Fig 1.
The transitions of the multistate model.
The multistate model contained four states for the Peromyscus leucopus mice: (1) susceptible juveniles, (2) Borrelia burgdorferi-infected juveniles, (3) susceptible adults, and (4) B. burgdorferi-infected adults. The solid arrows show the five possible transitions in this system. The possible transitions are labeled, for example, the transition rate ψ14 is the probability that a susceptible juvenile (stage 1) will transition into an infected adult (stage 4) by the next capture occasion. The transition probabilities measure the instantaneous probability that an individual will change its state after surviving the time interval.
Table 1.
Summary of the transition rates.
Fig 2.
Seasonal and annual variation in the tick burden on mice.
Average monthly burden of immature Ixodes scapularis ticks (larvae and nymphs) on Peromyscus leucopus mice showed a seasonal pattern over the four years of the study (1999, 2000, 2001, and 2002) for each of the four areas (Control Area, Mallard Road, Nauyaug Point, New Area). Tick burden has units of number of ticks per mouse. There are five sampling months within each year (May, June, July, August, September). The size of the circle is proportional to the number of mice on which the average is based (range: 1 to 64). The properties in the New Area were not sampled in 1999.
Fig 3.
Seasonal and annual variation in Borrelia burgdorferi infection of mice.
Monthly prevalence of Borrelia burgdorferi-infected Peromyscus leucopus mice varied over the four years of the study (1999, 2000, 2001, and 2002) for each of the four areas (Control Area, Mallard Road, Nauyaug Point, New Area). The prevalence is a proportion and therefore does not have units. There are five sampling months within each year (May, June, July, August, September). The size of the circle is proportional to the number of mice on which the prevalence is based (range: 1 to 64). The properties in the New Area were not sampled in 1999. There is no estimate for September 2000 because the mice were not tested for B. burgdorferi infection.
Table 2.
Body weight, tick burden, and prevalence of Borrelia infection for the six combinations of sex and stage.
Table 3.
Multistate capture-mark-recapture (CMR) models of the Peromyscus leucopus mice.
Fig 4.
Effect of month and area on the mouse survival rate.
Monthly survival rates for Peromyscus leucopus mice (A) increased over the course of the summer and (B) differed among the four areas. The survival rate is the probability that a mouse will survive a period of 30 days. The survival rates are shown for a reference mouse, which is an adult female susceptible mouse living in the control area in May 2000. Shown are the means and the 95% confidence limits. The parameter estimates include variation due to model uncertainty.
Fig 5.
Effect of month, sex, and Borrelia infection on the mouse recapture rate.
Recapture rates for (A) Peromyscus leucopus mice over the course of the summer and for (B) susceptible and infected adult female and male mice. The recapture rate is the probability of encountering a marked mouse during a given sampling occasion. The recaptures rates are shown for a reference mouse, which is an adult female susceptible mouse living in the control area in May 2000. Shown are the means and the 95% confidence limits. The parameter estimates include variation due to model uncertainty.
Fig 6.
Effect of month and year on the infection rate.
The infection rate of Peromyscus leucopus mice (A) decreased over the course of the summer and (B) differed among years of the study. The infection rate is the instantaneous probability that a mouse will acquire a Borrelia burgdorferi infection after surviving through a time interval of 30 days. The infection rates are shown for a reference mouse, which is an adult female susceptible mouse living in the control area in May 2000. Shown are the means and the 95% confidence limits. The parameter estimates include variation due to model uncertainty.
Fig 7.
Effect of stage and area on the infection rate.
The infection rate was higher for adult than juvenile Peromyscus leucopus mice and differed among the four areas. The infection rate is the instantaneous probability that a mouse will acquire a Borrelia burgdorferi infection after surviving through a time interval of 30 days. The infection rates are shown for a reference mouse, which is an adult female susceptible mouse living in the control area in May 2000. Shown are the means and the 95% confidence limits. The parameter estimates include variation due to model uncertainty.