Micro - ch.26 - Nervous System Infections

neuron

basic cells of nervous system messages between brain → spinal cord → body

Describe a neuron

dendrites - soma - axon - axon terminals - synapse

What is a nerve?

a bundle of axons + blood vessels + protective tissue

neuroglia

“glial cells”

supporting cells of nervous system (support, protect, nourish)

CNS - Central Nervous System

brain and spinal cord

process info and controls actions

PNS - Peripheral Nervous System

all other nerves

connects CNS to limbs +organs

Meninges

3 protective layers of tissue that cover CNS

• protects CNS from injury and contains cerebrospinal fluid (CSF) barrier against infection

blood brain barrier (BBB)

protective shield of tightly packed cells that control what substances pass blood to brain

• O2 and glucose

• certain pathogens have still adapted to BBB

Meningitis

inflammation of meninges

• “Neisseria meningitidis”

• droplets - bloodstream - attack CNS

quickly life threatening

photophobia - purple spotted rash

Encephalitis

inflammation of the brain (damaging)

• most common HSV or West Nile virus

Hemophilus influenza

**not the flu

type b (HiB) bacteria

droplets - bloodstream - CNS

in children

Streptococcus pneumonia

“pneumonococcal meningitis”

vaccines for children and elderly

spreads vertical transmission - immunocompromised

Streptococcus agalactia

urinary tract/GI tract

• adults: spreads through GI/urinary

• children: during birth or utero

spreads and infects nervous system

Listeriosis

Listeria monocytogenes

food borne - can cook off

flu-like symptoms in women → cross placenta → fetal meningitis → sepsis or stillbirth

Botulism

Clostridium botulism

• adults: toxin in canned food/improperly preserved foods

• infants: ingest spores classically in honey

S/S: flaccid paralysis, drooping eyelids, SOB, “floppy baby syndrome”

Leprosy

PNS infection

“Hansen’s disease”

• spread through long-term close contact

• not highly contagious

S/S: numbness + skin discolored patches/nodules due to lower temp.

• leads to disfigurement

• limb loss from numbness - infection

What animal has leprosy and can spread?

armadillos - reservoirs due to lower body temps

Poliomyelitis

“Polio”

fecal-oral route, saliva

intestinal cells → bloodstream → CNS (motor neurons)

minor flu-like symptoms

• < 1% paralytic polio

flaccid paralysis

Naegleria fowleri

“brain eating amoeba”

rapid and >97% fatal brain infection

• in warm fresh water (lakes, poorly chlorinated pools)

nose → olfactory nerve → CNS

Rabies

“Rhabdovirus” - bullet shape

• saliva through bite or exposure ot mucosal membrane

inhalation → PNS → CNS → encephalitis

3-12 weeks incubation

fatal if untreated

What are some S/S of rabies?

tingling, hydrophobia/refuse to drink, agitation

• PEP - post exposure prophylaxis:

  • after exposure before S/S

  • wound cleaning

  • veterinary meds at risk

Arboviral encephalitis

transmitted through arthropod (mosquitos, ticks)

bug bite → replicates in bloodstream → BBB → CNS → inflammation of brain

• confusion, seizures, paralysis

Cryptococcal meningoencephalitis

fungal infection - often in bird droppings

pigeons

inhalation of spores

• meningitis

African sleeping sickness

protozoan parasite

• bite of tsetse fly

near water in rural sub-Saharah Africa

**2 stages

1st stage of African Sleeping sickness

headache

lymph nodes swell

fever

fatigue

bloodstream and spreads to lymphatic

Stage 2 of African Sleeping sickness

nocturnal insomnia

daytime somnolence

coma → death if untreated

crosses BBB

Sheep scrapie

fatal - degenerative brain disease

• sheep and goats

misfolded proteins/priors

Intense itching = rub against objects

Cruetzfeldt-Jacob (CJD)

fatal, rare, prion disease

• sporatic (unknown trigger)

• fatal within one year

what does Cruetzfeldt-Jacob turn into?

Mad Cow Disease

Kuru

foreign people of Papu New Guinea

• human prion disease

cannibalism (ritual consumption)