By Linda on Mar 2, 2011 in Infections | comments(0)
Link: http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=21157575&retmode=ref&cmd=prlinks
Excerpt:
Using multilocus sequence analyses (MLSA), we investigated the phylogenetic
relationship of spirochaete strains from North America previously assigned
to the genospecies Borrelia bissettii. We amplified internal fragments of 8
housekeeping genes (clpA, clpX, nifS, pepX, pyrG, recG, rplB, and uvrA)
located on the main linear chromosome by polymerase chain reaction.
Phylogenetic analysis of concatenated sequences of the 8 loci showed that
the B. bissettii clade consisted of 4 closely related clusters which
included strains from California (including the type strain DN127-Cl9-2/p7)
and Colorado that were isolated from Ixodes pacificus, I. spinipalpis, or
infected reservoir hosts.
Several strains isolated from I. scapularis clustered distantly from B.
bissettii. Genetic distance analyses confirmed that these strains are more
distant to B. bissettii than they are to B. carolinensis, a recently
described Borrelia species, which suggests that they constitute a new
Borrelia genospecies. We propose that it be named Borrelia kurtenbachii sp.
nov. in honour of the late Klaus Kurtenbach. The data suggest that
ecological differences between B. bissettii and the new Borrelia genospecies
reflect different transmission cycles. In view of these findings, the
distinct vertebrate host-tick vector associations and the distributions of
B. bissettii and B. kurtenbachii require further investigation.
By Linda on Jan 20, 2011 in Infections | comments(0)
Link: http://eutils.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&id=20941513&retmode=ref&cmd=prlinks
Excerpt:
Invasive species, including pathogens, can have important effects
on local ecosystems, including indirect consequences on native
species. This study focuses on the effects of an invasive plant
pathogen on a vertebrate community and Ixodes pacificus, the
vector of the Lyme disease pathogen (Borrelia
burgdorferi) in California. Phytophthora ramorum, the causative
agent of sudden oak death, is a non-native pathogen killing trees
in California and Oregon. We conducted a multi-year study using a
gradient of SOD-caused disturbance to assess the impact on the
dusky-footed woodrat (Neotoma fuscipes) and the deer mouse
(Peromyscus maniculatus), two reservoir hosts of B. burgdorferi,
as well as the impact on the Columbian black-tailed deer
(Odocoileus hemionus
columbianus) and the western fence lizard (Sceloporus
occidentalis), both of which are important hosts for I. pacificus
but are not pathogen reservoirs.
Abundances of P. maniculatus and S. occidentalis were positively
correlated with greater SOD disturbance, whereas N. fuscipes
abundance was negatively correlated. We did not find a change in
space use by O. hemionus.
Our data show
that SOD has a positive impact on the density of nymphal ticks,
which is expected to increase the risk of human exposure to Lyme
disease all else being equal. A positive correlation between SOD
disturbance and the density of nymphal ticks was expected given
increased abundances of two important hosts: deer mice and
western fence lizards. However, further research is needed to
integrate the direct effects of SOD on ticks, for example via
altered abiotic conditions with host-mediated indirect effects
By Linda on Jun 17, 2010 in Infections | comments(0)
Excerpt:
In the far-western United States, the nymphal stage of the
western black-legged tick, Ixodes pacificus, has been implicated
as the primary vector to humans of Borrelia burgdorferi sensu
stricto (hereinafter referred to as B. burgdorferi), the
causative agent of Lyme borreliosis in North America. In the
present study, we sought to determine if infection prevalence
with B. burgdorferi in I.
pacificus nymphs and the density of infected nymphs differ
between dense-woodland types within Mendocino County, California,
and to develop and evaluate a spatially-explicit model for
density of infected nymphs in dense woodlands within this
high-incidence area for Lyme borreliosis. In total, 4.9%
(264) of 5431 I. pacificus nymphs tested for the presence of B.
burgdorferi were infected. Among the 78 sampling sites, infection
prevalence ranged from 0 to 22% and density of infected nymphs
from 0 to 2.04 per 100 m(2). Infection prevalence was highest in
woodlands dominated by hardwoods (6.2%) and lowest for redwood
(1.9%) and coastal pine (0%). Density of infected nymphs also was
higher in hardwood-dominated woodlands than in conifer-dominated
ones that included redwood or pine. Our spatial risk model, which
yielded an overall accuracy of 85%, indicated that warmer areas
with less variation between maximum and minimum monthly water
vapor in the air were more likely to include woodlands with
elevated acarological risk of exposure to infected nymphs. We
found that 37% of dense woodlands in the county were predicted to
pose an elevated risk of exposure to infected nymphs, and that
94% of the dense-woodland areas that were predicted to harbor
elevated densities of infected nymphs were located on
privately-owned land.
