If there’s one constant in the world, it’s every living thing is looking for food while avoiding becoming a meal. Farmers fight weeds, bacteria and fungus from the moment seeds go into the ground until the crop is harvested. Ranchers are on constant alert for predators waiting for the right opportunity to secure an easy meal.

In growing food, there’s a constant battle against pests, both seen and unseen. One of agriculture’s greatest successes over the past 75 years has come from managing these threats even if they’re not eliminated entirely.

The New World screwworm (NWS) is a parasitic pestilence of fly larvae that burrows into open wounds on livestock causing serious to fatal injury to infected animals. NWS was a scourge in the United States until 1966 when a government program used sterile flies to eradicate the breeding stock.

This biological barrier eventually banished the NWS to the Caribbean and South America, but recent sightings in Central America and Mexico have put the United States on alert. Like any fence, the barrier occasionally develops some weak spots. An outbreak occurred in Texas in 1976 and the NWS cropped up again in the Florida Keys in 2016, affecting wild deer there.

Vigilance is key to halting the most recent migration, and officials are working to reverse the course of NWS before it can reestablish in the United States. While not cheap, these efforts provide enormous economic benefits, with one U.S. government estimate showing an outbreak similar to the one in 1976 could cause nearly $2 billion in losses.

The reemergence of NWS into the public discourse is also an opportunity to highlight how dedicated farmers and ranchers are in caring for their livestock. It’s easy for someone outside of the industry to only see cattle grazing in a pasture as they drive by on the highway and believe the animals are largely on their own.

While this is the time of year cattle are likely to have the least amount of interaction with their caretakers, it’s still substantially more than what a passersby can see from the road. There are regular water checks, replenishment of supplemental mineral and salt in addition to periodic fence checks.

This is in addition to more thorough assessments when rotating cattle to fresh pasture. When I was growing up, moving cattle to a new pasture always involved a stop at the pens to spray the cattle with a mild insecticide to combat flies, ticks and other biting insects. This also offered the chance for close evaluation of the herd.

We’d start the day before sunrise so we could move the cattle when it was coolest, and the observation started as soon as we began guiding them to the pen. We studied the strides looking for any sign of a limp or lethargy that could indicate an illness. Once in the pen, we paid close attention to posture, coat, eyes and mouth for any signs of sickness or distress. Any potentially sick animals would be separated for further evaluation and treatment if necessary.

Catching problems early makes them much easier to solve. Screwworms are still a threat, but through care and vigilance they were spotted early, and mitigation measures are underway to protect all the herds in the United States.