Climate change and habitat fragmentation drive the occurrence of Borrelia burgdorferi, the agent of Lyme disease, at the northeastern limit of its distribution.

Lyme borreliosis is rapidly emerging in Canada, and climate change is likely a key driver of the northern spread of the disease in North America. We used field and modeling approaches to predict the risk of occurrence of Borrelia burgdorferi, the bacteria causing Lyme disease in North America. We combined climatic and landscape variables to model the current and future (2050) potential distribution of the black-legged tick and the white-footed mouse at the northeastern range limit of Lyme disease and estimated a risk index for B. burgdorferi from these distributions. The risk index was mostly constrained by the distribution of the white-footed mouse, driven by winter climatic conditions. The next factor contributing to the risk index was the distribution of the black-legged tick, estimated from the temperature. Landscape variables such as forest habitat and connectivity contributed little to the risk index. We predict a further northern expansion of B. burgdorferi of approximately 250-500 km by 2050 - a rate of 3.5-11 km per year - and identify areas of rapid rise in the risk of occurrence of B. burgdorferi. Our results will improve understanding of the spread of Lyme disease and inform management strategies at the most northern limit of its distribution.

Poleward expansion of the white-footed mouse (Peromyscus leucopus) under climate change: implications for the spread of lyme disease.

The white-footed mouse (Peromyscus leucopus) is an important reservoir host for Borrelia burgdorferi, the pathogen responsible for Lyme disease, and its distribution is expanding northward. We used an Ecological Niche Factor Analysis to identify the climatic factors associated with the distribution shift of the white-footed mouse over the last 30 years at the northern edge of its range, and modeled its current and potential future (2050) distributions using the platform BIOMOD. A mild and shorter winter is favouring the northern expansion of the white-footed mouse in Québec. With more favorable winter conditions projected by 2050, the distribution range of the white-footed mouse is expected to expand further northward by 3° latitude. We also show that today in southern Québec, the occurrence of B. burgdorferi is associated with high probability of presence of the white-footed mouse. Changes in the distribution of the white-footed mouse will likely alter the geographical range of B. burgdorferi and impact the public health in northern regions that have yet to be exposed to Lyme disease.

Performance standards for therapeutic abdominal paracentesis.

Large-volume paracentesis, the preferred treatment for patients with symptomatic tense ascites due to cirrhosis, has traditionally been performed by physicians as an inpatient procedure. Our objectives were to determine (1) whether large-volume paracentesis could be performed safely and effectively by gastrointestinal endoscopy assistants and as an outpatient procedure, (2) whether the risk of bleeding was associated with either thrombocytopenia or prolongation of the prothrombin time, and (3) the resources used for large-volume paracentesis. Gastrointestinal endoscopy assistants performed 1,100 large-volume paracenteses in 628 patients, 513 of whom had cirrhosis of the liver. The preprocedure mean international normalized ratio for prothrombin time was 1.7 +/- 0.46 (range, 0.9-8.7; interquartile range, 1.4-2.2), and the mean platelet count was 50.4 x 10(3)/microL, (range, 19 x 10(3)/microL - 341 x 10(3)/microL; interquartile range, 42-56 x 10(3)/microL). Performance of 3 to 7 supervised paracenteses was required before competence was achieved. There were no significant procedure-related complications, even in patients with marked thrombocytopenia or prolongation in the prothrombin time. The mean duration of large-volume paracentesis was 97 +/- 24 minutes, and the mean volume of ascitic fluid removed was 8.7 +/- 2.8 L. In conclusion, large-volume paracentesis can be performed safely as an outpatient procedure by trained gastrointestinal endoscopy assistants. Ten supervised paracenteses would be optimal for training the operators carrying out the procedure. The practice guideline of the American Association for the Study of Liver Diseases which states that routine correction of prolonged prothrombin time or thrombocytopenia is not required is appropriate when experienced personnel carry out paracentesis.