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The page below is a sample from the LabCE course Tickborne Diseases. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Ioxodes scapularis on blade of grass/CDC

Well-developed hypostome with teeth/CDC

How Ticks Cause Disease

In order to cause some tickborne diseases, the tick vector attaches to blades of grass or other vegetation and hang out waiting for a host to brush by it. They do not jump or fall on hosts. In other tickborne diseases, the ticks live in rodent burrows or cabins and come out at night for a rapid feed.
When a tick is preparing to feed, it may take from ten minutes to two hours. Some ticks bite where they land, while others move around the host hunting for softer skin, such as the armpit or the umbilicus. Once there, the tick pinches the skin and inserts its feeding tube. Some ticks secrete a cement-like substance, while others have teeth or barbs on the feeding tube to stay attached. The tick slowly sucks the host's blood over several days in some cases, while in other cases, ticks feed in about 30 minutes. After feeding, the tick will release and continue its life cycle in nature.
Many ticks secrete small amounts of saliva containing ingredients that may anesthetize the bite, so it goes unnoticed. Other substances modulate the host's immune system. This increases the tick's ability to feed by disrupting the host's ability to defend itself by affecting keratinocytes in the skin, B-cells and T-cells, neutrophils, mast cells, and basophils. Cytokines, chemokines, and complement may also be altered to allow the ticks' greater access to host blood.
Pathogenic microorganisms are frequently located in the midgut of the tick and it may take minutes or hours for it to be transmitted by regurgitation, through saliva, or coxal fluid. In the case of soft ticks, transmission may be very fast. Once infected, the disease microorganism can be passed transovarially or from larva to nymph to tick. Some diseases can be transmitted from one tick to another during feeding through the host's blood.