Tapeworms, notes Goldberg, are a large and diverse group of parasites. There are estimated to be more than 1,500 known species of the pathogenic flatworms, many of which are adapted to specific animal hosts. Of those, perhaps a few dozen can infect humans and other primates.
According to Goldberg, the tapeworm found in Mahal is an unknown species in the newly categorized Versteria genus, which has been found in weasels in either Africa or North America. Furthermore, Mahal's tapeworm was in its larval form. "Larval tapeworms infect the tissues of animals," says Goldberg. "This life stage is different from the adult form, which is the long, wormlike stage we usually think of."
When certain tapeworm larvae in the tissues of an "intermediate" host are eaten by a predator, they grow into the more familiar adult form, which live in the intestine and produce eggs.
Sometimes, Goldberg explains, parasites like larval tapeworms infect animals they are not supposed to, as seems to be the case with Mahal. "It's possible the parasite was expecting to be in a mouse but found itself inside an orangutan," says Goldberg, noting that tapeworm eggs can move through the environment in complex ways. Mahal was therefore probably an "aberrant" host, and the larval form of the tapeworm infected practically every organ in his body.
"For reasons we don't understand, tapeworms sometimes go haywire," Goldberg says, adding that how and when Mahal became infected remain mysteries. "It is possible he was infected a few weeks before he died. Or he may have been infected several years ago and the tapeworm was dormant and suddenly started to multiply out of control."
To identify the culprit, Goldberg and his team used a technique known as "deep sequencing" to characterize all of the DNA in Mah
|Contact: Tony Goldberg|
University of Wisconsin-Madison