Communicable Diseases Overview

Communicable Diseases

• Communicable diseases are illnesses spread from one organism to another, caused by pathogens.
• Non-communicable diseases are not infectious.

Types of Pathogens

• Four main types: bacteria, viruses, fungi, and protists.

How Pathogens Spread

• Airborne: Spread via coughs, sneezes (e.g., flu, tuberculosis).
• Direct Contact: Spread through skin or sexual contact (e.g., HIV, athlete's foot).
• Water and Food: Contaminated water or food (e.g., cholera, salmonella).
• Vectors: Insects carrying pathogens (e.g., mosquitoes and malaria).

Examples of Communicable Diseases

Bacterial Diseases

• Salmonella (Food Poisoning): Spread by contaminated food; symptoms include fever, vomiting, diarrhea; prevention includes good food hygiene and poultry vaccination.
• Gonorrhea (STD): Spread by sexual contact; symptoms include painful urination and thick discharge; prevention includes condoms and antibiotics (though antibiotic resistance is increasing).

Viral Diseases

• Measles: Spread by droplets from coughs and sneezes; symptoms include fever, rash, and potential complications like pneumonia or brain infections; prevention is via the MMR vaccine.
• HIV (Human Immunodeficiency Virus): Spread by bodily fluids (unprotected sex, needle sharing); symptoms begin as flu-like, progressing to AIDS (weakened immune system); prevention includes condoms and antiretroviral drugs.

Fungal Diseases

• Rose Black Spot (plants): Spread by water or wind; symptoms include spots on leaves, affecting photosynthesis; treatment involves fungicides and removing infected leaves.
• Athlete's Foot (humans): Spread by direct contact, often in damp environments; symptoms are itchy, flaky skin, commonly between toes; prevention includes keeping feet dry and using antifungal creams.

Protist Diseases

• Malaria: Spread by mosquitoes (a vector); symptoms include recurring fevers and fatigue, potentially fatal; prevention includes mosquito nets, insect repellent, and antimalarial drugs.

Body's Defense Mechanisms

• Skin: Physical barrier against pathogens.
• Nose Hairs & Mucus: Trap microbes.
• Stomach Acid: Kills bacteria.
• White Blood Cells:
  • Phagocytosis: Engulf and destroy pathogens.
  • Antibody Production: Target specific pathogens.
  • Antitoxin Production: Neutralize bacterial toxins.

Preventing and Treating Communicable Diseases

• Vaccination: Stimulates the immune system to fight pathogens.
• Good Hygiene: Washing hands, sanitizing surfaces.
• Quarantine & Isolation: Prevents the spread of infection.
• Antibiotics: Kill bacteria (don't work on viruses).
• Antiviral Drugs: Slow down viral replication.
• Fungicides: Kill fungal infections.
• Vector Control: Reducing insect populations (e.g., draining stagnant water to stop mosquitoes).

Vaccination

• Vaccines use a weakened or inactive form of the pathogen to trigger an immune response.
• The immune system creates antibodies and memory cells.
• Memory cells provide faster, stronger protection against future infections.

Herd Immunity

• High vaccination rates make it harder for diseases to spread.
• Protects vulnerable individuals who cannot be vaccinated.

Antibiotic Resistance

• Overuse of antibiotics leads to bacteria evolving resistance.
• Examples like MRSA (Methicillin-Resistant Staphylococcus Aureus) are problematic.

Practical Investigation

• Investigating the effect of disinfectants and antibiotics on bacterial growth involves measuring the zone of inhibition.
• A larger zone indicates greater effectiveness.

Key Points Summary

• Communicable diseases have various causes (bacteria, viruses, fungi, protists).
• Pathogens spread through various methods.
• The body has defense mechanisms against pathogens.
• Vaccination is a vital preventative measure.
• Antibiotic resistance is an important issue.
• Practical investigations help assess the effectiveness of disease treatments.