Frozen Shrimp: Deliciously Deadly (Vibrio vulnificus)

(**Istituto Zooprofilattico Sperimentale delle Venezie (IZSVe)**, 2015)

Setting the scene – It’s Memorial Day weekend. The pools have just opened, the grills have been pulled from their hibernation in garages cluttered with floaties and roller skates just waiting to be unpacked for a summer of fun. Parents near and far are unwrapping 24 packs of hot dogs and hamburgers, breaking out the buns, ketchup, and, best of all, taking those bags of frozen seafood out of their freezers to be enjoyed by the more “adult” crowd. Because what says, “here’s to three months of crippling heat” like grilled shrimp and a margarita?

So what makes these small, pink delicacies so dangerous anyway? So long as you wash your hands properly, they certainly can’t hurt you? As much as I’d love to say that were true, it’s just not. Shockingly, a Consumer Report (c. 2015) found that up to “60 percent of 342 samples [284 raw, 58 cooked] of frozen shrimp it tested contained Salmonella, Vibrio, Listeria, or E. coli, and 2 percent tested positive for the superbug MESA (Methicillin-resistant Staphylococcus aureus…” (Food Safety News, 2015) That can be a little unsettling for some who are afraid of germs, but the less phobic would probably question ‘aren’t we going to throw these into a pan anyway?’

While this is a fairly typical train of thought, I do regret to inform you that Vibrio vulnificus is actually one of the most harmful bacteria before it even hits the pan. After thawing your shrimp, it’s pretty common to reach right into that shrimpy water and peel, disposing of those hard-shell husks in the kitchen trash. Do you have a small cut on your finger? Bingo. That’s one way the tiny bacterium can trojan horse its way directly into your body.

You see, what a lot of people don’t know is that the same scary bacteria that causes necrotizing fasciitis (i.e. flesh eating bacteria) in unknowingly river dwellers is also caused by the same Vibrio vulnificus bacteria found in our frozen shrimp. It can also cause sepsis – a bacterial infection of the blood which can cause skyrocketing temperatures, disorientation, gastrointestinal upset, severe weakness, and, worst of all, septic shock – which can lead to sudden drops in blood pressure, organs failure, and even death. (CDC, n.d.)

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Vibrio vulnificus is a gram-negative bacteria. While it has a peptidoglycan wall to help keep its shape, it also has a membrane made of lipopolysaccharides surrounding this wall to give it that extra layer of protection against antibiotics. It is also a facultative anaerobe, meaning that it can survive with or without oxygen – using it when it is available and employing fermentation when it isn’t. Vibrio vulnificus can grow in the gut, upper respiratory tract, and on our skin.

That’s a bunch of technical jargon to say, Vibrio vulnificus can cause rapidly devolving skin infections and GI problems, which are even harder to treat. Anyone who develops an infection caused by this bacteria in particular will be treated with antibiotics such as “tetracycline, third-generation cephalosporins, and imipenem,” to name a few. (Medscape, 2021) For patients with underlying conditions, such as liver dysfunction or a compromised immune system are more at risk of developing “septic shock… [which has a mortality rate of] 50%.” (Medscape, 2021) For healthier individuals, this doesn’t typically happen. With antibiotics and a period of acute illness over several days, it’s survivable – unpleasant, but survivable. In general, while this bacteria causes over 90% of illness from household seafood, it is still pretty rare. The CDC “estimates that vibriosis causes [roughly] 80,000 illnesses each year in the United States. About 52,000 of these illnesses are estimated to be the result of eating contaminated food.” (CDC, n.d.) Just for reference, the population of the United States, as of 2019, is estimated to be 328.2 million – meaning that Vibrio vulnificus causes 0.0244% of illness, of which 0.0158% results from our shrimpy friends and their oceanic brethren.

So should you fret about mishandled dinner shrimp possibly killing you? Probably not. But you should still remember to save yourself the trouble and buy some gloves the next time you want to make those tropical shrimp skewers. If I’ve learned anything during the COVID-19 pandemic, it’s that no matter how sure you are that you don’t have a small cut on your hand, the hand sanitizer you splash on every day will undoubtedly prove you wrong.

That’s all for this issue of Agent of the Week. Tune in next time when we talk about none other than… Rabies! To all the pet lovers out there, remember to keep your pets vaccinated and leave the friendly, neighborhood possums the hell alone.

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