. 2019; 10: 1596.
Published online 2019 Jul 10. doi: 10.3389/fmicb.2019.01596
PMCID: PMC6635642
PMID: 31354683

Protozoan Parasite Babesia microti Subverts Adaptive Immunity and Enhances Lyme Disease Severity


Lyme disease is the most prominent tick-borne disease in the United States. Co-infections with the tick-transmitted pathogens Babesia microti and Borrelia burgdorferi sensu stricto are becoming a serious health problem. B. burgdorferi is an extracellular spirochete that causes Lyme disease while B. microti is a protozoan that infects erythrocytes and causes babesiosis. Testing of donated blood for Babesia species is not currently mandatory due to unavailability of an FDA approved test. Transmission of this protozoan by blood transfusion often results in high morbidity and mortality in recipients.

Infection of C3H/HeJ mice with B. burgdorferi and B. microti individually results in inflammatory Lyme disease and display of human babesiosis-like symptoms, respectively.

Here we use this mouse model to provide a detailed investigation of the reciprocal influence of the two pathogens on each other during co-infection.

We show that

  • burgdorferi infection attenuates parasitemia in mice while
  • B. microti subverts the splenic immune response, such that a marked decrease in splenic B and T cells, reduction in antibody levels and diminished functional humoral immunity, as determined by spirochete opsonophagocytosis, are observed in co-infected mice compared to only B. burgdorferi infected mice


  • immunosuppression by B. microti in co-infected mice showed an association with enhanced Lyme disease manifestations.

This study demonstrates the effect of only simultaneous infection by B. burgdorferi and B. microti on each pathogen, immune response and on disease manifestations with respect to infection by the spirochete and the parasite. In our future studies, we will examine the overall effects of sequential infection by these pathogens on host immune responses and disease outcomes.



Two of the authors recently completed a review of literature on concurrent Babesia and Lyme infections:

Due to the high prevalence of infection and the issues of congenital transmission and transmission through blood transfusion, the issue of concurrent infection and what it does to animal and human health is of paramount importance.

For more on Babesia: Symptom checklist within this link as well as treatment options.

While a current article downplays Babesia in Canada, another article shows it’s much more of a problem than suspected:  This clearly shows there were more than 200 Babesia transfusion-transmissions reported. It also shows you don’t have to reside in an endemic area or travel to an endemic area to get it. The article also clearly points out that the geographic range of ticks is expanding, which means the pathogens they carry will as well.

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