Tick-borne disease

Tick-borne diseases
An eschar suggestive of tick bite

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Kiran Singh, M.D. [2] Associate Editor(s)-in-Chief: Ilan Dock, B.S.

Overview

Tick-borne diseases are diseases or illnesses transmitted by ticks. As the incidence of tick-borne illnesses increases and the geographic areas in which they are found expand, it becomes increasingly important that health professionals be able to distinguish the diverse, and often overlapping, clinical presentations of these diseases.

Pathophysiology

Tick-borne illnesses are caused by infection with a variety of pathogens, including rickettsia and other types of bacteria, viruses, and protozoa. Because ticks can harbor more than one disease-causing agent, patients can be infected with more than one pathogen at the same time, compounding the difficulty in diagnosis and treatment.

Life Cycle and Spread of Disease

General Tick Life Cycle

This image displays an example of the tick lifecycle, based on stages and the months that they are most likely to occur during.

• A tick's life cycle is composed of four stages: hatching (egg), nymph (six legged), nymph (eight legged), and an adult.
• Ticks require blood meal to survive through their life cycle.
• Hosts for tick blood meals include mammals, birds, reptiles, and amphibians. Ticks will most likely transfer between different hosts during the different stages of their life cycle.
• Humans are most often targeted during the nymph and adult stages of the life cycle.
• Life cycle is also dependent on seasonal variation.
• Ticks will go from eggs to larva during the summer months, infecting bird of rodent host during the larval stage.
• Larva will infect the host from the summer until the following spring, at which point they will progress into the nymph stage.
• During the nymph stage, a tick will most likely seek a mammal host (including humans).
• A nymph will remain with the selected host until the following fall at which point it will progress an adult.
• As a adult, a tick will feed on a mammalian host. However unlike previous stages, ticks will prefer larger mammals over rodents.
• The average tick life cycle requires three years for completion.
  • Different species will undergo certain variations within their individual life cycles.

Spread of Tick-borne Disease

• Ticks require blood meals in order to progress through their life cycles.
• The average tick requires 10 minutes to 2 hours when preparing a blood meal.
• Once feeding, releases anesthetic properties into its host, via its saliva.
• A feeding tube enters the host followed by an adhesive-like substance, attaching the tick to the host during the blood meal.
• A tick will feed for several days, feeding on the host blood and ingesting the host's pathogens.
• Once feeding is completed, the tick will seek a new host and transfer any pathogens during the next feeding process.

Tick-borne disease Classification

Bacterial

Disease	Organism	Vector	Endemic Regions
Borreliosis (Lyme Disease)	Borrelia burgdorferi sensu lato (bacterium)	Wood Tick (Dermacentor Variabilis), D. andersoni	United States: Eastern Region Southwest Region
Relapsing Fever	Borrelia Species; Borrelia hermsii, Borellia Parkeri, Borellia duttoni, Borrelia miyamotoi	Ornithodoros species	Widespread: Spain Saudi Arabia Asia Africa Canada Western United States
Typhus (Diseases associated with the transfer of Rickettsia Bacteria as listed below)
Rocky Mountain Spotted Fever	Rickettsia Rickettsii	Wood Tick (Dermacentor Variabilis), D. andersoni	United States: Eastern Region Southwest Region
Helvetica Spotted Fever	Rickettsia Helvetica	Ixodes Ricinus (European)	Europe: Sweden Switzerland France Laos
Ehrlichiosis Anaplasmosis	Ehrlichia Chaffeensis, E. Equi	Lone Star Tick (Amblyomma Americanum), Ixodes Scapularis	United States: South Atlantic Regions South-central Regions
Tularemia	Francisella Tularensis	D. Andersoni, D. Variabilis	United States: Widespread throughout the region, including higher populations in the Southeast, South-central, and the West.

Viral

Disease	Organism	Vector	Endemic Regions
Tick-borne Meningoencephalitis	TBEV virus	Ixodes Scapularis, I. Ricinus, I.persulcatus	Widespread: Europe Northern Asia
Colorado Tick Fever	CTF virus	Dermacentor andersoni	United States: Western Region
Crimean-Congo Hemorrhagic Fever	CCHF virus	Hyalomma marginatum, Rhipicephalus bursa	Widespread: South Asia North Africa Southern Europe
Severe Febrile Illness	Heartland Virus	Lone Star Tick (amblyomma americanum)	United States: Missouri Tennessee

Protozoan

Disease	Organism	Vector	Endemic Regions
Babesiosis	Babesia microti, B divergens, B.equi	Ixodes Scapularis, I. pacificus	Widespread: Northeastern United States Europe Asia

Differentiating Tick-Borne Disease

Bacterial

Disease	Symptoms	Treatment
Borreliosis (Lyme Disease)	Flu-like illness, fatigue, fever, arthritis, neuroborreliosis, cranial nerve palsy, carditis and erythema migrans.	Antibiotics Doxycycline- if not pregnant. or Amoxicillin- if pregnant
Relapsing Fever	Consistently documented high fevers, flu-like illness, headaches, muscular soreness or joint pain, altered mental state, painful urination, rash, and rigors.	Antibiotics Doxycycline Tetracycline Erythromycin**
Typhus (Diseases associated with the transfer of Rickettsia Bacteria as listed below)
Rocky Mountain Spotted Fever	Fever, alterations in mental state, myalgia, rash, and headaches.	Antibiotics Doxycycline Tetracycline.
Helvetica Spotted Fever	Rash: spotted, red dots. Respiratory issues, muscle pain, and headaches.	Antibiotics Broad-spectrum antibiotic therapy Phenoxymethylpenicillin.
Ehrlichiosis Anaplasmosis	Fever, Headache, Chills, Malaise, Muscle Pain, Nausea, Confusion, Conjunctivitis, or Rash. (60% in children and 30% in adults.)	Antibiotics Doxycycline, dosages should begin prior to lab results if ehrlichiosis is suspected. Adults- 100mg every 12 hours. Children (under 100lbs/45kg)- 2.2 mg/kg body weight, twice a day.
Tularemia	Ulceroglandular, Glandular, Oculoglandular, Oroglandular, Pneumonic, Typhoidal.	Antibiotics Streptomycin Gentamicin Doxycycline Ciprofloxacin.

Primary method of treatment**

Viral

Disease	Symptoms	Treatment
Tick-borne Meningoencephalitis	Early Phase: Non-specific symptoms including fever, malaise, anorexia, muscle pains, headaches, nausea, and vomiting. Second Phase: Meningitis symptoms, headache, stiff neck, encephalitis, drowsiness, sensory disturbances, and potential paralysis.	No specific drug therapy. May require hospitalization and supportive care, including anti-inflammatory drugs, corticosteroids, or, if necessary, incubation and ventilator support.
Colorado Tick Fever	Common symptoms include fever, chills, headache, body aches, and lethargy. Other symptoms associated with the disease include sore throat, abdominal pain, vomiting, and a skin rash. A biphasic fever is a hallmark of Colorado Tick Fever and presents itself in nearly 50% of infected patients.	There are no current therapies associated with Colorado Tick Fever. The majority of patients exhibiting symptoms recover completely, however severe cases require hospitalization.
Crimean-Congo Hemorrhagic Fever	Initially infected patients will likely feel a few of the following symptoms; headache, high fever, back and joint pain, stomach pain, vomiting, flushed face, red throat petechiae of the palate, and potentially changes in mood as well as sensory perception.	Treatment for Crimean-Congo Hemorrhagic Fever is primarily supportive including balancing electrolytes, oxygen abnormalities, and if necessary, hemodynamic support. In vitro, Crimean-Congo Hemorrhagic Fever is responsive to an antiviral treatment with Ribavirin.
Severe Febrile Illness

Protozoan

Disease	Symptoms	Treatment
Babesiosis	Non-specific flu like symptoms.	Atovaquone combined with Azithromycin or Clindamycin combined with Quinine.

Diagnosis

Physical Examination

A round red rash with a 2-5 mm central black area (eschar, an area of dead tissue) as shown in the photo is suggestive of a tick bite.

Laboratory Findings

In general, specific laboratory tests are not available to rapidly diagnose tick-borne diseases. Serological tests are frequently performed, but may be unreliable in differentiating acute from chronic conditions.

Risk Factors

People who spend time outdoors and/or have pets that go outdoors are at risk for tick-borne disease.

Treatment

Medical Therapy

• If there is a collection of pus, the area will need to be incised and drained.
• Antibiotic treatment is often justified based on clinical presentation alone.
• Doxycycline is often used to treat suspected bacterial tick-borne disease. Usually one dose is given to cover Lyme disease.

Related Chapters

• Lyme disease
• Tick-borne meningoencephalitis
• Rocky Mountain Spotted Fever
• Babesiosis
• Ehrlichiosis
• Relapsing fever
• Colorado tick fever
• Tularemia
• Tick paralysis
• Cytauxzoonosis