Statewide Passive Surveillance of Ixodes scapularis and Associated Pathogens in Maine
The blacklegged tick, Ixodes scapularis, is the primary vector of multiple human pathogens, including the causative agents of Lyme disease, anaplasmosis, and babesiosis. Both I. scapularis and its associated pathogens have expanded their geographic range throughout the northeastern Unites States and into northern New England. Through this study, we present an updated distribution of I. scapularis in Maine and report the first statewide passive surveillance infection and coinfection prevalence of Borrelia burgdorferi, Anaplasma phagocytophilum, and Babesia microti within the state’s I. scapularis population. In 2019, we collected 2016 ticks through a passive surveillance program, in which Maine residents submitted tick samples for identification and/or pathogen testing. We used a single multiplex quantitative PCR assay to detect tickborne pathogens in 1901 tick samples. At the state level, we found:
- Bo. burgdorferi and A. phagocytophilum infection rates of adults (42.4%, 11.1%) were nearly double that of nymphs (26.9%, 6.7%)
- B. microti prevalence was similar for both adults (6.5%) and nymphs (5.2%).
- Spatially, we found an uneven distribution of both tick activity and pathogen prevalence, with both increasing on a north to south gradient.
- We also noted a potential association between the ratio of adult to nymphal ticks and the incidence of tickborne disease in human populations, with counties that exhibit high rates of human disease also maintaining low adult to nymph ratios.
- We detected Bo. burgdorferi in ticks from all counties, except Aroostook, although we only tested five samples from this county.
- Excluding Aroostook, the county-level Bo. burgdorferi prevalence ranged from 30.0% (Piscataquis) to 50.0% (Franklin and Waldo) in adults and 0% (Piscataquis and Somerset) to 43.8% (Knox) in nymphs.
- High disease incidence counties did not necessarily have higher prevalence rates within submitted ticks.
- Knowledge of anaplasmosis is not as widespread as Lyme disease, which may lead to the underdiagnosis of this disease.
- The sporadic distribution of B. microti is consistent with a pathogen that is colonizing a new location and has not yet reached an even spatial distribution (Diuk-Wasser et al. 2016).
- B. microti is also thought to spread more quickly in areas where Bo. burgdorferi is prevalent due to an immune interaction in reservoir hosts such as white-footed mice (Peromyscus leucopus) or deer mice (P. maniculatus) (Dunn et al. 2014).
- B. microti is likely to continue spreading throughout Maine.
It is interesting that researchers acknowledge that multiple infections occur due to an immune interaction yet severely ill patients are still viewed myopically to only have Lyme disease. Our conflict-riddled public health ‘authorities’ continue to promote ancient mythology, deny persistent infection, and treat patients with a mono-therapy that has never been adequate. Treating co-infections isn’t even on their radar.