Tick Bites

1668 Tick Bites BIBLIOGRAPHY. Jan Liska, et al., “Thyroid carcinoma,”

Curr Opinions in Oncology (v.18/1, 2006). B.S. Hetzel, “Iodine deficiency disorders (IDD) and their eradication,” Lancet (v.12/2, 1983); World Health Organization, “Iodine status worldwide,” WHO Global Database on Iodine Deficiency, (World Health Organization, 2004).

Charitha Gowda Deipanjan Nandi Duke University School of Medicine

Tick Bites A tick bite is the resulting injury from a tick sting, which could produce a local inflammatory reaction, a systemic toxemia, or after an incubation period, a tick-borne disease such as those caused by virus, rickettsias, bacteria, and protozoans. Ticks are hematophagic arthropods and bite humans and/or animals to obtain blood. From an epidemiological point of view, it is important to mention that in some countries (particularly in northern and developed countries) more vectorborne diseases are transmitted by ticks than by any other agent. During the past 30 years, tick-borne diseases have taken on increased importance as humans (in many cases with their pets) have moved into rural areas and increased their recreational outdoor activity, thus being more frequently exposed to tick bites. Taxonomically, medically important ticks belong to the class Arachnida, order Acarina and suborder Ixodes with two families: Argasidae (with the genuses Argas, Otobius, and Ornithodoros) and Ixodidae (with the genuses Amblyomma, Dermacentor, Boophilus, Ixodes, Rhipicephalus, and Haemophysalis). Most important ticks belong to the last family, being responsible of transmission of diseases such as Rocky Mountain spotted fever, Q fever, boutonneuse fever, ehrlichiosis, tularemia, Colorado tick fever, Queensland tick typhus, Siberian tick typhus, tularemia, Central European tick-borne encephalitis, Congo-Crimean fever, tick-borne relapsing fever, babesiosis, and Lyme disease, among others. As blood feeders, ticks can be a nuisance; their bites can cause irritation and, in the case of some ticks, paralysis. The prevention of tick bites and the prompt detection and removal of attached ticks can reduce the

It is important for physicians to consider the illnesses associated with tick bites when patients present with influenza-like symptoms.

chances of infection. To limit the chance of getting a tick bite, it is recommended to avoid tick-infested areas when possible and avoid shortcuts through heavily wooded, tick-infested areas. Use caution when entering tick-infected areas by staying in the center of paths, avoiding sitting on the ground, and conducting frequent tick checks. Additionally, it is also advisable to dress properly by wearing light-colored clothing. The use of repellents is also important in preventing tick bites. The primary active ingredient in most repellents today is DEET (N,N-diethyl-3-methylbenzamide or N,N-diethyl-m-toluamide), which repels ticks and decreases the chance of bites (depending upon the concentration). Other repellent commonly used to prevent bites is permethrin (used frequently for the application on clothing or nets). It is important for physicians to consider the illnesses associated with tick bites when patients present with influenza-like symptoms. A petechial rash initially affecting the palms and soles of the feet is associated with Rocky Mountain spotted fever, whereas erythema migrans is associated with Lyme disease.

Tinnitus



Moreover, ticks can cause important dermatologic disease directly by their bite, which also require specialized medical attention. SEE ALSO: Flea Bites; Hemorrhagic Fever; Lyme Disease;

Medical Entomology; Parasitic Diseases.

BIBLIOGRAPHY. Paul Beaver, et al., Clinical Parasitology

(Lea & Febiger, 1984); Robert Bratton and Ralph Corey, “Tick-Borne Disease,” American Family Physician (v.71/12, 2005); Gordon Cook and Alimuddin Zulma, Manson’s Tropical Diseases (Saunders, 2003); Pablo Cova, General Principles of Entomology (FVSE, 1974); Becerri Flores and Romero Cabello, Medical Parasitology (McGraw-Hill, 2004); David Heymann, Control of Communicable Diseases in Man (APHA/PAHO/WHO, 2004); Daniel McGinleySmith and Sandy Tsao, “Dermatoses from Ticks,” Journal of the American Academy of Dermatology (v.49/3, 2003). Alfonso J. Rodriguez-Morales, M.D., M.Sc. Universidad de Los Andes Carlos Franco-Paredes, M.D., M.P.H. Emory University

Tinnitus Tinnitus is the perception of an abnormal sensation of sound in the ear or head in the absence of acoustic stimulation from external environment, from within body, due to hallucinations or due to mental illness. Spontaneous tinnitus is a significant interdisciplinary therapeutic problem; it is a common condition affecting around one in 10 of the population at any given time. For the majority of people, it is an annoyance rather than a major health issue; however, for approximately 0.5 percent of the population, tinnitus interferes with their ability to pursue a normal life. The effects of tinnitus are vast; some degree of hearing loss is found in the vast majority of tinnitus patients. In elderly patients, it most frequently coexists with sensorineural hearing loss. Tinnitus is also likely to disrupt cognitive functioning. Tinnitus is divided into two parts: objective and subjective. Objective tinnitus is caused by sounds generated in the body, while subjective tinnitus is caused by abnormal neural activity that is not evoked by sound. Tinnitus

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may present with symptoms of hyperacusis (condition characterized by oversensitivity to certain frequency ranges of sound). Tinnitus is a common symptom in otosclerosis patients; affective disorders, such as phonophobia (morbid fear of sound including ones own voice), and depression which may accompany severe tinnitus. Tinnitus is thought to be caused by abnormal neural activity, with possible involvement of the nonclassical ascending (extralemniscal, diffuse, or polysensory) auditory pathway that bypass the primary auditory cerebral cortex and provide subcortical connections to limbic structures (e.g., amygdala) among others. Pathogenesis of tinnitus is related to the ear, functional changes in the central auditory system, and perhaps the peripheral auditory system. The most probable place generating tinnitus in the auditory pathway is outer hair cells (OHC) inside the cochlea. There appears to be a loss of OHC although inner hair cells are intact. The changes in the central nervous system are induced through expression of neural plasticity, some of which may have been caused initially by abnormalities in the ear or the auditory nerve. The diagnostic approach in children and adolescents includes hearing tests such as pure-tone audiometry which determines hearing sensitivity and speech audiometry which is a functional test of earspecific speech discrimination performance. There is currently no cure for tinnitus; however, there are several treatment strategies that can alleviate the symptoms in some patients. Tinnitus of predominantly central origin has been treated successfully with benzodiazepines (although long-term use is not recommended) and GABAergic drugs such as gabapentin. Many studies advocate the use of hyperbaric oxygen (HBO2) therapy for the treatment for tinnitus. Other studies suggest that the therapeutic effects of HBO2 on tinnitus might be merely due to psychological mechanisms triggered by the attitude of the patient toward HBO2 therapy prior to the treatment. Fitting with hearing aids is an effective way of treatment in the majority of elderly patients with chronic tinnitus. Suppression of tinnitus by electrical stimulation via a cochlear implant has been studied in recent years. Some individuals who undergo cochlear implant surgery report total or partial relief of the symptoms even in the contralateral ear. Tinnitus patients may seek treatment with acupuncture, although this has not been demonstrated to be