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Learning objectives

  • Identify the most common acellular pathogens that can cause infections of the nervous system
  • Compare the major characteristics of specific viral diseases affecting the nervous system

A number of different viruses and subviral particles can cause diseases that affect the nervous system. Viral diseases tend to be more common than bacterial infections of the nervous system today. Fortunately, viral infections are generally milder than their bacterial counterparts and often spontaneously resolve. Some of the more important acellular pathogens of the nervous system are described in this section.

Viral meningitis

Although it is much more common than bacterial meningitis, viral meningitis is typically less severe. Many different viruses can lead to meningitis as a sequela of the primary infection, including those that cause herpes , influenza , measles , and mumps . Most cases of viral meningitis spontaneously resolve, but severe cases do occur.

Arboviral encephalitis

Several types of insect-borne viruses can cause encephalitis. Collectively, these viruses are referred to as arboviruses (because they are ar thropod- bo rne), and the diseases they cause are described as arboviral encephalitis . Most arboviruses are endemic to specific geographical regions. Arborviral encephalitis diseases found in the United States include eastern equine encephalitis (EEE), western equine encephalitis (WEE), St. Louis encephalitis, and West Nile encephalitis (WNE). Expansion of arboviruses beyond their endemic regions sometimes occurs, generally as a result of environmental changes that are favorable to the virus or its vector. Increased travel of infected humans, animals, or vectors has also allowed arboviruses to spread into new regions.

In most cases, arboviral infections are asymptomatic or lead to a mild disease. However, when symptoms do occur, they include high fever, chills, headaches, vomiting, diarrhea, and restlessness. In elderly patients, severe arboviral encephalitis can rapidly lead to convulsions, coma, and death.

Mosquitoes are the most common biological vectors for arboviruses, which tend to be enveloped ssRNA viruses. Thus, prevention of arboviral infections is best achieved by avoiding mosquitoes—using insect repellent, wearing long pants and sleeves, sleeping in well-screened rooms, using bed nets, etc.

Diagnosis of arboviral encephalitis is based on clinical symptoms and serologic testing of serum or CSF. There are no antiviral drugs to treat any of these arboviral diseases, so treatment consists of supportive care and management of symptoms.

Eastern equine encephalitis (EEE) is caused by eastern equine encephalitis virus (EEEV), which can cause severe disease in horses and humans. Birds are reservoirs for EEEV with accidental transmission to horses and humans by Aedes , Coquillettidia , and Culex species of mosquitoes. Neither horses nor humans serve as reservoirs. EEE is most common in US Gulf Coast and Atlantic states. EEE is one of the more severe mosquito-transmitted diseases in the United States, but fortunately, it is a very rare disease in the United States ( [link] ). US Centers for Disease Control and Prevention, “Eastern Equine Encephalitis Virus Disease Cases and Deaths Reported to CDC by Year and Clinical Presentation, 2004–2013,” 2014. http://www.cdc.gov/EasternEquineEncephalitis/resources/EEEV-Cases-by-Year_2004-2013.pdf. US Centers for Disease Control and Prevention, “Eastern Equine Encephalitis, Symptoms&Treatment, 2016,” Accessed June 29, 2016. https://www.cdc.gov/easternequineencephalitis/tech/symptoms.html.

Questions & Answers

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Rashmi
replication is a term related to generation of new DNA from a parental DNA.
Rashmi
role of microorganism as pathogens
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to live inside the host body, reproduction n destroy the immune system of host body.
Rashmi
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replication is a term related to generation of new DNA from parental DNA.
Rashmi
difference between endotoxin and exotoxin
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toxins released inside the cell or a body is endotoxin n toxins released outside the cell or a body is exotoxin.
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there are many we classify it according to their shapes gram negative or gram positive
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microbiology is the study of microorganism and microorganism are such as bacteria ,parasite, viruses and fungi and etc.. those are cant be seen with asked eyes and can be seen with help of microscope . I hope this helps you
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Bismarck Reply
the study of viruses
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virology,mycology,bacteriology
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identification n application of microorganisms
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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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