New England Journal of Medicine Reports on New Tick-borne Bacteria

Aug 5, 2011 | Sumiko Mekaru | Research & Policy

Ticks are known for carrying Lyme disease, Rocky Mountain Spotted Fever, Babesia, among other diseases. Now, there’s a new bacteria on the list. Researchers at the Mayo Clinic in Minnesota and from public health departments in Minnesota and Wisconsin, have identified a new type of Ehrlichia which sickened at least four people in those states.

There are several Ehrlichia species, but the two common which sicken humans (Ehrlichia chaffeensis and Ehrlichia ewingii) are not found in the MidWest. The researchers isolated this new species through molecular, culture, and serologic methods on patient blood samples and harvested ticks.  They have named their discovery ehrlichia species Wisconsin. Patients reported symptoms similar to the previously known Ehrlichia spp.: fever, fatigue, and headache.

This discovery is particularly important since ehrlichiosis had not been previously identified in this part of the United States.  Now that physicians know to test for it, the number of cases identified will likely increase rapidly.  

Ticks typically feed on rodents and deer, so other mammals are likely part of the life cycle of this bacteria. Among the many emerging human disease threats, 75% have a link to animals. As animal populations move due to changes in their environments (be it construction on their habitat, climate changes, or anything else) diseases that have not previously been seen in humans may have the opportunity to make that leap.  Given the relatively mild symptoms of the new Ehrlichia species, it is difficult to know if the organism has simply been present but undiagnosed in humans for decades. Additional studies will help describe its epidemiology and give more context to a very interesting discovery.

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