Application of mutagen sensitivity assay in a glioma case-control study.

Few risk factors for glioma have been identified other than ionizing radiation. The alkylating agent acrylamide is a compound found in both occupational and the general environment and identified as one of the forty known or suspected neurocarcinogens in animal models. The mutagen sensitivity assay (MSA) has been used to indirectly show reduced DNA repair capacity upon exposure to ionizing radiation in those with glioma compared to controls. In this study, MSA was used to assess its applicability to a glioma case-control study and to test the hypothesis that subjects with glioma may have lower DNA repair capacity after exposure to selected potential human neurocarcinogens (i.e. acrylamide), compared to controls. Approximately 50 case and 50 control subjects were identified from a clinic-based study that investigated environmental risk factors for glioma, who completed an exposure survey, and had frozen immortalized lymphocytes available. A total of 50 metaphase spreads were read and reported for each participant. The association of case-control status with MSA for acrylamide, i.e. breaks per spread, was examined by multivariable logistic regression models. The mean number of breaks per slide was similar between hospital-based controls and cases. In addition, case-control status or exposure categories were not associated with the number of breaks per spread. Although the MSA has been shown as a useful molecular epidemiology tool for identifying individuals at higher risk for cancer, our data do not support the hypothesis that glioma patients have reduced DNA repair capacity in response to exposure to acrylamide. Further research is needed before the MSA is utilized in large-scale epidemiological investigations of alkylating agents.

Prevalence of Anaplasma phagocytophilum and Babesia microti in Ixodes scapularis from a Newly Established Lyme Disease Endemic Area, the Thousand Islands Region of Ontario, Canada.

Blacklegged ticks (Ixodes scapularis) are vectors for several important human diseases, including Lyme disease, human granulocytic anaplasmosis (HGA), and human babesiosis, caused by Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti, respectively. The continued northward range expansion of blacklegged ticks and associated pathogens is an increasing public health concern in Canada. The Thousand Islands region of eastern Ontario has recently been identified as a new endemic area for Lyme disease in Canada, but the occurrence of other pathogens in ticks in this area has not been fully described. Our objectives were to determine the prevalence of A. phagocytophilum and B. microti in small mammals and questing ticks in the Thousand Islands area and identify the strains of A. phagocytophilum circulating in ticks in the area. Serum and larval ticks were collected from trapped small mammals, and questing ticks were collected via drag sampling from up to 12 island and mainland sites in 2006, 2009, and 2010. A. phagocytophilum was identified by PCR in 3.4% (47/1388) ticks from eight of 12 sites; the prevalence ranged from 8.9% in 2006 to 3% in 2009. All 365 ticks tested for B. microti were negative. Antibodies to A. phagocytophilum were detected in 2.8% (17/611) of white-footed mice (Peromyscus leucopus) at two of 11 sites in 2006, 2009, or 2010. All 34 A. phagocytophilum-positive ticks submitted for strain identification using single-nucleotide polymorphism genotyping assays targeting the 16S rRNA gene were identified as a variant strain (Ap variant-1), which is not commonly associated with human disease. Our findings suggest that people are at low risk of contracting HGA or human babesiosis due to locally acquired tick bites in the Thousand Islands area. However, continued surveillance is warranted as these pathogens continue to expand their ranges in North America.

Geography, deer, and host biodiversity shape the pattern of Lyme disease emergence in the Thousand Islands Archipelago of Ontario, Canada.

In the Thousand Islands region of eastern Ontario, Canada, Lyme disease is emerging as a serious health risk. The factors that influence Lyme disease risk, as measured by the number of blacklegged tick (Ixodes scapularis) vectors infected with Borrelia burgdorferi, are complex and vary across eastern North America. Despite study sites in the Thousand Islands being in close geographic proximity, host communities differed and both the abundance of ticks and the prevalence of B. burgdorferi infection in them varied among sites. Using this archipelago in a natural experiment, we examined the relative importance of various biotic and abiotic factors, including air temperature, vegetation, and host communities on Lyme disease risk in this zone of recent invasion. Deer abundance and temperature at ground level were positively associated with tick abundance, whereas the number of ticks in the environment, the prevalence of B. burgdorferi infection, and the number of infected nymphs all decreased with increasing distance from the United States, the presumed source of this new endemic population of ticks. Higher species richness was associated with a lower number of infected nymphs. However, the relative abundance of Peromyscus leucopus was an important factor in modulating the effects of species richness such that high biodiversity did not always reduce the number of nymphs or the prevalence of B. burgdorferi infection. Our study is one of the first to consider the interaction between the relative abundance of small mammal hosts and species richness in the analysis of the effects of biodiversity on disease risk, providing validation for theoretical models showing both dilution and amplification effects. Insights into the B. burgdorferi transmission cycle in this zone of recent invasion will also help in devising management strategies as this important vector-borne disease expands its range in North America.

Herbivory more limiting than competition on early and established native plants in an invaded meadow.

The dominance of nonnative plants coupled with declines of native plants suggests that competitive displacement drives extinctions, yet empirical examples are rare. Herbivores, however, can alter vegetation structure and reduce diversity when abundant. Herbivores may act on mature, reproductive life stages whereas some of the strongest competitive effects might occur at early life stages that are difficult to observe. For example, competition by perennial nonnative grasses can interfere with the establishment of native seeds. We contrasted the effects of ungulate herbivory and competition by neighboring plants on the performance of native plant species at early and established life stages in invaded oak meadows. We recorded growth, survival, and flowering in two native species transplanted as established plants, six native species grown from seed, and five extant lily species as part of two 2 x 2 factorial experiments that manipulated herbivory and competition. Herbivory reduced the performance of nearly all focal native species at early and established life stages, whereas competition had few measurable effects. Our results suggest that herbivory has a greater local influence on native plant species than competition and that reducing herbivore impacts will be required to successfully restore endangered oak meadows where ungulates are now abundant.