reemergence of the new world screwworm
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Claude 4 Sonnet (T) via @hdevalence.bsky.social
Thinking Summary
The user is asking about what is triggering the reemergence of the New World screwworm (Cochliomyia hominivorax). Looking at the embedded scientific paper, I can see several factors that are contributing to or enabling the reemergence: 1. The paper discusses the reemergence happening in Panama (2023) and Mexico (2024-2025) 2. It mentions climate factors as being important 3. There are management/control issues mentioned 4. The paper discusses various factors that could contribute to reemergence Let me look through the paper more carefully to identify the specific triggers mentioned: 1. **Control program breakdown**: The paper mentions that COMEXA was dissolved in 2012-2013, and the Chiapas plant closed due to absence of funding. Currently, the only operational facility for the production of sterile flies is in Panama. 2. **Climate change**: The paper discusses how climate change could intensify favorable conditions for the species throughout the year and expand its geographic range. It mentions that seasonal patterns and global warming are key factors. 3. **Natural populations persisting**: The paper notes that some regions, such as the Caribbean, have endemic populations that prevail year-round. 4. **Movement and trade**: The paper discusses how practices related to commercialization and informal mobility could facilitate its expansion by promoting the transport of livestock infested with screwworm larvae. 5. **Surveillance gaps**: The paper suggests that strengthening epidemiological surveillance measures regarding livestock movement is crucial. 6. **Environmental suitability**: The paper shows that many areas remain climatically suitable for the species. Let me provide a comprehensive answer about what's triggering the reemergence.
Based on the scientific paper, several interconnected factors are triggering the reemergence of the New World screwworm (Cochliomyia hominivorax):
Primary Triggers
1. Breakdown of Control Infrastructure
- The Mexico-U.S. Commission for the Eradication of the Screwworm (COMEXA) was dissolved in 2012-2013
- The Chiapas sterile fly production plant closed due to lack of funding
- Currently, only one operational sterile fly facility remains (in Panama), creating a major gap in control capacity
2. Climate Change Effects
- Global warming is creating more favorable conditions year-round
- Expanding the geographic range where the species can survive
- The paper notes that "climate change could intensify favorable conditions for the species throughout the year and expand its geographic range"
3. Endemic Reservoir Populations
- Caribbean populations have persisted as endemic reservoirs (258,689 cases in humans and animals from 1995-2015)
- South America remains endemic except for Chile
- These populations serve as continuous sources for reintroduction
Contributing Factors
4. Livestock Movement and Trade
- Increased cattle trade within North America (2 million head annually)
- Informal livestock mobility can transport infested animals
- The paper emphasizes that "practices related to commercialization and informal mobility could facilitate its expansion"
5. Surveillance Gaps
- Reduced epidemiological surveillance after eradication success
- Limited monitoring of livestock movement
- Delayed detection of initial cases
6. Environmental Suitability
- Large areas of North America remain climatically suitable
- High livestock density in suitable areas creates ideal conditions
- The paper shows extensive suitable habitat along both Pacific and Atlantic slopes of Mexico
The "Perfect Storm"
The reemergence represents a convergence of these factors: reduced control infrastructure, climate change expanding suitable habitat, persistent endemic populations nearby, and increased livestock movement - all occurring with reduced surveillance vigilance after decades of successful eradication.
The paper warns that "as little as 1% of a C. hominivorax original population can be sufficient to recover damaging densities in just a few generations," highlighting how quickly the situation can escalate once reintroduction occurs.