who can lay between 10 and 400 eggs during her laying. The hatching of maggots, also called "screwworms" occurs after barely a dozen hours. The worms then burrow into the flesh and feed on it, causing very painful infections and even necrosis in the mammal, according to the medical dictionary of the mammal. Academy of Medicine.

The larvae also secrete compounds that prevent the wound from healing and which attract other flies that lay eggs in the same wounds. They can dig holes around ten centimeters deep, particularly in cattle. The higher the temperature, the more the worms develop.

After 4 days, the worms reach a size of approximately 1.5 cm and fall from the wounds to bury themselves in the soil and pupate. Without treatment, the infection can be fatal. It can also kill an animal in just a fortnight.

No effective vaccine exists

The fly "man-eating fly" is found mainly in the countries of northern South America, northern Chile and northern Argentina. But several cases of human infection have been observed in the United States, the United Kingdom in 2013 and in Costa Rica last March.

In 1982, the United States had completely eradicated the species using the sterile insect technique (STI), a campaign of ;eradication. It consists of releasing millions of male flies, previously sterilized, into the wild.

Regularly confronted with this problem, Guyana has veterinary sprays, which are banned from marketing in Europe. But to date, there is no effective vaccine or product of biological origin.