Epidemiology and Spatial Emergence of Anaplasmosis, New York, USA, 2010–2018

Alexis Russell; Melissa Prusinski; Jamie Sommer; Collin O'Connor; Jennifer White; Richard Falco; John Kokas; Vanessa Vinci; Wayne Gall; Keith Tober; Jamie Haight; JoAnne Oliver; Lisa Meehan; Lee Ann Sporn; Dustin Brisson; P. Bryon Backenson

Disclosures

Emerging Infectious Diseases. 2021;27(8):2154-2162. 

In This Article

Results

Anaplasmosis Epidemiology

A total of 5,146 anaplasmosis cases were reported in NYS (excluding NYC) during 2010–2018, a median of 454 cases/year (range 220–1,112 cases/year) (Table 1). Statewide incidence increased 3.9-fold over the study period, from 2.0 cases/100,000 persons during 2010 to 7.6 cases/100,000 persons during 2018; peak incidence was 9.9 cases/100,000 persons during 2017. The most substantial increase occurred in the Capital Region, which showed an 8.4-fold increase, from 4.3 cases/100,000 persons during 2010 to 36.3 cases/100,000 persons during 2018; peak incidence was 49.2 cases/100,000 persons during 2017. Incidence tended to be higher in odd years, most notably within the Capital Region (Figure 1).

Figure 1.

Anaplasmosis incidence by state region, New York, SA, 2010–2018.

Anaplasmosis was most common among male case-patients and those identified as White and non-Hispanic (Table 2). Patients >50 years of age accounted for 72.6% of cases. Aside from fever, which is a requirement to meet confirmed or probable case status, the most commonly reported symptoms were malaise, myalgia, and chills. Rash was the least commonly reported symptom. The most common bloodwork findings were thrombocytopenia and increased levels of hepatic aminotransferases, each found in more than half of the patients. Hospitalization was reported in 35.2% of case-patients, and 0.5% (16 patients) died from anaplasmosis-related causes. Symptom onset and diagnosis occurred most often in the month of June, followed by July and May (Figure 2).

Figure 2.

Anaplasmosis cases by month of diagnosis and case status, New York, USA, 2010–2018.

Prevalence of A. Phagocytophilum

A total of 16,743 nymphal and 27,658 adult I. scapularis ticks was tested for A. phagocytophilum during 2010–2018; a total of 721 nymphs (4.3%) and 1,789 adults (6.5%) showed positive results (Table 3). Statewide prevalence of A. phagocytophilum increased in nymphal and adult I. scapularis ticks over the study period. A. phagocytophilum prevalence in nymphal I. scapularis ticks increased in 3 of 4 geographic regions over the study period, and there was an overall statewide increase from 2.4% during 2010 to 4.5% during 2018. Statewide prevalence of A. phagocytophilum in adult I. scapularis ticks increased significantly (p<0.01) from 4.0% during 2010 to 9.2% during 2018, and we observed an increase in prevalence in all 4 regions. There was a significant (p<0.0001) 4.1-fold increase in A. phagocytophilum prevalence in adult I. scapularis ticks in the Capital Region from 2.9% during 2010 to 12.0% during 2018. Site-level ERI (A. phagocytophilum–carrying ticks per 1,000 m2) ranged from 0 to 28.2 in nymphs and from 0 to 85.3 in adult I. scapularis ticks.

Spatial Analysis

Patient ZCTA was available for 5,138 (99.8%) cases. Yearly ZCTA-level incidence ranged from 0 to 1,818 cases/100,000 persons. Moran I analysis showed significant spatial autocorrelation (Moran index range 0.092–0.260; p<0.0001) of human incidence at the ZCTA level for all years, justifying hot spot analysis. Getis-Ord Gi* analysis yielded 1 statistically significant hot spot for each year during 2010–2018 (Figure 3). The 99% confidence hot spot for 2010 encompassed 14.2% of ZCTAs, 10.8% of the population, and 9.4% of the land area of NYS excluding NYC. All 3 of these factors increased significantly (p<0.0001) over the study period, and the 99% confidence hot spot during 2018 encompassed 30.0% of ZCTAs, 17.0% of the population, and 24.8% of the land area. The centroid of the hot spot moved 51.7 km north and 10.6 km west during 2010–2018. The hot spot expanded to include a larger portion of the Capital Region over the study period. Overlaying site-level ERI onto the hot spot analysis showed that collection sites that had high ERIs tended to be located within the anaplasmosis hot spot; however, multiple high-ERI sites across the Metro Region and sporadically throughout the Central and Western regions were located outside the hot spot. Nymphal ERI was significantly correlated (r range 0.340–0.536; p<0.05) to anaplasmosis incidence at the ZCTA level for 7 of the 9 years during 2010–2018. Adult ERI was significantly correlated (r range 0.291–0.695; p<0.01) to anaplasmosis incidence at the ZCTA level for all years during 2010–2018.

Figure 3.

Epidemiology and spatial emergence of anaplasmosis, New York, USA, 2010–2018. A) Incidence by ZIP code tabulation area, odd years, 2011–2017. B) Getis-Ord Gi* hot spots (https://pro.arcgis.com) and adult Ixodes scapularis tick ERI, odd years, 2011–2017. Conf., confidence; ERI, entomologic risk index.

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