TL;DR

• Screwworm Free Future is a new group seeking support to advance work on eradicating the New World Screwworm in South America.
• The New World Screwworm (C. hominivorax - literally "man-eater") causes extreme suffering to hundreds of millions of wild and domestic animals every year.
• To date we’ve held private meetings with government officials, experts from the private sector, academics, and animal advocates. We believe that work on the NWS is valuable and we want to continue our research and begin lobbying.
• Our analysis suggests we could prevent about 100 animals from experiencing an excruciating death per dollar donated, though this estimate has extreme uncertainty.
• The screwworm “wall” in Panama has recently been breached, creating both an urgent need and an opportunity to address this problem.
• We are seeking $15,000 to fund a part-time lead and could absorb up to $100,000 to build a full-time team, which would include a team lead and another full-time equivalent (FTE) role
• We're also excited to speak to people who have a background in veterinary science/medicine, entomology, gene drives, as well as policy experts in Latin America. - please reach out if you know someone who fits this description!
   

Cochliomyia hominivorax delenda est

Screwworm Free Future is a new group of volunteers who connected through Hive investigating the political and scientific barriers stopping South American governments from eradicating the New World Screwworm. In our shallow investigation, we have identified key bottlenecks, but we now need funding and people to take this investigation further, and begin lobbying.

In this post, we will cover the following:

• The current status of screwworms
• Things that we have learnt in our research
• What we want to do next
• How you can help by funding or supporting or project
   

What’s the deal with the New World Screwworm?

The New World Screwworm^[1] is the leading cause of myiasis in Latin America. Myiasis “is the parasitic infestation of the body of a live animal by fly larvae”. This^[2] footnote describes the infection in more detail, there are also many photos online if you want to see examples. Although it’s hard not to over-update on the ‘eww’ aspect it seems true that a screwworm infection is very painful. Infected animals display atypical behaviours associated with suffering – they stop eating, isolate themselves from their herds or groups, often can be seen attempting to bite or scratch at the affected areas, and towards the end of an untreated infection animals become lethargic, immobile and then die. 

Even when treatment is available for farmed animals, it involves the traumatic manual removal of larvae, typically without anaesthesia. This process requires opening the wound further with a knife to extract deeply burrowed larvae.

New World Screwworms were eradicated from North and Central America in the second half of the 20th century, in an US-led effort to reduce economic losses. This eradication protected millions of farmed and wild animals from screwworms.^[3] The eradication was done with the Sterile Insect Technique (SIT), a method where Screwworm pupae are irradiated with radiation that sterilises them. Since female screwworms only mate once in their lifetime, when the sterile males are released there is no reproduction, and the population shrinks.

For a long time, a “wall” of sterile screwworms at the Panama border prevented screwworms from returning to Central and North America. This large project requires over $15 million annually to release 20 million sterile flies in Panama. Unfortunately, this wall broke sometime in 2023, and screwworms have been speeding up Central America. One official we talked to said that they had “no control” over the current screwworm situation.

This wall-breaking adds both urgency and opportunity to act on screwworms now. There has been some media attention on the screwworm spread, and the US government has acted blocking cattle imports from Mexico after a recently reported case. From officials we’ve talked to, we know there are meetings between US and Latin American officials. We hope that this punctured equilibrium provides an opportunity to get the US government involved in eradication efforts in South America.

Two other things to note:

• There appears to be some new resistance of screwworms to the antiparasitic drugs Ivermectin and Doramectin.
• Climate change is expanding the habitable range of screwworms. This study concludes that, with rising temperatures, screwworms could become established year-round in the US.

If Screwworms were only a case about the large amount of preventable wild animal suffering, then this intervention probably wouldn’t be very tractable outside of EA circles. Fortunately, (or unfortunately) screwworms have a massive economic impact on Latin America. For example, this (slightly old) estimate says that the eradication of screwworms in Latin America would save farmers $3.5 billion annually^[4]. Other key country-specific figures:

• Screwworms cost about 41 million USD/year in Uruguay.

• They cost about 52 million USD/year in Argentina^[5].

• In Brazil, they cost 450 million USD/year just in navel myiasis^[6].

  • In the southern state of Rio Grande do Sul alone, costs are estimated at 28.3 million/year.

Because of this large economic incentive, screwworm eradication is much more tractable.

What we’ve learnt so far

Over the past months, we've been doing a literature analysis and meeting with government officials, with the aim of identifying the scientific and political barriers to screwworm eradication. We've identified five key bottlenecks:

1. Coordination Issues:
   The eradication efforts in North America were led and funded by the US and just went down the “corridor” of Central America. South America’s geography and multiple borders require transnational agreements and extensive coordination, which complicates the process. For example, eradicating screwworms in Uruguay requires cooperation from Brazil and Argentina to prevent re-infestation. Due to the border length, a biological barrier between South American countries like the one in Panama would be almost impossible to maintain.

   Uruguay currently has an SIT eradication project, (supported by the USDA and international organisations) which is dependent on the collaboration of Brazil and Argentina to succeed.

2. Lack of Awareness and interest:
   Authorities in South America show little interest in eradicating screwworms, despite farmers and experts considering it a priority. Our Interviewees suggest this is due to a status quo bias—farmers’ representatives are now used to screwworms, and consider eradicating them less urgent than other causes^[7]

   Relatedly, in Brazil we can't find data on the overall prevalence of the disease in cattle, even though ranchers are supposed to, by law, monthly report new cases to animal health authorities; we suspect that the disease is underreported.

3. Lack of Funding:
   SIT-based eradication programs are expensive. Central America succeeded in eradication largely because it was 80-90% US-funded. Uruguay’s current 10-year SIT based program is estimated to cost $114 million USD.
4. Technological Limitations:
   The Sterile Insect Technique works, but is expensive and requires continual release of screwworms. Gene drives are promising, however, a C. hominivorax gene drive is still in development, and they face large regulatory hurdles (eg. compliance with the Cartagena Protocol).

5. The role of the U.S.

   Screwworms were eradicated from North and Central America in a project led by the U.S. The Uruguayan eradication programme is funded by U.S. agencies. This makes the U.S. the main player in eradication efforts, and we think their role is crucial. If they decided to expand their plans to South America, this would be game-changing.

Future plans

Our research has convinced us that there is much work that can be done to accelerate screwworm eradication. With funding and staff, we would focus on X main areas:

• Political lobbying: Latin American representatives working on screwworm eradication are very scarce. Getting commitments from politicians sounds plausible, as they would achieve something almost no lawmaker has yet done: champion animal welfare, farmers' protection, rural development, and economic growth. This would greatly improve the chances of making eradication a transnational priority.
• Act as a coordinator facilitator organisation: often, countries are trapped in themselves, and are unable to work with other countries to achieve common goals. In an activity that requires as much coordination as screwworm eradication, an organisation actively coordinating countries through multilateral meetings, conferences, and other events would have great potential to maximise impact.  

• Accelerate research: screwworm eradication is partially constrained by knowledge gaps. Some of these have to do with the behaviour of political institutions and their seeming lack of interest in collaborating. But most of it revolves around the development of novel techniques to make eradication easier and cheaper. Currently, there is only one lab in Uruguay working on developing one of this novel technology: gene drives. With more funding and staff, we would work alongside research institutions and funders to push for more research into eradication alternatives^[8].

• Lobby the industry: While for farmers getting rid of screwworms is a priority, for their representatives it is seen as something that doesn’t merit much attention compared to other issues. Lobbying these farmers’ associations has the potential to accelerate screwworm eradication by improving political awareness.

Request for support

While we think the activities outlined above are crucial and necessary to accelerate the eradication of screwworms in South America, we are currently at capacity, and are unable to pursue any of them with the time and dedication required. We are, then, constrained by funding and expertise:

• Funding/time:
  Our volunteer team members have other commitments and can only dedicate ~5 hours per week to this project. To make significant progress, we need people working full-time, which requires funding.
  • Proposed solution:
    $15,000 for a part-time program director, and a research associate. With the capacity to expand to 100k for a full-time team 
    If you are an individual donor interested in funding us, drop us a message!
• Expertise 
  We are seeking connections with:
  • Veterinarians
  • Entomologists
  • People with Gene drive experience
  • Latin American policy experts
  • If you are one of these people or know someone who is, we want to talk to you!

If you are a funder or interested in funding suffering-reduction interventions, or an expert in disciplines relevant to eradicate screwworms, please reach out to us. We need your support to spare thousands of animals of extreme and excruciating suffering.

Relevant EA discussions on Screwworms:

• Wild Animal Initiative is planning on funding a research investigating the welfare effects of screwworm eradication
• Animal Ask has included eradicating screwworms from Brazil as one of the top priorities for impact in the country
• Policy advocacy for eradicating screwworm looks remarkably cost-effective — EA Forum
• Potentially actionable opportunity: eliminating the New World screwworm (flesh-devouring maggots that affect a billion animals each year)
• Cameron Meyer Shorb on dismantling the myth that we can’t do anything to help wild animals - 80,000 Hours
   

1. ^{^}

    There are other types of screwworms (Chrysomya bezziana, known as the Old World Screwworm), and other related flies that cause myaisis (such as the Lucilia cuprina). For the rest of the post, when we say ‘screwworms’ we will be referring to New World Screwworms.

2. ^{^}

    When female screwworm flies detect a small wound (even as small as a tick bite or scratch) they lay 200-400 eggs at the site. Within 12-24 hours, these hatch into larvae that feed on living tissue, using sharp mouth hooks to tear into healthy flesh. Unlike regular maggots that consume dead tissue, screwworm larvae secrete enzymes to liquefy and digest live tissue, preventing healing and enlarging the wound as they grow. Over 5-7 days, the larvae burrow deeper, causing severe pain as they feed on nerve-rich tissue. As the wound increases in size more female screwworms can lay eggs in the same wound, leading to a feed back cycle of more larvae → larger wound → more larvae. Without treatment, animals suffer painful deaths from tissue destruction, secondary infections, organ failure, fluid loss, exhaustion a combination of the above, or being caught by predator because of their weakened condition.

3. ^{^}

    FAOSTAT estimates ~500 million animals in 1999 (pg 633)

4. ^{^}

    According to an estimate, $3.5 billion could be saved in 2005 if screwworms were eradicated (pg 634). This is an annual cost of $5.8 billion after adjusting for inflation (2024).

5. ^{^}

    These two figures were mentioned in conversations with government officials.

6. ^{^}

    A 2014 study estimates $340 million USD/year, that is $450 USD in today’s money.

7. ^{^}

    Relatedly, in Brazil we can't find data on the overall prevalence of the disease in cattle, even though ranchers are supposed to, by law, monthly report new cases to animal health authorities; we suspect that the disease is underreported.

8. ^{^}

    Some of our unanswered questions include:

   How much cheaper (if at all) is developing and deploying a gene drive compared to SIT? Also, how much do sexing strains in SIT facilities reduce the cost of SIT?

   Are there any proposals in Brazil to use GMOs—as is already the case, for example, for Aedes mosquitoes and the Spodoptera caterpillar (p. 63 of this report)? And the use of gene drives? Would GMO release depend on a license from CTNBio, Anvisa, or another public agency?

   Cases of C. hominivorax in livestock seem to be subject to compulsory notification in Brazil (according to the regulatory standard in maps 50/13). However, NWS is not listed on the official notification page why? Are there open databases that we can consult (or request access to) about this? Or a database with data on slaughtered animals?

   Why are there no C. hominivorax reports in central Amazonas (IAEA, slide 12)? Is this due to missing data in remote areas, or could rivers and dense forests act as natural barriers, as the same claim for the Argentina-Uruguay border?