Week 11 Diseases of nervous system Flashcards
Meninges
Three layers: dura mater (in contact with skull), arachnoid mater, pia mater (in contact with blood vessel and brain)
Surrounds brain
Nervous system divisions
CNS: brain and spinal cord
PNS: nerves (communication between brain and rest of body)
Bacterial meningitis causes (3) and characteristics
Streptococcus pneumoniae, haemophilus influenza, neisseria meningitidis
All have capsule (protection from phagocytosis)
Enter CSF, then die rapidly
Bacterial meningitis symptoms (5)
Fever, headache, stiff neck, nausea, vomiting
Other causes of bacterial meningitis (3)
Listeria monocytogenes
Streptococci group B
Staphylococci
Haemophilus influenza characteristics
Aerobic, gram negative, normal throat flora
H. influenza diseases
bacterial meningitis, epiglottitis, otitis media, pneumonia
WHat about h. influenza contributes to pathogenicity
Capsular carbohydrate antigen type B (Hib)
Vaccine is based on this antigen
Neisseriaceae characteristics
Non spore forming diplococci, aerobic or facultative, gram negative
Pathogenic species of neisseriaceae and location
N. gonorrhoea and N. meningitidis
Found on human mucosal membrane
N. meningitidis medium
Chocolate agar (brown)- contains red blood cells which are heated and killed
N. meningitidis disease
meningococcal meningitidis
N. meningitidis serotypes
A (widespread epidemic, africa)
C (North america and other parts of world)
VAccine based on capsular polysaccharide for serotypes A and C
No vaccine for B
N. meningitidis treatment
doxycycline, ofloxacin, erythromycin
Meningitis signs and symptoms
Appearance of neutrophils and N. meningitidis in CSF smear
Can proliferate in blood leading to sepsis, then enters into nervous system (meninges)
Spreading rash on trunk, arms and legs, form crusty vesicles on skin surface
S. pneumoniae disease
streptococcal meningitis
S. pneumoniae location , vaccine, treatment
Nasopharyngeal region, vaccine against capsular antigen, penicillin
Clostridium characteristics
Obligate anaerobe (lacks cytochromes needed to use O2 as terminal hydrogen acceptor)
Catalase and peroxidase negative
Gram positive
Spore forming (when nutrients insufficient)
Ferments carbohydrates
Encapsulated alpha and theta/gamma? haemolysis
Clostridium species (4) and diseases
Perfringens: gas gangrene and food poisoning
Difficile: toxic enterocolitis (antibiotic associated pseudomembrane colitis)
Tetani (spores): tetanus
Botulinum: botulism
C. tetani
Obligate anaerobe, common in soil, produces spores
Potent neurotoxin (tetanospasmin) released when lysed or killed
Non communicable as does not spread from infectious site
Tetanospasmin MOA
Blocks relaxation pathways in muscles: they contract but cannot relax leading to paralysis and pain
C. botulinum
Spore forming, anaerobe
Produces potent exotoxin under anaerobic conditions
Serological types A-E (5)
Infant botulism can occur due to competition with normal flora
Botulinum exotoxin characteristics
Toxin not formed in acidic food eg tomatoes
Toxin destroyed with cooking heat
Type A spore most resistant to heat
Antibiotics not effective against toxin, instead neutralised with antitoxins A-E from mice
Leprosy cause
Mycobacterium leprae
Mycobacterium leprae characteristics
Acid fast, related to M. tuberculosis
Optimal growth temperature 30 degrees
Long generation time
Cannot be cultured outside body (armadillos used as lower body temp than humans)
Grows in PNS and on skin
Forms of leprosy (2)
Tuberculoid (neural): regions of skin lose sensation, surrounded by borders of nodules
Lepromatous (progressive): skin cells infected, disfiguring nodules form all over body
Tuberculoid leprosy- who it occurs in, diagnosis
In ppl with good immune system
Detection of acid fast bacteria in fluid from slit cut in cool site eg earlobe
Lepromin test: extract from advanced form injected into skin yields visible reactive, this test is negative in later stages of the disease
Lepromatous leprosy characteristics (5)
Occurs in people without effective cell mediated immunity
Mucous membrane of nose and face most affected
Clawed hands
Not very contagious, requires prolonged intimate contact
COmplications may occur but usually does not cause death
Viral diseases of nervous system (3)
Poliomyelitis
Rabies
Arbovirus encephalitis (eastern equine, western equine, st louise, california, japanese B, yellow fever, Powassan virus, dengue fever, colorado tick borne encephalitis)
Usually result in death
Poliomyelitis progression
Infection initiated by ingestion of virus
Multiplies in throat and small intestine, invades tonsils and lymph nodes in neck and ileum
Enters blood (viraemia), then central nervous system
Multiplies in cytoplasm of motor nerves and kills them resulting in paralysis
Polio diagnosis and prevention
Isolation of virus from faeces and throat, cell culture
Vaccines: salk (inactivated with formaldehyde), sabine (live attenuated)
Iron lungs mechanically respirate paralysed lungs
Rabies
Caused by rabies virus (rhabdovirus, bullet shape)
Always results in fatal encephalitis if untreated by vaccination
Human acquires from infected animal
Long incubation period enough to allow immunity to develop from post exposure vaccination
Rabies progression
Virus within peripheral nerves not accessible to immune system until cells of CNS destroyed
Agitation period: breakdown of NS cells
Calm period: virus multiplying within NS
Rabies symptoms
Spasms of mouth muscles and pharynx, hydrophobia, total destruction of CNS cells and death
Furious rabies
Animal restless, highly excitable, snap at anything within reach eg dog
Paralytic rabies
Animal not excited, relatively quiet, might snap if irritated eg cat
Rabies diagnosis
Presence of viral antigen in saliva, serum or CSF using immunofluorescence technique
Rabies treatment
Anti-rabies vaccine and immunoglobulins post exposure (prophylaxis)
Treatment for any unprovoked bite from animal not available for examination
Rabies vaccination (3)
Old (pasteur): attenuated, dried spinal cord of rabies infected rabbit
Human diploid cell vaccine (5-6 injections over 28 days)
Passive immunisation: human immunoglobulin
Arbovirus disease
Arboviral encephalitis
Arbovirus naming
Initial location of isolation and diseases they produce
Categorised based on morphology, biochemistry and antigenic similarities
Rabies carriers
Skunk, fox, bat, bobcat, raccoon, dog, cat
Arbovirus general characteristics
Enveloped virions with single stranded RNA
Envelope contains haemagglutinin and lipoproteins (so can be inactivated by lipid solvents)
Found in blood and tissues, but not stool
Diagnosed using serological techniques
What differentiates reoviridiae from other arboviruses
Reoviridiae are double stranded RNA viruses without envelopes
Reservoir and transmission of arboviruses
Infection transmitted from arthropods to susceptible vertebrate host
Invertebrate vectors of arboviruses (5)
Aedes mosquito, wood tick, tick , anopheles mosquito, flea
Survival of arbovirus between seasons (2)- needed as arthropods are not present in all seasons
Infected adult arthropods hibernate between seasons to survive
Transovarian transmission: infected female arthropod transmits virus to progeny
Mechanism of arboviruses
- Infection of vertebrate by a biting arthropod
- Virus amplifies in reticuloendothelial system
- Virus become localised in various target organs causing
cell necrosis, and inflammation which leads to fever - Transmission along neural pathway
- Enters CNS causing meningeal inflammation of neuronal dysfunction encephalitis
Yellow fever progression
Liver and hepatic cell necrosis
Haemorrhage due to failure of liver to produce clotting factor
Dengue haemorrhagic fever
Fever associated with rash and flu symptoms
Changes in small dermal blood vessels: increased vascular permeability and infiltration of mononuclear cells
Arbovirus treatment
None other than supportive care
Arbovirus prevention
Avoiding contact with infected arthropods, elimination of arthropod bleeding sites, use of insecticides
Arbovirus vaccination
Immunisation of horses and humans against west and east equine encephalitis
Cryptococcus neoformans characteristics
Fungal meningitis
Yeast like with spherical cell
Polysaccharide capsule
Mainly in soil contaminated with pigeon droppings
Cryptococcus neoformans transmission
Inhalation -> lung infection -> blood -> meninges
Cryptococcus neoformans identification
serology detecting antigen in CSF and blood
Trypanosoma gambiense and T rhodesiense
Cause african trypanosomiasis (sleeping sickness)
Protozoan parasites
Trypanosoma multiplies in Tsetse fly saliva, transmitted to human through bite
Bite -> blood stream -> spleen lymph nodes and liver
Trypanosoma symptoms
Invasion of CNS results in reduced concentration, ability to talk and walk
Extreme tiredness -> continual sleeping -> coma -> death
Trypanosoma reservoir
Game animals, cattle and sheep, common in Africa
Bovine spongiform encephalopathy (BSE)
Caused by prion
Mad cow disease (in cows), Creutzfeldt-Jakob disease in humans from transplanted nerve tissue, contaminated surgical instruments or meat from infected cows
Cause neurological damage
How do prions cause neurological damage
induce abnormal folding of specific normal cellular proteins in the brain from alpha protein (normal) to beta sheet (abnormal)
Prion classification
Nonliving, infectious proteins
