Think I'll pass on the pork from now on...

mosquito dissecting!!

So, when I last left off, I was exploring the fascinating activities behind outbreak investigations of infectious diseases.  There are many possible sources for a disease outbreak, and they come in different forms, therefore, it is critical to cover many bases during the investigation.  We learned that this a multi-faceted undertaking that requires collaboration among experts in different fields.  Everyone from doctors to zoologists to social scientists to lab technicians and more.  This course allowed us to meander down all these different avenues.

bait and Shannon trap

We went from larvae collecting and mosquito trapping in the first week, to rodent/bat trapping and animal necropsies in our second week.  After a nice day at the beach where I finally worked on my tan under the equatorial sun (much more efficient), we returned to the lab to make rat bait and label our traps.  At around 6pm, our group set up 36 traps in a dry rice field, each with a small ball of bait inside (consisting of peanut butter, oatmeal, raisins, and a lot of vanilla extract) and placed about 5 meters apart; the coordinates of each trap were taken using a GPS device.  At 5am the next morning, we returned to the field and found that at least 30% of those traps contained rodents.  It was pretty interesting to pick up the light, metal trap (wearing gloves of course) very cautiously and see if the trap door was shut or not.  Sometimes the door was shut but there was no animal inside (the sign of a poor trapping device), and sometimes, the smell of excrement indicated the presence of an animal before you even checked the door.

Thy setting up our traps..

these getups were extremely uncomfortable and hot!!

Later, we dissected and sampled some of the those mice, wearing Tyvek getups complete with rubber boots, battery-operated air pumps, air masks, and two layers of latex gloves.   That day, I received the most hands-on anatomy lesson of my life from the fine zoologists at NAMRU-6 who had flown in from Lima to contribute to the course.  If you've never heard of NAMRU, it's definitely worth looking up.  It was a bit of an ethical dilemma (not to mention emotional upheaval) for me to take the life of a cute little mouse and then desecrate its body the way I did, but I did it and have accepted my decision.  I wanted a field epidemiology experience and I certainly got it.

aawwww little insectivore!!

We also learned how to trap bats, using a very fine net that looks like natted women's hair (according to some of our colleagues) and is very easy to tangle.  It's best to put the nets up just before dusk and check them every 30 minutes to an hour for trapped bats.  We set up three nets and caught two bats: an insectivore and an herbivore.  I'd never seen bats that close up before.

heading out to see the mangroves!!

mangrove trees!

Another perk: we went bird watching in the national mangrove reserve in Tumbes!!  I had never seen mangroves before and certainly never really understood what it takes to catch flocks of birds in their natural habitats!  Too bad I didn't take my telephoto lens with me that day.  I would have been able to capture photographs of some of the beautiful birds that are native to the reserve, specifically the blue herring and the cool flamingoes that live there.  Either way, the mangroves were very impressive and it was fun to walk through the marshy terrain to get to the birds, where we hunted for fresh bird droppings that would be tested for influenza and other diseases in the event of an outbreak.


WARNING: GRAPHIC IMAGES AHEAD!!!

pig being euthanized.

Finally, came the necropsy of a pig heavily infected with Cysticercosis, a tissue infection that results from exposure to eggs from taenia, or tapeworm.  In Tumbes, Cysticercosis is endemic among pigs and humans, causing epilepsy and other complications in the latter.  If humans consume poorly cooked meat that belonged to a pig infected with the disease, they ingest the developed eggs (cysticerci - almost like larvae) contained within the meat, which grow into adult tapeworm.  Tapeworm in our small intestine is relatively benign compared with actual Cysticercosis in humans.  However the eggs that the tapeworm lays within the human digestive system are excreted in human feces and will reinfect the agent via the fecal-oral route, causing Cysticercosis.  Here is where the huge problem develops.  Cysticercosis seems to cause little-to-no physical symptoms in pigs, but can be extremely burdensome for humans.   The ingested eggs will penetrate the intestinal wall and circulate to the muscles (causing inflammation and calcification) and brain (causing seizures).

cysts on pig's heart

Pigs and humans become infected with Cysticercosis by consuming human feces that contains tapeworm eggs.  If either pigs or humans are consuming contaminated feces, it is the result of poor hygiene or poor maintenance of livestock, both of which are associated with poverty and lack of education or instruction.  Often times, a pig's worth is determined by whether or not it is infected with Cysticercosis (you can tell by pulling out its tongue and looking for cysts).  Often, people will knowingly sell contaminated meat in order to survive and feed their families.  Would you throw away the meat of your infected 200 lb pig if it meant putting food on the table for your family?  And what would you do if you didn't have enough money to buy wood to build a fence to keep your livestock separate from humans and their excrement?  The Cysticercosis center that hosted us in Tumbes is doing an operational research project in the area where they go out to the field to collect human feces samples and offer treatment with diagnosis, as well as test all pigs for the disease in order to keep humans from consuming contaminated meat.  If a pig is infected, the center will attempt to purchase the pig from the farmer or household for above market value (considering it is diseased), in order to keep the pig from being sold to unsuspecting clients.

infected pig meat

if you look really closely, you can see the cysts on the pig's brain

So we dissected this pig to determine just how much cysticerci were growing in its body.  First the pig was euthanized, and then its throat was slit.  The corpse was drained and skinned and then all organs are removed.  The meat was then cut into enough pieces for each of us to extract 30 healthy cysticerci for testing.  It was a pretty disgusting process and I actually haven't touched pork since that day.  I'm pretty grossed out by the animal to be honest.

But yea.. that was our field epidemiology course in Tumbes (in a nutshell).  I'm really grateful for the entire experience, most of which was subsidized by the same program that allowed me to spend the last 3 months in Perú.  I met some awesome students in the course and have also been adopted by a few employees at NAMRU whose brains I've been picking for advice and guidance as I try to find my own niche in the world of research and health interventions.

Next post: Cusco, Salkantay Trek, and my long anticipated visit to Machu Picchu - the highlight of my time in Perú.  Hopefully it won't take me a month to get this post up!!!