Deadly Snails Invading the US!

Yesterday evening my wife and I were having supper with family friends when a young lady – very much attuned to social media of diverse sorts, as so many of the youth these days – mentioned that she had been “bombarded” with alerts about dangerous snails in North Carolina.  This was completely out of the blue.  She’s not a biologist – does not follow technical news feeds – just a regular citizen of the Charleston area in her mid-20s.

NCWRC

I, very much the opposite, confessed complete ignorance of the situation.  So, our young friend whipped out her smart phone, deftly touched off three key strokes and a swipe, and there was the news.  Invasive Pomacea of the maculata/canaliculata sort have been reported in the Lumber River at Lumberton, NC.  But my goodness, the hysteria!

The media frenzy seems to have been kicked off by a perfectly responsible press release from the North Carolina Wildlife Resources Commission on Monday 2Oct23 [1].  Initially alerted by a concerned citizen, the NCWRC conducted a survey that did indeed confirm an invasive Pomacea population extending from the I-95 bridge just above Lumberton [2] to a boat ramp about 6 km downstream.  In measured tones, the press release cautioned:

“Apple Snail grazing habits can damage plants used by many native aquatic species and they have even been observed feeding on amphibian eggs. Additionally, Apple Snails can present human health risks. They may carry rat lungworm, which can cause a potentially fatal disease in humans if the snails are eaten raw or undercooked.”

From that relatively innocuous paragraph came the New York Post headline of 4Oct23, “Deadly Apple Snails found along North Carolina River,” and from CBS News, “Invasive snails that can be deadly to humans found in North Carolina.”  But my favourite headline came from the UK Daily Mail, “Invasive Snails Deadly to Humans are Invading the US!” [html] [pdf] 

The Lumber River continues into South Carolina to unite with the PeeDee River about 50 km downstream from Lumberton.  Another 80 km downstream by kayak through impenetrable swamp would bring us to the mouth of the Waccamaw River, from whence it is but 10 – 15 km back upstream to Socastee, SC, where invasive Pomacea were first reported in 2008 [3].  Whether the North Carolina population represents a new introduction, or simply a 150 km expansion of the South Carolina population, remains to be determined.

We saw a similar wave of concern spread through the Myrtle Beach area of South Carolina when the snails first arrived here 15 years ago, although much lower in amplitude and local in extent.  The local newspapers here described apple snails as merely “harmful” or “worrisome,” not “deadly.”

In retrospect, the NCWRC might have added significantly more context to their press release.  South Carolina researchers have found no evidence of Angiostrongylus parasitism in samples of Pomacea taken here in The Palmetto State [4].  Indeed, the extensive 2013 survey conducted by Teem and colleagues across Louisiana, Texas, Mississippi, and Florida yielded only 8 cases of Angiostrongylus parasitism in 296 Pomacea tested, all from the New Orleans area [5].  And as for cases of actual rat lungworm disease in humans, the CDC was only able to confirm 12 cases in the continental USA 2011 - 2017, the majority of which were linked to eating raw vegetables, not snails [6].

So when invasive Pomacea arrive in Virginia, here’s a suggestion for that press release.  Bold the clause, “if the snails are eaten.”  And suggest that the readership resist the temptation to pop one in their mouths.  Everything will be OK.

Notes

[1] Invasive Apple Snails Now Confirmed in North Carolina.  North Carolina Wildlife Resources Commission, 2October23. [html] [pdf]

[2] In my blog post of 13June18, I advocated legislation to build “a big, beautiful wall on the North Carolina line from Cape Hatteras to Tennessee, 50 feet tall by back-of-the-envelope calculation, Pedro himself manning the I-95 guardhouse just two mucus trails and one gigantic traffic jam North of the Border” to intercept just such a Pomacea invasion as North Carolina is now experiencing here in 2023.  See, I told you so.

[3] More about Pomacea in South Carolina:

• Pomacea spreads to South Carolina [15May08]
• Two dispatches from the Pomacea front [14Aug08]
• Pomacea News [25July13]
• Invasive species updates [13June18]

[4] Underwood, E.B., M.J. Walker, T.L. Darden & P.R. Kingsley-Smith (2019) Frequency of occurrence of the rat lungworm parasite in the invasive island apple snail in South Carolina, USA.  Journal of Aquatic Animal Health 31(2): 168 – 172.

[5] Teem, J.L., Y. Qvarnstrom, H.S. Bishop, A.J. DaSilva, J. Carter, J. White-Mclean, and T. Smith (2013)  The occurrence of the rat lungworm, Angiostrongylus cantonensis, in nonindigenous snails in the Gulf of Mexico region of the United States.  Hawaii J. Med. Publ. Health 72: 11 – 14.

[6] Liu EW, Schwartz BS, Hysmith ND, et al. (2018) Rat Lungworm Infection Associated with Central Nervous System Disease — Eight U.S. States, January 2011–January 2017. Morb Mortal Wkly Rep 67:825–828.