Infection Prevalence of Borrelia burgdorferi in Adult Blacklegged Ticks (Ixodes scapularis) from Pittsburgh Regional City Parks

Tashi Bharathan, Shannon Tepe

Abstract


Although Lyme disease is the most common vector-borne illness in the United States, its risk has mostly been studied in rural and suburban landscapes and not adequately in urban green spaces. Therefore, we investigated the relative abundance and distribution of adult blacklegged ticks (Ixodes scapularis) infected with Lyme disease-causing bacteria (Borrelia burgdorferi) in four Pittsburgh regional city parks. Ticks were collected using drags in fall 2015 and spring 2016. For each park twenty randomly chosen sites, which contained 10x10 m wooded plots and 100 m adjacent edges, were surveyed. The DNA of each tick was extracted and tested for the B. burgdorferi-specific OspA gene using real-time PCR. The real-time PCR results were validated using conventional PCR and gel electrophoresis for a B. burgdorferi-specific region of the fla gene. There was a significant difference between parks in the density of ticks as well as in the number of sites with ticks. They ranged from Highland Park with the highest density (2.70±0.64 ticks/100 m) and number of sites with ticks (90%) to Frick Park with the lowest density (0.10±0.06 ticks/100m) and number of sites with ticks (10%). The overall density of ticks along edges (1.7±3.5 ticks/100m) was significantly greater than in plots (0.40±1.0 ticks/100m). The overall infection prevalence of B. burgdorferi was 53.6% and not significantly different between parks. However, the density of infected ticks was significantly different with Highland Park having the highest (1.48±0.39 ticks/100m) and Frick Park the lowest (0.05±0.03 ticks/100m) densities. In conclusion, the density of ticks and infection prevalence of B. burgdorferi in these urban green spaces are comparable to rural and suburban areas highly endemic for Lyme disease. A recommendation is that preventative measures, such as posting trails with warning signs, be taken to reduce Lyme disease risk in the Pittsburgh regional city parks.

Keywords


Lyme Disease, PCR, Urban Green Spaces

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