America needs to produce and release some 600 million of sterile flies every week to contain the spread of the cattle screwworm between Panama and the United States, six times more than what is currently generated.
The challenge affects Latin America, a region that produces around 28% of beef consumed in the world and among the 7% and the 10% of milk, so the expansion of the pest can have consequences for food security beyond the affected livestock areas.
Given the resurgence, the Food and Agriculture Organization of the United Nations (FAO) and the International Atomic Energy Agency (IAEA) launched a project to strengthen the control of the pest in Central America, Mexico and the United States using the sterile insect technique.
The strategy consists of breeding larvae of the fly that causes the disease and subjecting them to radiation to make them sterile, without killing them or altering the characteristics they need to compete with wild specimens, which represents an advantage over the extensive use of pesticides.
Thus, the project contemplates optimizing this technology, training countries and accompanying its application with epidemiological surveillance, veterinary diagnosis, biosecurity and direct work with producers, explained the FAO Sustainable Livestock officer, Andrés González Serrano.
After becoming adult insects, the flies are transported in small planes and released in areas where epidemiological studies detect a higher concentration of the pest.
“Wild flies, which can reproduce, intersect with sterile ones, but in this mating no offspring, eggs or larvae are produced. Since they live for such a short time, we are gradually reducing the population,” explained González Serrano.
The effectiveness of this strategy was demonstrated during the process that allowed the screwworm to be eradicated from Mexico to Panama: the pest had been moved south and contained in the vicinity of Darién.
However, in the 2022 This barrier was no longer sufficient due to a combination of animal movements without health controls or traceability, environmental changes and climatic conditions that facilitated the movement of the fly.
Three floors to expand the answer
The Panama facility, managed jointly by that country and the United States, produces about 100 million of sterile flies per week, an amount that was sufficient while the plague remained contained, but which no longer responds to the current extent of the outbreak.
The Metapa plant, in Chiapas (southern Mexico), has already begun to produce and release flies, although it must gradually increase its capacity. To this will be added a facility in Texas (USA), whose operation will allow production to be brought closer to the highest risk territories.
These plants require high investments, specialized technology, laboratories with strict biosafety conditions and trained personnel to guarantee that the insects are sterile, but maintain the ability to compete and mate with wild flies.
Release is not done randomly. Health services use sampling, epidemiological studies and case records to determine the territories where there is a largest population of wild flies and concentrate flights there.
González Serrano estimated that, once the production of 600 million of flies weekly, a significant decrease in the insect population and new cases could be observed in a period of between twelve and eighteen months.
Complete eradication, however, could require several years of sustained work, public investment and coordination between countries.
“The sterile fly alone is not going to save us”
The specialist warned that producing more insects constitutes only one of the components of the response and does not replace the strengthening of health and veterinary systems.
“The sterile fly alone is not going to save us. We need to strengthen the capacity of veterinary services to diagnose in time, treat in time and connect with producers,” said González Serrano.
Livestock farmers are the first line of surveillance because they are usually the ones who detect the wounds. Quickly cleaning, disinfecting and protecting an injury can prevent the fly from laying its eggs and the animal from becoming a new source of spread.
One of the most vulnerable points is the navel of newborn calves, a natural wound that must be attended to immediately after birth to prevent it from being colonized by larvae.
The FAO specialist also highlighted the need to raise awareness among the population. A maggot wound on a cattle, horse, pet or wild animal should be reported to health services and not considered a problem that will go away on its own.
Sustainable livestock management and forest conservation are also part of the strategy, as reducing the distance between wildlife and productive areas increases contact and the risk of disease transmission.
The FAO also considers it essential that the ministries of Agriculture, Health and Environment share epidemiological information and coordinate their actions with neighboring countries.