Ticks are blood feeding external parasites of mammals, birds, and reptiles throughout the world. There are two well established types of ticks, the Ixodidae (hard ticks), and Argasidae (soft ticks). Both are important vectors of disease causing agents to humans and animals throughout the world. Ticks transmit the widest variety of pathogens of any blood sucking arthropod, including bacteria, rickettsiae, protozoa, and viruses. Some human diseases of current interest in the United States caused by tick-borne pathogens include Lyme disease, ehrlichiosis, babesiosis, rocky mountain spotted fever, tularemia, and tick-borne relapsing fever.
Different types of ticks:
1. Hard Ticks, family Ixodidae
Hard ticks have three distinct life stages. Larvae which emerge from the egg have six legs. After obtaining a blood meal from a vertebrate host, they molt to the nymphal stage and acquire eight legs. Nymphs feed and molt to the next and final stage - the adult, which also has eight legs. After feeding once more, the adult female hard ticks lay one batch of thousands of eggs and then die. Only one blood meal is taken during each of the three life stages. The time to completion of the entire life cycle may vary from less than a year in tropical regions to over three years in cold climates, where certain stages may enter diapause until hosts are again available. Many hard ticks can go for several months without feeding if not unduly digressed by environmental conditions.
Hard ticks seek hosts by an interesting behavior called "questing." Questing ticks crawl up the stems of grass or perch on the edges of leaves on the ground in a typical posture with the front legs extended, especially in response to a host passing by. Certain biochemicals such as carbon dioxide as well as heat and movement serve as stimuli for questing behavior. Subsequently, these ticks climb on to a potential host which brushes against their extended front legs. Hard ticks are most commonly collected for research by the use of "flags" or "drags" which are made from 1 m square pieces of roughly textured fabric such as fleece or flannel attached to a rod handle. The flags are slowly dragged across the surface of vegetation to collect questing ticks. Hard ticks feed for extended periods of time on their hosts, varying from several days to weeks, depending on such factors as life stage, host type, and species of tick. The outside surface, or cuticle, of hard ticks actually grows to accommodate the large volume of blood ingested, which, in adult ticks, may be anywhere from 200-600 times their unfed body weight (Sonenshine 1991).
2. Soft Ticks, family Argasidae
The life stages of soft ticks are not readily distinguishable. The first life stage to come out of the egg, a six legged larva, takes a blood meal from a host, and molts to the first nymphal stage. Unlike hard ticks, many soft ticks go through multiple nymphal stages, gradually increasing in size until the final molt to the adult stage. Some soft ticks pass through up to seven nymphal molts before they become adults. Soft ticks feed several times during each life stage, and females lay multiple small batches of eggs between blood meals during their lives. The time to completion of the entire life cycle is generally much longer than that of hard ticks, lasting over several years. Additionally, many soft ticks have an uncanny resistance to starvation, and can survive for many years without a blood meal (Furman and Loomis 1984).
Some soft ticks seek hosts by questing on low-lying vegetation, but the vast majority is nest parasites, residing in sheltered environments such as burrows, caves, or nests. Certain biochemicals such as carbon dioxide as well as heat and movement serve as stimuli for host seeking behavior. Soft ticks feed for short periods of time on their hosts, varying from several minutes to days, depending on such factors as life stage, host type, and species of tick. The feeding behavior of many soft ticks can be compared to that of fleas or bedbugs, as once established, they reside in the nest of the host, feeding rapidly when the host returns and disturbs the contents. The outside surface, or cuticle, of soft ticks expands, but does not grow to accommodate the large volume of blood ingested, which may be anywhere from 5-10 times their unfed body weight (Sonenshine 1991).
Soft ticks can be readily collected via dry ice traps. Blocks of dry ice emit large amounts of carbon dioxide, a host seeking stimulant. Traps are set in and around nesting areas of animal hosts. Soft ticks can be observed running along the surface of the ground towards the trap and are collected by hand, or inside a collection chamber in the trap. Many types of soft ticks can be artificially fed in the laboratory, thus reducing or eliminating the use of animals for certain studies. Some will feed through sausage casings filled with almost any type of mammal blood heated up to 37° C. Others can be fed blood through various types of membranes in the presence of biochemical and environmental feeding stimulants such as ATP, carbon dioxide, heat, and animal fur (Sonenshine 1993).
How Can I Prevent Tick Bites?
Ticks like to rest on low-lying brush and 'catch a ride' on a passing animal or person. The areas that hold a high risk of tick infestation are wooded areas, low-growing grassland, and the seashore. You should exercise caution where you go.
To reduce your chance of getting tick bites:
Avoid tick infested areas, when possible. Avoid short-cuts through heavily wooded, tick-infested areas. Use caution when you are entering tick-infected areas. Stay in the center of paths, avoid sitting on the ground, and conduct frequent tick-checks.
Dress properly. Wear light-colored clothing. This allows you to more easily see ticks on your clothing and gives you the opportunity to remove them before they can attach to your skin and feed. Wear a long-sleeved shirt and long pants. This reduces the skin area exposed to ticks. Also, tuck your shirt into your pants and pants into your socks. This keeps the ticks on the outside of your clothing and thwarts their efforts to crawl onto your skin. However, during warm or hot weather, this is not practical. So, if this advice is ignored, we suggest that you increase your vigilance in conducting tick-checks.
Use EPA-approved tick repellents.
During the summer months, it can be inconvenient to wear pants and long-sleeved clothing, so using repellents can help protect you from ticks. Wash off the repellents when you return inside, and children should always have an adult apply the repellent for them.
Conduct frequent tick-checks.
This includes a visual inspection of the clothing and exposed skin, followed by a naked, full-body examination in a private location. Be sure to check the scalp, behind and in the ears, and behind any joints.
Remember to check your pets too!
This is not only for your pets' safety but for your family's as well. Pets can bring ticks in from outside and put you and your family at risk for infection.
Prevent tick bites with our time-tested natural formula Bugs BeGone.
[Source: http://entomology.ucdavis.edu/faculty/rbkimsey/tickbio.html]
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