A troublesome trio, clockwise from top: blacklegged tick, lone star tick, and American dog tick.
The Washington-metropolitan region continues its woes with ticks and the illnesses that may result from the disease organisms they carry. Maryland and Virginia make the CDC’s list of the top 13 states reporting Lyme disease cases. This fact hits close to home as the Bug Guy and several people in my immediate circle of family and friends have contracted Lyme disease during the last decade. Just this week following a tease of warm weather, two friends removed ticks from their bodies. One unwanted blood sucker was the dastardly blacklegged tick, vector of Lyme disease.
Although they are very small, blacklegged tick nymphs can transmit Lyme disease.
The blacklegged tick, Ixodes scapularis, is the carrier of Lyme disease in our area while on the west coast the western blacklegged tick, Ixodes pacificus, is the culprit. Lyme disease can be a serious debilitating disease. In the short-term, flu-like symptoms including headache, fever and fatigue, are sometimes accompanied by an unmistakable bulls-eye rash called erythema migrans. An untreated infection becomes more serious when the bacterium moves to joints, the heart, and the nervous system. The microbe behind Lyme disease is a bacterium called Borrelia burgdorferi. Borrelia is transmitted by ticks from mammals and birds to humans. The northeastern region of our country is a hotbed for blacklegged ticks and often leads the nation in the annual number of cases of Lyme disease. The number of Lyme disease cases rises dramatically in May and June, peaks in July and August, and declines in autumn. However, in many parts of the country, ticks are active even on warm days in winter and Lyme disease is a year-round threat.
A question on people’s minds this year is the effect of the Polar Vortex and the prolonged winter on tick populations. Ticks have withstood the test of time and have seen mild and frigid winters come and go for millions of years. It is unlikely that the Polar Vortex put much of a dent in tick populations in Maryland this winter. Ticks are prone to drying out and unusually dry winters might put a dent in their populations. However, with above average snowfall and ample rainfall in the mid-Atlantic region, this winter was anything but dry. No help from Mother Nature there. What then drives boom and bust cycles in populations of blacklegged ticks?
A bull’s eye rash is one of the characteristic symptoms of Lyme disease.
One fascinating study found that as populations of small mammals like white-footed mice and chipmunks increased, tick populations also increased. These small forest dwelling mammals are favored hosts for newly hatched larval ticks but more importantly they are rife with Borrelia and serve as an excellent host for the ticks to acquire this infectious bacterium. Greater abundance of small mammals like mice and chipmunks follow years in which oak trees produce bumper crops of acorns in a phenomenon called masting. However, years of acorn bounty are followed by years of acorn scarcity, leaving behind hordes of hungry Lyme infested ticks to seek blood meals from humans and their pets. Yikes!
White-tailed deer are frequently implicated with ticks and Lyme disease; however, researchers found deer to be less important contributors to the risk of Lyme disease than populations of small mammals. When it comes to Lyme disease, blame the mighty mouse and the mighty oak more than Bambi. While the Polar Vortex may not have done in blacklegged ticks, small rodents like white-footed mice are susceptible to severe winter cold. A set-back in small mammal populations this year could translate into fewer ticks and fewer cases of tick borne diseases down the road.
Wow, fully engorged ticks get really big!
The second tick in my trio of trouble is the American dog tick. American dog tick and its cousin, Rocky Mountain wood tick, are the vectors of another serious disease called Rocky Mountain spotted fever. Although it is less common than Lyme disease, it is potentially life threatening. Contrary to the implication of its name, Rocky Mountain spotted fever is common east of the Rockies in states lining the Mississippi and in the Carolinas. Cases of Rocky Mountain spotted fever are relatively rare compared to those of Lyme disease. Cases of Lyme disease averaged more than 20,000 for the last several years while usually fewer than 1,000 cases of Rocky Mountain spotted fever occur annually in the US.
Fleshy pads called pulvilli at the ends of the legs help this American dog tick hold onto surfaces.
The third and most common tick I bumped into during the last several years is the lone star tick. Lone star ticks transmit several illnesses, including one known as Southern Tick Associated Rash Illness (STARI). Symptoms of STARI include a rash, fever, fatigue, and pain in muscles and joints. A second disease spread by the lone star tick is ehrlichiosis. This bacterium produces nasty flu-like symptoms including headache, joint ache, fever, fatigue, muscle ache, confusion, and several other disheartening symptoms. Recently, a friend living near Charlottesville, VA contracted ehrlichiosis and shared that it was the most unpleasant illness she ever experienced. Chronic arthritis and neurological problems have not been linked to this disease as they have to Lyme disease.
To reduce the risks of becoming a meal for a tick and the unfortunate recipient of Lyme disease, Rocky Mountain spotted fever, STARI, or ehrlichiosis, remember the word “AIR”. This stands for avoid, inspect, and remove.
“A” - Avoid ticks and their bites in the following ways:
- When taking Fido for a walk, stick to the path, trail, or pavement. You are unlikely to encounter ticks on non-grassy surfaces.
- If you enter habitats where wildlife and ticks are suspected such as grassy meadows, boarders of fields and woodlands, and vegetation along the banks of streams, wear long pants and light colored clothing. This will help you spot ticks on your clothes as they move up your body.
- Be a geek. Tuck your pant legs into your socks. This forces ticks to move up and over your cloths rather than under them where tasty skin awaits.
- Apply repellents labeled for use in repelling ticks. Some are applied directly to skin, but others can only be applied to clothing. Don’t forget to treat your footwear, socks, and pant legs; nymphal ticks that are a key vector of Lyme disease are often close to the ground. If repellents are used, be sure to read the label, follow directions carefully, and heed precautions particularly those related to children.
“I” - Inspect yourself, your family, and your pets thoroughly if you have been in tick habitats. Remember to do this when you return from the outdoors and when taking a shower. A thorough inspection may involve enlisting a helper to view those "hard to see" areas around back.
“R” - Remove ticks promptly if you find them. Removal within the first 24 hours can greatly decrease your risk of contracting a disease. If you find a tick attached, firmly grasp the tick as close to your skin as possible using a pair of fine forceps and slowly, steadily pull the tick out. Cleanse the area with antiseptic. The CDC and the Bug-Guy do not recommend methods of tick removal such as smearing the tick with petroleum jelly or scorching its rear end with a match. Cases of Lyme disease are the most common in children and seniors so take special care to keep kids of all ages safe when they play outdoors.
Ticks quest by waiting on blades of grass with legs extended ready to latch onto a passing animal.
Around the home, reduce habitat for small mammals that serve as the blood meal for ticks and the source of disease causing bacteria. Remove piles of brush, unstacked wood, and rubbish that serve as a refuge for rodents and other small mammals. Mow and remove unkempt grasses, weeds, and other vegetation at the edge of the lawn. Mulch beds that border the transition zone between lawn and forest edge. By opening up these areas, raptors and other predators may more easily spot and remove small mammals. Design patios and play areas for children away from forest edges where ticks are more likely to be found. If you follow these precautions, you can greatly reduce the risk of encountering ticks and associated illnesses, while still enjoying the great outdoors.
Is this lone star tick sprinting to find a meal or to avoid the camera?
References
Special thanks to tick wranglers Chris, Joe, Ryan, Al, Eric, and Christina and to Kim and Sheri who shared their tales and images of Lyme disease and were the inspiration for this episode. The great article “Climate, Deer, Rodents, and Acorns as Determinants of Variation in Lyme-Disease Risk” by Richard S Ostfeld, Charles D Canham, Kelly Oggenfuss, Raymond J Winchcombe, and Felicia Keesing, and the following websites were used as sources for this episode.
To learn more about ticks and the diseases they carry, please visit the following websites:
http://www.cdc.gov/ncidod/dvbid/lyme/index.htm
http://www.cdc.gov/ticks/diseases/rocky_mountain_spotted_fever/