Blacklegged ticks (Ixodes scapularis Say) are the vector for pathogens that cause more cases of human disease than any other arthropod. Lyme disease is the most common, caused by the bacterial spirochete Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt, and Brenner) in the northeastern United States. Further knowledge of seasonal effects on survival is important for management and modeling of both blacklegged ticks and tick-borne diseases. The focus of our study was on the impact of environmental factors on overwintering success of nymphal blacklegged ticks. In a three-year field study conducted in Connecticut and Maine, we determined that ground-level conditions play an important role in unfed nymphal overwintering survival. Ticks in plots where leaf litter and snow accumulation were unmanipulated had significantly greater survival compared to those where leaf litter was removed (p = 0.045) and where both leaf litter and snow were removed (p = 0.008). Additionally, we determined that the key overwintering predictors for nymphal blacklegged tick survival were the mean and mean minimum temperatures within a year. The findings of this research can be utilized in both small- and large-scale management of blacklegged ticks to potentially reduce the risk and occurrence of tick-borne diseases.

The dilution effect in the zoonotic disease transmission cycle theorizes that an increased diversity of host species will alter transmission dynamics, result in a decrease in pathogen prevalence, and potentially lower human disease incidence. The interrelationship of Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt, and Brenner) (Spirochaetales: Spirochaetaceae), the etiological agent of Lyme disease (LD), and its primary vector, blacklegged ticks (Ixodes scapularis Say) (Acari: Ixodidae), is a commonly used example of the dilution effect, suggesting that an increased diversity of host species will be found in large, undisturbed forested tracts and lower diversity in fragmented forests. Given that Connecticut woodlands are mature with heavy upper canopies and generally poor habitat quality, we hypothesized there would be higher diversity of host species resulting in lower prevalence of B. burgdorferi in white-footed mice (Peromyscus leucopus Rafinesque) (Rodentia: Cricetidae) in forested residential areas. Using camera and live small mammal trapping techniques, we determined there was a greater richness of reservoir host species, significantly higher encounters with hosts, and significantly lower B. burgdorferi host-infection in residential areas as compared to large, intact forested stands. Furthermore, we determined that the driving factor of pathogen dilution was not host species diversity, but rather overall encounter abundance with alternative hosts, regardless of habitat type. Our study challenges major concepts of the dilution effect within the Connecticut landscape and calls for new managerial actions to address the current state of our woodlands and abundance of host species in the interest of both forest and public health.

Pathogens transmitted by ticks are the leading cause of arthropod-associated human diseases in the United States and managing the risk of exposure to potentially infected ticks is of vital public health importance. A 3-year integrated tick management program to control blacklegged ticks, Ixodes scapularis, the primary vector for the pathogenic agents of Lyme disease, human anaplasmosis, and babesiosis, was implemented in the town of Redding in southwestern Connecticut beginning in 2013. Combinations of white-tailed deer, Odocoileus virginianus, reduction, area application of the entomopathogenic fungus Metarhizium anisopliae, and fipronil-based rodent bait boxes were evaluated for their ability to reduce nymphal I. scapularis over 3 years. Interference from local hunters prevented sufficient, sustained deer removal previously reported to negatively impact I. scapularis abundances (i.e., <5 deer/km). The combination of fipronil-based bait boxes and broadcast application of M. anisopliae had the most impact of any treatment combination; questing nymphs were reduced 78-95% within each year and Borrelia burgdorferi-infected questing nymphal I. scapularis encounter potential was reduced by 66% as compared with no treatment in the third year of the study. A combination of the broadcast application of M. anisopliae and small rodent-targeted fipronil-based bait boxes is an effective low-toxicity integrated approach that significantly reduced encounters with B. burgdorferi-infected questing nymphal I. scapularis on individual properties.

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