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Open Access item Phylogeographic analysis reveals association of tick-borne pathogen, Anaplasma marginale, MSP1a sequences with ecological traits affecting tick vector performance
Naranjo, María Victoria
Mangold, Atilio J.
Kocan, Katherine M.
Fuente García, José de la
|Citation:||BMC Biology 7(57): (2009)|
|Abstract:||Background: The tick-borne pathogen Anaplasma marginale, which is endemic worldwide, is the type species of the
genus Anaplasma (Rickettsiales: Anaplasmataceae). Rhipicephalus (Boophilus) microplus is the most important tick vector of
A. marginale in tropical and subtropical regions of the world. Despite extensive characterization of the genetic diversity
in A. marginale geographic strains using major surface protein sequences, little is known about the biogeography and
evolution of A. marginale and other Anaplasma species. For A. marginale, MSP1a was shown to be involved in vectorpathogen
and host-pathogen interactions and to have evolved under positive selection pressure. The MSP1a of A.
marginale strains differs in molecular weight because of a variable number of tandem 23-31 amino acid repeats and has
proven to be a stable marker of strain identity. While phylogenetic studies of MSP1a repeat sequences have shown
evidence of A. marginale-tick co-evolution, these studies have not provided phylogeographic information on a global scale
because of the high level of MSP1a genetic diversity among geographic strains.|
Results: In this study we showed that the phylogeography of A. marginale MSP1a sequences is associated with world
ecological regions (ecoregions) resulting in different evolutionary pressures and thence MSP1a sequences. The results
demonstrated that the MSP1a first (R1) and last (RL) repeats and microsatellite sequences were associated with world
ecoregion clusters with specific and different environmental envelopes. The evolution of R1 repeat sequences was found
to be under positive selection. It is hypothesized that the driving environmental factors regulating tick populations could
act on the selection of different A. marginale MSP1a sequence lineages, associated to each ecoregion.
Conclusion: The results reported herein provided the first evidence that the evolution of A. marginale was linked to
ecological traits affecting tick vector performance. These results suggested that some A. marginale strains have evolved
under conditions that support pathogen biological transmission by R. microplus, under different ecological traits which
affect performance of R. microplus populations. The evolution of other A. marginale strains may be linked to transmission
by other tick species or to mechanical transmission in regions where R. microplus is currently eradicated. The information
derived from this study is fundamental toward understanding the evolution of other vector-borne pathogens.
|Description:||13 pages, 6 tables, 3 figures.|
|Publisher version (URL):||http://dx.doi.org/10.1186/1741-7007-7-57|
|Appears in Collections:||(IREC) Artículos|
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