Icky Tropical Diseases

As Devon and I get more involved with this project in Liberia, we’re discovering a lot about the nature of public health projects. First, all the nouns you’re allowed to use are either inscrutable Latinate terms, such as Phytolocca dodecandra (“ten-sided crazy plant”) and Biompalaria pfefferi (“mollusk best served with pepper sauce and a strong merlot”) or indecipherable TLAs. Oh, sorry – Three Letter Abbreviations.

The short story, using the apparent PHV (“public health vernacular”) is that we’re looking at a joint CARI/LIBR proposal to implement part of the Liberian PRS (based on accepted MDGs) by following WHO guidelines for using LGAs to implement an MDA treating Schistosoma haematobium/mansoni with Praziquantel and an (apparently ancillary) PHEP convincing people not to pee in the river.

Now, outside of the world of public health, the part there that makes sense is “convincing people not to pee in the river.” Which, it turns out is the hard part. Because schistosomiasis is what is technically known as an ITD (“Icky Tropical Disease”). No, I’m kidding. In fact it’s known as a NTD – a Neglected Tropical Disease. There’s a large research center in North Carolina (the RTI NTD Center) devoted to it and its buddies. No,

I’m not kidding there – even with a large research center devoted to it, it’s a neglected disease. Schistosomiasis is second only to malaria in terms of parasitic impact in tropical countries. WHO (the World Health Organization – try to keep up here) estimates that 200 million people are afflicted with it – 100 million in Africa alone.

And I’m not really kidding about the “icky” part either. That’s the thing about tropical diseases: they’re gloriously icky. James Cameron wants another scary flesh-eating alien creature? We’ve got ’em all here. How to start?

Let’s start with the egg, which looks like a typical aquatic insect egg, except that it has a spike sticking out the side to show you it means business. In water, the eggs hatch into miracidia, little football shaped larvae that swim around until they find a snail to infect. Once inside the snail, the miracidium transforms into a “mother” larva and splits off “daughter” parasites that migrate to the poor snail’s stand-in for a liver. Once these daughter larva set up shop there, they each start churning out thousands of little barracuda-like circariae, which re-enter the water in search of the real meat: humans.

Are you still with me? Not eating dinner now, I hope?

Okay, once the circariae detect exposed human skin, they attach, burrow through and enter the bloodstream, setting off on the trematode equivalent of Honduras’ “gringo trail”. Up to the lungs for a week or so, down to the liver to find a mate, then cruise the bloodstream for a while to decide whether to settle in your bladder, kidney, or – for the more adventuresome – your brain or spinal chord. Point of reference, these things are about a centimeter long, and they’re taking joyrides through your circulatory system deciding where they want to set up shop.

Oh, and when they do? Starts to get messy. At maturity (oh, six to eight weeks), these little Easter bunnies start producing eggs. Lots of eggs. Estimates are about 3000 eggs. Every day. Did I mention that these guys can live for 20 years? Do the math. No, wait. Don’t do the math.

So now, we’ve got eggs, and the eggs don’t really want to be in your body. So they start working their way toward some sort of opening (remember that spike I mentioned?). They’re done with you, and they don’t care if they trash the joint on the way out. They usually make it to the digestive system or urinary canal, where they get peed or pooped back into the water supply, ready to hatch and go looking for snails all over again.

Sorry – I did recommend that you not be eating dinner while reading this, right? (more details, with pictures, at http://en.wikipedia.org/wiki/Schistosoma_mansoni)

But the point is that Devon and I are going to Liberia, because, among other things, Liberia’s got a nasty schistosomiasis problem (note: “nasty” and “schistosomiasis” go together like “stupid” and “Jessica Simpson”). The Liberian government has a plan to eradicate schistosomes from the upper county marshlands where the country used to grow rice, its staple crop. You get rid of the schistosomes, and lots of good things happen. To the economy, to the nation’s health – all around. But it’s not going to be easy. You’ve got to treat the infected people (easy), you’ve got to treat the marshes (much more difficult), and have to, absolutely have to get them to stop peeing in the water. That, it looks like, is going to be the really hard part.

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