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 whether the New World screwworm flies need an existing wound or if they create them. Let me look at the scientific paper to find this information. From the paper, I can see this information: 1. The paper mentions that females lay eggs in wounds of warm-blooded animals 2. It mentions that "umbilical lesions are a natural attraction for C. hominivorax" 3. The paper shows images of flies laying eggs in animal wounds 4. It mentions that the larvae "feed on the host tissue, causing severe lesions" From the paper text: "Females can lay up to 500 eggs per oviposition, typically performing around four ovipositions within 15 min (Fig. 1c-f), with eggs hatching within 12–24 h at 35 °C. The larvae feed on the host tissue, causing severe lesions before completing their development and falling to the ground to pupate" And: "Newborn animals are the most vulnerable, as umbilical lesions are a natural attraction for C. hominivorax" This suggests they need existing wounds to lay eggs in, but the larvae then expand these wounds significantly by feeding on tissue. Let me check if there's more specific information about this... The paper describes that they cause "myiasis" which is infestation by fly larvae in living tissue. The images show flies laying eggs in existing wounds. So it appears they need existing wounds initially, but then the larvae create much more extensive damage.
Based on the research paper, New World screwworm flies require existing wounds to lay their eggs - they cannot create the initial wound themselves.
Here's what the paper reveals about their behavior:
Initial Wound Requirement
- Female flies lay eggs in existing wounds of warm-blooded animals
- They are particularly attracted to umbilical lesions in newborn animals
- The paper shows images of flies laying eggs in animal wounds (Figure 1d)
- Any break in the skin - from cuts, scratches, castration, dehorning, or natural processes like birth - can serve as an entry point
Secondary Damage Creation
However, once the eggs hatch, the situation becomes much worse:
- Larvae feed on living tissue, causing the original small wound to become a severe, expanding lesion
- The feeding larvae create "severe lesions" that grow much larger than the original wound
- This tissue destruction is what makes screwworm infestations so devastating - a minor scratch can become a life-threatening wound
Why This Matters
This biological requirement is actually important for prevention strategies:
- Wound management in livestock is critical
- Newborn animals are especially vulnerable due to umbilical wounds
- Timely treatment of any cuts or injuries can prevent infestation
The paper notes that mortality rates can reach up to 20% in affected animals, largely because the larvae transform minor wounds into major, infected lesions that can kill the host if untreated.
So while the flies themselves don't create wounds, they turn small existing wounds into potentially fatal ones.