Western gray squirrel - host of Lyme disease?

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15962792&query_hl=14

* *J Med Entomol. 2005 May;42(3):388-96.

*Western gray squirrel (Rodentia: Sciuridae): a primary reservoir host
of Borrelia burgdorferi in Californian oak woodlands?*

*Lane RS, Mun J, Eisen RJ, Eisen L.*

Division of Insect Biology, Department of Environmental Science,
Policy and Management, University of California, Berkeley, CA 94720,
USA. blane@xxxxxxxxxxxxxxxxxxx

In California, dense woodlands have been recognized as important
biotopes where humans are exposed to the nymphal stage of the western
blacklegged tick, Ixodes pacificus Cooley & Kohls, the primary vector
of
the Lyme disease spirochete Borrelia burgdorferi sensu stricto (s.s.),
in the far-western United States. To identify the principal reservoir
host(s) of this spirochete, and of closely related spirochetes in the
B.
burgdorferi sensu lato (s.l.) complex, in dense woodlands in Mendocino
County, California, approximately 50 species of birds and mammals,
including wood rats and kangaroo rats, were evaluated as potential
hosts
for vector ticks and borreliae in 2002 and 2003. Although polymerase
chain reaction (PCR) and sequencing analyses revealed that many
vertebrate species had been exposed to one or more members of the B.
burgdorferi s.l. spirochetal complex, only the western gray squirrel,
Sciurus griseus, fulfilled the major criteria for a reservoir host of
B.
burgdorferi s.s. Ear-punch biopsies from eight of 10 squirrels
collected
from five separate woodlands were PCR-positive for B. burgdorferi s.s.,

47% of I. pacificus larvae (n = 64) and 31% of nymphs (n = 49) removed
from squirrels contained B. burgdorferi s.l., and the engorgement
status
of I. pacificus larvae was associated positively with acquisition of
spirochetes. Overall, 83 and 100% of the amplicons sequenced from
PCR-positive I. pacificus larvae and nymphs, respectively, were
identified as B. burgdorferi s.s, Among the five remaining positive I.
pacificus larvae, three contained B. bissettii and two had
uncharacterized B. burgdorferi s.l. Borrelia burgdorferi s.s. was
detected in one of five larvae and zero of two nymphs of the Pacific
Coast tick, Dermacentor occidentalis Marx, that likewise had been
removed from squirrels. The rickettsial agent of human anaplasmosis,
Anaplasma phagocytophilum, was detected in the blood or ear biopsies of

two squirrels and in one (1.6%) of 64 I. pacificus larvae and two
(4.1%)
of 49 nymphs obtained from squirrels. The one rickettsial-positive
larva
was coinfected with B. burgdorferi s.s. The apparently high reservoir
potential of S. griseus for B. burgdorferi s.s., plus the fact that the

geographic distribution of this squirrel coincides well with that of
most reported human cases of Lyme disease in this region, indicated
that
it may be essential for maintaining foci of B. burgdorferi s.s. in
certain types of woodlands. The findings with respect to A.
phagocytophilum, although of less certain significance, suggest that S.

griseus could serve as a secondary host of this rickettsia.

PMID: 15962792 [PubMed - in process]

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