My patients are understandably concerned when they are bitten by a tick.  Ticks are arthropods related to mites, spiders, and scorpions.  More than any other of their arthropod cousins, ticks are vectors (carriers) of diseases.

Understanding the life of a Tick.

There are two families of ticks.  Argasidae are soft ticks also called one-host ticks since they live on one vertebrate animal host throughout their life.  Ixodidae are hard ticks that use 3 hosts and are the other tick family.  It is by the Ixodidae family of ticks that almost all diseases that infect humans are carried and transmitted through bites.  In this family are the Deer tick, Dog tick and LoneStar tick which spread most tick-borne diseases to humans.

Ticks hatch from eggs in a nest of leaf litter or other places depending on the species.  Some species that carry Rocky Mountain Spotted Fever are infected from the egg stage. When the larval form emerges from the egg it has only 6 legs.  Each stage feeds on one blood meal before entering the next stage.  The larvae, after eating its blood meal, molts into a numph form  and has eight legs in this and the next stage of its life.  Again the nymph eats one blood meal, and molts into the adult.  Nymphs are most dangerous for spreading Lyme disease because they are so small and often are not noticed.  It takes about two days for a tick to transmit Lyme disease but only about 8 hours for Rocky Mountain Spotted Fever.  The exact minimum time for Lyme transmission is still being investigated.  When people find numerous seed ticks on them they have usually encountered a group of Lone Star nymphs.  Lone Star ticks are agressive in attacking humans and other mammals.  The adult tick has only one purpose, breed and make more ticks.  To do that it must have a blood meal in the adult stage.  The males will eat several small meals and may mate several times.  The female will eat a meal days or even weeks long, gain up to 600 times her unfed adult weight, mate once, and lay her eggs before she dies.  The amount of that meal determines the amount of eggs she will lay.  Removing ticks quickly is necessary to prevent transmission of disease.  Removal in less than 24 hours almost guarantees that Lyme disease was not transmitted.

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