We have only known about Lyme disease since 1975, but now the discovery of an amber-encased 15-million-year-old tick has revealed that the bacteria that causes the disease has been around much, much longer than the human race. The discovery was made by George Poinar, Jr. from Oregon State University, and the findings were published in Historical Biology. 

Lyme disease is caused by the bacteria in the genus Borrelia, which uses ticks as vectors to infect a variety of organisms. Upon infection, the disease produces flu-like symptoms, including fatigue, fever and headache. It can be easily treated with antibiotics in the earliest stages, and it is very important to seek treatment as soon as possible. Without treatment, the infection can progress and it could affect the nervous system, heart, and joints.

"Ticks and the bacteria they carry are very opportunistic," Poinar said in a press release. "They are very efficient at maintaining populations of microbes in their tissues, and can infect mammals, birds, reptiles and other animals. 

“In the United States, Europe and Asia, ticks are a more important insect vector of disease than mosquitos," he continued. "They can carry bacteria that cause a wide range of diseases, affect many different animal species, and often are not even understood or recognized by doctors. It's likely that many ailments in human history for which doctors had no explanation have been caused by tick-borne disease."

The study utilized four ticks that had been preserved in amber. Bacteria typically doesn’t fossilize well, but amber protects it from conditions that would otherwise destroy the colony. Poinar discovered that the ticks had large amounts of bacteria that look very much like species of Borrelia. 

Throughout his career, Poinar has found evidence of disease like malaria and leishmania in the fossil record, and thinks it is likely that dinosaurs were infected by bacteria similar to what we see today. He also states that for as long as there have been humans, there have been ticks that were likely passing along disease. 

In 1991, researchers discovered Ötzi the Iceman, a naturally mummified human who was encased in ice in the mountains between Austria and Italy about 5,300 years ago. DNA evidence revealed that Ötzi was in poor health prior to his death and was infected with Lyme disease. This is the oldest known evidence of a human to have the disease.

In this same research, Poinar also discovered ticks that had bacterial cells which resemble the Rickettsia bacteria, which causes Rocky Mountain spotted fever. Those results were published in the journal Cretaceous Research.