BIOL 222 - Lecture 11: Tuberculosis, Malaria, Ebola Pt 2

tuberculosis

long-lasting infectious disease caused by a bacterium called Mycobacterium tuberculosis

most commonly affects the lungs, but can infect almost any organ

spread is usually through airborne droplets when an infected person coughs, talks, or sneezes

sanatorium

before antibiotics existed, TB patients were treated in special hospitals

treatment included fresh air, rest, good nutrition

idea was to strengthen the body so it could control the infection

mycobacterium tuberculosis

the bacterium that causes tuberculosis

it grows very slowly and has a unique cell wall

mycolic acid

wax-like fatty substance in the cell wall of Mycobacterium

it makes the bacteria resistant to drying, resistant to many disinfectants, able to survive inside immune cells

because of mycolic acid, TB bacteria require special staining (acid-fast stain)

transmission

TB spreads when a person with active lung infection expels bacteria into the air, and another person breathes them in

requires prolonged close contact

tubercles

small, firm nodules that form in the lungs when the immune system walls off TB bacteria

granulomatous lesion

type of immune structure in which immune cells (especially macrophages) surround and contain an invader

in TB, granulomas = tubercles

they prevent spread but don't always kill the bacteria

primary tuberculosis

first infection a person gets when exposed

often mild or even symptomless because the immune system contains it

secondary (reactivation) tuberculosis

when dormant TB bacteria inside granulomas become active again, usually because immune system weakens (HIV, stress, old age, malnutrition) or another illness occurs

this form is more severe and more contagious.

extrapulmonary tuberculosis

TB infection occurring outside the lungs, such as bones (Pott's disease), kidneys, brain (TB meningitis), lymph nodes

more common in children and immunocompromised people

tuberculin skin test (Mantoux test)

diagnostic test for TB exposure

tiny amount of TB protein is injected under the skin

if the immune system has "seen" TB before, the skin becomes swollen and red within 48-72 hours

positive test means past exposure, vaccination OR active infection (it does NOT confirm which one)

malaria

parasitic disease transmitted by Anopheles mosquitoes

causes fever, chills, anemia, and can be fatal

plasmodium falciparum

the most dangerous malaria-causing parasite species

leads to severe malaria, cerebral malaria

highest mortality

found mainly in Africa but occurs worldwide in tropical regions

asexual phase

part of the parasite's life cycle that occurs in humans

parasite multiplies inside red blood cells

sporozoite

form of the parasite injected into the human bloodstream by a mosquito

these travel to the liver to begin infection

sexual phase

this part occurs inside the mosquito

when a mosquito bites an infected person, it takes in the sexual forms of the parasite; they reproduce inside the mosquito, new sporozoites form, mosquito becomes infectious

anti-malarial drugs

medications that kill malaria parasites or stop them from multiplying

artemisinin combination therapy (ACT)

most effective modern treatment

uses artemisinin + another drug to prevent resistance

antifolate combination drugs

block folic acid metabolism in the parasite

tetracycline & doxycycline

antibiotics used to prevent malaria (prophylaxis), or in combination with other drugs for severe cases

they inhibit parasite protein synthesis

chloroquine

classic antimalarial that used to be very effective

many Plasmodium falciparum strains are resistant

sickle-cell disease

genetic condition where red blood cells become sickle-shaped

people with one sickle-cell gene (sickle-cell trait) have protection against malaria

this is why the trait is common in malaria-endemic regions (natural selection favored it)

ebola

severe viral disease caused by the Ebola virus

spread through direct contact with bodily fluids (blood, vomit, feces, urine, sweat, etc.)

symptoms include fever, severe weakness, vomiting, diarrhea, internal and external bleeding (in severe cases)

mortality can be very high

hemorrhagic fever

group of illnesses that cause uncontrolled bleeding due to damage to blood vessels and clotting problems

Ebola is one of the viruses that cause viral hemorrhagic fever

bleeding occurs because blood vessels become leaky, platelets drop, clotting factors fail

this is what makes Ebola particularly dangerous