Context: Recently, the US reported its first human case of New World screwworm infestation, a flesh-eating parasite once eradicated in 1966 through the Sterile Insect Technique.
Relevance of the Topic: Prelims: Key facts about New World Screwworm.
What is the New World Screwworm?
- The New World screwworm is a type of blue-grey blowfly, scientifically called Cochliomyia hominivorax. The parasite’s Latin name (hominivorax) literally means man-eater, reflecting its destructive nature.
- It is mainly found in South America and the Caribbean though outbreaks have occurred in other regions.
- Female screwworms are attracted to open wounds or natural entry points like the nasal cavity of warm-blooded animals and rarely humans.
- A single female can lay up to 300 eggs at once, and nearly 3000 eggs during her lifespan of 10-30 days. These eggs hatch into larvae (maggots) that burrow into living flesh in a screw-like manner, feeding on tissue.
- After feeding, the larvae fall to the ground, burrow into the soil, and later emerge as adult flies.
Deadly threat of New World Screwworm Infestations:
- New World screwworm infestations can be extremely painful, especially in humans, with a high mortality rate if left untreated.
- Once an infestation starts, it 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 enlarge the wound to the point of causing severe infection and sepsis.
Symptoms of Infestation include:
- Wounds or sores that do not heal
- Bleeding from open sores
- Feeling larvae movement within a skin wound or sore
- A foul-smelling odour from the site of the infestation.
Reasons for the recent spread of New World screwworms:
- The US eradicated screwworms in 1966 using the sterile insect technique, where billions of sterile males were released to prevent reproduction.
- This method was later used to eliminate screwworms in Mexico (1970s), Central America (early 2000s), and to contain a Florida outbreak in 2017. Despite eradication efforts, new cases have recently been reported in Panama, Costa Rica, Nicaragua, and Honduras.
- Experts suggest movement of infested cattle across borders as possible reasons for the recent spread of New World screwworms.