Dr George Poinar Jr. of Oregon State University has found a fossilized flea carrying ancient coccobacillus bacteria. The discovery was announced in the latest issue of the Journal of Medical Entomology.
Atopopsyllus cionus may carry evidence of an ancestral strain of the bubonic plague (Yersinia pestis). Image credit: George Poinar Jr.
Dr Poinar determined that the flea, named Atopopsyllus cionus, is entirely new to science. It was preserved in a piece of 20-million-year-old amber from amber mines in the northern mountain range Cordillera Septentrional of the Dominican Republic.
“Its basic characteristics are so strange that it deserves its own genus,” Dr Poinar said. And in fact, the genus name the scientist has applied to the insect means ‘strange flea’ in Greek.
The specimen also shows the connection between insects and pathogenic microorganisms.
“I’ve spent a lot of time looking for pathogens that are vectored by insects in amber. I was quite excited when we found pathogens inside the flea in the anal area,” Dr Poinar said.
“We found bacteria that have the characteristics of bubonic plague bacteria (Yersinia pestis). We can’t say they’re plague bacteria. All we can say is their morphology is similar to that which is shown to be associated with plague.”
If indeed the fossil bacteria are related to plague bacteria, the discovery would show that this scourge, which killed more than half the population of Europe in the 14th century, actually had been around for millions of years before that, traveled around much of the world, and predates the human race.
“They are a coccobacillus bacteria; they are seen in both rod and nearly spherical shapes; and are similar to those of Yersinia pestis. Of the pathogenic bacteria transmitted by fleas today, only Yersinia has such shapes.”
“Aside from physical characteristics of the fossil bacteria that are similar to plague bacteria, their location in the rectum of the flea is known to occur in modern plague bacteria,” Dr Poinar said.
“And in this fossil, the presence of similar bacteria in a dried droplet on the proboscis of the flea is consistent with the method of transmission of plague bacteria by modern fleas.”
These findings are in conflict with modern genomic studies indicating that the flea-plague-vertebrate cycle evolved only in the past 20,000 years, rather than 20 million.
However, today there are several strains of Yersinia pestis, and there is evidence that past outbreaks of this disease were caused by still different strains, some of which are extinct today.
“While human strains of Yersinia could well have evolved some 10,000 to 20,000 years ago, ancient Yersinia strains that evolved as rodent parasites could have appeared long before humans existed. These ancient strains would certainly be extinct by now,” Dr Poinar said.
The researcher also found trypanosomes in the specimen.
“So we know that this flea was vectoring at least two pathogens. It shows that even back at that time, pathogens were established in fleas in the West Indies. They could have affected rodents because we found rodent hair in the amber. This shows the antiquity of the relationship between vector, host, and pathogen,” he explained.
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George Poinar Jr. A New Genus of Fleas with Associated Microorganisms in Dominican Amber. Journal of Medical Entomology, published online September 15, 2015; doi: 10.1093/jme/tjv134
