Reports of the declining state of the world’s fisheries aside, there’s a whole new frontier opening up in the world of ocean life.
They’re called “emerging diseases”: small, aggressive specks of life working like hell to get noticed in a mostly hostile environment. Kind of like “emerging indie-rock,” just less noisy and more likely to stick around.
Many of the diseases aren’t exactly new, they’re just cropping up in new places as a side-effect of how good we are at detecting tiny things. And while your best chance of catching a nasty marine disease probably still involves a raw oyster, every new virus or bacterium that shows up in a water sample is another possible period of porcelain worship for you. And, joking aside, death by diarrhoea happens some 1.8 million times per year, with 90% of its victims younger than 5.
Still, you don’t read a lot about the culprits, at least in part because once you get down to the level of microscopic things there are few terms familiar enough for a reader to hang onto. I mean, the bright and ferociously well-informed Scribble readership can probably keep their bacteria straight from their viruses, but is that true for USA Today’s? Even for our lofty selves, the smugness evaporates as soon as we go one level down: Where would you file Hepatitis E? the polyomaviruses? the adenoviruses? The rotaviruses? The enterococcans? The nematodes? Which of those contain DNA? (And no, the answer is not all of them.)
The pattern with most of these emerging diseases is that they’ve become better at surviving in places we assume are unlivable. Salt water is a great example – it’s famously antiseptic and has long been considered a great receptacle for treated and untreated wastewater. But several bits of biological fine print seem to have created some loopholes. With more humans in the world flocking to the same number of beaches, more contaminants are washing directly into the water – where odds are they spend less time combating the elements before encountering another bather. One more reason to surf alone.
A University of Miami study put 10 normal-looking, clean adults with good jobs into a kiddie pool filled with 4,700 liters of sea water. After 15 minutes, they found that on average, each person had contributed 600,000 enterococcus (indicative of fecal contamination) and 6 million staphylococcus (skin infection) colony-forming units. Each person. Finally I understand what those signs mean by “Please shower before bathing.”
Cooperation is another way microbes confound us. The bacterium that causes cholera, Vibrio cholerae, is not especially dangerous to people until it winds up in the gut of a little zooplankton called a copepod. Then it becomes one of the most dangerous of all waterborne illnesses.
The cholera-copepod link is pretty well known – Rita Colwell helped figure it out and soon found that Bangladeshi women could use folded sari cloth to filter out copepods from their drinking water. The Vibrio bacteria passed straight through the filter, but cholera infection still dropped by about 80% because the copepods were gone.
Alliances like this seem to be another stratagem pathogens have for staying alive long enough to do us in. Last year I got to write about Rebecca Gast‘s work isolating Legionella and other bacteria and amoeba from sea water. It appeared that shortly after riding out of the sewer outfall pipe, some bacteria managed to get themselves ingested by amoeba. They were quite happy with the arrangement, as the insides of the amoeba were more hospitable than the surrounding sea water. As time goes on, the colonies inside the amoeba grow in number and virulence.
Enter large, sunburned man bobbing in inflatable seahorse ring, slurping from warm can of beer. In the world of emerging diseases, that’s a picture that’s not going to get any prettier.
A single table of contents in a single journal like Water Research offers enough material to go on and on. But I don’t even know what most of these things are – I don’t even know what they sort of are. I guess we can be thankful that, like so much of the rest of science, there are people making their careers solving problems we may never hear of. Ignorance is bliss. So far, anyway.