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New Study Highlights Ups and Downs in Tick Management

04/26/2019


 



blacklegged tick nymph - Ixodes scapularis

In its nymph stage, the blacklegged tick (Ixodes scapularis) seeks small-mammal hosts, commonly white-footed mice and chipmunks. Host-targeted tick-management methods such as bait boxes and “tick tubes” take advantage of rodent behavior to expose ticks to pesticides. A new study shows bait boxes hold a clear edge in effectiveness, but their current price point likely remains a barrier to their broad adoption. (Photo credit: Flickr/Andrew NussCC BY 2.0)



A new study of two tick-management methods that target ticks’ small mammal hosts shows one of them holds a clear edge in effectiveness—but it comes at a steeper price.


Bait boxes and “tick tubes” both take advantage of rodent behavior to expose ticks to pesticides. The former takes the common rodent bait box design and adds an extra element: a cloth wick soaked in tick-killing acaricide that the animal must contact on its way in and out of the box. Tick tubes, on the other hand, are filled with cotton—also infused with acaricide—for rodents to use for nesting material. In both cases, ticks that are attached to the rodent host, or attach soon after, die after exposure to the acaricide.


Robert Jordan, Ph.D., research scientist at the Monmouth County (New Jersey) Mosquito Control Division, and independent medical entomologist Terry Schulze, Ph.D., have previously studied these host-targeted methods and recently conducted a two-year study to compare their effect on levels of host-seeking ticks in suburban residential areas. Their results are presented in a new report published last week in the Journal of Medical Entomology.


Deploying the bait boxes and tick tubes—known as the Select Tick Control System and Damminix Tick Tubes, respectively—on separate properties in Monmouth County, New Jersey, over two years, Jordan and Schulze found that the bait boxes decreased the presence of host-seeking nymphs of the blacklegged tick (Ixodes scapularis) by 79 percent compared to the year prior to deployment, but the tick tubes led to just a 20 percent reduction.


Why the difference? Jordan says the preferences of the two primary rodent hosts, white-footed mice and chipmunks, are likely at play.


“We believe that the presence of chipmunks as a significant host for sub-adult ticks in our study area substantially affected our results,” he says. “The much greater effective control of host-seeking ticks appeared to be due to the higher acceptance of the Select TCS bait boxes by target small mammals—chipmunks apparently ignored the Damminix cotton balls as a nesting material—and the ability of bait boxes to treat both mice and chipmunks.”


The findings build on previous work showing the effectiveness of rodent bait boxes for tick control, but Jordan and Schulze acknowledge a significant hurdle to wider adoption of the bait box-method: They’re too expensive for most homeowners’ budgets. The boxes cost roughly $45 each, and a one-acre property would call for at least 20 boxes per year, installed by a licensed pest-management professional. (By comparison, Damminix tick tubes retail for about $75 for a box of 24 and can be sold directly to and administered by consumers). Past surveys have shown, though, that most homeowners are willing to spend about $100 a year on tick control.


“Because residential tick control is now, and likely to be for the foreseeable future, the responsibility of individual homeowners and their privately hired pest control contractors, any integrated approach to achieving tick control has to be designed to deliver predictable efficacy at a price point acceptable to the homeowner and marketable by pest control professionals,” Schulze says.


As in most pest-control contexts, tick management lacks any “silver bullet” solution, and so bait boxes and tick tubes should be viewed as two tactics to be used within a multifaceted approach, Jordan and Schulze say. “Host-targeted treatments like Select TCS may best be used in an integrated tick management approach in which habitat-targeted acaricide applications are made prior to deployment in order to provide rapid reduction of I. scapularis nymphs in high-risk areas in an effort to minimize tick exposure until the host-targeted products become effective,” Jordan says.


As ticks continue to loom as a public-health concern, researchers continue to better understand ticks and the disease-causing pathogens they carry as well as methods to manage human exposure to them. The findings in this new study “support the need for more research on the ecology of residential and suburban habitats that may affect the effectiveness of host-targeted tick control, including how small mammal host community composition and habitat-use differ in different human-modified environments,” Schulze says.



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