The Effect of Immune System on Tick Attachment and Tick Attraction to Rodent Hosts

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The “80/20 rule” describes a phenomenon whereby 80% of the on-host parasites are found on 20% of the host population. This dichotomy in parasite numbers between parasite-carriers and non-carriers has been observed in Ixodes scapularis, an important disease vector in the United States. There is a gap in our understanding of the causality behind the 80/20 phenomenon, although it may be linked to immune status of the host. Currently, host-targeted tick control is limited to broad spectrum treatment of local hosts, without regard to tick host choice and subsequent tick-host burdens. This has led to stagnation in the development of novel tick control options because of the limited knowledge of tick host selection. Thus, it is imperative to understand the mechanisms behind tick host selection on this disproportionally small group of hosts to protect human health by advancing control of tick-borne disease transmission in the environment.  

The project purpose is to analyze how mouse odors related to immune system status influence tick host selection to interrupt the transmission and natural history of tick-borne disease vectors. Expansion of our current methods of tick control is necessary as Lyme disease and other tick-borne illness cases continue to increase. We anticipate determining that tick preference for mouse hosts is influenced by immune status, and identifying differences in volatile profiles. This project is in collaboration with the USDA, ARS.

Broad Objectives for field research: 

Objective 1. Identify if blacklegged tick presence on small mammal hosts follow the Pareto principle in central Pennsylvania in wooded and edge habitats.

Objective 2. Determine tick attraction to small mammal hosts with tick burdens vs. without ticks. 

Broad objectives for laboratory research: 

Objective 1. To determine attraction differences of I. scapularis between body odor of healthy mice, immune stimulated, and immune deficient mice.

Objective 2. To assess I. scapularis attraction to waste products (urine and feces) produced by healthy mice, immune stimulated, and immune deficient mice. 

Objective 3. To identify volatile compounds expressed by healthy mice, immune stimulated, and immune deficient mice, and assess their role in I. scapularis attraction.