The list of illnesses carried by summer's insect pests is daunting: encephalitis, West Nile virus, Rocky Mountain spotted fever, malaria, dengue fever, Lyme disease, and even plague! According to the Centers for Disease Control (CDC) Web site, "human plague in the United States has occurred as mostly scattered cases in rural areas (an average of 10 to 15 persons each year)." Plague is an infectious bacterial disease usually transmitted by a flea. Yes, this is the same disease that killed millions of people in the Middle Ages. Who knew it was still a threat?
Scientists have even coined the taxonomically meaningless but handy term "arbovirus" to describe viruses transmitted to vertebrates (like us) via blood-feeding arthropods, such as mosquitoes, ticks, and fleas (ARthropod-BOrne VIRUS). Visiting the CDC Web site is enough to make a person shun the outdoors and slather oneself with DEET before venturing to carry out the trash.
So what's a gardener to do?
The first thing to do is look at the statistics. Take West Nile virus, currently in the news as the latest insect-borne scourge. As of mid July 2005, 61 cases of West Nile virus have been reported in the United States so far this year. In 2004 there were a total of 2539 cases reported nationwide, and 100 deaths were attributed to the virus. (It appears that many cases are reported long after the fact, so the 61 so far this year may or may not turn out to be a downturn in the incidence of the disease.) In comparison, according to the CDC almost 700,000 annual deaths can be attributed to heart disease, 40,000 to car accidents, and 20,000 to the flu. So although it makes sense to be aware of the dangers posed by West Nile virus, it's important to put it in perspective. Eat right, exercise, don't smoke, and wear your seat belt -- these are all far more important than worrying about getting bitten by a mosquito. Or, to put it another way, the chances of dying from West Nile appear to be about the same as dying by lightning strike.
That said, it still makes sense to be aware of the dangers. And, frankly, the nuisance factor of ticks, mosquitoes, and fleas warrants finding ways to repel them, even if their potential as disease carriers is relatively remote.
When possible, wear long-sleeved shirts, long pants, and socks outdoors. Use a repellent on exposed skin and on thin clothing, since mosquitoes can bite through it. Follow the insect repellent's label instructions carefully. For example, do not spray repellent containing DEET on the skin under your clothing; rather, spray it onto your clothing.
Exclude mosquitoes from your home by installing tight-fitting screens on windows and doors. Minimize mosquito-breeding areas by removing all sources of standing water, including small ones, such as plant saucers, and old tires. Dump birdbaths and pet water dishes and replace with fresh water at least twice weekly.There are several commercial products available to kill mosquito larvae in ponds; follow the label directions carefully to maximize their effectiveness.
Report sightings of dead birds to local authorities; don't handle them. Dead birds can indicate the presence of West Nile virus in a region. Remember, however, that birds die from many other causes besides the virus, so there's no need to panic.
Taking these precautions will go a long way toward preventing your exposure to mosquito-borne diseases, such as West Nile virus and La Crosse encephalitis, and, perhaps more importantly, will minimize the aggravation mosquitoes can cause.
In addition to the disease-carrying capacity of ticks, these bloodsuckers have the revolting trait of attaching themselves leechlike to your skin while they gorge on your blood. Unfortunately, ticks are also very common, as any dog owner will tell you. Ticks are not insects but rather arachnids, more akin to spiders than mosquitoes. The most common type of tick, the dog tick, doesn't transmit the infamous Lyme disease, though it can be a vector for the bacteria causing the much less common Rocky Mountain Spotted fever. Only about 500 to 800 cases of Rocky Mountain spotted fever are reported each year.
In contrast, 23,763 cases of Lyme Disease were reported in 2002. Lyme disease is caused by a bacterium and is transmitted to humans by the bite of infected blacklegged ticks, sometimes called deer ticks. These ticks are tiny, about the size of a sesame seed, much smaller than the more common dog tick. Lyme disease can cause a variety of symptoms, including rash, fatigue, chills, fever, headache, and muscle and joint aches. It can usually be treated with antibiotics if caught soon enough.
How can you protect yourself against ticks? Avoid known tick-infested areas. Understand their habits: Ticks make their way onto the edges of leaves and branches, then wait to hitch a ride on a passing host, so avoid brushing against vegetation. Some ticks, such as deer ticks, need moist environments to survive, so you're less likely to encounter them in dry, sunny areas. When hiking, stay to the middle of the path. Tuck your pant legs into your socks so that ticks cannot reach your skin. Keep lawns mowed, and remove debris and brush piles.
Perform daily tick checks, examining your and your children's bodies after spending time outdoors. If you find an attached tick, remove it promptly. Grasp the tick's mouthparts from the side with a fine tweezers and pull gently but steadily upward. Avoid crushing the tick. After removing the tick, disinfect the bite with rubbing alcohol. Inspect dogs and cats daily, too. Oral tick medications and tick collars can be helpful in managing ticks on pets.
More nuisance than health threat, fleas can nonetheless transmit typhus, cat scratch fever, and the above-mentioned plague, but the risk is negligible. However, the itching induced by flea bites can be maddening, and vigorous scratching can result in infection and scarring. Your best weapon in the battle against flea infestation is your trusty vacuum cleaner. Frequent vacuuming can dramatically reduce pest populations. Focus your attention on crevices and corners where fleas like to hide, and dispose of the bag outside immediately. Wash pet bedding in hot water at least weekly.
In the battle against pest insects, skip the bug zappers. Though the electrical zaps may sound productive, the devices actually kill far more beneficial insects than pests. Avoid homemade pest repellents that contain concentrated essential oils, especially pennyroyal, as these can cause serious side effects. An herbal infusion may be safe, but it's best to check with an experienced herbalist.
Many people want to avoid using repellents containing DEET. This is a matter of personal choice: The chemical is an effective repellent, but long-term use may pose risks. Always follow label directions carefully, especially when using the repellent on children.
Although a visit to the CDC Web site is enough to make even the sanest person afraid to leave the house, the reality is that the likelihood of contracting a life-threatening, insect- or tick-borne disease is very small. Take reasonable precautions, pay attention to your health and note any aberrations, and contact your physician if you have any concerns.
Article published on June 23, 2008.