Nervous System Diseases Flashcards
microbial diseases of the NS
- central and peripheral NS
- CNS= brain and spinal cord
- PNS = all nerves that branch off of the CNS; cranial and peripheral nerves
3 important functions of the NS
- sensory
- integrative
- motor
Defenses of the NS
- mainly structural
- bony casings
- cushion of CSF
- Blood-brain barrier
- immunologically privileged site
Normal Biota of the NS
- no normal biota
- any microorganisms in the PNS or CNS are a deviation from the healthy state
Meningitis
Encephalitis
Meningoencephalitis
- inflammation of meninges
- inflammation of the brain
- inflammation of both
Most common Bacterial Meningitis
- Neisseria meningitis
- Streptococcus pneumoniae
- Haemophilus influenzae
- worldwide incidence
- 3 types of bacteria cause 70% of bacterial meningitis
- all 3 possess a capsule that protects them from phagocytosis
- other bacteria may cause meningitis
Meningitis caused by Microorganisms
- inflammation of the meninges
- many different microorganisms can cause an infection
- more serious forms caused by bacteria
- Typical symptoms: headache, painful or stiff neck, fever and usually an increased number of WBC in the CSF
Diagnosis of meningitis
- perform a spinal tap (lumbar puncture) to obtain cerebrospinal fluid
- gram stain for morphology
- Latex agglutination tests on CSF
- prompt chemotherapy a must because of fast progress of disease
- start w/ broad spectrum 3rd generation cephalosporins and adjust treatment as learn more about the isolate
meningitis
- many different species of bacteria
- Neisseria meningitis
- Streptococcus pneumoniae
- Haemophilus influenzae
- Listeria monocytogenes
Fungi:
- Cryptococcus neoformans
- Coccidiodes immitis
- Co or previous viral infections can facilitate meningitis
Hemophilus influenzae
- gm neg. rod, aerobic
- endotoxins; capsule
- Hib vaccine caused decrease in occurrence
- ear infections
- respiratory route
- sporadic cases
- 6% mortality
Neisseria meningitdis
- gm neg. coccus
- endotoxins: released into circulation
- activates WBC
- cytokines released
- damage to blood vessels
- Petechiae develop
- vascular collapse; hemorrhage; petechiae
-vaccine used in military and colleges
-epidemics
-death in a few hrs in severe cases
mortality 10%
-respiratory route
Petechiae
-pinpoint, round spots that appear on the skin as a result of bleeding under the skin
Streptococcus pneumoniae
- gm pos. cocci
- respiratory route
- 26% mortality
- vaccines have reduced incidence
- common flora in nasopharyngeal region
Clostridium tetani
- gm pos. rod, anaerobe, produces exotoxin
- Neurotoxin which blocks the relaxation pathway of muscles; very potent toxin
- tetanus called lockjaw
- toxoid vaccine, booster every 10yrs
Tetanus
- “rusty nail” tho to be the cause before bacteria discovered but now know that the spores of the organism can be found in the soil
- newborns in developing countries contract tetanus when umbilical cord stump is exposed to spore
rabies virus
- fatal encephalitis
- long incubation period of weeks to months gives time for post-exposure immunization
- bite, inhalation of saliva from injected skunk, bat, fox, raccoon
- treat w/ antibodies and/or human diploid cell vaccine
- identify infected animal w/ immunofluorescent study of the brain
- look for negri bodies
- Great Britain. Australia, New Zealand and Hawaii are free of rabies
- Only strict vaccination policies keep countries rabies-free
pathology of rabies infection
- virus enters tissue from saliva of biting animal
- virus replicates in muscle near bite
- virus moves up PNS to CNS
- virus ascends SC
- virus reaches brain and causes fatal encephalitis
- virus enters salivary glands and other organs of victim
Leprosy (Hansen’s Disease)
- Mycobacterium leprae
- Acid-fast rod that grows best at 30C
- very long generation time= 12days
- cannot be grown on laboratory media. have not been able to provide the organism all the growth factors that it needs
- grow organism in armadillos or in the footpads of nude mice
Mycobacterium leprae
- acid fast, slow grower in PNS (12 d gen time)
- prefer cooler parts of body
- not very contagious
- grows in PNS and skin cells
- transmission requires prolonged contact w/ an infected person
- historically patients w/ leprosy were isolates but today they are treated at outpatients clinics w/ antibiotics which make them noncontagious
- Tuberculoid (neural form): loss of sensation in ski areas; positive lepromin test
- -lepromatous (progressive) form: disfiguring nodules over body, negative lepromin test
Leprosy cases
- 100-250 new cases in the US annually; most imported from tropical areas
- half a million new cases worldwide
- millions of ongoing cases worldwide: Asia, Africa, Brazil
- combination of drugs used for 6-12 months depending on the stage of the disease: dapsone, rifampin and clofazimine
Polio
- highly infectious disease. invades the NS and can cause irreversible paralysis in a matter of hours
- caused by the poliovirus
- most people (90%) have no or mild symptoms
- those w/ symptoms-include fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs
Spread of Polio
- Direct person to person contact
- contact w/ infected mucus from the nose or mouth
- contact with infected feces
- enters thru the mouth and nose, multiplies in the throat and intestinal tract, and absorbed and spread thru the blood and lymph system
- develop symptoms of disease (5-35 days) *average 7-14 days)
how does the virus infect the nerve cell?
- Virus enters the central nervous system (the spinal cord and brain) either by traveling along peripheral nerves or via the circulatory system.
- Virus shows attraction for nerve cells that control muscles
- Poliovirus infects and destroys motor neurons, leaving virtually untouched adjacent nerve cells that control sensation, bowel movement, bladder function, and even sexual arousal.
Polio: Acute flaccid paralysis (AFP)
- one in 200 infections leads to irreversible paralysis, usually in legs
- virus entering the blood stream and invading the CNS
- virus destroys the nerve cells that activate muscles
- affected muscles are no longer functional and the limb becomes floppy and lifeless- a condition known as acute flaccid paralysis (AFP)
Polio: Bulbar polio
- more extensive paralysis, involving the truck and muscles of the thorax and abdomen
- most serious type, poliovirus attacks the nerve cells of the brain stem, reducing breathing capacity and causing difficulty in swallowing and speaking
- among those paralyzed, 5-10% die when their breathing muscles become immobilized
Post-polio syndrome
- Around 40% of people who survive paralytic polio may develop additional symptoms 15–40 years after the original illness.
- post-polio syndrome – include new progressive muscle weakness, severe fatigue and pain in the muscles and joints
- Could be because the nerve pathways that took over after polio are now less active
transmission of polio
- An infected child passes live virus in the feces
- Polio is spread through person-to-person contact, food and water
- Poor hygiene, poor sewage treatment or poor latrines lead to transmission
- Herd immunity prevents transmission
Polio Vaccine: Salk vaccine: IPV
- inactivated polio vaccine
- not “live”; very safe
- good protection from paralytic polio
- does not provide strong protection in the gut
- poliovirus can multiply in gut
- excreted in feces and spread to other people
- more expensive
- used in developed countries where polio has been eliminated: cost benefit analysis
Polio Vaccine: Sabin Vaccine: OPV
- oral polio vaccine
- easy to administer
- inexpensive
- good protection
- multiples in gut and released in feces- “immunizes” others in contact
- rarely causes paralytic polio in people
- rarely mutates and become more like the wild type
- not used in countries where polio has been eliminated
endemic countries
Polio-endemic countries have never stopped transmission of wild poliovirus.
Afghanistan
Nigeria
Pakistan
India removed 2011
countries with reestablished transmission of polio
Countries with re-established transmission have active and persistent poliovirus transmission of more than 12 months following an importation.
Angola
Chad
Democratic Republic of the Congo
countries with imported poliovirus
- Countries with imported poliovirus are experiencing ongoing outbreaks following an importation.
- Congo, Liberia, Mali, Niger, Uganda, Kenya, Guinea, Gabon, Côte d’Ivoire, Central African Republic, China
Polio virus types
Three types: Type 1, 2, 3
Type 2 poliovirus has been eliminated in the wild – the last wild type 2 poliovirus was detected in India in 1999.
-In this final stage of polio eradication, only type 1 and type 3 wild poliovirus continue to circulate in endemic areas. Both are highly infectious and both cause paralytic polio. Type 1 is the most pervasive strain of poliovirus, with type 3 highly localized in northern India, northern Nigeria, Pakistan and Afghanistan.
