Communicable Diseases Overview

Communicable Diseases

• Pathogens include viruses, bacteria, protists, and fungi. These microorganisms cause infectious diseases. They infect plants and animals, often spreading through direct contact, water, or air.

Viruses

• Viruses are very small.
• They infect host cells and replicate inside them, often thousands of times, replicating their DNA and protein coats to make new viruses.
• This leads to cell bursting and the release of new viruses into the bloodstream. This damages the host.

Bacteria

• Bacteria are small.
• They multiply rapidly through a process called binary fission.
• They produce toxins that damage cells.

Protists

• Some protists are parasitic, harming animals and humans.
• They live inside their host, often causing damage.

Fungi

• Fungi can be single-celled or made of thread-like structures (hyphae).
• They produce spores, which spread to other organisms.

How Diseases Spread

• Direct contact (e.g., touching, kissing).
• Contact with contaminated surfaces.
• Droplet infection (e.g., coughing, sneezing).
• By water (drinking contaminated water).

Reducing Disease Damage

• Improve hygiene practices like handwashing and disinfection.
• Reduce contact with infected individuals.
• Vaccinations create immunity using weakened pathogens.

Viral Diseases

• Some viral diseases like measles cause dangerous symptoms such as fever, rash, and complications like blindness and brain infections.
• These viruses spread through droplets produced by coughing or sneezing.
• Vaccinations can help prevent these spread.

Other Diseases

• Diseases like Salmonella include fever, abdominal cramps, vomiting, and diarrhea; spread through contaminated food
• Gonorrhea has symptoms like thick discharge and pelvic pain; transmission is through sexual contact.
• Athlete's foot causes itchy scaly rash between toes, spreading via direct contact.
• Rose black spot causes dark spots on plant leaves, reducing growth; spread by wind.
• Malaria is a protist disease with severe fever caused by protists multiplying in blood cells, spread via mosquitoes; prevention involves mosquito control.

Human Defense Systems

• Human defense systems prevent pathogens from entering the body.
• Skin acts as a physical barrier.
• The nose stops particles from entering the lungs.
• Hydrochloric acid in the stomach kills pathogens.
• The immune system (white blood cells) has phagocytosis, where white blood cells engulf and digest pathogens.

Antibodies and Antitoxins

• Antibodies attach to antigens on pathogens, often causing pathogens to clump together.
• Antitoxins are chemicals that neutralize the effects of toxins produced by pathogens.

Drug Testing

• New drugs must undergo testing to evaluate their safety and effectiveness. Tests for:
  • Safety: Side effects.
  • Efficacy: Effectiveness against diseases.
  • Dosage: Optimal quantity

Stages of Testing

• Pre-clinical trials: Testing on cell cultures and animals.
• Animal testing: Testing on animals.
• Human clinical trials: Testing on healthy volunteers; increasing dosage.

Monoclonal Antibodies

• Monoclonal antibodies are produced by fusing antibody-producing lymphocytes with tumor cells (creating hybridomas).
• Monoclonal antibodies are identical.
• These have many uses (e.g., pregnancy tests, treating diseases).