Giardia lamblia is an intestinal parasite that exists all over the world and causes diarrhea. Above all, it affects young individuals, and in the third world the infection is extremely common. At present roughly 200 million people are infected with Giardia; Sweden has 1,500 cases each year, with infection spreading at day-care centers and via polluted water. Recently the Norwegian city of Bergen experienced a major water-borne epidemic, with 1,300 people infected by the parasite. Young animals can also get Giardia infections, which entail major costs for agriculture. It is not known why Giardia makes people sick, or why some people are more susceptible than others.
Today's issue of Science includes an article by Swedish and American researchers describing the genetic sequence and biology of Giardia lamblia and comparing it with other organisms. Among other things, the article shows that the parasite differs in several ways from other organisms when it comes to the copying and reading of DNA. The parasite also lacks several common signal proteins, but, on the other hand, it has many enzymes of the protein kinase and protein phosphate type whose functions are still unknown.
"Research on the parasite will be radically changed, and new methods that were previously unusable can now be applied. This means that there is great potential for finding new medicines, vaccines, and diagnostic tools much more quickly and efficiently. This opens new paths for finding treatment for this severe disease," says Associate Professor Staffan Svärd, Uppsala University, co-author of the study being published.
Giardia is a remote relative of human beings, which is reflected in the fact that many basic processes occur in both cell types, but the analysis of the genome shows that the parasite's processes are much more simply structured. This means that much more complicated processes in humans can be understood more readily.
"It's easier to do a puzzle with 4 pieces compared with 40 pieces, and it shows us what pieces are most important in the human puzzle," explains Staffan Svärd.