Taming of the Screw, Act One.

Have you seen the headlines? “Horrific Flesh-Eating Parasite”.

The current news reports on New World Screwworm are all nearly identical, frantically vying for your attention with gore and fear. The screwworm saga is actually pretty cool, and it’s being sold short by the goremongers. It has grisly Fear Factor-type details, yes, but it also contains some fascinating bits of history, geography, groundbreaking science, and the story of a heroic research group that was determined to succeed no matter what the obstacles.

First, some gore: the infamous New World Screwworm is actually a fly (that, despite its scandalous reputation, looks just like every other fly you’ve ever met) which produces some very badly-behaved babies. The vast majority of flies are decomposers that deposit their eggs on organic garbage and dead tissue. They are the ones graciously removing roadkill and dumpster overflow from our environment. One of them—the Common Green Bottle Fly—even has babies working in the medical field, meticulously cleaning out infected wounds for live human patients. Sterile larvae (“maggots”) from a medical supply company are deposited directly onto injuries that have failed to heal. These larvae remove all non-viable (“dead”) material—literally causing it to vanish—and clear the way for healthy tissue to be built over the defect. It is a well-known fact that they perform this task more precisely than a human surgeon ever could. You may have heard how other sorts of fly assist homicide detectives in determining a victim’s time of death. New World Screwworm, on the other hand, is the predatory, self-serving outcast of the family; its babies will only eat living flesh. That is agonizing for the victim, and it is a process that expands until the animal falls down dead. It is thus an essential part of this insect’s life cycle to kill large warm-blooded individuals. Think cattle, goats, wildlife, pets, and humans. That wasn’t too gruesome, was it? I will, however, need to be somewhat more graphic toward the end of the story.

Now, the history: in the 1930’s and 40’s, NWS was a day-to-day threat in mainland United States, as well as all of its current haunts in South America, Central America, and various Caribbean islands. Despite what you see in lurid news pieces, screwworm isn’t a great threat to you personally. It is, however, really brutal for animals that live in close quarters. It’s especially bad for those that don’t move too fast or far, worst for those that have a lot of youngsters tagging along. Which is, in fact, a pretty tidy definition of “farm animal”. Ranchers of that decade lost hundreds of thousands of animals per year, and hundreds of millions of dollars went right into the stomachs of these voracious maggots. Screwworm can easily wipe out entire generations of baby cows, sheep, goats, and pigs by entering through its favorite portal, the navel of a newborn mammal. Please try not to picture that, because I am reserving the gore for the end, and this is only the first chapter. We’ve yet to hear about the brilliantly innovative entomologists who set out to save the Western Hemisphere using an army of eunuch flies.

What?

Dr M.S. Regan