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Humans Gave Big Cats Ulcers

By Ker Than
LiveScience Staff Writer
posted: 28 June 2006
07:57 am ET

Early humans living in Africa's open savannahs probably made easy pickings for large predatory cats, but a new study suggests that at least one of the meals didn't sit well.

A large cat dining on the entrails of one our early ancestors thousands of years ago contracted an ulcer-causing bacteria that spread to lions, cheetahs and tigers and which persists to this day, a new study concludes.

The strange finding will be detailed in an upcoming issue of the journal PLoS Genetics.

Too similar

Helicobacter pylori are bacteria that cause chronic stomach pains and ulcers in humans. Other animals, including non-human primates, are infected by other Helicobacter species that are only distantly related to H. pylori. The one exception is H. acinonychis, a microbe that infects large felines such as lions, tigers and cheetahs.

The microbes responsible for ulcers in humans and big cats are so similar that scientists speculated they were once one species. According to this theory, the microbe diverged after either a human ate a cat infected with the ulcer-causing bacteria or a cat ate an infected human.

To determine who or what ate whom, the researchers compared the genomes of the two bacteria species. They found that many of the inactive genes in H. acinonychis, the species that infects large cats, are more fragmented, or broken, than their still-functioning counterparts in H. pylori.

This strongly suggests that the direction of the host jump was from humans to cats, and not the other way around, the researchers say.

"It is very unlikely that such gene fragmentations could be restored to yield intact genes, which is what would have been necessary" if the bacteria jumped from cats to humans, said study team member Mark Acthman of the Max-Planck Institute in Germany.

The researchers think the host jump happened only once because many of the gene fragmentations are uniform among different strains of H. acinonychis.

Fighting to get sick

Based on similarities in the genomes of the two bacteria species, the researchers estimate that the host jump from humans to large cats took place about 200,000 years ago.

"The feline was probably a tiger, cheetah or lion but we don't know which," Achtman told LiveScience.

After the first cat was infected, the bacteria probably spread to other feline species during deadly fights for territory, explained another researcher on the project, Stephan Schuster of Pennsylvania State University.

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Originally posted by Zebra

Halfmooner - how do you find these weird and interesting stories? You have just made my day. (Of course, it's 12:01AM here, so something weirder could still come along....)

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Out of Africa--with Worms Volume 55 Number 2, March/April 2002

by Mark Rose

The latest tapeworm research suggests a time frame for human migration out of Africa, and also reveals that people gave the parasite to domestic animals such as pigs--not the other way around.

According to Eric P. Hoberg, a zoologist with the U.S. Department of Agriculture, and his colleagues, tapeworms probably jumped from predators to humans between 2 and 2.5 million years ago, when hominids inhabited savannah environments in sub-Saharan Africa and were likely hunting or scavenging the same prey favored by hyenas and lions. Of the three tapeworms that infect people today, the researchers linked one, Taenia solium, most closely to a species that uses hyenas and African hunting dogs as its hosts. The other two, T. saginata and T. asiatica, are linked most closely to a species with lions as its host. Because T. solium and the pair T. saginata/T. asiatica are only distantly related, it appears that two tapeworms independently made the jump to hominids: the ancestor of T. solium, and a single parent species of both T. saginata and T. asiatica.

The amount of genetic difference between T. saginata and T. asiatica suggests that they split from a single human-adapted species by 160,000 years ago, says Hoberg. Worm-carrying human populations may have migrated out of Africa at or before this time, leading to the separation of parasite populations that evolved into the two species. Cattle eventually became the intermediate host in T. saginata, pigs in T. asiatica. Because domestication took place much later, around 10,000 years ago, and because neither animal comes from a sub-Saharan progenitor, the transmission of tapeworms had to be from humans to cattle and pigs, not the reverse.

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