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.
Medical Author: William C. Shiel Jr., MD, FACP, FACR
Lyme
diseaseis caused by infection with a bacterium called a spirochete(Borrelia burgdorferi) and is transmitted to
humans by infected ticks (Ixodes scapularis and I. Pacificus). Patients with
early stage Lyme disease 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.
The U.S. Centers for Disease Control and Prevention
(CDC) released the results of a six-year survey study of Lyme disease from 1992 to
1998. During this period, a total of 88,967 cases of Lyme disease were reported
to CDC by 49 states and the District of Columbia, with the number of cases
increasing from 9,896 in 1992 to 16,802 in 1998. The researchers concluded that
the increase in reported cases is probably a result of both a true increase in
incidence within known high-risk areas as well as more complete reporting as a result of enhanced Lyme disease surveillance. They noted that surveillance capabilities and public awareness of Lyme disease have increased during this period.
Researchers also note that Lyme disease remains underreported with an estimated
seven to 12 cases for each reported case.
Ticks are scientifically classified as Arachnida (which 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
Web
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
one
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 vectors (transmitters) of diseases for humans and animals. Ticks can
transmit disease to many hosts; some cause economic harm such as Texas fever
(bovine babeiosis) in cattle that can kill up to 90% of yearling cows. Ticks act
as vectors when pathogens 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
What are tick bite symptoms?
Unfortunately, the tick bite is usually painless and remains that way even after
the tick stops the blood meal and falls off of the skin. Later, the bite site
may develop itching, burning, redness, and rarely, localized intense pain (some
soft tick bites) in some individuals. A few individuals may be sensitive or
allergic to tick bites (tick saliva secretions) and develop rash, shortness of
breath, swelling, numbness, or paralysis. However, the majority of individuals
with tick bites develop no symptoms, and many do not remember getting bitten.
Some immediate symptoms that infrequently or rarely develop during or
immediately after a tick bite may be fever, shortness of breath, weakness, vomiting,
swelling, weakness or paralysis, headache, confusion, or palpitations.
Individuals with these symptoms should be seen immediately by a doctor.
The word "rash" means an outbreak of red bumps on the body. The way people use this term, "a rash" can refer to many different skin conditions. The most common of these are scaly patches of skin and red, itchy bumps or patches all over the place.
Bed bugs (from the insect family Cimicidae) are small, reddish-brown tick-like insects that feed by sucking the blood of mammals. They are often found in poorly sanitized areas or in crowded living quarters.
Lyme disease is a bacterial illness, which is spread by ticks when they bite the skin. Initially the disease affects the skin causing a reddish rash associated with flu-like symptoms. It takes weeks to months after the initial redness of the skin for its effects to spread throughout the body. Lyme disease can be treated with antibiotics. Lyme disease can be prevented by using tick avoidance techniques.
Chiggers are a mite belonging to the Trombiculidae family. Chiggers are most commonly found in grassy fields, gardens, parks, forests, and moist areas around lakes or rivers. Contrary to popular belief, chiggers do not burrow into the skin. Chiggers insert a feeding structure into the skin and inject enzymes that destroy host tissue. The chiggers then feed on this dead tissue. The most common symptom of a chigger bite is itching. Treatment generally includes antihistamines and calamine lotion.
Headaches can be divided into two categories: primary headaches and secondary headaches. Migraine headaches, tension headaches, and cluster headaches are considered primary headaches. Secondary headaches are caused by disease. Headache symptoms vary with the headache type. Over-the-counter pain relievers provide short-term relief for most headaches.
Itching can be a common problem. Itches can be localized or generalized. There are many causes of itching to include: infection (jock itch, vaginal itch), disease (hyperthyroidism, liver or kidney), reactions to drugs, and skin infestations (pubic or body lice). Treatment for itching varies depending on the cause of the itch.
Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.). Fever is part of the body's own disease-fighting arsenal: rising body temperatures apparently are capable of killing off many disease- producing organisms.
Nausea is an uneasiness of the stomach that often precedes vomiting. Nausea and vomiting are not diseases, but they are symptoms of many conditions. The causes of vomiting differ according to age, and treatment depends upon the cause of nausea and vomiting.
The majority of spiders in the United States are harmless. Two exceptions include the black widow spider and the brown recluse spider. Symptoms of a harmless spider bite generally involve redness, irritation, and pain. alized symptoms of bites from black widow and brown recluse spiders may include: nausea and vomiting, fever, headache, abdominal pain, joint pain, and more. In general, a brown recluse spider bite or black widow spider bite may require medical attention. The information includes pictures of the brown recluse and black widow spiders for identification.
Rocky Mountain spotted fever (RMSF) is an infectious disease that's transmitted by the bite of a tick infected with the Rickettsia rickettsii bacterial organism. Initial symptoms of RMSF include fever, nausea, vomiting, muscle pain and severe headache. Later symptoms include rash, abdominal pain, joint pain, and diarrhea. Treatment usually involves a tetracycline antibiotic.
Bug bites and stings have been known to transmit insect-borne illnesses such as West Nile virus, Rocky Mountain spotted fever, and Lyme disease. Though most reactions to insect bites and stings are mild, some reactions may be life-threatening. Preventing bug bites and stings with insect repellant, wearing the proper protective attire, and not wearing heavily scented perfumes when in grassy, wooded, and brushy areas is key.
West Nile virus (West Nile encephalitis) is a brain infection caused by a virus. People become infected with the virus after they're bitten by a mosquito that has fed off of a bird that's infected with the West Nile virus. Symptoms in humans include fever, headache, rash, body ache, and swollen lymph nodes.
Travelers should prepare for their trip by visiting their physician to get the proper vaccinations and obtain the necessary medication if they have a medical condition or chronic disease. Diseases that travelers may pick up from contaminated water or food, insect or animal bites, or from other people include malaria, meningococcal meningitis, yellow fever, hepatitis A, typhoid fever, polio, and cholera.
Viral hemorrhagic fever(s), or VHFs are a group of illnesses caused by distinct families of viruses. Many of these viruses are life-threatening, and classified as biosafety level four (BSL-4) pathogens. Viral hemorrhagic fever viruses are caused arenaviruses, filoviruses, bunyaviruses, and flaviviruses. The viruses are carried in rodents and transmitted through urine, fecal, saliva, or other body excretions from the infected rodents. Symptoms of viral hemorrhagic fever include marked fatigue, dizziness, muscle aches, loss of strength, fever, and exhaustion. Severely ill patients may also suffer shock coma, seizures, delirium, kidney failure, or nervous system malfunction. There is no established cure for viral hemorrhagic fever.
Tularemia (rabbit fever) is an infection caused by the Francisella tularensis bacteria. People can become infected with tularemia by coming into contact with infected animals or via a tick bite. Symptoms and signs include fever, headache and rash. Tularemia is treated with streptomycin or gentamicin.
Viral hemorrhagic fevers (VHFs) refer to a group of illnesses that are caused
by several distinct families of viruses. In general,
the term "viral hemorrhagic fever" is used to describe a severe multisystem
syndrome (multisystem in that multiple organ systems in the body are affected).
Characteristically, the overall vascular system is damaged, and the body's ability to regulate itself is
impaired. These symptoms are often accompanied by hemorrhage (bleeding);
however, the bleeding is itself rarely life-threatening. While some types of
hemorrhagic fever viruses can cause relatively mild illnesses, many of these
viruses cause severe, life-threatening disease.
The Special Pathogens Branch (SPB) primarily works with hemorrhagic fever
viruses that are classified as biosafety level four (BSL-4) pathogens. A
list of these viruses appears in the
SPB disease information index. The Division
of Vector-Borne Infectio...
