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Eukaryotes and Fungal Diseases

Eukaryotic Diseases

Mycoses: Fungal Infections

  • Definition: Mycoses refer to fungal infections affecting humans or animals.
  • Types of Transmission:
    • Ingestion: Consumption of contaminated food or water.
    • Vector Transmission: Spread through organisms acting as carriers.
    • Direct Skin Contact: Physical contact with contaminated surfaces.
    • Inhalation: Breathing in fungal spores.
  • Contagious Mycoses:
    • Most mycoses are not contagious, with dermatophytes (e.g., ringworm) being an exception.

Fungal Diseases

Clinical Manifestations:

  • Types of Mycoses:
    • Superficial: Affecting the outer layers of skin, hair, and nails.
    • Subcutaneous: Penetrate deeper into the skin but usually localized.
    • Systemic: Infections that spread throughout the body, more serious.

Examples of Systemic Mycoses:

  • Histoplasmosis: Caused by Histoplasma capsulatum.
    • Transmission: Inhalation of spores from soil enriched by bat or bird droppings.
  • Blastomycosis: Caused by Blastomyces dermatitidis.
  • Coccidioidomycosis: Caused by Coccidioides immitis.
    • Characteristics: Dimorphic fungi that exist as molds in soil.

Common Fungal Pathogens Encountered:

  1. Aspergillus
  2. Candida
    • Candida albicans: Can lead to opportunistic infections such as thrush or vaginal yeast infections.
  3. Cryptococcus
    • Cryptococcus neoformans: Causes pneumonia or meningitis, particularly in immunocompromised individuals.
  4. Dermatophytes:
    • Cause skin infections (e.g. Athlete's foot, ringworm)

Mycotoxicosis and Mycetismus

  • Mycotoxicosis: Poisoning caused by fungal toxins present in food.
  • Mycetismus: Poisoning from consuming toxic mushrooms.
  • Health Impacts:
    • Can trigger allergic responses due to fungal spores or metabolites.

Diagnostic and Prognostic Details

  • Diagnosis: Often involves identifying yeast forms in clinical specimens and considering exposure history.

Vector-Borne Fungal Diseases

Key Example: Ergotism

  • Cause: Due to the fungus Claviceps purpurea found in grains and cereals.
  • Symptoms: Can lead to hallucinations and gangrene due to vasoconstriction.

Protozoal Diseases

Key Diseases and Causes

  • Dysentery: Severe diarrhea with blood, often caused by Entamoeba histolytica.
    • Transmission: Contaminated food/water; fecal-oral route.
  • Trichomoniasis: Caused by Trichomonas vaginalis, a sexually transmitted protozoan.

Implications on Human Health

  • Dysentery claims ~100K lives annually in untreated areas.

Viral Diseases

Animal Viruses

  • HIV (Human Immunodeficiency Virus): Leads to AIDS, affecting the immune system chronicity.
  • Prion Diseases: Neurodegenerative diseases caused by protein misfolding.
    • Examples: Creutzfeldt-Jakob disease, Kuru, Bovine Spongiform Encephalopathy.

Drug Treatments

  • Antiviral Drugs: Targets specific stages of viral replication cycle.
  • Vaccination: Generally more effective for prevention compared to treatments post-infection.

Bacterial Diseases

  • Antibiotics: Standard treatment for bacterial infections, not effective against viruses.

Key Points on Specific Viruses

  • Herpes Simplex Virus (HSV): Can lead to cold sores or genital herpes, remains latent in the body.
  • Varicella Zoster Virus (VZV): Causes chickenpox and can reactivate as shingles.
  • Ebola: High mortality rate; direct contact transmission from infected individuals or animals.
  • Influenza: Seasonal epidemic, managed with vaccines.

Summary of Non-Viral Infectious Agents

Vaccine Development Challenges

  • Fungi share similarities with human cells, complicating vaccine development.
  • Important fungal pathogens are often not life-threatening if the host has a healthy immune response, yet can be serious in immunocompromised patients.