762 - Climate Change and the Seroprevalence of Borrelia burgdorferi over 25 Years in Rhode Island

Background: The Ixodes scapularis tick (deer tick or black-legged tick) is the primary vector of Borrelia burgdorferi, the causative agent of Lyme disease. Climatic conditions, specifically temperature, relative humidity, and rainfall, have been shown to affect I. scapularis tick densities. We hypothesized that temperature and moisture correlate with the frequency of human Lyme disease.

Methods: We have carried out a biannual B. burgdorferi serosurvey on Block island, Rhode Island over the past 25 years using a standard B. burgdorferi two-tier ELISA and Western blot assay. Residents of the Island were invited to participate and we only used first visit results. We analyzed B. burgdorferi seroprevalence and weather pattern trends (temperature, rainfall, relative humidity) among a cohort of 2,439 Block Island residents over the past 25 years.

Results: During the months in which ticks are active, we found that both temperature and relative humidity increased on Block Island over the past 25 years (p=0.04 and p=0.03, respectively). We also found that the seroprevalence of B. burgdorferi on the Island increased over the course of the study (p< 0.01), and that increased temperature and moisture in a given season is associated with increased B. burgdorferi seroprevalence in the following season. For example, we found that every inch increase in total rainfall in a given season was associated with a 2% (95% CI 1.01-1.03) increase in the odds of B. burgdorferi seropositivity during the following season.  Similarly, we found that every degree Fahrenheit increase in temperature in the spring was associated with a 2% (95% CI 1.02-1.03) increase in the odds of seropositivity in the fall.

Conclusion: We conclude that increasing temperature and moisture are associated with increased frequency of B. burgdorferi infection in humans.