EDITORIAL 2: US confirms it’s first human case flesh-eating new world screwworm
Context
The Department of Health and Human Services recently reported the first human case of the flesh-eating parasite, the New World screwworm, in the United States.
What is New World screwworm?
- Screwworms are a type of blue-grey blowfly, typically found in South America and the Caribbean.
- Screwworms — specifically females — are attracted to and lay eggs on and in open wounds or another entry point like a nasal cavity in warm-blooded animals and, rarely, humans.
- One female can lay up to 300 eggs at a time and may lay up to 3,000 eggs during her 10- to 30-day lifespan, according to the CDC.
- These eggs hatch into larvae (known as maggots), which burrow into the wound using their sharp mouth hooks to feed on the living flesh, leading to infestation.
- After feeding, the larvae fall into the ground, burrow into the soil and emerge as adult screwworm flies.
- The parasites are named after the screwlike way they burrow into the tissue.
- Their Latin name, Cochliomyia hominivorax, “literally means man-eater”.
What are the symptoms of infestation?
- New World screwworm infestations can be extremely painful, especially in humans, with a high mortality rate if left untreated.
- That is because once an infestation starts, that often attracts more flies that lay more eggs. And depending on where the wound is, the maggots can make their way into vulnerable tissue like the brain, or the wound can get quite big, and then you get sepsis.
- According to the CDC, symptoms of infestation include: wounds or sores that do not heal; bleeding from open sores; feeling larvae movement within a skin wound or sore; and a foul-smelling odour from the site of the infestation.
Why are screwworms spreading now?
- The US eradicated New World screwworms in 1966 by using a method called the sterile insect technique.
- This involved rearing billions of sterile insects inside factories and releasing them into the air in affected regions.
- If the females on the ground mate with a sterile male, at least with a screwworm, that’s all they’ll mate with so that female won’t produce any offspring.
- This technique helped remove New World screwworms not only in the US, but also in Mexico in the 1970s and Central America in the early 2000s.
- In 2017, the method was again implemented to control a small outbreak in Florida.
- However, recently, new cases of New World screwworm infestation have been reported in Panama, Costa Rica, Nicaragua and Honduras.
Conclusion
There could be several factors behind the reemergence of the infestation. These include the movement of infested cattle and the possibility that the current strain of sterilised flies is less effective than in the past.