Lyme Disease Is Widespread in the New York City Metro Area

Lyme disease risk extends across the New York City metropolitan region
Cases have been reported among residents of urban and rural counties
Living in the city does not eliminate the possibility of exposure

Lyme disease is not confined to rural communities. Evidence of Borrelia burgdorferi infection has been documented throughout the broader New York City metropolitan region.

This has important implications for clinicians and patients who may underestimate Lyme disease risk based on an urban address alone.

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Evidence Across the New York City Metro Area

Herrin and colleagues examined canine Lyme disease test results and reported human cases across 30 counties in the New York City metropolitan statistical area. The region included counties in New York, New Jersey, Connecticut, and Pennsylvania.

The investigators analyzed 234,633 canine test results collected between 2001 and 2010. Depending on the county, the percentage of dogs testing positive for antibodies to B. burgdorferi ranged from 1.2% to 27.3%.

The authors also noted that 7.1% of pet dogs tested in New York State were seropositive.

Evidence of exposure was found among dogs tested in both densely populated and less-developed counties.

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Human Lyme Disease Cases Varied Widely

Reported human Lyme disease rates included in the study ranged from:

• 0.5 cases per 100,000 people in some counties
• As many as 438.7 cases per 100,000 people in others

As expected, the highest rates generally occurred in counties with lower population density and more forested land. However, the investigators also found more canine positive tests and reported human cases than their model predicted in several densely populated counties, including:

• Queens
• Bronx
• Kings County (Brooklyn)
• New York County (Manhattan)
• Hudson County, New Jersey

These findings challenge the assumption that people living in urban counties have no meaningful Lyme disease risk.

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Where Were the Urban Infections Acquired?

The study could not determine where individual infections occurred. A person or dog living in New York City may have been exposed locally or while traveling outside a densely developed area.

The authors suggested that many infections among urban residents and their dogs were likely acquired during travel to suburban, rural, or forested areas.

Possible routes of exposure include:

• Travel between urban, suburban, and rural communities
• Outdoor activities in wooded or brushy areas
• Visits to parks and other green spaces
• Pets encountering ticks and carrying them into the home

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Forest Fragmentation May Increase Exposure

The authors also discussed a “crossroads” phenomenon. Roads, housing, and other development can divide forests into smaller areas, creating more forest-edge habitat.

These edges bring people, pets, wildlife, and ticks into closer contact and may increase opportunities for exposure.

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Dogs as Sentinels of Lyme Disease Risk

Dogs can serve as useful indicators of Lyme disease risk because they share many of the same environments as people and are routinely tested for antibodies to B. burgdorferi.

In this study, the percentage of positive canine tests correlated with population-adjusted human Lyme disease reports. Counties with higher canine seropositivity generally had higher reported rates of human disease.

Canine testing can help identify communities where human exposure may also warrant closer attention.

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Clinical Implications

Clinicians should not exclude Lyme disease from the differential diagnosis solely because a patient lives in New York City or another densely populated community.

A careful exposure history should include:

• Travel to nearby endemic regions
• Time spent in parks, wooded areas, or forest-edge habitats
• Outdoor occupational or recreational activities
• Exposure involving dogs and other pets

Because the study used historical canine and human data, its precise county rates should not be interpreted as estimates of current risk. Nevertheless, it demonstrates that Lyme disease exposure and reported illness extend throughout the interconnected New York City metropolitan region.

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Clinical Takeaway

Lyme disease risk is not limited to rural areas. People living in New York City and surrounding metropolitan counties may be exposed locally or while traveling elsewhere in the region. Clinicians should consider Lyme disease in patients with compatible symptoms and evaluate their complete exposure history rather than relying on their home address alone.

Related Articles:

Babesia microti in Suffolk County, New York

Tick Bite Risk for Pet Owners

Urban Ticks Carry Lyme and Miyamotoi

Reference:

1. Herrin BH, Beall MJ, Feng X, Papeş M, Little SE. Canine and human infection with Borrelia burgdorferi in the New York City metropolitan area. Parasit Vectors. 2018;11:187. doi:10.1186/s13071-018-2774-z.

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Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention