Microbial Diseases of the Cardiovascular and Lymphatic Systems

Cardiovascular System

• Function: Transports nutrients, gases, hormones, waste.

• Components: Heart (pump), blood (transport fluid), vessels.

• Circuits: Pulmonary (lungs) & systemic (body).

Lymphatic System

• Function: Drains excess interstitial fluid, filters pathogens.

• Structures:

  • Lymph: Interstitial fluid returned to blood.

  • Lymph nodes: Contain B- and T-cells; filter lymph.

  • Organs: Spleen, thymus, bone marrow.

  • Drainage: Thoracic duct (left) & right lymphatic duct (right).

• Cells: B-cells (bone marrow), T-cells (thymus), macrophages.

🦠 Sepsis & Blood Infections

Definitions

• Bacteraemia: Bacteria in blood.

• Septicaemia: Multiplying bacteria in blood.

• Sepsis: Inflammatory response to septicaemia.

• Severe sepsis: Blood pressure drop.

• Septic shock: Uncontrollable low blood pressure.

Key Points

• Causes: Mainly bacterial, especially E. coli, MRSA.

• Pathogenesis: Cytokine storm → organ damage.

• Diagnosis:

  • NICE guidelines: blood tests, lactate, creatinine.

  • Early warning scores.

• Treatment: Antibiotics, fluid resuscitation.

🧫 Bloodstream Infections (UK Data)

• Most common cause: E. coli (rising trend).

• MRSA: Declining; still largely hospital-acquired.

• Puerperal Sepsis: Strep. pyogenes post-childbirth; early detection essential.

• Historical note: Semmelweis → Hand hygiene reduced maternal deaths.

❤ Bacterial Infections of the Heart

Endocarditis

• Types:

  • Subacute: Alpha-haemolytic streptococci

  • Acute: Staph. aureus

• Entry: Dental work, piercings, wounds.

• Symptoms: Fever, chills, weight loss, cough, heart murmur.

• Complications: Vegetations, valve destruction, emboli.

Pericarditis

• Cause: Viral (Coxsackievirus), bacterial (Staph., Pneumo), fungal.

• Symptoms: Chest pain, breathlessness, dry cough.

• Often self-limiting.

🕷 Arthropod-Borne Diseases

Plague (Yersinia pestis)

• Forms: Bubonic, septicemic, pneumonic.

• Vector: Flea (Xenopsylla cheopis), reservoir = rats.

• Treatment: Antibiotics; high mortality if untreated.

Lyme Disease (Borrelia burgdorferi)

• Vector: Ticks; reservoir = deer.

• Symptoms:

  • Early: Bull’s-eye rash, flu-like.

  • Late: Arthritis, Bell’s palsy, meningitis, myocarditis.

• Chronic issues: Fatigue, neurocognitive problems.

🧬 Viral Diseases

Epstein-Barr Virus (EBV / HHV-4)

• Causes: Glandular fever (mono), Burkitt’s lymphoma.

• Transmission: Saliva.

• Symptoms: Fatigue, swollen nodes, liver/spleen enlargement.

• Associated Cancer: Burkitt’s (endemic = EBV + malaria).

Cytomegalovirus (CMV / HHV-5)

• Transmission: Body fluids.

• Effects: Asymptomatic or mild; serious in neonates & immunocompromised.

• Congenital CMV: Hearing loss, microcephaly, learning delay.

Viral Hemorrhagic Fevers (VHFs)

• Examples: Ebola, Lassa, Marburg.

• Symptoms: Fever → bleeding, vascular collapse.

• Risk in UK: Very rare; imported cases only.

• Vaccine: Ervebo (Ebola) – highly effective.

🧫 HIV/AIDS

Virus Overview

• Retrovirus: Targets CD4+ cells (T-helper, macrophages).

• Leads to: Immune suppression → opportunistic infections.

Infection Stages

1. Acute: Flu-like illness.

2. Clinical latency: Years without symptoms; CD4 declines.

3. AIDS: Severe immunodeficiency.

Treatment

• Not curable, but treatable.

• Antiretroviral Therapy (ART): Drug combinations to suppress replication.

• PrEP: Pre-exposure prophylaxis (tenofovir + emtricitabine).

Drug Classes

• NRTIs, NNRTIs, Protease inhibitors, Fusion inhibitors, Integrase inhibitors.

🧫 Protozoan Diseases

Toxoplasmosis (Toxoplasma gondii)

• Transmission: Cat feces.

• Risk groups: Pregnant women, immunocompromised.

• Complications: Miscarriage, encephalitis, eye damage.

Malaria (Plasmodium spp.)

• Vector: Anopheles mosquito.

• Cycle: Liver → RBCs → symptoms.

• Symptoms: Cyclical fever, chills, headache, vomiting.

• Long-term: Cognitive issues, growth delay, miscarriage.