Screw-worm

(This column was published in the February 27, 1995 Buffalo News.)

   It was at the end of one of those television pitches by a federal 
legislator about government waste. My attention had wandered, but it was 
suddenly recaptured when the speaker offered an example of such waste: screw-
worm research. That odd name, screw-worm, rang a bell. I had heard it before 
but I couldn't recall where. To refresh my memory I had to do a little 
research of my own. (Concerned readers will be happy to know that my work was 
not government supported.)

   Here is a summary of what I found. The screw-worm is the larva of a fly 
that is twice as big as a house fly. The adult fly lays hundreds of eggs on 
wounds of warm-blooded animals, particularly livestock and among wildlife 
frequently deer. In about 12 hours the eggs hatch into the screw-worm maggot 
which feeds on the injury and grows to maturity in about five days. It is at 
this time that its name is acquired: it burrows head down into the flesh and 
the rings around its body give it the appearance of a half-drilled carpenter's 
screw.

   When fully grown the larva drops to the ground where it pupates into an 
adult fly, the entire life cycle taking just three weeks.

   Infested wounds develop a disgusting smell, drawing other flies. According 
to E. F. Knipling, "Because of the recurved spines and their aggregating 
behavior in the wounds, the infested animals cannot readily dislodge the 
larvae by licking or biting. Animals are literally eaten alive. In areas of 
high fly densities, infested animals not found are virtually doomed for a slow 
traumatic death."

   Leland Howard tells us that the fly "also frequently attacks man. The most 
common cases are those where the fly has laid its eggs in the nostrils.'' 
There it destroys the soft tissues of the palate and Howard adds, ""Fatal 
cases in men are not rare."

   Clearly the screw-worm is not an attractive insect. Nor has it been an 
inexpensive pest. In the 1930s over a million cases of infestation were 
reported each year and in 1974 Gulf state losses alone were estimated at $200 
million. Fortunately the screw-worm does not tolerate cold and its population 
reservoirs remained along the southern United States border. Northern 
infestations occurred only when infected livestock were transported here.

   Now enter government entomological researchers. In the 1970s they raised 
billions of male flies, sterilized them by irradiation and released them 
through the southern states and Mexico. These flies overwhelmed the wild 
population and the females they inseminated produced eggs that did not hatch. 
The result: within ten years the pest was virtually stamped out in both 
countries and billions of agriculture dollars were saved.

   The eradication program had many early detractors. But its final 
overwhelming success is perhaps best told by a cowboy who lived through the 
bad years. Joel Nelson's delightful doggerel includes the following:

   Now usually gov'met programs are a minimal success
     But the one that stopped the screwworm has dang shore passed the test.
   Cause it pushed the critter southward and I hope he's there to stay.
     Here's to the Mission Fly Lab and the U.S. D. of A.

   It appears from what I found that the screw-worm problem has been at least 
temporarily alleviated. Perhaps that legislator is right: we don't need any 
more screw-worm related research. Indeed we do need oversight of governmental 
operations, but I still fear that important federal programs like the one I 
have described might die as the result of such uninformed sound bites.