One of the monkeys discovered a tick feeding and already bloated with its blood meal. The monkey pulled it free. Something punctured the body of the tick – claws perhaps, or teeth - and monkey blood leaked out. Discarded, or dropped by accident (would the monkey not have preferred to eat this tasty morsel?), the tick fell into the resin and stuck there, still oozing blood.
The tick wasn’t the only organism to die in the resin that day. Within the tiny monkey red blood cells, there were piroplasms – parasites that multiply asexually inside blood cells, burst out, and invade new blood cells. Eventually, the process produces male and female forms that can reproduce only after being ingested by a tick, in a blood meal.*
Fossil Red Blood Cells
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| Like the tick in this article, this mosquito was discovered in amber in the Dominican Republic. Image by Didier Desouens CC BY-SA 4.0 (not licensed for upload to Facebook) |
Infection with Piroplasms: Babesia, Theileria, Cytauxzoon
Was the monkey sick? Possibly. The destruction of red blood cells caused by the multiplication of the parasites can lead to severe anemia and even death. Babesia bigemina is a notorious killer of cattle in the United States. Theileria parva causes East Coast fever and death in African cattle. Cytauxzoon felis kills domestic cats in the United States. Some infections go unnoticed, however, and animals can develop immunity. It’s possible the monkey wasn’t all that bothered by its infection.
Throughout the ensuing millennia, ticks continued to bite mammals and infect them with piroplasms, and no one even knew it was happening until the early 1880s when Theobald Smith and Frank Kilbourne proved that a tick transmitted Babesia bigemina to cattle. Not only did they solve the mystery of what was causing Texas cattle fever, it was the first proof that creatures such as insects and arachnids (spiders, ticks, mites etc.) could spread diseases with their bites.
It took about another 75 years before anyone documented a case of piroplasms infecting humans, and then only in humans who lacked a spleen. Caused by Babesia divergens, there were very few such cases, and the disease remained a medical rarity until recently. In 1969, Babesia microti began turning up in the United States in the same places where Lyme disease is emerging. Today, it’s a spreading infection in the United States and Canada, striking thousands of people every year, and killing some.
Evolution of Babesia
Lots of people still haven’t heard of Babesia, much less piroplasms, and for the rest of us, they still seem quite new. So the discovery of organisms resembling Babesia sp. fossilized in amber that might well be more than 20 million years old is delightful.
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| Amber is fossilized tree resin. It has unique properties for preserving organisms that become embedded in it. Image by Wibowo Djatmiko CC BY-SA 3.0 |
Photographs published in the report of this finding are tantalizing, though not as clear as a modern-day blood film. What they mostly do is make me want to sit down at a microscope and look at that magnificent piece of amber myself!
*Researcher George Poinar Jr. can’t be absolutely certain that the animal the tick was feeding on was a monkey, or that the parasites in the blood are piroplasms; however, after considering other evidence – red blood cell and parasite characteristics, the fossil record, knowledge of primates, piroplasms, and other organisms alive today etc. – this is most likely the correct interpretation.
Read the paper in the Journal of Medical Entomology:
Poinar, George, Jr. (2017) “Fossilized Mammalian Erythrocytes Associated with a Tick Reveal Ancient Piroplasms.” J Med Entomol tjw247. doi: 10.1093/jme/tjw247
Further Reading About Babesia and Other Piroplasms
CDC. Surveillance for Babesiosis - United States, 2014: Annual Summary
Drisdelle, Rosemary. 2017 "Babesiosis Cases Likely on the Rise." Outbreak News Today
Schmidt, Gerald D. and Larry S. Roberts. Foundations of Parasitology 8th Ed. New York: McGraw Hill, 2009.
