Bb in Wisconsin, new strain characterized
- From: overman74@xxxxxxxxxxx
- Date: 30 May 2005 16:07:23 -0700
Presence of Borrelia burgdorferi (Spirochaetales: Spirochaetaceae) in
Southern Kettle Moraine State Forest, Wisconsin, and Characterization
of Strain W97F51
Authors: Caporale, D. A.; Johnson, C. M.; Millard, B. J.
Source: Journal of Medical Entomology, May 2005, vol. 42, no. 3, pp.
457-472(16)
Publisher: Entomological Society of America
Abstract:
Lyme disease, caused by Borrelia burgdorferi Johnson, Schmidt, Hyde,
Steigerwalt & Brenner; babesiosis, caused by Babesia microti Franca;
and human granulocytic ehrlichiosis, caused by Anaplasma
phagocytophilum Bakken & Dumler have been reported in Wisconsin, mainly
in the endemic areas of the northwestern part of the state.
People exposed to blacklegged ticks, Ixodes scapularis Say, from this
region can potentially contract one or all of these diseases
concurrently. Within the past several years, there have been cases of
Lyme disease reported from southeastern Wisconsin, an area that
contains deer, mice, and similar vegetation found at regions with high
endemicity. However, past white-tailed deer surveys suggested no
existence of I. scapularis in southeastern Wisconsin.
However, in 1996, we identified questing adult I. scapularis in the
southernmost part of the Southern Kettle Moraine State Forest, Walworth
County. To determine whether an established population of I. scapularis
exists in this region, we performed a detailed survey of the abundance
of host-seeking I. scapularis adults and the presence and abundance of
subadults feeding on white-footed mice, Peromyscus leucopus Rafinesque.
We also tested for possible infections of B. burgdorferi, Ba. microti,
and A. phagocytophilum in ticks and B. burgdorferi harbored by mice.
In 1997 and 1998, a total of 249 P. leucopus mice and 118 questing
adult I. scapularis ticks, in addition to 157 larvae and seven nymphs
feeding on mice, were collected and their locations were recorded from
the Nordic trails of the Southern Kettle Moraine State Forest. Only one
P. leucopus and its attached engorged I. scapularis nymph were infected
with B. burgdorferi, whereas none of the engorged larvae attached to
mice were infected. However, 4.2% of questing adult I. scapularis were
infected with B. burgdorferi. The abundance of questing adult I.
scapularis was 1.6 ticks per hour. The prevalence of subadult ticks on
mice was 27%, with a mean intensity on infested mice of 2.0. I.
scapularis adults were not infected with either Ba. microti or A.
phagocytophilum.
A unique strain of B. burgdorferi s.l. (W97F51) was discovered, showing
33 nucleotide substitutions and one codon insertion in a 567-bp
fragment of the OspB gene, compared with Borrelia bissettii (strain
Ca389). The sequences of ospA, ospB, ospC, fla, and rrs genes and the
rrf-rrl intergenic spacer region were compared between W97F51 and other
B. burgdorferi s.l. species. Although W97F51 was most genetically
related to B. bissettii, the genetic identity of W97F51 was less than
that of B. bissettii conspecifics.
This study documents the existence of an established population of I.
scapularis and the presence of B. burgdorferi with a novel strain in
southeastern Wisconsin.
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