COS 96-6 - The ecology of an emerging tick-borne pathogen, Babesia microti: How host quality affects disease risk

Thursday, August 11, 2011: 9:50 AM
10B, Austin Convention Center
Michelle H. Hersh1, Michael Tibbetts2, Mia Strauss3, Richard S. Ostfeld4 and Felicia Keesing3, (1)Department of Biology, Eastern Michigan University, Ypsilanti, MI, (2)Biology, Bard College, Annandale-On-Hudson, NY, (3)Program in Biology, Bard College, Annandale-On-Hudson, NY, (4)Cary Institute of Ecosystem Studies, Millbrook, NY

Confirmed cases of human babesiosis, caused by the protozoan blood parasite Babesia microti, are increasing in New York state. B. microti is spread to humans via the bite of an infected black-legged tick (Ixodes scapularis). Ticks can obtain B. microti from a suite of vertebrate wildlife hosts. White-footed mice (Peromyscus leucopus) have been shown to be competent reservoirs of B. microti, but systematic surveys of reservoir competence for multiple wildlife hosts are lacking. We use real-time PCR to test for presence of B. microti in over 2,300 newly molted nymphal ticks collected from eight mammal and four bird hosts in 2009 and 2010. We then assess variation in reservoir competence between host species, expressed as the mean percent of infected ticks produced per host, and compare this to background levels of B. microti in questing nymphs.


We found clear differences in reservoir competence for B. microti between host species. Preliminary data show comparably high levels of reservoir competence were found in white-footed mice (mean and standard error: 17.5% ± 8.2), eastern chipmunks (Tamias striatus, 18.1% ± 9.4), and short-tailed shrews (Blarina brevicauda, 18.2% ± 10.6). Reservoir competence was low (<3%) in several other hosts including Virginia opossums (Didelphis virginiana), Eastern gray squirrels (Sciurus carolinensis), and all four species of birds tested. Interestingly, raccoons (Procyon lotor) have moderate levels of reservoir competence (9.9% ± 3.7), but may carry a distinct strain of B. microti. We discuss these findings in relation to reservoir competence of the same hosts for Borrelia burgdorferi, the causal agent of Lyme disease, and implications for managing landscapes to lower tick-borne disease risk to humans.

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