Call it a tale of three species: an innocuous snail, a deadly parasite, and a single-celled, amoeba-like organism (a protist). Attempting to read that tale is Ms. Lynn Hertel, a Ph.D. student in our Biology Department. Ms. Hertel, is stalking the eastern coast of Brazil, seeking the snail and the disease-fighting protist that it sometimes hosts.The parasite in this tale causes schistosomiasis, a disease that inflicts liver and intestinal problems in more than 200 million people in 77 countries, mostly in South America and Africa. It ranks second only to human malaria in morbidity, mortality and economic loss due to a parasitic disease. "This is mostly a disease that infects children," said Eric Loker, Lynnís major professor, who also works on the project.
The parasite is a flatworm. The larval stage of the flatworm burrows into the skin from water supplies, reaches the circulatory system and eventually resides in the blood vessels around the intestines. As it grows, it deposits thousands of eggs that get trapped in the liver and intestines, which then damages their function. The result is a chronic infection that sometimes kills, but mostly leads to reduced energy and constant sickness, with symptoms similar to acute cirrhosis of the liver.
The snail is key to both the cause and the cure of the disease. The parasite is absolutely dependent on these specific snails, which are small, flat, and about the size of a quarter. In areas of the world where this snail is lacking, the disease is also lacking. A number of years ago, Dr. Chris Bayne, a zoologist at Oregon State University, discovered the protist was living inside laboratory maintained snails that were resistant to flatworm infection. He and his colleagues observed that the protist could kill the snail stage of the parasite. Ms. Hertel was able to confirm those observations and, indeed, found that these protists are able to kill the parasite in as little as two hours. She also was able to get DNA from the protist to sequence key parts of its genome to determine the relationship of this protist to other protists.
No human form of the parasite exists in the U.S., although there are varieties that infect birds and can cause a skin rash in people. The human version is highly unlikely to become a problem within this country, because the species of snail that carries it doesn't live here. But, it's a different story for travelers. Many U.S. citizens traveling abroad, especially Peace Corps volunteers, come back with schistosomiasis. There is a drug available to treat the disease, but it's not very effective in countries where the parasite lives and, as yet, it is not possible to immunize against it.
If this research by UNM biologists plays out, finding ways to fight the disease through the snail could be a very important breakthrough. As part of her Ph.D. research, Ms. Hertel is working in Brazil, at the Institute of Oswaldo Cruz in Rio de Janeiro and at the Federal University of Pernambuco in Recife, looking for more snails that carry the protist. The information she gathers about them may help scientists find better ways to fight the spread of this dreaded disease; one day these protists may be placed in snails to stop the disease from spreading.
Is this a useful discovery? Absolutely! Is it the magic bullet that will eradicate this disease from the world? Absolutely not! But with appropriate documentation, one could think about modifying these snails so they all have the protist symbiont. Lynnís research is funded by a Grove Scholarship from the Biology Department and by the National Institutes of Health.†
Return to UNM Biologists in the News
Return to UNM Biologists in the News