This week's bug of the week is not a bug at all. Rather, it is another arthropod known as a tick. For the past several weeks I have been wandering the ecotone between forest and meadow collecting ticks. Until recently my success has been limited, but with the return of warm, humid weather ticks are showing up in droves.

Ticks are obligate parasites and must feed on the blood of animals to complete their development. Proteins and other nutrients found in blood are used for growth, development, and the production of eggs. Like all arthropods, ticks must shed their exoskeletons, or molt, to grow and these bouts of molting are punctuated by periods of attachment to animals to feed on blood. Contrary to popular belief, ticks do not always have eight legs. After hatching from the egg, tick larvae have only six legs. After a bout of host feeding the larva molts into an eight-legged nymph. Nymphs feed again and molt to eight–legged adults. Adults then feed on animals again before dropping to the ground to lay eggs that often number in the thousands. Some ticks will obtain all of their blood meals from a single host but others like the American dog tick and black-legged tick will move on and off hosts between bouts of feeding. In cooler climates it may take 2 - 3 years for ticks to complete their life cycle from egg to larva to nymph to adult to egg.

Microbial agents of disease such as the bacteria that cause Rocky Mountain spotted fever, Rickettsia rickettsia, or Lyme disease, Borrelia burgdorferi, are picked up from wild animals outdoors such as mice or chipmunks. After engorging on the infected wild host, the tick will drop to the ground to molt. The infected tick will then find a new host such as you or me and the microbe can be passed to us as the tick feeds. The microbe will then infect the cells within our body and multiply and produce the characteristic symptoms and illnesses associated with Rocky Mountain spotted fever or Lyme disease.

Most of my encounters of the tick kind to date have been adult American dog ticks, Dermacentor variabilis, the primary eastern vector of Rocky Mounted spotted fever. This is the larger of the two ticks in the photograph. The smaller tick is an Ixodes species, likely Ixodes scapularis the eastern vector of Lyme disease. To find a new host, ticks move onto vegetation such as grass and rest with their forelegs outstretched such as the American dog tick in the photograph. This interesting host behavior is called "questing". Questing ticks may respond to odors, heat, movement, and vibrations of passing hosts, and quickly climb aboard if the opportunity presents.

To reduce the risks of becoming a meal for a tick and the unfortunate recipient of Lyme disease or Rocky Mountain spotted fever, consider the following. If you enter habitats where wildlife and ticks may abound such as grassy meadows, the borders 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. Tuck your pant legs into your socks. This forces ticks to move up rather than under your cloths. Perform a thorough tick inspection of yourself and your family if you have been in tick habitats. This may involve enlisting a helper to view those "hard to see" areas around back. Apply repellents to exposed skin. Several repellents, such as those containing DEET, are available and very effective in preventing ticks from attaching. If you use repellents, be sure to read the label and follow directions carefully, particularly as they relate to children. Some repellents may be applied to clothing before they are worn.

If you find a tick attached to your skin, using a pair of fine forceps firmly grasp the tick as close to your skin as possible, and then using slow, steady force pull the tick out. Cleanse the area with antiseptic. In the case of Lyme disease it may take more than a day for infected ticks to transmit the disease to you so prompt removal can greatly decrease your risk of contracting a disease. Methods of tick removal such as smearing the tick with petroleum jelly or scorching its rear end with a match don't work. So remember: removing a tick in time, prevents Lyme.

References

For more information on ticks, Rocky Mounted spotted fever, and Lyme disease, visit the following websites:

http://www.agnr.umd.edu/MCE/Publications/PDFs/FS595.pdf
http://www.cdc.gov/ncidod/dvrd/rmsf/index.htm
http://www.cdc.gov/ncidod/dvbid/lyme/index.htm