Introduction to Screwworm and its Impact
The screwworm, a parasitic fly whose larvae infest open wounds of warm-blooded animals such as cattle, horses, pets, and wildlife, has recently raised concerns in Nuevo León, Mexico. This pest causes severe physical damage and productivity losses in the agricultural sector.
Second Case Confirmed in Nuevo León
The Mexican Secretariat of Agriculture reported a second case of screwworm in Nuevo León, specifically in the municipalities of Sabinas Hidalgo and Montemorelos. This discovery is alarming as the region borders the United States, previously considered screwworm-free.
According to the Grupo de Consultores de Mercados Agrícolas (GCMA), the case originated in Chiapas, which has the highest number of active cases in Mexico.
- As of October 4, 2025, there have been a total of 7,885 cases in Mexico, with 7,195 controlled and cured, and 690 remaining active (8.7% of the total).
- Chiapas leads with 3,959 cases, followed by Oaxaca (910) and Tabasco (890).
- The appearance of two cases in the northern region is a critical point for the containment and binational surveillance zone.
Economic and Trade Implications
Juan Carlos Anaya, director of the GCMA, stated that the outbreak has caused economic impacts on the livestock sector, particularly among feedlots. These businesses face an approximate increase of 600 pesos per head due to additional costs for controlling the screwworm.
As a result, the temporary suspension of live cattle exports to the United States has been enforced. Mexico is actively conducting an eradication campaign that includes the release of over 3 million sterile screwworm flies, inspection, treatment, and curing of 1.7 million heads of cattle, as well as verification of 27,000 shipments.
Furthermore, a screwworm sterile fly production plant is being built in Metapa, Chiapas, in collaboration with Senasica and international authorities.
Shared Responsibility for Screwworm Control
Anaya emphasized that “screworm control is a shared responsibility. Producers, accumulators, and feedlot operators are urged to maintain constant vigilance, report any suspected cases promptly, and reinforce biosecurity measures in their production units.”
Key Questions and Answers
- What is the screwworm? The screwworm is a parasitic fly whose larvae infest open wounds of warm-blooded animals, causing severe physical damage and productivity losses.
- Why is the second case in Nuevo León concerning? The discovery of screwworm in Nuevo León is alarming because the region borders the United States, which was previously considered screwworm-free.
- What are the economic impacts of screwworm outbreaks? Screwworm outbreaks cause increased costs for controlling the parasite, particularly in feedlots, affecting the livestock sector’s profitability.
- What measures are being taken to control screwworm? Mexico is conducting an eradication campaign involving the release of sterile screwworm flies, inspection and treatment of cattle, and construction of a sterile fly production plant.
