Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.
Ticks are scientifically classified as Arachnida (a classification
that includes spiders). The fossil record suggests ticks have been around at least 90 million years.
Most tick bites do not transmit harmful microbes.
There are a variety of tick-borne diseases.
There is a wide range of symptoms that usually develop days to weeks after the tick bite. The symptoms depend on the particular microbe that is transmitted.
For all tick bites, local cleansing and antibiotic cream may be applied.
There are safe and effective methods for the removal of all types of ticks.
What are ticks?
Ticks are small arachnids. Ticks require blood meals to complete their complex life cycles. Ticks are scientifically classified as Arachnida (a
classification that includes spiders). The
fossil record suggests ticks have been around at least 90 million years. There
are over 800 species of ticks throughout the world, but only two families of
ticks, Ixodidae (hard ticks) and Argasidae (soft ticks), are known to transmit
diseases or illness to humans. Hard ticks have a scutum, or hard plate, on their
back while soft ticks do not.
Ticks have a complex life cycle that includes eggs, larvae, nymphs, and adult
male and female ticks. The larvae, nymphs, and adults all need blood meals.
Usually, the female adult (hard tick) is the one causing the most bites as males
usually die after mating. Ticks do not jump or fly. They simply reach out with
their legs and grab or crawl onto a host. Although some larvae have preferred
hosts, most ticks in the nymph or adult phase will attach a get a blood meal
from several different kinds of animals, including humans. Except for a few
species of larval ticks, the immature phases (larvae, nymphs) usually are even
less selective about where they get a blood meal and are known to bite snakes,
amphibians, birds, and mammals. Larvae are very small (about 1/32 of an inch with
six legs), while nymphs are about 1/16-1/8 inch with eight legs and adults about
3/16-1/4 inch with eight legs. The complex life cycles are described in the last
citation below, and all of the web citations include pictures of various species
of ticks. Although ticks will die eventually if they do not get a blood meal,
many species can survive a year or more without a blood meal. The hard ticks
tend to attach and feed for hours to days. Disease transmission usually occurs
near the end of a meal, as the tick becomes full of blood. It may take hours
before a hard tick transmits pathogens. Soft ticks usually feed for less than
hour. Disease transmission can occur in less than a minute with soft ticks. The
bite of some of these soft ticks produces intensely painful reactions.
Ticks are transmitters (vectors) of diseases for humans and animals. Ticks can
transmit disease to many hosts; some cause economic harm such as Texas fever
(bovine babesiosis) in cattle that can kill up to 90% of yearling cows. Ticks act
as vectors when microbes in their saliva and mouth secretions get into the
host's skin and blood. Ticks were understood to be vectors of disease in the
mid-1800s, and as investigative methods improved (microscopes, culture
techniques, tissue staining), more information showed the wide variety of
diseases that could be transmitted by ticks.
Picture of a tick
There are many common names for various ticks (for example, dog tick, deer tick, and African tick), and these names appear in the scientific literature, too. Most common names represent a genus of ticks (see below). However, the common name "red" may be used by people to describe almost any tick that has had a blood meal.
Lyme disease is caused by infection with a bacterium called a spirochete(Borrelia burgdorferi) and is transmitted to humans by infected ticks.
Patients with early stage Lyme disease symptoms have a characteristic rash(erythema migrans) accompanied by nonspecific symptoms (for example, fever, malaise, fatigue, headache, myalgia, and arthralgia). Lyme disease can usually be treated successfully with standard antibiotics.