April 14 was International Chagas Day. What is Chagas? This is a disease caused by a parasite living in the blood. The disease itself is named after Carlos Chagas, who in 1909, first recognized the disease and how it was transmitted. The specific parasite that causes Chagas Disease is called Trypanosoma cruzi, named by Chagas in honor of his former teacher, Oswaldo Cruz.

Most historians now believe that Charles Darwin suffered from Chagas disease.

In March of 1835, in Lujan, Argentina Darwin wrote the following in his journal: “At night I experienced an attack (for it deserves no less a name) of …, the great black bug of the Pampas”. The bugs that Darwin referred to are “kissing bugs” because they are drawn to the moisture of the lips and eyes. Kissing bugs transmit Chagas.

Throughout his life Darwin suffered symptoms we now recognize as due to Chagas. At the time they thought his symptoms were purely psychosomatic.

The disease is relatively rare in the U.S. even though we do have kissing bugs in the U.S. and kissing bugs have been collected in southeast Nebraska. However, Chagas Disease is just one of thousands of parasitic diseases in the world. Most of us are familiar with things like tapeworms and Giardia, but hopefully not the disgusting pinworm. These worms live in the tissues of the intestine, but when it comes time to reproduce, they chew their way into the rectum and then leave the body through the anus, causing severe anal itching. They lay their eggs on the surface of the anus. The eggs are sticky and if you scratch your itching anus you can get the eggs on your hands, which can then be transmitted to food or directly back to your mouth. If you scratch your backside…wash your hands!

Life is not easy for a parasite! Take the liver fluke for example. Each year it is believed that in China and Southeast Asia this flatworm infects over 17 million people. The adult worms live in the liver. They face a problem - how to reproduce without their offspring becoming so numerous they end up killing the host. They have to get the “kids” into another body. How? Their eggs are carried out of the body in the wastes of the person. Human manure is a common fertilizer, particularly in flooded rice fields. The eggs in the manure float around and settle on the vegetation in the field. Snails then pick up the eggs while feeding on the vegetation.

Once in the snail the eggs hatch into a larval form. The larva burrows into the tissue of the snail. If the snail died of old age that would be the end of it, but, alas, the snail gets eaten by a fish. The larva of the fluke now burrows into the muscles of the fish and forms a cyst. It lives there until another animal, in this case a human, eats the fish. In Southeast Asia fish are eaten raw! Once in the digestive system of the person the cyst is dissolved and the adult form of the fluke makes its way to the liver to start the process all over again.

Think of it. To survive, this worm has to endure and avoid all the immune and digestive systems of three different animals. It has to find a way to get its young out of the body. Its eggs have to be picked up by another animal that has to be eaten by yet another animal, only to have one more animal eat that one!

Parasites may well be the most complicated and interesting life forms on earth so maybe on the 14th, instead of just one, relatively simple parasite, Trypanosoma cruzi, we should be celebrating the whole bunch of them…except of course, those disgusting pinworms!