The Resurgance of a Menace.. ** Squirm Alert **

[Silas_Sancona]

****  Fair warning   ..For those a bit squeem-ish when it comes to gross things,  you might want to look away..   ****

A few years back, i'd mentioned something ..somewhere.. regarding an insect " pest " that  legitimately qualifies as a threat.. Not necessarily to plants,  but  to ..anything else, inc. humans.. 


While flies themselves are pretty gross creatures, the New World Screw worm,  Cochliomyia homnivorax  ups the " Gross " factor  ..just a bit..  The Latin name literally translates to " Man Eater "  ..and yes, this Bug- eyed, Obligate Parasite can kill a man ( ..or woman ) and was once one of the greatest threats to livestock in the US  " back in the day "  ...up until it was eradicated from the US in the early 80s.

That campaign continued thru the 90s / earlier 2Ks until this insect was beaten back to -roughly- the Darien Gap in Panama. Beyond that, in South America, and some islands in the Caribbean where it hangs on,  the efforts to fully take out this insect has been challenging due to terrain, costs, and / or political will.

It was gone here in the states until it quietly reappeared in the FL. Keys sometime in 2016 where the outbreak seen there killed numerous Key Deer, and was detected in a stray Dog in Homestead just north of the designated quarantine zone there before the control measures used to knock down this insect worked as planned.

Fast forward to last summer, and while doing my yearly " check in " on efforts to control / any new, general research on this insect,  there were reports coming out of both Panama and Costa Rica of new outbreaks being seen in some areas of both countries.

Tack on another year and it appears the threat posed by this insect is quickly spreading across all of Central America, with a detection noted in Chiapas in the last couple weeks.. This is occurring despite re-invigorated and stepped up efforts to get the more severe outbreaks in Panama and Costa Rica under control again..

When i'd read the last reports of it being detected in Guatemala, i had a feeling it wouldn't be long until it reached southern Mexico.. That has happened..  Question now is ..how far north will it progress? ..and can the control efforts currently underway stop the advance - before- outbreaks are detected much closer to the US?

Before full eradication, when it roamed the US, outbreaks were seen as far west as central California, As far north as the Central Plains and Southeastern states, north of FL. It was also sporadically detected in the upper Midwest during years when conditions were ideal.

Another question regarding this current resurgence involves whether or not the female flies of this species have gained some sort of new ability to " sus out " the sterilized males released and now avoid them..  That would destroy the current means of effective control of course.  Maybe a vaguely rumoured strain of the species that was rumoured to possess some resistance to radiation, that is spreading into new areas is responsible?? ..Time will tell...


Regardless, putting this out there as a " Keep your eyes -and ears- on this situation over the coming months " kind of  advise, rather than a " The sky is about to fall " alarm.  Understand the difference..



Highly doubt this fly will return to the US  -in any great numbers at least- but,  We'll have to see since  -so far- the extra aggressive response to this current situation isn't seeming to have much effect.. That said, ..as was the case in the past when the battle began, full, regional control can take up to several years..

In that time, reports of sporadic, localized outbreaks aren't completely out of the question further north in Mexico, and / or possibly in FL. again, and perhaps the border regions of Texas / other states, depending on what weather events occur..  It is thought that the outbreak seen in FL. was a result of flies being blown north from Cuba by a Hurricane.  Should such occur, it wouldn't be out of the question that the occasional sterilized fly turns up in someone's yard.

Won't post it here but there is a really good observation on iNaturaliust that details the trademark markings of adult NWS flies, ...as compared to the ..roughly, 4 or 5 other species of similar looking fly species that are common in the US,  None of which cause the same issues as NWS.

One significant step has apparently been made in that the US has now suspended all imports of Cattle from Mexico. I don't doubt restrictions on the importation / movement of other livestock may occur if outbreaks expand north beyond far southern Mexico over the coming months.

Something to monitor casually,  but closely.. 


Related articles...  Will add more  when / if  need be..

*** As stated at the top,  .If gross things make ya' squirm,   turn away ***

Scientists built a great wall to keep out the ‘man devourer’ – but now it’s fighting back

https://www.cdc.gov/coca/hcp/trainings/resurgence-new-world-screwworm.html

https://u.osu.edu/beef/2024/11/27/cattle-imports-from-mexico-restricted-after-new-world-screwworm-detection/

https://publications.aap.org/aapnews/news/30599/Twice-eradicated-parasite-threatens-northward?autologincheck=redirected

[Looking Glass]

Screw worms and bot fly larva.  Two things I don’t need around the yard.  I go outside and work for hours at a time til sun set, getting bit by tombs of mosquitos all day long.  I don’t wear bug spray or react to the bites anymore.  It just leaves a flat tiny red dot with no itching.   Horse flies and deer flies are annoying, but a can’t imagine having to worry about this.  Tropical worms please stay in the tropics.  

 

I used to remove bot fly larva from our animals growing up on a mini farm.  It was rare, bit memorable.   You’d occasionally see sick, small mammals, like deer mice, with them hunting or fishing.  I can’t imagine screw worms.   That’s a whole other level with a lot of impact on farming.  

 

[Silas_Sancona]

A quick update on the NWSW situation in Mexico and Central America as we head into the warm season...

As thought, despite the battles being waged against it down there over the past few months, positive detections continued to increase thru the winter months, with numerous newer detections made in southern Mexico, more in nearby Belize, Honduras, and El Salvador.

At the same time, the USDA resumed cattle / other livestock imports from Mexico back in January.

According to the latest info from the USDA, it appears two near SIT ( Sterile Insect Technique ) facilities will be set up somewhere in southern Mexico over the next few months, north of where the most recent confirmed detections have been made..  Will have to wait and see whether or not they'll be up and dispersing sterile flies before fertile flies manage to move north of where these facilities are planned for.

With that said, as mentioned before, and esp. in light of recent developments,  don't rule out sterile flies being sighted near or just north of the Mexico / U.S. border,  perhaps in S. FL. if blown north, beyond where the planned releases are by any hurricane that tracks across the western Gulf of Mexico / toward the us from the Yucatan later on this year..

A current map of positive detections, via APHIS / USDA.  COPEG's map is greatly outdated..



While it doesn't mention exactly where they'll be set up, a related article mentioning the USDA working with Mexico and COPEG to set up the new rearing facilities..  I'm sure more information will come out over the coming months. 
https://www.aphis.usda.gov/news/program-update/establishing-new-world-screwworm-sterile-fly-barrier-zone-mexico-prevent


Will be watching to see if any detections start showing up in northern Veracruz, Yucatan and Quintana Roo, and along the Pacific coast in Southern Oaxaca. ..Let alone anywhere further  north / west of that part of Mexico. < Hopefully not >

As a side note, Came across this  https://pmc.ncbi.nlm.nih.gov/articles/PMC7789611/    interesting article discussing how while N.W. Screw Worm can infest Pigs, which obviously inc. feral hogs / wild Boar, they appear to suffer relatively minor effects and can be a significant means of dispersal that can go un-noticed, wild Boar esp. 

Think we're the only country w/ an extensive Boar issue?.. Well established problem in both Mexico and the rest of Central / South America as well.

Will check in on this again sometime in May.

[Silas_Sancona]

June  / start of summer 2025 NWSW update:

Once again, as thought might occur as spring warmth / start to the rainy season in S. Mexico gets underway, Positive NWSW detections have reached the southern end of the Mexican Plateau / further north into Veracruz..  ...as of the dates of the last map update below..






Possible  *** But  NOT  confirmed  / yet reported ****   there have been detections further north ( Up on / along either side of the Plateau ) / east ( Yucatan Pen. ) of those listed currently. 


While the " confirmed / logged confirmed " detections are still quite a distance from the U.S., they are close enough ( within 700 miles ) that the USDA shut down all livestock imports into the U.S. from Mexico for the time being. ....And anyone involved in the livestock end of the AG. industry here in the U.S. are on elevated  notice to watch for any possible cases.  Stepped up urgency regarding reactivation of former / starting new..  Sterile Fly facilities in Mexico,  and possibly the U.S. ( Texas = Being discussed currently ) 


While NWSW is not present in northern Mexico right now,  article link  below mentions the  slim ( atm ) but reasonable possibility that flies could reach the border region, ..TX end esp.     by late summer or early fall    ..if...  Emphasize IF   everything that could hasten it's spread north were to come together. 

Note too how quickly they spread across Central America when this latest breakout began on the 2nd map above. 

https://www.abqjournal.com/news/article_873fb5dc-f79b-461a-bd23-4b78fb0c7e3c.html

Hopefully that doesn't happen but,   ..it's enough of a potential that ..everyone.. whether involved in raising livestock, or pet owners..

....Time to start educating yourselves on this serious threat.. ..No matter how gross the research into it might be to the easily squeamish...  


Should Texas decide to get a Sterile Fly facility up and going / Mexico does the same in any of the border states over the next few months, Flies may be seen as batches of them are released in preemptive target areas along the border, or nearby. 


Next update: Start of July.. 

[Silas_Sancona]

August 1st check in... after skipping July..

As thought, confirmed detections continue to inch further north...   How much further north could they get before October??? ..That's the big question atm.. and no, while both Mexico and Texas are in the process of ramping up their Sterile Fly facilities, neither will be operational before we reach -at least- November  ..If not until sometime in 2026. 


Aside from flies being spread around via livestock movement, NWSW is now well within where wild Boar are fairly common in Mexico. 

While all wildlife is capable of moving NWSW to new areas,  it is wild Boar ..and native Javalina.. which can move long distances quite easily, and are skilled at avoiding capture that i myself are most concerned about at this time.. 





On the map above,  i included some chicken scratch to sorta outline what to keep an eye on over the next 2-3 months..

#1: Where the latest confirmed detections have been recorded.  Also includes a " plausible " area where sightings / outbreaks may be occurring in wildlife / livestock,  but haven't been reported..  Lots of extremely remote, very rugged terrain in that part of Mexico which = high likelyhood of screw worm issues occurring " under the radar "  ** thoughts on that specific aspect are my own. Is not an "official" suggestion **



#2:  ...IF...  things continue to progress as they have so far, #2 outlines the most likely area of Mexico for new reports, outside of area 1 by mid / late September, esp. on the eastern side of Mex... 



#3:  the northern-most " possible " positive detection report(s)  outcome boundary by October..   esp. if hurricane season ramps up and that side of the Gulf sees the brunt of any storms over the next 2-3 months..  Depending on the weather during that time, you could extend the " possible detection area " in S. TX a little further north..  Warmer / wetter? = perfect conditions for further spread..



#4: While the SIT program did successfully push it south of Panama,  NWSW issues have remained endemic / sporadic in Cuba and some of the Caribbean islands since the species was first encountered / named.

SIT elimination campaigns have garnered some success in the Caribbean, but haven't yet completely eliminated it. 

 It is thought that Cuba  ..or one of the nearby islands..  was the source region of the last U.S. outbreak that occurred in the FL. Keys / Homestead area back in 2016..  Flies are thought to have been swept north, into the Keys by one of the Hurricanes that passed over both areas, before reports started to occur ( ..in the Keys )



#5:  Because detections continue to increase across the Yucatan section of Mexico, it is possible that flies from this latest surge on the continent successfully land on Cuba,  and/or other nearby islands   and mix genes with flies there.. 

...If that did occur, and a super-charged surge started to spread rapidly across Cuba, then southern FL. would be under threat once again, under the same kind of circumstances that moved flies to the keys during the 2016 outbreak.. ( #6 )   Obviously, like any other critter,  flies could hitch a ride on a boat passing between Cuba and Key West too..





Overall, next 3 months = keeping a close eye on/ fingers crossed.    Beyond that?  We'll have to wait and see how things are looking as we head into this winter.. 

Abnormally cold weather in Cen / Southern Texas / the southeast  beat back NWSW surges a few times in the past when the fly was present in the U.S. before the SIT program began. 

Beyond that?  if in S. TX?  do some research on a product called Swormlure-5.  Appears the Ag dept there will be using it again to catch any early signs the flies have arrived in the state. 

Nasty as it is, rotting Liver set in traps attracts them too..


...Unless something major occurs before, We'll see how things are looking next month.