Flies for most are relatively annoying, they buzz around, land on our food, our bodies, etc. and most of the time flies present very little issue for humankind besides being an annoying nuisance.
However, there are some flies that are particularly problematic for humans and animals, some of them bite which can be quite painful. New World screwworms (Cochliomyia hominivorax) are causing a buzz of trouble and while they are currently not in the United States, they are everywhere between Panama and Mexico and could move upward into the States.
American farmers, entomologists, and animal scientists are all reasonably concerned with the economic threat they pose to the livestock industry and possibly human health. Being able to identify New World screwworms is extremely important because as it turns out there is a very close look alike - secondary screwworms (Cochliomyia macellaria.)
A diagnostic feature of secondary screwworms is that while like New World screwworms, which have three stripes on their backs but also different, secondary screwworm stripes are all the same length starting from the back of the head moving downward - this isn’t the case with New World screwworms. They are both metallic blue in color with moderate to bright reddish orange colored eyes. Another key difference is that secondary screwworms do not pose a threat to human or animal health whereas New World screwworms can.
New World screwworms are the larvae of the group of parasitic flies known as “Bot flies” which are a special group of flies that depend on other organisms to reproduce and grow. So farmers must remain diligent to keep their livestock safe from these pests and the very best wayto do so is to be educated about the flies. Presently both the USDA and the Texas A&M AgriLife both have many helpful links to help with identification and what to expect.
Monitoring cattle and doing routine inspections to ensure they do not have open wounds which the flies are in search of to lay their eggs at for the maggots to feast on for their development. Applying low but effective doses of spray on insecticides on the cattle has proven to be an effective general fly management strategy to ensure cattle health. In terms of humans, discouraging flies from lingering on you when they land is a way to prevent threats, covering open skin wounds with bandages and treating them with doctor approved medications.
Should you feel that you have discovered New World screwworm flies, taking samples is crucial. A jar with +80% alcohol will help preserve the flies long enough for a researcher to identify them. Where do you find these people? You can always take samples to your local AgriLife extension office, which is the best option, or if you are close enough to a college or university they may be able to help as well.
At the end of the day we are all the first line of defense in combating these insect pests and protecting both ourselves and our livestock from them. Staying diligent and being informed about the potential threat these insects pose and whether they have or haven’t yet resurfaced inside the United States is absolutely essential. State and federal agricultural scientists are doing their absolute best to stay diligent and also very articulate in their work to ensure all of us and livestock can remain safe but they can only do so much, so stay informed.
