Micro CH 18

What protects the cardiovascular system from infection, and what are the differences between viremia, bacteremia, septicemia, and septic shock?

• Blood is normally sterile because of WBCs, antibodies, complement proteins, spleen, and lymph nodes.

• Viremia: viruses in blood.

• Bacteremia: bacteria in blood (often temporary after dental work, brushing teeth, minor injuries).

• Septicemia (Sepsis): bacteria multiply in blood, triggering systemic inflammation.

• Septic Shock: severe sepsis causing persistent hypotension, poor tissue perfusion, organ failure, and high mortality.

What causes malaria, and which Plasmodium species infect humans?

• Protozoan Plasmodium

• Four species:

  • P. falciparum (most severe)

  • P. vivax

  • P. malariae

  • P. ovale

• Humans = intermediate host

• Female Anopheles mosquito = definitive host.

Describe the malaria life cycle and how it causes disease.

1. Mosquito injects sporozoites.

2. Parasites infect liver cells.

3. Merozoites enter RBCs.

4. RBCs rupture repeatedly.

5. Mosquito ingests parasites from infected person.

Disease results from:

• RBC destruction → anemia

• Fever-producing chemicals released when RBCs burst

• High glucose consumption → hypoglycemia

• Liver and spleen enlargement from parasite accumulation.

What are the symptoms, transmission, prevention, and treatment of malaria?

• Incubation: ~10 days

• Symptoms: malaise, fatigue, aches, nausea, diarrhea, chills, cyclic fever (48–72 hrs), sweating

• Spread by female Anopheles mosquito

• Common in Africa; children most affected

• Prevention: mosquito control, bed nets, repellents, staying indoors, prophylactic drugs, vaccines (not fully protective)

• Treatment: quinine or chloroquine (if susceptible)

What is endocarditis, and what are the differences between acute and subacute forms?

• Infection of the heart's inner lining (usually mitral or aortic valve).

• Acute: rapid, destructive; usually Staphylococcus aureus, also S. pyogenes, S. pneumoniae, and N. gonorrhoeae.

• Subacute: slower; occurs after damaged valves from rheumatic fever or congenital defects. Bacteria form biofilms on damaged valves.

What are the risk factors, symptoms, transmission, and prevention of endocarditis?

Risk factors:

• Rheumatic fever

• Prosthetic valves

• Congenital heart disease

• IV drug use

• Dental procedures

• Surgery

Symptoms:

• Fever

• Fatigue

• Weakness

• Joint pain

• Anemia

• Heart murmur

• Edema

• Abnormal heartbeat

• Enlarged spleen (subacute)

• Clubbing (late disease)

Classic findings:

• Petechiae

• Janeway lesions = painless

• Osler nodes = painful

Transmission:

• Acute: surgery, trauma, IV drug use

• Subacute: brushing teeth, dental work, minor cuts

Prevention:

• Prophylactic antibiotics before certain dental/surgical procedures.

What is sepsis, what causes it, and what are the SIRS criteria?

Sepsis = SIRS + infection caused by an overwhelming cytokine response.

Effects:

• Vasodilation → hypotension

• Increased vascular permeability → edema

SIRS criteria:

• HR >90

• RR >20

• WBC <4,000 or >12,000

• Temp <36°C or >38°C

What happens during severe sepsis and septic shock?

Severe sepsis:

• Lactic acidosis

• Oliguria

• Mental status changes

• Hypotension

• Hypoperfusion

Septic shock:

• Persistent hypotension despite fluids

Major complications:

• DIC: widespread clotting → bleeding, tissue death, amputations

• ARDS: fluid-filled lungs causing respiratory failure

• MODS: failure of multiple organs

Every untreated hour increases death risk by ~8%.

What causes plague, how is it transmitted, and what are its forms?

Cause:

• Yersinia pestis

Transmission:

• Flea bites from infected rodents

Bubonic plague:

• Buboes

• Fever

• Chills

• Bacteremia

• Septicemia

• Tissue necrosis ("Black Death")

Pneumonic plague:

• Lung infection

• Bloody sputum

• Cough

• Difficulty breathing

Prevention:

• Rodent and flea control

• Good sanitation

What causes infectious mononucleosis, and what are its signs and complications?

Cause:

• Epstein-Barr virus (EBV)

• "Kissing disease"

Incubation:

• 30–50 days

Symptoms:

• Sore throat

• Fever

• Cervical lymphadenopathy

• Gray-white throat exudate

• Rash

• Enlarged spleen/liver

• Severe fatigue

Lab finding:

• Leukocytosis (infected B cells then activated T cells)

Important:

• EBV is an oncovirus, increasing the risk of certain cancers.

What are hemorrhagic fevers, and how do they cause disease?

Viruses infect blood and lymphatics, damaging capillaries and disrupting clotting, causing internal/external bleeding, shock, and possible death.

Describe Ebola's reservoir, transmission, symptoms, and prevention.

• Reservoir: fruit bats

• Endemic in Africa

• Incubation: 2–21 days (average 8–10)

Early ("dry") phase:

• Fever

• Fatigue

• Muscle aches

• Headache

Late ("wet") phase:

• Vomiting

• Diarrhea

• Internal/external bleeding

• Shock

Transmission:

• Body fluids only

• Not airborne

• Contagious only after symptoms begin

Prevention:

• Isolation

• PPE

• Safe handling of body fluids

• Safe burials

Compare Yellow Fever and Dengue Fever.

Yellow Fever

• Africa & South America

• Aedes mosquito

Dengue Fever

• Southeast Asia

• India

• Caribbean

• Central & South America

• Aedes mosquito

Match each disease with its key organism/vector and hallmark.

Disease	Key Association
Malaria	Plasmodium → Anopheles mosquito → cyclic fever & anemia
Acute Endocarditis	Staphylococcus aureus
Subacute Endocarditis	Damaged valves + dental procedures + biofilms
Sepsis	SIRS + Infection
Septic Shock	DIC + ARDS + MODS
Plague	Yersinia pestis → flea bites → buboes
Mono	Epstein-Barr virus → kissing disease → fatigue
Ebola	Body fluids only (not airborne)
Yellow Fever	Aedes mosquito
Dengue Fever	Aedes mosquito
Janeway lesions	Painless
Osler nodes	Painful