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Meninges

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layers that protect the brain and spinal cord

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Blood-brain barrier

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infections compromise this

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Meningitis

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inflammation of meninges

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Encephalitis

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inflammation of the brain

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Meningoencephalitis

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inflammation of both meninges and brain

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Bacterial Meningitis

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Initial symptoms of fever, headache, and stiff neck
Followed by nausea and vomiting
May progress to convulsions and coma
Diagnosis by Gram stain and latex agglutination of CSF
Treatment: Cephalosporins, vancomycin
Most common causes in US:
Haemophilus influenzae
Neisseria meningitidis
Streptococcus pneumoniae

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Haemophilus influenzae Meningitis

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Occurs mostly in children (6 months to 4 years)
Gram-negative aerobic bacteria, normal throat microbiota
80% of people are healthy nasopharyngeal carriers
Prevented by Hib vaccine

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Neisseria Meningitis

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Also called meningococcal meningitis
Caused by N. meningitidis
Gram-negative, aerobic cocci with a capsule
10% of people are healthy nasopharyngeal carriers
Begins as throat infection, rash
Vaccination recommended for college students

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Streptococcus pneumoniae Meningitis

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Also called pneumococcal meningitis
Caused by S. pneumoniae (a gram-positive diplococcus)
70% of people are healthy nasopharyngeal carriers
Most common in children (1 month to 4 years)
Mortality: 30% in children, 80% in elderly
Prevented by vaccination

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Tetanus

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Caused by Clostridium tetani
Gram-positive, endospore-forming, obligate anaerobe
Grows in deep wounds
Tetanospasmin (neurotoxin) released from dead cells blocks relaxation pathway in muscles
Lockjaw presents first
Prevention by vaccination with tetanus toxoid (DTP) and booster (dT) required every 10 years
Treatment with tetanus immune globulin

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Botulism

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Caused by Clostridium botulinum
Gram-positive, endospore-forming, obligate anaerobe
Intoxication comes from ingesting botulinal toxin
Botulinal toxin blocks release of neurotransmitter, causing flaccid paralysis; die from respiratory and cardiac failure
Prevention
Proper canning
Nitrites prevent endospore germination in sausages
Botox
Chronic headaches, muscle contractions, Parkinson’s, MS
Treatment: Supportive care and antitoxin

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Infant Botulism

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results from C. botulinum growing in intestines

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Wound Botulism

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results from growth of C. botulinum in wounds

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Leprosy

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Also called Hansen’s disease
Historical and biblical disease
Isolation could have led to its near disappearance
Caused by Mycobacterium leprae
Acid-fast rod that grows best at 30°C.
Grows in peripheral nerves and skin cells
Transmission (via secretions) requires prolonged contact with an infected person
Disfiguring nodules over body
Immunocompromised individuals

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Poliomyelitis (Polio)

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Poliovirus
Fecal-oral transmission
Outbreak in Vermont in summer of 1894
Initial symptoms: Sore throat and nausea
Viremia may occur; if persistent, virus can enter the CNS and cause respiratory failure
Destruction of motor cells and paralysis occurs in <1% of cases
Prevention: vaccination
Sabin vaccine: oral; live virus that is shed in feces
Vaccine derived cases
Salk vaccine: inactivated virus; series of 3 shots
Eradication of polio targeted by CDC

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Rabies

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Caused by the rabies virus
Untreated- fatal
Transmitted by animal bite

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Furious rabies

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animals are restless then highly excitable

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Paralytic rabies

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animals seem unaware of surroundings

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Preexposure prophylaxis

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injection of human diploid cells vaccine (HDCV)

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Postexposure treatment

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vaccine plus rabies immune globulin (RIG)

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Arboviral Encephalitis

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Arboviruses
Arthropod-borne viruses that belong to several families
Symptoms range from chills, headache, fever to death
Prevention: controlling mosquitoes
Diseases associated: Western equine encephalitis, Eastern equine encephalitis, St. Louis encephalitis, California encephalitis, and West Nile encephalitis

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Cryptococcus neoformans Meningitis

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Also called cryptococcosis
Soil fungus associated with pigeon and chicken droppings
Transmitted by the respiratory route; spreads through blood to the CNS
Mortality up to 30% in immunocompromised patients

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African Trypanosomiasis

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African sleeping sickness
Trypanosoma brucei
Chronic (2 to 4 years); fever, deterioration of CNS
Fatal without treatment
Transmitted from animals to humans by tsetse fly
Prevention: Elimination of the vector

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Naegleria fowleri

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Protozoan infects nasal mucosa from swimming water
Lakes in summertime
Proliferates in brain, feeds on brain tissue
100% fatal

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Transmissible Spongiform Encephalopathies

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Caused by prions
Normal protein in brain encounters the abnormally folded form of the same protein (prion)
Causes sponginess in brain
Typical diseases
Sheep scrapie
Creutzfeldt-Jakob disease
Bovine spongiform encephalopathy (Mad Cow Disease)
Chronic and fatal

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Creutzfeldt-Jakob disease

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Unknown source
Transmissible via transplants
Human growth hormone
prion disease of nervous system

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Bovine spongiform encephalopathy

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Outbreak in cattle 1986 in Great Britain
Cattle feed from sheep infected with scrapie
FDA banned parts of cattle carcass likely to contain prions or meat from “fallen” cattle
Percentage of cattle tested in US; all are tested in Europe and Japan
prion disease of nervous system

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Preventing prion diseases

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Difficult to destroy
Surgical instruments sterilized by
NaOH
+ extended autoclaving at 134°C

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