Definition:
A pathogen is a microscopic organism, such as a virus, bacterium, fungus, or parasite, capable of causing disease in its host.
Transmissible Disease:
Transmissible diseases are those that can spread from one individual to another. Common modes of transmission include direct contact, airborne particles, contaminated surfaces, and vectors like mosquitoes.
Pathogen Transmission:
(a) Direct Contact: Spread through bodily fluids like blood, saliva, or through physical touch.
(b) Indirect Transmission: Occurs via contaminated surfaces, food, water, air, or through animal vectors.
Body’s Barriers to Pathogen Entry:
- Skin: Acts as a physical barrier.
- Nasal Hairs: Trap particles in the air.
- Mucus: Traps and removes pathogens.
- Stomach Acid: Kills many ingested pathogens.
Mosquito as a Vector:
Mosquitoes can transmit diseases like malaria and dengue fever through their bites, introducing pathogens into the host’s bloodstream.
Malaria Pathogen:
The malaria pathogen is a Plasmodium parasite transmitted through the saliva of infected mosquitoes. Once in the bloodstream, it travels to the liver and then infects red blood cells.
Mosquito Control for Malaria:
Controlling the mosquito involves disrupting its life cycle, targeting breeding sites like stagnant water, and using insecticides to reduce mosquito populations.
HIV (Human Immunodeficiency Virus):
HIV attacks the immune system, weakening the body’s ability to fight infections. It is transmitted through unprotected sex, sharing needles, and from mother to child during childbirth or breastfeeding.
AIDS (Acquired Immune Deficiency Syndrome):
AIDS is the advanced stage of HIV infection, characterised by a severely compromised immune system, making the individual susceptible to opportunistic infections.
HIV Control Methods:
Prevention involves safe practices, condom use, needle exchange programs, antiretroviral therapy (ART), and public awareness campaigns.
Cholera:
Cholera is caused by the bacterium Vibrio cholerae and is often transmitted through contaminated water or food. It leads to severe diarrhoea and dehydration, requiring prompt medical intervention and rehydration therapy.
Importance of Controlling Cholera Spread:
- Clean Water Supply: Prevents ingestion of contaminated water.
- Hygienic Food Preparation: Reduces the risk of food contamination.
- Good Personal Hygiene: Minimizes person-to-person transmission.
- Waste Disposal: Prevents environmental contamination.
- Sewage Treatment: Aids in eliminating pathogens, reducing waterborne transmission.
Cholera Toxin and its Effects:
- The cholera bacterium produces a toxin.
- This toxin induces the secretion of chloride ions into the small intestine.
- Osmotic movement of water into the gut occurs, leading to:
- Diarrhea: Frequent, watery bowel movements.
- Dehydration: Loss of water from the body.
- Loss of Ions: Electrolyte imbalance, affecting blood composition.
Effects of Excessive Alcohol Consumption:
- Reduced Self-Control: Impairs decision-making and judgment.
- Depressant: Slows down the central nervous system.
- Effect on Reaction Times: Slower reflexes and response times.
- Liver Damage: Chronic alcohol use can lead to liver diseases.
- Social Implications: Impact on relationships, work, and overall well-being.
Effects of Tobacco Smoke and Toxic Components:
- Nicotine: Highly addictive substance.
- Tar: Causes respiratory issues, leading to bronchitis and emphysema.
- Carbon Monoxide: Reduces oxygen-carrying capacity, straining the heart.
- Associations:
- Bronchitis: Inflammation of the bronchial tubes.
- Emphysema: Damage to lung tissue, reducing elasticity.
- Lung Cancer: Strongly linked to tobacco smoke.
- Heart Disease: Increased risk due to cardiovascular strain.
- Smoking During Pregnancy: Associated with reduced birth weight and potential developmental issues in infants.
Drug Definition:
A drug is any substance taken into the body that modifies or affects chemical reactions within the body.
Use of Antibiotics for Bacterial Infections:
Antibiotics are substances that inhibit the growth of or kill bacteria, and they are used to treat bacterial infections. They work by targeting specific components or processes in bacteria, disrupting their ability to survive and replicate.
Antibiotics and Viruses:
Antibiotics are effective against bacteria but do not have an impact on viruses. Viral infections, such as the common cold or flu, are not treated with antibiotics. Viruses have different structures and processes that antibiotics cannot target.
Minimizing Antibiotic-Resistant Bacteria (e.g., MRSA):
- Selective Use: Antibiotics should only be prescribed when necessary, avoiding misuse or overuse.
- Completing Courses: Patients should complete the entire prescribed antibiotic course, even if symptoms improve, to eliminate all bacteria.
- Proper Diagnosis: Ensure accurate identification of bacterial infections before antibiotic prescription.
- Preventative Measures: Emphasize preventive strategies like vaccinations and hygiene to reduce the need for antibiotics.
- Public Awareness: Educate the public, healthcare providers, and policymakers about the risks of antibiotic resistance and the responsible use of antibiotics.
Immunity
Active Immunity:
- Active immunity involves the defense against a pathogen through the production of antibodies within the body.
Pathogen Antigens:
- Each pathogen has distinct antigens with specific shapes that trigger an immune response.
Antibodies and Pathogen Defense:
- Antibodies are proteins that bind to antigens, leading to direct destruction of pathogens or marking them for destruction by phagocytes.
Antibody-Antigen Specificity:
- Specific antibodies have complementary shapes that precisely fit specific antigens.
Active Immunity Acquisition:
- Active immunity is gained after an infection by a pathogen or through vaccination.
Vaccination Process:
(a) Weakend pathogens or their antigens are administered.
(b) Antigens stimulate an immune response by lymphocytes, leading to antibody production.
(c) Memory cells are generated, providing long-term immunity.
Role of Vaccination:
Vaccination helps control the spread of transmissible diseases by promoting immunity in individuals, reducing the severity of illness, and preventing outbreaks.
Passive Immunity:
Passive immunity is a short-term defense against a pathogen through acquired antibodies, such as those passed across the placenta or present in breast milk.
Importance of Breastfeeding:
Breastfeeding is crucial for developing passive immunity in infants as it provides them with maternal antibodies, enhancing their defense against infections.
Memory Cells in Passive Immunity:
Memory cells are not produced in passive immunity, leading to a temporary defense.
HIV and the Immune System:
HIV decreases lymphocyte numbers and reduces the ability to produce antibodies, weakening the immune system. This compromises the body’s ability to defend against infections and diseases.
