PUBLIC HEALTH SUPPLEMENT: Tick-Borne Diseases

Several diseases, including Lyme disease, Rocky Mountain spotted fever and human ehrlichiosis, are transmitted by ticks. Find out what you can do to protect your staff and your customers.

The average person probably doesn’t think much about ticks. Maybe he or she pays these pests an occasional second thought while taking the dog for a hike in the woods, but that’s most likely where it ends. As a PCO, however, you owe ticks a great deal more consideration..

Worldwide, the mosquito is the No. 1 arthropod vector of human disease — as many as 500 million people contract or die of malaria alone throughout the world every year, said Sandra R. Evans, U.S. Army Center for Health Promotion and Prevention, Aberdeen Proving Ground, Aberdeen, Md. But it is a different story in the United States.

"Narrowing the geographic focus to North America, or the United States, ticks are the major vector for arthropod-borne diseases of humans, and Lyme disease is not the only illness they transmit," she said. "There are approximately 10 tick-borne diseases of concern in the United States." (See related story on page 5.)

LYME DISEASE. Ticks are most widely known for transmitting Lyme disease. In 1998, the Centers for Disease Control and Prevention (CDC) reported 16,801 cases of the disease.

Lyme disease was first recognized in 1975 following an outbreak of cases in Lyme, Conn. It is caused by a spiral-shaped bacterium, or spirochete, known as Borrelia burgdorferi. "The pathogen can cause a wide range of symptoms, which can sometimes become debilitating, but are usually not fatal," Evans said. "The spirochetes are found in the mid-gut of the tick, and once the tick begins to feed on a host the spirochetes begin to multiply, travel to the salivary glands, and flow with the tick’s saliva into the bite site. It usually takes at least 24 hours, or longer, for an infected tick to transmit infection to the host. Tick densities, as well as infection rates in tick populations, are very localized, and can vary greatly from county to county and even within individual counties."

One of the most common, early symptoms of Lyme disease is a red, ring-like rash called erythema migrans (EM), which occurs at the site of the tick bite, and expands frequently to at least several inches in diameter. It is oftentimes clear in the center and has a reddened border. Other common early symptoms are flu-like in nature: fever, headache, muscular and joint aches and pains, and extreme fatigue. The rash and/or other early symptoms appear within three days to one month following a tick bite. But as many as 40 percent of patients do not exhibit the rash at all, she said.

As the disease progresses, multiple secondary EM lesions can appear on other parts of the body. Episodes of joint pain increase in frequency and duration. The nervous and cardiac systems become affected. A common early neurological symptom is Bell’s palsy (a paralysis of one side of the face). Difficulties with memory, concentration, and equilibrium may be experienced. Heart symptoms include dizziness, weakness and an irregular heartbeat.

Long-term effects and permanent damage can include debilitating arthritis and severe neurological deficits.

The disease can be treated with oral antibiotics (doxycycline or amoxicillin), but it is more easily cleared up the sooner it is treated. "Not all ticks are infected," Evans said, "so in most cases it is not a good idea to get antibiotics solely for a tick bite with no symptoms."

www.cdc.gov

Centers for Disease Control and Prevention

www.lymediseaseinformation.com

Phizer Lyme Disease and Related Disorders Pamphlet

www.riaes.org

Rhode Island Agricultural Experiment Station

www.state.ct.us/caes/FactSheetFiles/IndexHeadingFiles/Fstick.htm

Connecicut Agricultural Experiment Station Fact Sheets

www.imugen.com

Imugen Inc.

www.lyme.org

Lyme Disease Foundation Inc.

www.aldf.com

American Lyme Disease Foundation Inc.

www.lymenet.org

Lyme Disease Network of New Jersey

www.afpmb.org

Armed Forces Pest Management Board

ROCKY MOUNTAIN SPOTTED FEVER. Despite its name, Rocky Mountain spotted fever (RMSF) is most prevalent in the eastern part of the United States, not the Rocky Mountains. It was first discovered and studied in a Rocky Mountain state (Montana), and it is from that area that its name is derived. Routinely, the highest numbers of cases are reported from North Carolina. In 1998, there were 365 cases of RMSF reported for the United States.

Like Lyme disease, RMSF has a hallmark rash associated with it (but those are the only two tick-borne diseases that do). RMSF exhibits a red spotted rash that starts on the extremities and quickly spreads to cover most of the body. Other symptoms of RMSF are flu-like, including high fever, severe headache and nausea/vomiting. "It is a disease that progresses quickly," Evans said, "you get very sick fast." While Lyme disease is not considered a fatal disease (although it can be extremely debilitating), RMSF, as well as most of the other tick-borne diseases, can be fatal, she reported.

OTHER DISEASES. More recently recognized tick-borne diseases include two types of human ehrlichiosis: human monocytic ehrlichiosis (HME) and human granulocytic ehrlichiosis (HGE). "The main differences between the two are that 1) different types of white blood cells are infected (granulocytes in the case of HGE, and monocytes in the case of HME); 2) they are caused by two different, although closely-related, organisms; and 3) they are transmitted by two different species of ticks," Evans said.

Other tick-borne diseases include: Babesiosis, relapsing fever, Colorado tick fever, tularemia, Powassan encephalitis and tick paralysis.

"All of the these tick-borne diseases are caused by microorganisms with the exception of tick paralysis, which is caused by a neurotoxic chemical that is secreted by the tick in its saliva as it feeds, causing an ascending paralysis that can eventually lead to death," Evans said. "Fortunately, if the tick is discovered and removed, symptoms usually resolve quickly and completely."

Only four of these tick-borne diseases are nationally reportable in the United States: Lyme disease, RMSF, HME, and HGE. RMSF has been reported for many decades; Lyme disease since 1991; and most recently, HME and HGE since 1999. "Therefore, our knowledge of the incidence of the others is more anecdotal," Evans said.

THE TICKS. Different species of ticks transmit different diseases (or groups of diseases). "There are three tick species that you are most likely to find associated with human tick bites and disease: the black-legged tick (more commonly known as the deer tick), the lone star tick and the American dog tick," Evans said.

The black-legged tick (Ixodes scapularis) is the major vector for Lyme disease, HGE and babesiosis. The highest concentrations of these diseases are in the northeastern and mid-Atlantic seaboard states, and in the upper Midwest (Wisconsin and Michigan), not surprisingly, in areas where the black-legged tick is the most prevalent. The vector for these diseases along the Pacific coast is a closely related tick known as the western black-legged tick (I. pacificus), but it looks the same. A single black-legged tick can be co-infected with two or even all three of these disease organisms, and therefore has the potential to transmit more than one infection simultaneously.

The lone star tick (Amblyomma ameri-canum) is the vector for the monocytic form of human ehrlichiosis (HME), which is most prevalent in the southeastern and south central states. It may also be responsible for transmitting a disease similar to Lyme disease ("Lyme-like illness"), which is currently the subject of much medical and entomological controversy and investigation.

The American dog tick (Dermacentor variabilis) is the major vector for RMSF and is most prevalent in the southeastern quadrant of the United States.

Habitat. Ticks survive best in moist areas that are protected from intense sunlight so that they don’t desiccate. This includes woods and woodland edges, leaf litter, high grass, weeds and shrubby undergrowth. These are the same areas that are preferred by mice and other rodents (which act as hosts for juvenile ticks/larvae and nymphs), because they can easily hide, nest, and forage for food. The hosts for ticks, primarily deer, also inhabit woods, woodland edges, and shrubby areas because of the protective cover, leaves, twigs, etc. Ticks are less likely to be found in well-mowed and manicured expanses of lawn.

How to Prevent Disease. There are many ways to help you (and your customers) prevent tick-borne diseases. Evans said the most important is good customer relations. "An enthusiastic personality, good communication skills, and professional manner are important; otherwise, regardless of how well you know the subject, you may not give that impression," she said. "Unfortunately, completely ridding a property of ticks, especially for the long term, is not feasible. Many factors are at play, and an integrated control approach will be necessary, not the least of which will be for the homeowner to buy into the inevitability and importance of employing personal protective techniques. You will need to educate and convince the homeowner of this integrated approach."

In addition, PCOs and homeowners can use several personal protective techniques (see related story on page 4).

A canine Lyme disease vaccine has been in use for about a decade and in December 1998, the first human Lyme disease vaccine (LYMErix®) was licensed by the Food and Drug Administration. It currently remains the only human Lyme disease vaccine available. That vaccine, developed by SmithKline Beecham, involves a series of inoculations but will not protect against any other tick-borne illness, nor is it effective against strains of the Lyme disease pathogen found outside North America, Evans said.

Pesticide application. In addition to strategies aimed at preventing tick-borne disease, there are two basic methods to control ticks with pesticides: by targeting the host or by targeting the habitat. In a host-targeted program, one technique consists of disseminating cardboard tubes containing permethrin-treated cotton. Mice gather the cotton to use as nesting material. Permethrin then kills immature ticks on the mice as they use their nests. Studies have shown that while the method is scientifically and environmentally sound, the results in actually controlling questing ticks is unpredictable, and may have only limited utility as part of an integrated program.

The second way is more conventional, by using a habitat-target program. In this method, liquid formulations are aimed at questing ticks (i.e., nymphs in the spring; larvae in the summer; adults in the fall.) Granular formulations will penetrate leaf litter better to reach nymphs overwintering in the fall; or larvae as they hatch from eggs in the early summer. High-pressure sprayers may disturb the leaf litter enough to reach larvae and nymphs in the leaf litter. Pesticides are generally effective in controlling the stage of tick at which they are aimed; however, reducing the number of one stage by controlling the previous one will be limited in a small area (most residential sites) because of constant reintroduction of ticks via mammal hosts.

CONCLUSION. Ultimately, tick control takes a comprehensive approach. "There are three factors that influence getting the tick control/Lyme disease prevention job done right," Evans said. "The first is knowledge. You must know the tick and its ecology in your area. This comes from such sources as experience, colleagues, extension agents, scientific literature, local universities, etc.

"The second is interpersonal communication skills and integrity. This allows you to develop rapport with your customer and gives you the ability to effectively transfer your knowledge. This, in turn, builds understanding, trust, and success because the homeowner participates in maintaining optimum tick control and protecting him or herself.

"The third factor is technical skill: Good surveillance techniques are important to accurately delineate the situation so that you can choose the best integrated control techniques, including appropriate acaricide applications," Evans said.

Share these tips with your customers to help them prevent tick bites. Many of these guidelines can also be used by PCOs who are working in tick-infested areas.

• Long pants tucked into boots or socks.

• Wear a long-sleeved shirt and make sure it is tucked into pants.

• Light-colored clothing makes it easier to spot ticks.

• Treat clothing with permethrin repellent.

• Apply DEET repellent to skin that is not covered by clothing.

• Use the buddy system; another person has a better view of your back, neck, etc.

• Once indoors, remove your clothes and shower, checking your skin carefully.

• Place clothes in a hot dryer for 20 to 30 minutes to kill any undetected ticks.

• Check children and pets carefully.

• Grasp the tick’s mouthparts as close to the skin as possible with fine-tipped tweezers. Gently and steadily pull straight back until the barbed mouthparts can be eased out of the skin. Be patient.

• Do not squeeze the body of the tick as this may force infective fluid into you.

• Do not apply any substance, including petroleum jelly, fingernail polish (or remover), repellents, pesticides or a lighted match to the tick while it is attached. These materials are ineffective, or worse, might agitate the tick, causing it to regurgitate infective fluid into the bite site.

• Wash the bite site with soap and water and apply an antiseptic.

• Save the tick for future identification should the victim develop disease symptoms. Preserve the tick by placing it in some alcohol or by keeping it in the freezer. Discard the tick after one month as all known tick-borne diseases will generally display symptoms within this time period.
• If you or your customer develops flu-like symptoms or otherwise feels sick following a tick bite, seek medical attention immediately.

Tick-borne diseases of humans in North America

Lyme disease Bacteria

Rocky Mountain spotted fever Rickettsia

Human monocytic ehrlichiosis Ehrlichia

Human granulocytic ehrlichiosis Ehrlichia

Relapsing fever Bacteria

Babesiosis Protozoa

Tularemia Bacteria

Colorado tick fever Virus

Powassan encephalitis Virus

Tick paralysis Neurotoxin

Pfizer Central Research has produced a pamphlet called "Lyme Disease." It discusses ticks, tick bites, tick removal, symptoms, treatment and ways to prevent Lyme disease. To order copies of the pamphlet, contact Pfizer at 860/441-5544 or on the Internet at www.lymediseaseinformation.com. Pfizer distributes up to 50 pamphlets for free. Orders greater than 50 will be billed at 4 cents per copy.

Malaria

Dengue fever

Lyme disease

Rocky Mountain Spotted Fever (and related diseases)

Ehrlichiosis

Plague

Endemic Typhus

Chagas’ diseas

Tick-borne encephalitis

Mosquito-borne encephalitis

Eastern Equine Encephalitis

St. Louis Encephalitis

West Nile Virus

LaCrosse encephalitis

Cockroach allergens

Dust mites

Spider bites

Fire ant stings