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BMC Genomics. 2016 Nov 7;17(1):888.

Babesia microti from humans and ticks hold a genomic signature of strong population structure in the United States.

Author information

1
Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, 06520, USA.
2
Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT, 06520, USA.
3
Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, 21205, USA.
4
Department of Internal Medicine, Section of Infectious Diseases, Yale School of Medicine, New Haven, CT, 06520, USA.
5
Department of Anthropology, University of Iowa, Iowa City, IA, 52242, USA.
6
Nantucket Cottage Hospital, Nantucket, MA, 02554, USA.
7
Institut de Biologie Computationnelle, University de Montpellier, 34095, Montpellier, Cedex 5, France.
8
Department of Epidemiology of Microbial Diseases, Yale School of Public Health, New Haven, CT, 06520, USA. mad2256@columbia.edu.
9
Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, NY, 10027, USA. mad2256@columbia.edu.

Abstract

BACKGROUND:

Babesia microti is an emerging tick-borne apicomplexan parasite with increasing geographic range and incidence in the United States. The rapid expansion of B. microti into its current distribution in the northeastern USA has been due to the range expansion of the tick vector, Ixodes scapularis, upon which the causative agent is dependent for transmission to humans.

RESULTS:

To reconstruct the history of B. microti in the continental USA and clarify the evolutionary origin of human strains, we used multiplexed hybrid capture of 25 B. microti isolates obtained from I. scapularis and human blood. Despite low genomic variation compared with other Apicomplexa, B. microti was strongly structured into three highly differentiated genetic clusters in the northeastern USA. Bayesian analyses of the apicoplast genomes suggest that the origin of the current diversity of B. microti in northeastern USA dates back 46 thousand years with a signature of recent population expansion in the last 1000 years. Human-derived samples belonged to two rarely intermixing clusters, raising the possibility of highly divergent infectious phenotypes in humans.

CONCLUSIONS:

Our results validate the multiplexed hybrid capture strategy for characterizing genome-wide diversity and relatedness of B. microti from ticks and humans. We find strong population structure in B. microti samples from the Northeast indicating potential barriers to gene flow.

KEYWORDS:

Apicomplexan; Coalescent analysis; Hybrid capture; Population genomics; Tick-borne pathogen

PMID:
27821055
PMCID:
PMC5100190
DOI:
10.1186/s12864-016-3225-x
[Indexed for MEDLINE]
Free PMC Article
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