Temporal and Geographic Trends in Babesiosis and Human Granulocytic Anaplasmosis (HGA) in New York State: 1986-2007

Background: Babesiosis and Human Granulocytic Anaplasmosis (HGA) are tick-borne diseases transmitted by the deer tick or black-legged tick (Ixodes scapularis), the same vector that carries Lyme disease. While Lyme disease is the most prevalent and well-known tick-borne disease, cases of babesiosis and HGA have continued to increase in New York State since they became reportable in 1986 and 1996 respectively.

Objectives: To determine the incidence of both diseases over time and the counties of New York State most at risk, and to determine if the trends match those exhibited by Lyme disease.

Methods: SAS was used to calculate descriptive statistics of demographic data and incidences by county of babesiosis and HGA, as well as to analyze data over time. Analysis of Variance (ANOVA) was used to compare incidences between counties. ArcGIS was used to map the frequency of disease in each county.

Results: There has been a significant increase in the incidence of babesiosis over time in New York State (p=.0002) with a dramatic increase in the East Hudson Valley Region (p<.0001). HGA has also seen a large increase in incidence over time (p=.0095) especially within Dutchess and Columbia counties (p<.0001).

Conclusions: The disease frequency pattern shows that babesiosis and HGA are spreading farther north and west than has been seen before, and are following the same historical patterns as the spread of Lyme disease. The patterns of Lyme disease spread can be used to predict future patterns of babesiosis and HGA and provide appropriate recommendations to local health departments.