CH20 Infectious disease of nervous system and eyes

Nervous system

Brain, spinal cord, nerves

No normal flora!! Sterile environment

Meningitis

Bacterial infection

Symptoms : high fever, headache, nausea, vomiting, drowsiness, confusion, stiff neck

Cerebrospinal fluid should usually be clear however if cloudy usually a sign (due to WBC, bacteria, elevated protein + decreased glucose)

Common pathogens causing for Bacterial Infections

Usually age dependent

Listeria monocytogenes : causes death in the unborn due to it crossing the placenta

Streptococcus agalacteae (Group B strep) : newborns, normal flora in vaginal canal of approx 1/3 of women

Haemophilus influenzae : young children, vaccination

Neisseria meningitidis : teens, young adults, can be epidemic, vaccination

Streptococcus pneumoniae : elderly, vaccination

How to determine meningitis?

lumbar tap/puncutre

Clostridium tetani

Route of organism’s entry : skin puncture

Exotoxin targets the nervous system → neurotoxin (blocks muscle relaxation pathway so antagonistic muscles spontaneously contract → results in spasms)

Vaccination against exotoxin

Clostridium botulinum

Foodborne illness by consumption of the potent exotoxin (not an infection but instead an intoxication)

Exotoxin (neurotoxin) prevents secretion of acetylcholine, muscles do not contract (paralysis), including the failure of the diaphragm to move

Mycobacterium leprae

Aka Leprosy or Hansen’s Disease

Transmission via aerosols or breaks in the skin

Organism multiplies in the skin, mucous membranes and nerve cells

Virulence factors : Slow grower, protection from phagocytosis and can grow in the WBC which protects them → remains viable for years with no obvious signs of illness, until immune system attacks the infected WBC and releases the organism

Destroys nerves (loss of sensation) and disfigurement (loss of facial features and digitsh

How to diagnose Leprosy?

Acid fast stain due to the organism not growing on agar

Rabies

Transmitted by bite/scratch of an infected animal

Virus travels along peripheral nerves and then enters central nervous system → fatal encephalitis (inflammation of brain tissue)

Symptoms : pain/itching at infection site, fever, headache, malaise, hydrophobia, seizures, disorientation, hallucinations

Treatment involves both a vaccine and human rabies immunoglobulin (HRIG)

Arboviral Encephalitis

West Nile and eastern equine encephalitis (EEE)

Mosquito is the vector (birds are natural hosts of kicroganism)

Virus is capable of crossing the blood brain barrier (results in encephalitis)

Symptoms : flu like symptom that progress into more serious, EEE has a significant mortality rate (30%+)

Treatment : supportive care

Prevention : mosquito control

Cryptoccocus neoformans

Fungal infection

Yeast found commonly in soil with pigeon droppings (or from their dander) and it will dry and be aerosolized

Symptoms present as bacterial meningitis

Virulence factor : capsule (seen in an India ink prep of CSF)

Often seen in AIDS and other immunocimpromised patients

how does crypotococcus neoformans work?

Inhalation of yeast → lung infection → blood stream → meninges

African Trypanosomiasis

Aka African Sleeping sickness (organism is Trypanosoma Brucei)

Vector : tsetse fly

Found predominantly in Central and Eastern Africa

Identified by finding protozoan in blood of CSF

Symptoms : headache, abnormal neurological function, extreme drowsiness → get more and more tired until coma or death if untreated

Bacterial infections of the eye

Conjunctivitis (Pink Eye)

Neonatal Gonorrheal Opthlamia

Trachoma (Chlamydia trachomatis)

Pink Eye

Common causes : Haemophilus, Moraxella, Streptococcus

Highly contagious

Symptoms : pink eye, a lot of discharge

Neonatal Gonorrheal Opthalmia

Conjunctivitis by Neisseira gonorrhoeae

Acquired as newborn passes through the birth canal

Can lead to cornea ulceration → blindness

Why all newborns eyes are rrrated with erythromycin or tetracycline (used to be silver nitrate)

Trachoma

Chlamydia trachomatis

Transmitted to newborns via the birthing canal and adults via hand contact

Protozoan infection of eye

Acanthamoeba keratitis

Amoeba found in fresh water, hot tubs and soil

Became more common with increased use of contact lenses

Can be hard to diagnose

Treated with antiprotozoan eye drops