We Dropped The Ball, Folks!

Iwas truly flabbergasted when I first heard that the New World Screw Worm was on the move toward Texas again, after having been wiped out in the United States and Northern Mexico in the late 1960s and early 1970s. This should never have happened again. We failed to treat this as an on-going, serious international threat, a major public health problem very likely to cross borders again, if it remained an issue in countries south of us. What happened to “Treat there, never here”?

We learned then (or at least I thought we had) to control screwworms effectively through international cooperation in prevention, as well as how to treat the animal and human victims when they were infected, and we knew (but we obviously didn’t remember) how much pain and suffering the victims endured and the economic loss that hit the agricultural sector. Now these pests are back, and even Fayette County will likely not remain unaffected, since cases have now been detected in the Texas Hill Country. The greatest threat comes from the transport of infected animals into other areas nearby, though locally it’s the flies that spread the infestation.

The flies lay their eggs in any open wound or body orifice of mammals, and humans are not excluded. The “wound” can be as minor as an insect bite, and the orifice is anything that they can get to, including eyes, ears, nose, and mouth, even genitalia and anal area if we expose those areas. In cattle, newborn calves are particularly at risk, because the umbilical cord is an attractive site for egg-laying.

I remember all too well the hours every week my grandfathers both added to their schedules, daily having to scrutinize every farm animal carefully (horses, sheep and goats, cattle, dogs, cats, whatever), to be sure they were quiet, not agitated, not demonstrating any unusual behavior like not eating, emanating a foul odor, isolating themselves, tossing their heads, trying constantly to scratch or rub their bodies in a particular spot, or showing any purulent or sanguineous wounds, and especially to check the newborns until their umbilical areas healed completely. When any such problem surfaced, the veterinarian came out to the farm, to check over all the animals, and treat those infected. Some farmers and ranchers learned how to treat their own animals, but they were required to send off all the screwworms removed, or otherwise to kill and dispose of them in ways that would assure none of them burrowed into the ground as larvae, and then emerged later as flies to further spread the infestation in that area.

I did not live around any of the veterinarians here then, so I don’t know what their own lives were like, but I don’t imagine it was fun treating those wounds, where every single worm had to be removed and killed by immersion into an alcohol solution, and then samples be sent off for verification, for the worms were not distinguishable visually from blowflies except by microscopic examination by experts. The animals’ wounds then had to be plugged with a thick vaseline-type paste full of medications to help the healing and to assure that no additional eggs could be laid in that wound by another screwworm fly, nor any more worms survive to reach larval stage.

Now, when we need to be dropping about a million sterile male flies a week in each county affected and nearby, to assure that all the female flies in the area lay only infertile eggs, there’s only one plant in our hemisphere producing these flies, it’s in Panama, and its production has mostly been dedicated to areas where screwworm is endemic in South and Central America, as well as southern Mexico. Usually the screwworm thrives in tropical climates, so cold and dry temperatures are a deterrent to its spread. We know, however, that our summers are getting warmer and our winters shorter, so the flies may find our area more hospitable now than they did decades ago.

USDA (a co-owner with Panama of the plant there) is ramping up production at additional locations in northern Mexico and South Texas, so we will have more sterile fly production capacity soon. Let’s hope all those sterile fly releases west of us are effective, and we never see this problem here in our area this summer or anytime again: once was enough for my lifetime.