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.