Tick-borne encephalitis (patient information)
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Tick-borne encephalitis |
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Tick-borne encephalitis On the Web |
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Risk calculators and risk factors for Tick-borne encephalitis |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Ilan Dock, B.S.
Overview
Tick-borne encephalitis is caused by a virus transmitted through the bite of an infected tick. Three types of the virus exist, including the Far East, European, and Siberian subtypes. The Ixodidae family of ticks is the primary vector associated with transmission, with other modes of transmission including the consumption of unpasteurized, raw milk.[1] Pathogenesis occurs as the virus binds to a host cell receptor. Through a series of reactions, the virus enters the cell, is translated, and hi-jacks the host cell's replication machinery. After which immature virions are released within the cell, to ultimately spread infection. Viral replication will often occur within subcutaneous tissue. Replication also occurs within the lymph nodes, causing immense damage to the immune system. A later phase of the virus results in an infection of the CNS as the immune response increases the permeability of the blood-brain barrier. [2]
What are the symptoms of Tick-borne encephalitis virus?
Common symptoms include:
- Fever
- Malaise
- Anorexia
- Muscle aches
- Headache
- Nausea
- Vomiting
What are the causes of Tick-borne encephalitis virus?
Tick-borne diseases are most often transmitted during a blood meal, either by a nymph of adult tick. Blood meals will occur with a higher rate of incidence from the late spring into the early fall, with the highest rate of tick-borne encephalitis viral (TBEV) infections during the early and late summer. The primary disease vector for TBEV is the Ixodidae tick family, found throughout most of Eurasia. The virus itself is a member of the flavivirus genus, with three distinct subtypes. The virus is a (+)ssRNA genome enclosed in a capsid protein. It begins by locating a host cell receptor. The virus is internalized through the process of endocytosis. During this time the virus hi-jacks the host cells replication machinery, in order to replicate many times within the host cell. Upon completion the cell releases many immature virions for further progression of the disease. [2]
Who is at risk for Tick-borne encephalitis virus?
The primary risk factors associated with tick-borne encephalitis are exposure to endemic environments and the consumption of unpasteurized dairy products. More severe infections have been reported in individuals over the age of 50 years.
How to know you have Tick-borne encephalitis virus?
An array of laboratory tests exist to assist with the diagnoses of tick-borne encephalitis. Polymerase chain reactions are most effective during the first week of infection. An early detection as a result of a successful PCR enables quicker medical treatment and ultimately a potentially higher survival rate. Other test useful during the later stages of infection include immunofluorescence assays, antibody titers, ELISA, and other serologic tests. [2]
When to seek urgent medical care?
Early onset signs include fever, lethargy, and overall weakness. As the infection progresses, further clinical manifestations will present themselves in the form of tachycardia, changes in blood pressure, sensitivity of the eye and skin, and the appearance of a rash. Signs may appear to be similar to other diseases within the umbrella of tick-borne fevers however a biphasic infection period (early onset symptoms, remission period, and second phase of symptoms) is a characteristic sign of tick-borne encephalitis.
Treatment options
Treatments for tick-borne encephalitis may be categorized according to a mainstay, phosphrenyl treatment, an antibiotic therapy, and homeopathic, herbal treatments. Phosphrenyl treatment is similar to interferon treatment for Hepatitis C, utilized as both a therapeutic and prophylactic agent. Antibiotic therapies are useful as many disease vectors responsible for transmission of tick-borne encephalitis also carry many other tick-borne diseases. An antibiotic therapy may be helpful in anticipating any potential tick-borne co-infections. Antibiotics have also been useful in deactivating certain characteristics of the virus. However certain antibiotic therapies have proven to activate the virus. Thus for this reason, certain antibiotics, such as streptomycin, should not be prescribed during the course of infection. Homeopathic therapies, such as ledum, motherwort, and blackcurrant have inactivating effects on tick-borne encephalitis virus.
Prevention of Tick-borne encephalitis virus
Tick- borne encephalitis prevention strategies are based on avoiding potential, infected tick bites. Avoiding tick bites may be accomplished through limiting exposure to endemic areas. However if it is impossible or impractical to avoid these areas, several preventative strategies may be implemented. These strategies are indicated under the Prevention title below. Other prevention strategies include a proper removal of the tick. This process is also outlined below under the title, the best way to remove a tick.
What to expect (Outlook/Prognosis)?
The prognosis is usually good for the majority of infected patients. Many patients will appear to be asymptomatic during the course of infection. For individuals displaying signs and symptoms, the clinical manifestations will typically reside after the first wave of non-specific flu like symptoms. However as mentioned earlier, a second phase can occur. The prognosis for patients undergoing this course of infection is still fairly good. Yet, patients experience an infection of the central nervous system are more prone to long term complications.
Possible complications
Progression of the disease may present itself as aseptic meningitis, encephalitis, or myelitis. Complications are commonly associated with this later phase, including the aforementioned meningitis and encephalitis as well as long term cognitive dysfunction and limb paresis. The prognosis is usually good for the majority of infected patients. Many patients will appear to be asymptomatic during the course of infection.
Sources
References
- ↑ Tick-borne encephalitis transmission. http://www.cdc.gov/vhf/tbe/transmission/index.html Accessed February 5, 2016.
- ↑ 2.0 2.1 2.2 Tick-borne Encephalitis Virus: A General Overview. http://cdn.intechopen.com/pdfs-wm/20866.pdf. Accessed February 4, 2016.