February 28, 2014
Famous Orangutan’s Death Caused By Newly-Discovered Tapeworm
April Flowers for redOrbit.com - Your Universe Online
A famous orangutan that lived an extraordinary life, died in a rather extraordinary way as well.
A team of researchers, led by Tony Goldberg of the University of Wisconsin-Madison's School of Veterinary Medicine, used cutting-edge genetic diagnostics to document the cause of Mahal's untimely death. Their findings, published in a recent issue of Emerging Infectious Diseases, identify a species of tapeworm previously unknown to science and newly recognized as a threat to primates.
"At the beginning, all we had were Mahal's clinical condition and a tissue sample," says Goldberg, professor in the Department of Pathobiological Sciences and associate director for research in the UW-Madison Global Health Institute. "We knew there was some type of infection in there. It could have been nearly anything. The list of potential agents was enormous."
Goldberg, among his other qualifications, is a veterinarian and an expert in the identification of emerging and rare diseases in humans and other primates. His research team included Annette Gendron of the UW-Madison Research Animal Resources Center, David O'Connor of the UW-Madison Department of Pathology and Laboratory Medicine, and veterinarians Roberta Wallace and Victoria Clyde from the Milwaukee County Zoo, as well as UW-Madison students and colleagues at the University of Florida. The team identified an unrecognized species of tapeworm in the genus Versteria as the agent of Mahal's death.
According to Goldberg, tapeworms are a large and diverse group of parasites with an estimated 1,500 known species of the pathogenic flatworms. Many species are adapted to specific animal hosts, with only perhaps a dozen that can infect humans or other primates.
The tapeworm that killed Mahal is an unknown species in the newly categorized Versteria genus, which, until now, has been found in weasels in either Africa or North America. Mahal's tapeworm was still 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."
Some tapeworms, present in the tissues of an "intermediate" host in their larval forms, grow into their more familiar adult form when the intermediate host is eaten by a predator. The adult forms live in the intestine and produce eggs.
However, sometimes parasites such as larval tapeworms will infect animals they are not supposed to. This 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. He noted that tapeworm eggs can move through the environment in complex ways. Because Mahal was most likely an "abhorrent" host, the tapeworm larvae infected practically ever 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."
The team used a technique known as "deep sequencing" to identify the culprit. Deep sequencing allowed them to characterize all the DNA in Mahal's tissue samples. They found that 97 percent of the genetic material belonged to Mahal. Because the orangutan genome is known and sequenced, however, they were able to pick out the foreign DNA from the parasite.
The unique facilities at the Wisconsin National Primate Research Center AIDS Vaccine Research Laboratory made the team's results possible.
After filtering out the orangutan's DNA, the team was left with a small percentage of DNA sequences roughly similar to Torenia solium, also known as the pork tapeworm, which afflicts humans. Additional genetic testing was performed and these results were compared to banked DNA sequences of known tapeworm species. This allowed the team to place the tapeworm inside of Mahal in the newly proposed genus Versteria.
"This was an unknown species and a very unusual presentation," says Goldberg. "On hindsight, there was nothing that could have been done to prevent it by anyone at the zoo or anywhere else, and by the time the infection made Mahal sick it had already gotten out of control. This was an unfortunate quirk with very sad consequences."