Borrelia Miyamotoi in Urban Areas: Ticks Expanding Into Cities

Ticks carrying Lyme disease and related pathogens are increasingly being identified in urban environments. Studies suggest that city parks, woodland edges, and recreational green spaces may serve as habitats for infected ticks.

This raises an important question: are urban areas becoming a growing source of tick exposure? Findings from England indicate that tick populations may be well established in certain city settings.

Questing ticks were collected from grassland, hedges, parks, woodland, and woodland edges in Salisbury, an urban area in Wiltshire, England. Ticks were identified at more than 50% of the 25 surveyed sites.

Investigators found that these ticks carried pathogens relevant to human health. “DNA of Borrelia burgdorferi sensu lato was detected in 18.1% of nymphs collected,” according to Hansford from Public Health England. Two nymphs also tested positive for Borrelia miyamotoi, an emerging tick-borne pathogen.

Tick Activity and Infection Patterns

The prevalence of infected ticks increased between 2013 and 2014. Nymphs were active across all three seasons, with the highest activity observed in the spring.

Among the Borrelia species identified:

• Borrelia garinii was found in 42% of infected ticks
• Borrelia valaisiana was identified in 36%

These findings reflect a diverse population of Borrelia species circulating within urban environments.

Evidence of Urban Transmission Cycles

The repeated presence of ticks in multiple life stages at several sites suggests that transmission cycles may be established within urban green spaces.

A “hot spot” was identified at one location with high tick density and all developmental stages present. Other sites may have been influenced by nearby rural habitats.

The greatest number of ticks were found along woodland edges, areas commonly used for recreation.

Both birds and dogs may play a role in transporting ticks into urban habitats.

“Dogs appeared to be walked across multiple green space habitats on the same day,” notes Hansford. “They may act as transporters of ticks into and between urban environments.”

Urban Risk Beyond England

The expansion of ticks into urban settings has also been reported in the United States. In Chicago, investigators identified a high percentage of infected ticks, raising concerns about exposure in populated areas.

These findings suggest that tick exposure is not limited to rural or wooded regions.

Clinical Perspective

Ticks are expanding into environments where people live, walk, and recreate. Urban parks and green spaces may represent an underrecognized source of exposure.

Patients may benefit from awareness of tick bite prevention, review of Lyme disease symptoms, and consideration of coinfections following potential exposure.

References

1. Hansford KM et al. Ticks and Borrelia in urban and peri-urban habitats. Ticks Tick Borne Dis. 2016.
2. Jobe DA et al. Lyme disease in urban areas, Chicago. Emerg Infect Dis. 2007.

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