Given the global environment we live and work in today, New World Screwworms have always been a threat to the U.S. cattle herd. The confirmation of New World Screwworms being found in a person in Maryland who had traveled from Guatemala should put livestock raisers on alert. Complacency in a market where prices in one country are affected by decisions in another suggests a lack of understanding of the interconnectedness of the modern food supply. Now is the time to focus on solutions for the present and look ahead to preventative measures for the future.
Current estimates suggest it will take two to three years to open a sterile fly facility in Texas, the first state to likely bear the burden of an influx of screwworms. Fast-tracking the building and opening of that facility is of paramount importance to the present. According to a report in Reuters, the USDA estimated about 500 million sterile male flies a week would be needed to push the flies back from their current location in Mexico to the Darien Gap, between Panama and Colombia.
The previous eradication of screwworms was a concerted effort to first contain their spread and then kill the pests before maturation. Screwworms mature into flies, at that stage, the males are extremely aggressive and females mate only once before death. The previous eradication effort required large-scale production of sterile male flies that were released into the wild to breed with females. The result was production of non-viable eggs and generational deaths of females, leading to a collapse of the population in the United States.
Once eradication has been achieved again, assuming it can be, sterile insect release protocols for the U.S. so ramp up of male fly production does not have the same lag time being experienced now. Anticipation of the arrival of a highly invasive pest that is endemic in other parts of the world is something we must get better at in the future.
There is currently no preventative medicine available for screwworms. While we wait for fly facilities to be built, now is the time for development of a preventative medication for livestock and wildlife. There are several preventative medications currently available for livestock and New World Screwworms are not a new species. Developing a livestock and food chain safe medication to prevent their infestation of host animals should be prioritized.
Earlier this year, the southern border was briefly closed to all imported cattle to protect U.S. cattle from possible infection from screwworms. Screwworms infest livestock, and wildlife, by laying eggs in open wounds and orifices, and can kill an animal in seven to 14 days if left untreated. Livestock infected by screwworms, if caught in time, can be treated but treatment is challenging particularly for range cattle.
To treat effected livestock, they must be quarantined. Infested areas are treated by having any live larvae and/or eggs removed from infested sites by hand. Infested sites can then be disinfected and treated with a topical larvicide. Afterward, the animal can be treated with systemic antiparasitic medication. Livestock should then be monitored and treated in the same manner until no additional worms and/or larvae appear to be present on the animal.
Eradicated in the United States since the 1960s, North American Screwworms, a parasite in cattle may make an eventual return. Screwworms are most commonly found in livestock, pets, and wildlife; in extremely rare cases, they are found in people and birds. With the national cattle herd the smallest it has been since the 1950s, and beef prices high, an invasive pest like screwworms could be a challenge for consumers and ranchers alike. Now, however, is the time to address our present and future needs for concerns like screwworms by being proactive about prevention and innovation.
Pam Lewison is a farmer, Pacific Research Institute fellow, and director of the Washington Policy Center’s Initiative on Agriculture.
