Human pathogens associated with the blacklegged tick Ixodes scapularis: a systematic review

Area of Science:

• Veterinary Entomology
• Medical Entomology
• Public Health Microbiology

Background:

• The blacklegged tick (Ixodes scapularis) is a vector for Borrelia burgdorferi (sensu stricto), the agent of Lyme disease.
• Blacklegged tick populations are expanding into southern Canada, increasing exposure to tick-borne pathogens.
• This systematic review evaluates public health risks associated with expanding blacklegged tick populations and their harbored pathogens.

Purpose of the Study:

• To systematically review and assess the public health risks posed by pathogens carried by the blacklegged tick (Ixodes scapularis).
• To document the full spectrum of human pathogens transmitted by blacklegged ticks in light of increasing Lyme disease awareness.

Main Methods:

• Systematic review conducted following PRISMA guidelines.
• Searched multiple databases (Ovid MEDLINE, Embase, BIOSIS, Scopus, Environment Complete) for studies from 2000-2015.
• Included studies with field-collected blacklegged ticks, excluding those solely focused on Borrelia burgdorferi; quality assessed.

Main Results:

• Seventy-eight studies were included; 16 of 91 distinct taxa harbored by blacklegged ticks are human pathogens.
• Pathogens include species of Anaplasma, Babesia, Bartonella, Borrelia, Ehrlichia, Rickettsia, Theileria, and Flavivirus.
• While Borrelia burgdorferi and Anaplasma phagocytophilum are current concerns in Ontario, other identified pathogens represent future threats.

Conclusions:

• This is the first systematic assessment of human pathogens associated with the blacklegged tick.
• The expanding range of blacklegged ticks necessitates awareness of the diverse range of potential tick-borne diseases.
• Monitoring and understanding these pathogens are crucial for future public health strategies.