The number of confirmed cases of myiasis caused by the screwworm has risen to 4 in the state of Mapastepec, Chiapas, with two new confirmations. The patients, adults from the Altamira ejido, have been hospitalized in the state capital, Tapachula, for treatment. Frida Viridiana Coutiño Jiménez, the public health commissioner in Mapastepec, has issued a preventive alert to avoid further contagion in the area.
The authorities are urging the population to report any contaminated livestock without the need for the ranch to be quarantined. Chiapas is home to 60% of the country’s myiasis cases caused by the screwworm, which affects horses, sheep, goats, and chickens.
The Screwworm: A Historical Plague
Since the screwworm reappeared last year, the government and state authorities have been closely monitoring rural areas with high presences of the Cochliomyia hominivorax fly, whose larvae infest open wounds and cause myiasis in both animals and humans. This poses a high risk of other diseases.
In 2024, the first human case of myiasis was recorded on April 18 in the municipality of Acacoyagua, affecting an elderly woman who was later discharged after showing signs of improvement. The second infection was confirmed on May 8 in a 50-year-old man from the municipality of Tuzantlán, who presented symptoms of myiasis in a wound caused by a dog bite.
Economic Impact of Livestock Infestation
The reappearance of the screwworm has led to the temporary suspension of Mexican livestock exports to the United States, resulting in significant economic losses for farmers. To combat this, measures that were effective in the past are being implemented, including the release of sterile male flies that mate with wild females and disrupt the reproductive cycle.
The screwworm has caused millions of dollars in losses due to the devaluation of infested livestock. The infestation has also led to problematic behavior in livestock, directly affecting animal-based food production. The government and producers have had to invest significant resources in control measures, in addition to being unable to export livestock to countries free of the plague, such as the United States.
The Dangers of the Screwworm
The harmful effects of the screwworm are caused by the myiasis produced by its larvae. In animals, infested wounds secrete a serosanguinous liquid and have a strong odor of rotting flesh, causing intense pain. This is accompanied by a depressive effect, leading to harmful behaviors such as loss of appetite and isolation.
The infestation occurs through wounds, which become inflamed and painful as the larvae feed on living tissue. The larvae cause significant damage to tissue as they grow and move, and in extreme cases, can reach internal areas of the head or other parts of the body, depending on the start of the infestation.
Without treatment, myiasis can be fatal due to the infections it causes, especially in newborns, within 7 to 14 days if left untreated. Therefore, it is essential for the authorities that the entire population takes preventive measures to avoid contact with the fly that causes this myiasis, which has already affected 4 people in the state of Chiapas.