Infectious Diseases Manifesting in the Cardiovascular and Lymphatic Systems: Microbiology Study Notes

Chapter 21: Infectious Diseases Manifesting in the Cardiovascular and Lymphatic Systems

Overview

This chapter explores the anatomy, defenses, and infectious diseases affecting the cardiovascular and lymphatic systems. It covers causative agents, transmission modes, symptoms, diagnosis, prevention, treatment, and epidemiology of major diseases.

Anatomical Features of the Cardiovascular and Lymphatic Systems

Cardiovascular System

• Heart: Central organ pumping blood through arteries (oxygen/nutrients) and veins (CO2/waste).

• Blood Vessels: Arteries, veins, capillaries; facilitate exchange of gases, nutrients, and waste.

• White Blood Cells (WBCs): Macrophages, neutrophils, basophils, eosinophils; key players in immune response.

Key Terms:

• Viremia: Viruses in the blood (e.g., meningitis-causing viruses).

• Fungemia: Fungi in the blood.

• Bacteremia: Presence of bacteria in the blood.

• Septicemia: Bacteria flourishing and growing in the bloodstream.

Lymphatic System

• Source of Immune Cells: Lymphocytes (B cells, T cells, NK cells).

• Organs: Lymph nodes, tonsils, spleen, thymus, bone marrow.

• Functions: Immune surveillance, filtration of lymph, production of immune cells.

Natural Defenses of the Cardiovascular and Lymphatic Systems

• Innate Immunity: Non-specific defense mechanisms (e.g., phagocytosis by macrophages).

• Adaptive Immunity: Specific immune responses (e.g., antibody production by B cells).

Normal Biota

• Microorganisms may be present, but there is no established normal microbiome.

• Low-level microbial "infections" may contribute to diseases with no clear infectious cause.

Major Infectious Diseases of the Cardiovascular and Lymphatic Systems

Endocarditis

Endocarditis is the inflammation of the inner lining of the heart (endocardium), often affecting heart valves.

• Acute: Rapid onset, severe symptoms.

• Subacute: Gradual onset, milder symptoms (fever, anemia, abnormal heartbeat, chills, Osler's nodes, Janeway lesions).

Disease	Causative Organism(s)	Transmission	Diagnosis	Prevention	Treatment	Distinctive Features	Epidemiology
Acute Endocarditis	Staphylococcus aureus, Streptococcus pyogenes, S. pneumoniae, Enterococcus, Pseudomonas aeruginosa	Parenteral	Blood culture	Aseptic surgery, injections	Vancomycin, surgery	Acute onset, high fatality	Increased incidence
Subacute Endocarditis	Alpha-hemolytic streptococci, others	Endogenous transfer	Blood culture	Prophylactic antibiotics	Broad-spectrum antibiotics, surgery	Slower onset	N/A

Sepsis and Endotoxic Shock

Sepsis is a life-threatening condition caused by the body's response to infection, leading to tissue damage and organ failure. Endotoxic shock is a severe form of sepsis due to gram-negative bacteria releasing endotoxins.

• Active multiplication of organisms in blood.

• Loss of blood pressure, respiratory alkalosis, altered mental state, chills, GI symptoms.

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
Bacteria or fungi	Parenteral, endogenous transfer	Cell wall/membrane components	Blood culture, sequencing	N/A	Broad-spectrum antibiotics, susceptibility testing	1.7 million cases, 270,000 deaths/year (US)

COVID-19

COVID-19 is caused by SARS-CoV-2, affecting multiple organ systems including the cardiovascular system.

• Transmission: Droplet, airborne

• Virulence: Attachment to ACE-2, induction of autoimmunity

• Diagnosis: RT-PCR, antibody/antigen tests

• Prevention: Vaccines, mitigation

• Treatment: Antivirals (e.g., paxlovid™)

• Epidemiology: Global spread

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
SARS-CoV-2	Droplet, airborne	ACE-2 attachment, autoimmunity	RT-PCR, Ab/Ag tests	Vaccine, mitigation	Antivirals	Worldwide

The Plague (Bubonic Plague)

Bubonic plague is a zoonotic disease caused by Yersinia pestis, transmitted by fleas and direct contact.

• Symptoms: Buboes, septicemia, pneumonia

• Mortality: 30-50% with treatment, 100% without

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
Yersinia pestis	Flea vector, droplet, direct contact	Capsule, plasminogen activator	Genomic methods	Flea/animal control, vaccine	Streptomycin/ciprofloxacin	Endemic in western US, Africa; Category A bioterrorism agent

Tularemia

Tularemia is a zoonotic disease caused by Francisella tularensis, transmitted by ticks and direct contact with infected animals.

• Symptoms: Fever, chills, malaise, lymphadenopathy, pneumonia, ulceroglandular lesions

• Mortality: 30% without treatment

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
Francisella tularensis	Tick vector, direct contact, airborne	Intracellular growth	Culture, serology, lymph node aspiration	N/A	Gentamicin/streptomycin	Several hundred cases/year (US); Category A bioterrorism agent

Lyme Disease

Lyme disease is a zoonotic infection caused by Borrelia burgdorferi, transmitted by ticks.

• Symptoms: Fever, chills, headache, fatigue, joint/muscle aches, swollen lymph nodes, erythema migrans rash

• Progression: Cardiac and neurological symptoms, polyarthritis

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
Borrelia burgdorferi	Tick vector	Antigenic shifting, adhesins	Sera testing	Tick avoidance	Doxycycline/amoxicillin	25,000-30,000 cases/year (US); endemic in NA, Europe, Asia

Infectious Mononucleosis

Caused by Epstein-Barr virus (EBV), transmitted via direct/indirect contact and parenteral routes.

• Symptoms: Fatigue, fever, inflamed throat, swollen lymph nodes, enlarged spleen/liver, rash

• Distinctive Feature: Lifelong persistence

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Distinctive Features	Epidemiology
Epstein-Barr virus (EBV)	Direct/indirect contact, parenteral	Latency, host DNA incorporation	Blood count, Monospot, ELISA	N/A	Supportive	Lifelong persistence	500 cases/100,000/year (US)

Anthrax

Anthrax is a zoonotic disease caused by Bacillus anthracis, transmitted via air, soil, animal hides, and food.

• Symptoms: Cutaneous (blisters, swelling), gastrointestinal (nausea, vomiting, diarrhea), inhalation (cough, chest pain, severe respiratory distress)

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
Bacillus anthracis	Vehicle (air, soil, food), indirect contact	Triple exotoxin	Culture, fluorescent antibody	Vaccine for high-risk, antibiotics post-exposure	Consult CDC	2,000-20,000 cases/year (global); Category A bioterrorism agent

Hemorrhagic vs. Nonhemorrhagic Fevers

Hemorrhagic Fevers	Nonhemorrhagic Fevers
Agents infect blood/lymphatics Extreme fevers, internal hemorrhaging RNA enveloped viruses Aedes mosquitoes Prevalence fluctuates globally	High fever without capillary fragility Mostly bacterial, one protozoan (Babesia)

Chagas Disease

Chagas disease is caused by Trypanosoma cruzi, transmitted by triatomine bugs ("kissing bugs") and vertical transmission.

• Acute phase: Fever, tiredness, headache, body aches, diarrhea, vomiting, eyelid swelling (Romaña's sign)

• Chronic phase: Heart issues, digestive problems (enlarged esophagus/colon)

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
Trypanosoma cruzi	Triatomine bug, vertical	Antioxidant enzymes, host antigen co-opting, autoimmunity	Blood smear, serology	Insect control	Consult CDC	230,000 cases (US); endemic in Central/South America; neglected parasitic infection

Malaria

Malaria is caused by Plasmodium species, transmitted by Anopheles mosquitoes.

• Symptoms: Cyclic fever, chills, anemia, splenomegaly, cerebral symptoms

• Virulence: Multiple host stages, antigenic variation, ability to sequester in tissues

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
Plasmodium falciparum, P. vivax, P. ovale, P. malariae	Anopheles mosquito, vertical	Antigenic variation, sequestration, multiple host stages	Blood smear, serology	Mosquito control, vaccine (RTS,S)	Artemisinin-based combination therapy	300 million cases/year globally; high mortality in children

Human Immunodeficiency Virus (HIV)

HIV is a retrovirus that attacks the immune system, leading to AIDS if untreated.

• Transmission: Sexual contact, blood, vertical

• Symptoms: Pneumonia, weight loss, swollen lymph nodes

• Prevention: Barrier protection, PrEP/PEP, needle safety

• Treatment: Antiretroviral therapy (ART)

• Epidemiology: 1.2 million living with HIV in US; global pandemic

Causative Organism(s)	Transmission	Virulence Factors	Diagnosis	Prevention	Treatment	Epidemiology
HIV-1, HIV-2	Sexual, blood, vertical	Immune evasion, latency	Serology, PCR	Barrier protection, PrEP/PEP	ART	Global pandemic

Summary Table: Key Infectious Agents and Features

Disease	Causative Agent	Transmission	Key Symptoms	Prevention	Treatment
Endocarditis	Bacteria (Staph, Strep, etc.)	Parenteral, endogenous	Fever, anemia, heart issues	Aseptic techniques	Antibiotics, surgery
Sepsis	Bacteria, fungi	Parenteral, endogenous	Fever, low BP, chills	N/A	Antibiotics
COVID-19	SARS-CoV-2	Droplet, airborne	Respiratory, cardiovascular	Vaccines	Antivirals
Plague	Yersinia pestis	Flea, droplet	Buboes, fever	Flea control, vaccine	Antibiotics
Tularemia	Francisella tularensis	Tick, direct contact	Fever, ulcers	N/A	Antibiotics
Lyme Disease	Borrelia burgdorferi	Tick	Fever, rash, arthritis	Tick avoidance	Antibiotics
Mononucleosis	EBV	Contact	Fatigue, fever	N/A	Supportive
Anthrax	Bacillus anthracis	Air, soil, food	Blisters, GI, respiratory	Vaccine	Antibiotics
Chagas Disease	Trypanosoma cruzi	Triatomine bug	Fever, heart/GI issues	Insect control	Consult CDC
Malaria	Plasmodium spp.	Mosquito	Fever, anemia	Mosquito control, vaccine	Antimalarials
HIV	HIV-1, HIV-2	Sexual, blood	Immunodeficiency	Barrier, PrEP/PEP	ART

Additional info:

• Some tables and details were expanded for clarity and completeness.

• Scientific names are italicized as per academic convention.

• Key terms and concepts are defined for self-contained study.