[Technically Speaking] An ounce of prevention is worth a pound of cure—Part II

As discussed in last month’s column, in the continental United States, we have two major diseases, West Nile virus and Lyme disease, which are transmitted by arthropods, mosquitoes and ticks respectively. Each year, both of these diseases are potentially hazardous to the health of tens of thousands of Americans. The good news is that with appropriate measures the risk of exposure to these diseases can be minimized. This is where our industry can have a significant impact.

We bring two things to the table: the tools and materials to control the arthropods that transmit these diseases; and the knowledge to educate the public and media regarding measures individuals can take to protect themselves, their families and pets. As previously discussed in last month’s column, West Nile virus, a mosquito-transmitted disease, has captured the limelight recently by rapidly spreading across the U.S. in the past four years; however, the number of individuals affected by West Nile virus (~2,000 cases in 2003) pales in comparison to the number of Lyme disease cases that occur each year (more than 20,000).

While Lyme disease can be extremely debilitating, it does not typically cause direct mortality. However, there is a less frequently encountered tick-borne disease, Rocky Mountain spotted fever (~1,000 cases/year), which can cause death. There are also several encephalitic-like diseases that ticks transmit.

The tick life cycle is different from most pests we encounter — it consists of four life stages: egg, larva (six legs), nymph and adult, the latter two stages have eight legs. Depending on the species, we deal with ticks that feed on three different hosts (e.g., black-legged, lone star, Rocky Mountain wood and American dog ticks) or a single host (e.g., brown dog tick).

In the case of three-host ticks, each stage in the tick life cycle feeds on successively larger host animals. For instance, the black-legged tick larvae feed on small rodents, e.g., deer mice, the nymphs feed on larger animals e.g., raccoons, and the adults feed on even larger animals, e.g., deer. In Lyme disease transmission the infective stage is the nymph and it is this stage feeding on humans that can result in contracting the disease. The life cycle of three-host ticks requires several months to two years to complete. They lay several thousand eggs, can live unfed for a year and rarely survive for long periods indoors.

The one-host ticks live in close proximity to their host animals, such as a dog. They feed and drop off the host animal to molt and once they have molted crawl back onto the host animal for the next blood meal. All life stages can be found in close proximity to the host animals, e.g., kennel, bedding, etc. One-host ticks survive better in protected environments as opposed to living outdoors. In comparison to three host ticks, they can not survive as long without a blood meal and do not lay as many eggs.

Tick control involves a series of steps that are essential to a successful tick management program:

Inspection: Identify the type of tick that is causing the problem. Ticks can be collected from infested domestic animals, humans and occasionally indoors if they drop off the host animal. Outdoors, a white flannel cloth (24 by 36 inches) can be drug through suspected tick habitats and the ticks collected off the underside of the cloth.

Sanitation: This does not mean removing food sources. Sanitation is removing tick and small animal habitat and the resources they require for survival, e.g., mowing the lawn and fringe areas, removing ground clutter, minimizing ground covers, etc.

Personal Protection: This effort not only benefits your customers but protects your pest management technicians from contracting these diseases. Wear light colored clothing and pull your socks over the outside of your pant legs. Perform a tick check because tick removal within 24 hours of attachment usually prevents disease transmission. Treat your clothing with a repellent containing permethrin and your skin with a repellent containing DEET.

Animal Control: This involves two issues, controlling domestic animals and removing wildlife that serve as intermediate hosts for ticks. One of the best methods of preventing tick introduction is to control domestic animals, i.e., don’t allow cats and dogs to roam into tick-infested areas. Remove small rodents and other wildlife from around structures.

Animal Treatment: Homeowners should be directed to a veterinarian to obtain on-animal treatments for pets, e.g., ingestible and spot-on liquid treatments for tick and flea control. Dipping pets before they return from a kennel should be considered.

Perimeter Treatment: This will probably provide the best long-term control in the immediate vicinity around structures and if applied in the right area will reduce the tick population immediately. The questing habit of ticks necessitates that they crawl up onto higher vegetation so that they can crawl onto a prospective host as it passes by.

Thus, pesticide applications should be concentrated where the vegetation is higher, particularly in woods-turf interfaces and anyplace where vegetation is overgrown. The most effective formulations are liquid applications of microencapsulates, emulsifiable concentrates and wettable powders, in decreasing order of preference (based on longevity of the products). Applications of granules and other materials to the soil line are much less effective because ticks spend little time at ground level, however, this type of application may be useful where outdoor-housed pets spend most of their time.

A recently introduced approach to perimeter treatments is the Maxforce Tick Management System. This has proven especially effective in reducing black-legged ticks associated with the transmission of Lyme disease. The system involves placing around the property perimeter baited (non-toxic) boxes containing a wick impregnated with fipronil. When the mice enter the box to feed on the bait they contact the wick and receive a little dose of fipronil sufficient to kill ticks that parasitize the mice. The system is environmentally responsible, i.e., significantly reducing the amount of chemical needed to control ticks using traditional sprays; it does not kill the mice; and within two years can virtually eliminate ticks in the immediate area.

Unfortunately, the most significant drawbacks to TMS are the heavy-duty plastic bait box that cannot be serviced and the label requirement to replace the boxes every 60 days. This makes the system very costly to maintain. Hopefully, the U.S. Environmental Protection Agency may see the error of their ways in creating an unnecessary amount of plastic waste and allow the manufacturer to develop a tamper-resistant, yet serviceable bait station.

Vector control is a no-lose proposition: it is a service many customers are seeking and it is a service our industry is easily capable of providing. It is foolhardy to let this opportunity pass your company by.

The author is technical director of American Pest Management, Takoma Park, Md. He can be reached at 301/891-2600 or rkramer@giemedia.com.