Monday, May 19, 2014

The leech of my concerns


My blog about foot rot stimulated some interest and inquiries about other parasites.  By far the most dangerous are the mosquitoes that can carry malaria, dengue, filariasis and other lovely malaise-inducers.   But the parasites that seem to gross people out the most are the land leeches.  I've seen grown adults almost paralytic with fear (or revulsion) when faced with removing a leech from their skin.

Most of us are familiar with aquatic leeches, those nasty suckers that made Bogart quiver in African Queen.  They lurk in murky waters and attach to unsuspecting swimmers.  But what many people in the US don't know is that there are land leeches in many tropical rainforests.  They glom on to vegetation in the understory with their large rear sucker, waving their anterior sucker in the breeze and waiting to detect the presence of a passing animal.  As the animal passes the anterior sucker gloms on to the animal and the posterior sucker releases, and the leech has hitched a ride.  It happens with such speed and finesse you never feel it.

I first encountered land leeches in Borneo.  They were ubiquitous and we all had bites on the first day building our camp.  Field workers in Sabah wore "leech socks" made of a tight fabric that you wear inside your shoe and outside your long pants, tied with a drawstring above the calf.  This keeps them from working their way inside your pants or down into you shoe.  Leeches landing below the knee have to work slink up to your waist before getting a good shot at a meal.  This gives us a chance to flick them off before they attach.  But even with leech socks, leech bites became so regular I hardly noticed them after donating blood a dozen times.  They eventually find a hole in your clothes or slip under your waistband and dining begins.  There are no leech socks in PNG-- sort of pointless since most people wear shorts and are bare foot.  I made them myself in camp with flour sacks.

When they get to the right bit of skin, they drill into you while firmly sucked in place.  Regular friction from clothes and walking won't dislodge them; it is like they are glued on.  They secrete a mild anesthetic and an anti-coagulant as they drill in and start drinking your blood.  As they drink they swell up to about four times their un-fed body size.  They look quite gross and bloated after a few hours of gorging on your corpuscles.  When they drop off when full, or when you pull them off, the remaining anti-coagulant ensures the little piercing bleeds insanely for hours, and stays bright, oxygenated red.  A bleeding leech bite looks a lot worse than it is!

The Pawai'ia told me that cassowaries they hunted often had leeches inside their mouths.  There were little leeches that sat on fruit on the forest floor and I'm sure when a cassowary picked up and swallowed the fruit the leech stayed in the mouth for a nice easy meal.  These same small leeches sometimes somehow made their way to my beard enshrouded mouth, but I could feel the little suckers slide over my lips.  Chomp and spit and the problem solved without breaking stride.  But others were more insidious...

One night I had trouble sleeping, something seemed to be in my eye.  I headed to the bathroom mirror and with my headlamp.  If I looked down I could spy something dark way back on back side of the eyeball.  My first leech-in-the-eye.  I tried washing it out with sterile saline.  Leeches hate salt right?  Not eye leeches apparently.  It was not painful fortunately, but I could feel it slide around sometimes.  A bit disconcerting, but I did not want the bastard drilling in any further.  It was time for creative first aid.

I had some fine needle-tipped forceps for dissecting.  But I did not want to poke around the back of my eye, holding the lid up with one hand and the sharp forceps in the other.  So I tightly wrapped the tips with a bit of cotton, soaked that with saline as lubricant, and probed away. 

It wasn't easy, as the bastard would move when touched, but I managed to get a grasp on it and slowly pulled.  But the leech was not giving up that easy and it held on with its anterior sucker.  It stretched thrice its length, then snapped free of my grasp like a little rubber band.  The leech was not amused, nor was I.  It took quite a bit of gentle wrestling, twisting, pulling and swearing but the 185 pound primate won over the cooked rice grain-sized invertebrate.

This was not the last such episode and I developed a fair bit of finesse pulling leeches from my eyes and those of colleagues.  The leeches seemed to discover that the rim of my binoculars was a great place to wait.  I'd see some bird in the canopy, raise my binoculars to my eyes and feel the tell tale sucker take hold. I'd urge whoever was with me to grab the sucker before it slipped to the dark side of the eye.   I carried a little mirror in my field bag to help if I was alone.  No washing hands, no sterile technique, you had about 20 seconds to make the grab before it was safe from fingers.  More than one assistant was startled to have me run through the woods pulling my eyelids back with my hands shouting "get this fucker out of my eye."  Only one person had the misfortune of having one go nasal.  But I don't want to gross anybody out with that story.  Just another minor inconvenience of field work in cassowary country.