Database Reference
In-Depth Information
Chapter 7
Lyme Disease
1
7.1 Lyme Disease Model
Over the past 20 years since Lyme disease was first diagnosed, it has been identi-
fied as the most common vector-borne disease in the United States. The repopula-
tion of white-tailed deer in the United States of America has been associated with
the emergence of this disease. The tick vector,
Ixodes scapularis,
harbors
Borre-
lia burgdorferi (B.b.)
, the organism responsible for Lyme disease
2
. The larval and
nymphal stages feed on intermediate hosts, which are mostly small mammals and
birds. The adult tick prefers to feed on deer, but will also feed on dogs and people.
The main intermediate host in the northeast United States is the white-footed mouse.
Mice and chipmunks may serve as reservoirs for
B
in nature since they maintain
active infections for at least 3 to 4 months. In the Midwest, however, it has been
determined that the eastern chipmunk may be equally important as an intermediate
host. The ticks appear to follow the migration of deer but deer may be simply an
amplification host; they are able to clear infection from
B
.
b
.
within a few days.
To investigate the ecology of Lyme disease, we model a 1-hectare (0.1 kmˆ2)
oak forest and run that model on a weekly time interval, beginning with the first
week of spring (T
.
b
.
0.5. In our model we concentrate on the inter-
relationships among acorn production, white-footed mice (
Peromyscus leucopus
),
white-tailed deer (
Odocoileus virginianus
), and the blacklegged tick (
Ixodes scapu-
laris
). Specifically, we explore a hypothesis recently put forth by Ostfeld, Jones,
and Wolff,
3
which states that the risk for human Lyme disease, due to increases in
nymphal tick activity, should be greater approximately two years following a large
mast event.
=
0), and DT
=
1
Thanks to M. Roberto Cortinas for helping develop the model of this chapter.
2
Randolph, S.E. General Framework for Comparative Quantitative Studies on Transmission of
Tick-Borne Diseases Using Lyme Borreliosis in Europe as an Example.
J. Med. Entom.
32(6)1995,
767-77.
3
Ostfeld, Richard S., Clive G. Jones, and Jerry O. Wolff. 1996. Of mice and mast.
Bioscience
46,
5: 323-330.
