What do we need to know about disease ecology to prevent Lyme disease in the northeastern United States?

Genetic structure of the white-footed mouse in the context of the emergence of Lyme disease in southern Québec

The white-footed mouse (Peromyscus leucopus) has expanded its northern limit into southern Québec over the last few decades. P. leucopus is a great disperser and colonizer and is of particular interest because it is considered a primary reservoir for the spirochete bacterium that causes Lyme disease. There is no current information on the gene flow between mouse populations on the mountains and forest fragments found scattered throughout the Montérégie region in southern Québec, and whether various landscape barriers have an effect on their dispersal. We conducted a population genetics analysis on eleven P. leucopus populations using eleven microsatellite markers and showed that isolation by distance was weak, yet barriers were effective. The agricultural matrix had the least effect on gene flow, whereas highways and main rivers were effective barriers. The abundance of ticks collected from mice varied within the study area. Both ticks and mice were screened for the presence of the spirochete bacterium Borrelia burgdorferi, and we predicted areas of greater risk for Lyme disease. Merging our results with ongoing Lyme disease surveillance programs will help determine the future threat of this disease in Québec, and will contribute toward disease prevention and management strategies throughout fragmented landscapes in southern Canada.

Serum antibodies to Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti in recaptured white-footed mice

A mark-release-recapture study was conducted during 2007 through 2010 in six, tick-infested sites in Connecticut, United States to measure changes in antibody titers for Borrelia burgdorferi sensu stricto, Anaplasma phagocytophilum, and Babesia microti in Peromyscus leucopus (white-footed mice). There was an overall recapture rate of 40%, but only four tagged mice were caught in ≥2 yr. Sera from 561 mice were analyzed for total antibodies to B. burgdorferi and A. phagocytophilum by using whole-cell or recombinant (VlsE or protein 44) antigens in a solid-phase enzyme-linked immunosorbent assay or to whole-cell B. microti by indirect fluorescent antibody staining. Antibody prevalences were highly variable for B. burgdorferi (from 56% to 98%), A. phagocytophilum (from 11% to 85%), and B. microti (from 11% to 84%) depending on the site and time of sampling. Of 463 mice with antibodies, 206 (45%) had antibodies to all three pathogens. Changes in antibody status for some mice from negative to positive (117 seroconversions) or from positive to negative (55 reversions) were observed. Seroconversions were observed in 10.1% of 417 mice for B. burgdorferi, 18.0% of 306 mice for A. phagocytophilum, and 6.6% of 304 mice for B. microti; reversion rates were 5.3, 5.9, and 4.9%, respectively. Antibodies to all pathogens persisted in some mice over several weeks while, in others, there were marked declines in titration end points to negative status. The latter may indicate elimination of a certain pathogen, such as A. phagocytophilum, or that mouse immune systems ceased to produce antibodies despite an existing patent infection.

Biodiversity and disease: a synthesis of ecological perspectives on Lyme disease transmission

Recent reviews have argued that disease control is among the ecosystem services yielded by biodiversity. Lyme disease (LD) is commonly cited as the best example of the 'diluting' effect of biodiversity on disease transmission, but many studies document the opposite relationship, showing that human LD risk can increase with forestation. Here, we unify these divergent perspectives and find strong evidence for a positive link between biodiversity and LD at broad spatial scales (urban to suburban to rural) and equivocal evidence for a negative link between biodiversity and LD at varying levels of biodiversity within forests. This finding suggests that, across zoonotic disease agents, the biodiversity-disease relationship is scale dependent and complex.