1. Chapter 27 Nervous System Infections
Medgar Evers College
Microbiology
Prof. Santos

2. Anatomy and Physiology
The brain and spinal cord make up the central nervous system.
The network of nerves throughout the body is called the peripheral nervous system.
The PNS is connected to the CNS by bundles of nerve fibers that penetrate the vertebral body.
The PNS is made up of Motor Nerves and Sensory Nerves.

3. Bacterial Nervous System Infections
Bacteria can infect the brain and spinal cord, causing abscesses.
In Hansen’s disease, they can infect the peripheral nerves.
More commonly, bacteria infect the meninges and cerebrospinal fluid, causing meningitis.

4. Meningitis Meningitis is an intense inflammatory response.
White blood cells accumulate in the cerebrospinal fluid which causes the brain to swell.
The three important causes of bacterial meningitis are Haemophilus influenzae, Neisseria meningitidis, and Streptococcus pneumoniae.

5. Meningitis
Streptococcus pneumoniae is the leading cause of meningitis in adults. The organism is prominent cause of otitis media, sinusitis, and pneumonia, condition that often proceed pneumococcal meningitis.
Neisseria meningitidis differs from the other causes in that it is often responsible for epidemics of meningitis.

6. Bacterial Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Meningococcal Meningitis
Neisseria meningitidis. The meningococcus. A gram-negative diplococcus. There are 13 antigenic groups of N.meningitidis. Most serious infections are due to A,B,C,Y, and W135. incubation period: 1 to 7 days
Mild cold, severe throbbing headache, fever, pain, stiffness of the neck and back, nausea, and vomiting. Deafness and alterations in consciousness, progressing to coma. Purplish spots called petechiae may develop. The infected person may develop shock and die within 24 hours.
Infection is acquired by inhaling airborne droplets from the respiratory tract of another person. The meningococci attach to the mucous membrane and multiply. They are then taken in by the respiratory tract epithelial cells, pass through them, and invade the bloodstream. The blood carries the organisms to the meninges and cerebral spinal fluid.
A vaccine composed of purified A, C, Y, and W135. Mass prophylaxis treatment with an appropiate antibacterial medications , such as Rifampin, can help in controlling epidemics.

7. Bacterial Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Listeriosis ( a food borne disease).
Listeria Monocytogenes is a motile , non-spore-forming , facultatively anaerobic, gram positive rod that can grow at 4 degrees Celsius. Incubation Period: a few days to 2-3 months.
Fever, muscle aches, and sometimes nausea or diarrhea.
The mode of entry in isolated cases is usually obscure but it is generally via the gastrointestinal tract. The bacteria penetrate the intestinal mucosa and enter the bloodstream.
Thoroughly cook meats and avoid contaminated countertops, wash all vegetables, and pregnant women should avoid soft cheeses. L. monocytogenes have remained susceptible to Penicillin.

8. Bacterial Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Hansen’s Disease (Leprosy)
Mycobacterium leprae. It is aerobic, acid-fast, rod-shaped, and typically stains in a beaded manner. Incubation period: 3 months to 20 years.
Anaesthetic skin lesions, deformed face, loss of fingers or toes.
Invasion of small nerves of skin; multiplication in macrophages; attack of immune cells against infected nerve cells causes deformity.
No vaccine. Treatment includes dapsone plus rifampin for months or years; clofazimine added for lepromatous disease.

9. Bacterial Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Botulism
Clostrium botulinum. An anaerobic, gram-positive, spore-forming, rod- shaped bacterium. Incubation period: 12 to 36 hours.
Blurred or double vision, weakness, nausea, vomiting, diarrhea; generalized paralysis and respiratory insufficiency.
C. botulinum endospores germinate in food and release neurotoxin. Toxin is ingested, is absorbed in the small intestine and enters the bloodstream. Toxin acts by blocking the transmission of nerve signals to the muscles producing paralysis.
Enemas and stomach washing to remove toxin, cleaning infected wounds of dirt and dead tissue, intravenous administration of antitoxin and artificial respiration.

10. Viral Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Viral Meningitis
Most cases: small non-enveloped RNA enteroviruses of the picornavirus family, usually coxsackie or echoviruses. Mumps virus common in unimmunized populations. Incubation Period: 1 to 2 weeks for enteroviruses. 2 to 4 weeks for mumps.
Abrupt onset, fever, severe headache, stiff neck, often vomiting, sometimes sore throat, large parotid glands, rash, or chest pain.
Viremia from primary infection seeds the meninges. Fewer leukocytes enter cerebrospinal fluid than with bacterial infections, and many are mononuclear, usually no decrease in CSF Glucose.
No specific treatment. Prevention: handwashing, avoiding crowded swimming pools during enterovirus epidemics; mumps vaccine.

11. Viral Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Viral Encephalitis
Usually caused by one of four arboviruses, LaCrosse, St. Louis, western equine, or eastern equine.
Incubation Period: First systems within a few days; encephalitis symptoms often within the first week.
Abrupt onset, fever, headache, vomiting, disorientation, paralysis, seizures, deafness, coma.
Infected mosquito introduces virus. Replication of virus at the site of the mosquito bite, further replication in lymph nodes, them viremia that seeds brain tissue. Nerve cells in the brain invaded and destroyed, causing death, or permanent disabilities.
No accepted treatment for arboviral encephalitis. Prevention: Chicken sentinels to warn of arbovirus epidemics. Insecticides and other anti-mosquito preventative measures.

12. Viral Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Infantile Paralysis, Polio (Poliomyelitis)
Polioviruses 1, 2, and 3; members of the picornavirus family.
Incubation Period: 7 to 14 days.
Headache, fever, stiff neck, nausea, pain, muscle spasm, followed by paralysis.
Poliovirus enters the body orally; infect the throat and intestinal tract and then invade the bloodstream. It enters the nervous system and attack the motor nerves causing paralysis.
Artificial ventilation for respiratory paralysis; physical therapy and rehabilitation. Prevented by injecting Salk’s inactivated vaccine or Sabin’s orally administered attenuated vaccine.

13. Viral Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Rabies
Rabies virus, single-stranded RNA, rhabdovirus family; has an unusual bullet shape. Incubation Period: Usually 30 to 60 days.
Fever, headache, nausea, vomiting, sore throat, cough at onset; later, spasms of the muscles of mouth and throat, coma, and death.
Bite of rabid animal. Virus multiples at site of bite, then travels via nerves to CNS where it spreads outward to infect heart and other organs.
Immediately wash wound and apply antiseptic; inject rabies vaccine and human rabies antiserum as soon as possible. No effective treatment once symptoms begin.

14. Fungal Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Cryptococcal Meningoencephalitis.
Filobasidiella (Cryptococcus) neoformans, an encapsulated yeast.
Incubation period: variable.
Headache, vomiting, confusion, and weight loss; slight or no fever; symptoms may progress to seizures, paralysis, coma and death.
C.Neoformans fungus becomes airborne with dust, enters the body through inhalation and infects the lung. The organism multiples and enters the bloodstream infecting the meninges and brain tissue.
amphotericin B with flucytosine or itraconazole. No preventative measures

15. Protozoan Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
African Sleeping Sickness
Trypanosoma brucei, a flagellated protozoan.
Incubation period: weeks to several years.
Tender nodule at site of tsetse fly bite; fever, enlargement of lymph nodes; later, involvement of the CNS, uncontrollable sleepiness, headache, poor concentration, unsteadiness, coma, and death.
During the bite of an infected tsetse fly, the protozoan enters the wound in the fly’s saliva, multiplies, then enters the bloodstream and lymphatic system. As new cycles of parasites are released, their surface protein changes and the body is required to respond with a new antibody.
Suramin; when CNS is involved, melarsoprol or eflornithine. Prevention: protective clothing, insecticides, clearing of brush where flies breed, pentamidine.

16. Prion Disease of the Nervous System
Cause
Symptoms
Pathogenesis
Treatment
Transmissible Spongiform Encephalopathy
Proteinaceous infectious particles known as prions; lack nucleic acids; amino acid sequence to a normal protein, but folded differently, and relatively resistant to proteases, heat, radiation, and disinfectants.
Behavioral changes, anxiety, insomnia, fatigue, progressing over weeks or months to muscle jerks, lack of coordination and dementia.
Replication first occurs in the spleen and other lymphoid tissues. Prions replicate in dendritic cells by converting normal proteins to more prions; transmission to the brain; aggregation into masses outside the nerve cells; cell malfunction and death.
There is no treatment. invariably