Lesson Notes By Weeks and Term v3 - Senior Secondary 1
Causes and prevention communicable diseases
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Causes and prevention communicable diseases
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Subject: Health Education
Class: Senior Secondary 1
Term: 3rd Term
Week: 2
Theme: Communicable And Non Communicable Diseases
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state causes and factors necessary for communicable diseases to occur. state how communicable diseases can be prevented
A. Definition of Communicable Diseases Communicable diseases, also known as infectious diseases, are illnesses caused by specific infectious agents or their toxic products, which are transmitted from an infected person or animal to a susceptible host, either directly or indirectly. Examples prevalent in Nigeria include malaria, typhoid, cholera, tuberculosis, measles, and HIV/AIDS. B. Causes of Communicable Diseases (Causative Agents) Communicable diseases are caused by various types of microscopic organisms, often referred to as pathogens or causative agents.
These include:
1. Bacteria: Single-celled microorganisms that can cause disease by multiplying rapidly and producing toxins. Nigerian
Examples: Typhoid Fever: Caused by Salmonella typhi, often transmitted through contaminated food and water.
Cholera: Caused by Vibrio cholerae, leading to severe diarrhoea and dehydration, common during rainy seasons in areas with poor sanitation.
Tuberculosis (TB): Caused by Mycobacterium tuberculosis, affecting the lungs primarily and spread through airborne droplets.
2. Viruses: Extremely small infectious agents that can only replicate inside the living cells of other organisms. Nigerian
Examples: Measles: Highly contagious, causing rash, fever, and cough.
Influenza (Flu): Respiratory infection.
HIV/AIDS: Human Immunodeficiency Virus, which weakens the immune system, leading to Acquired Immunodeficiency Syndrome.
Lassa Fever: Endemic in some parts of West Africa, transmitted through contact with infected rodent excreta.
3. Fungi: Eukaryotic organisms that can cause infections (mycoses) when they invade tissues. Nigerian
Examples: Ringworm (Tinea): Fungal infection of the skin, hair, or nails.
Candidiasis: Yeast infection, often affecting mucous membranes.
4. Protozoa: Single-celled eukaryotic organisms that can be parasitic. Nigerian
Examples: Malaria: Caused by Plasmodium parasites, transmitted by the female Anopheles mosquito. A major health problem in Nigeria.
Amoebiasis: Caused by Entamoeba histolytica, leading to dysentery.
5. Parasitic Worms (Helminths): Multicellular organisms that live as parasites in the human body. Nigerian
Examples: Ascariasis (Roundworm): Caused by Ascaris lumbricoides, transmitted through contaminated soil.
Schistosomiasis (Bilharzia): Caused by Schistosoma species, transmitted through contact with contaminated water containing infected snails. C. Factors Necessary for Communicable Diseases to Occur (The Epidemiological Triad) For a communicable disease to occur and spread, three main factors must interact: the agent, the host, and the environment. This is often represented as the "Epidemiological Triad."
1. Causative Agent: This refers to the pathogen (bacteria, virus, fungi, protozoa, worm) responsible for the disease. Characteristics influencing disease occurrence: Virulence: The severity of the disease the agent can cause.
Pathogenicity: The ability of the agent to cause disease.
Infectivity: The ability of the agent to invade and multiply in a host.
Antigenicity: The ability of the agent to stimulate an immune response in the host.
Dose: The amount of the agent required to cause infection.
Resistance: The agent's ability to survive in various conditions or resist drugs. Nigerian Context
Example: A highly virulent strain of Vibrio cholerae in contaminated water (high dose) will likely cause a severe cholera outbreak.
2. Host: This is the person or animal that harbours the infectious agent. Characteristics influencing disease susceptibility: Age: Infants and elderly are often more susceptible (e.g., measles in children).
Immunity: Previous exposure or vaccination status (e.g., vaccinated individuals are less likely to contract measles).
Nutritional Status: Malnourished individuals have weakened immune systems (e.g., higher susceptibility to tuberculosis).
Genetic Predisposition: Some individuals may be genetically more resistant or susceptible to certain diseases.
Lifestyle: Smoking, drug use, sexual behaviour (e.g., HIV/AIDS).
Co-morbidities: Presence of other diseases (e.g., diabetes increases susceptibility to infections). Nigerian Context
Example: A child in a rural Nigerian community, unvaccinated against measles and malnourished, is a highly susceptible host.
3. Environment: This encompasses all external factors that influence the agent's survival, the host's exposure, and the transmission of the disease. Characteristics influencing disease transmission: Physical Environment: Climate (temperature, humidity, rainfall - e.g., malaria transmission increases during rainy season), geography, availability of clean water, sanitation facilities.
Biological Environment: Presence of vectors (e.g., mosquitoes for malaria, rats for Lassa fever), animal reservoirs, population density. * Socioeconomic Environment: Poverty, poor housing, illiteracy, lack of access to healthcare, cultural practices (e.g., open against measles and malnourished, is a highly susceptible host.
3. Environment: This encompasses all external factors that influence the agent's survival, the host's exposure, and the transmission of the disease. Characteristics influencing disease transmission: Physical Environment: Climate (temperature, humidity, rainfall - e.g., malaria transmission increases during rainy season), geography, availability of clean water, sanitation facilities.
Biological Environment: Presence of vectors (e.g., mosquitoes for malaria, rats for Lassa fever), animal reservoirs, population density.
Socioeconomic Environment: Poverty, poor housing, illiteracy, lack of access to healthcare, cultural practices (e.g., open defecation contributing to cholera spread, cultural beliefs hindering vaccination). Nigerian Context
Example: An urban slum in Lagos characterized by overcrowding, inadequate waste disposal, and contaminated water sources provides an ideal environment for cholera outbreaks. D. Modes of Transmission (How Communicable Diseases Spread) Understanding how diseases spread is critical for effective prevention.
1. Direct Contact: Person-to-person: Physical contact such as touching, kissing, sexual intercourse (e.g., STIs like HIV, gonorrhoea), skin-to-skin contact (e.g., ringworm, scabies).
Droplet spread: Expulsion of infectious droplets from respiratory tract during coughing, sneezing, talking, which travel a short distance and land on mucous membranes of a susceptible host (e.g., influenza, common cold, measles, tuberculosis).
Animal-to-person: Bites or scratches from infected animals (e.g., rabies). Nigerian Context
Example: A child with measles coughing directly on an unvaccinated sibling.
2. Indirect Contact: Fomites: Contaminated inanimate objects such as doorknobs, toys, handkerchiefs, shared cutlery (e.g., common cold, conjunctivitis).
Vehicle-borne: Contaminated inanimate substances (vehicles) like food, water, blood, drugs.
Food-borne: Consuming contaminated food (e.g., typhoid, food poisoning).
Water-borne: Drinking contaminated water (e.g., cholera, giardiasis).
Blood-borne: Transfusion of contaminated blood, sharing needles (e.g., HIV, Hepatitis B). Nigerian Context
Example: A street hawker selling peeled oranges exposed to flies or washed with unclean water, leading to typhoid.
3. Airborne Transmission: Infectious agents suspended in the air over longer distances and for longer periods than droplets, usually as droplet nuclei (evaporated remnants of droplets) or dust particles (e.g., tuberculosis, measles, chickenpox). Nigerian Context
Example: Sharing a poorly ventilated room with an active TB patient.
4. Vector-borne Transmission: Infectious agents transmitted by living organisms (vectors), usually arthropods, which carry the pathogen from an infected host to a susceptible one.
Mechanical vector: Carries the pathogen on its body parts (e.g., flies carrying cholera bacteria from faeces to food).
Biological vector: The pathogen multiplies or develops within the vector before transmission (e.g., Anopheles mosquito for malaria, tsetse fly for sleeping sickness). Nigerian Context
Example: The Anopheles mosquito transmitting malaria parasites from an infected person to a healthy one. E. Prevention of Communicable Diseases Prevention strategies aim to break the chain of infection at any point (agent, host, environment, transmission).
1. Strengthening Host Resistance: Immunization/Vaccination: Introducing a weakened or dead form of the pathogen or its toxins into the body to stimulate the immune system to produce antibodies.
Nigerian Context: The National Programme on Immunization (NPI) provides vaccines for diseases like measles, polio, diphtheria, whooping cough, tetanus, tuberculosis (BCG), and Hepatitis
B. Parents should ensure children complete their immunization schedule.
Improved Nutrition: A balanced diet strengthens the immune system, making individuals less susceptible to infections (e.g., consuming fruits, vegetables, protein sources readily available in Nigeria).
Healthy Lifestyle: Regular exercise, adequate rest, and avoiding harmful substances like tobacco and excessive alcohol.
2. Controlling the Environment and Breaking Transmission: Personal Hygiene: Handwashing: Frequent and thorough handwashing with soap and clean water, especially before eating, after using the toilet, and after coughing or sneezing.
Food Hygiene: Washing fruits and vegetables thoroughly, cooking food properly, storing food safely, avoiding raw or undercooked foods, using clean utensils and water for food preparation.
Water Hygiene: Boiling drinking water, using water filters, treating water with chlorine tablets, sourcing water from safe and clean sources (boreholes, treated tap water).
Body Hygiene: Regular bathing, changing clothes, maintaining oral hygiene.
Environmental Sanitation: Proper Waste Disposal: Regular and safe disposal of household and community waste (e.g., using covered bins, community waste collection, avoiding open dumping).
Adequate Sewage and Excreta Disposal: Using flush fruits and vegetables thoroughly, cooking food properly, storing food safely, avoiding raw or undercooked foods, using clean utensils and water for food preparation.
Water Hygiene: Boiling drinking water, using water filters, treating water with chlorine tablets, sourcing water from safe and clean sources (boreholes, treated tap water).
Body Hygiene: Regular bathing, changing clothes, maintaining oral hygiene.
Environmental Sanitation: Proper Waste Disposal: Regular and safe disposal of household and community waste (e.g., using covered bins, community waste collection, avoiding open dumping).
Adequate Sewage and Excreta Disposal: Using flush toilets or well-maintained pit latrines; avoiding open defecation.
Vector Control: Mosquitoes: Sleeping under insecticide-treated nets (ITNs), draining stagnant water, clearing bushes, indoor residual spraying.
Flies: Covering food, proper waste disposal.
Rodents: Trapping, proper food storage, good sanitation to deny them food and shelter.
Isolation and Quarantine: Isolation: Separating sick individuals from healthy ones to prevent disease spread (e.g., isolating a Lassa fever patient).
Quarantine: Restricting the movement of healthy individuals exposed to a communicable disease for a period to observe for symptoms and prevent further spread (e.g., during an Ebola outbreak).
Health Education and Awareness: Educating the public about disease causes, transmission, and prevention methods. This is crucial in Nigeria for behaviour change.
Safe Sexual Practices: Abstinence, fidelity, and consistent use of condoms to prevent sexually transmitted infections like HIV/AIDS, syphilis, and gonorrhoea.
3. Controlling or Eliminating the Causative Agent: Early Diagnosis and Treatment: Identifying and treating infected individuals promptly reduces the reservoir of infection and prevents further transmission (e.g., prompt treatment of malaria, TB, or typhoid).
Antibiotics/Antivirals: Appropriate use of medications to kill or inhibit the growth of pathogens. Introduction (10 minutes)
Teacher Activity: Begins by asking students to name some common illnesses they or people they know have experienced (e.g., malaria, cough, diarrhoea). Leads a brief discussion on whether these illnesses can "spread" from one person to another. Introduces the term "communicable diseases" and states the lesson objectives.
Student Activity: Students brainstorm and share names of common illnesses. Participate in the discussion, attempting to identify which diseases are "spreadable." Development: Key Concepts (40 minutes)
Activity 1: Understanding Causative Agents (15 minutes)
Teacher Activity: Explains the different types of causative agents (bacteria, viruses, fungi, protozoa, worms) using Nigerian examples for each. May use charts or diagrams of microorganisms if available. Asks students to identify one common disease in Nigeria for each agent type.
Student Activity: Students listen, take notes, and identify common Nigerian diseases associated with each causative agent. They may share personal experiences with such diseases or knowledge from their communities.
Activity 2: The Epidemiological Triad (20 minutes)
Teacher Activity: Introduces the concept of the Epidemiological Triad (Agent, Host, Environment) as necessary factors for disease occurrence. Explains each component in detail, linking it to the Nigerian context (e.g., a malnourished child as a host, poor sanitation as an environmental factor, Plasmodium as an agent). Draws a simple diagram of the triad on the board.
Student Activity: Students draw the Epidemiological Triad. In pairs or small groups, they discuss and provide one Nigerian example for how each component contributes to a specific disease (e.g., how the Salmonella typhi agent, a non-immune host, and contaminated water environment lead to typhoid). Groups share their examples.
Activity 3: Modes of Transmission (15 minutes)
Teacher Activity: Explains the different modes of transmission (direct, indirect, airborne, vector-borne, vehicle-borne) with relevant Nigerian examples. May ask students how malaria is spread to introduce vector-borne transmission.
Student Activity: Students listen and take notes. In pairs, they discuss how diseases like cholera or measles are transmitted and identify the mode of transmission. They share their answers.
Development: Prevention Strategies (30 minutes)
Activity 4: Preventing Communicable Diseases (25 minutes)
Teacher Activity: Guides a discussion on various prevention strategies, categorizing them under strengthening host resistance, controlling the environment/breaking transmission, and controlling the agent. Emphasizes practical applications relevant to Nigerian homes and communities (e.g., handwashing before eating fufu, ITN use). Uses a "think-pair-share" approach for each category.
Student Activity: Students participate in the discussion. In pairs, they list practical ways they can prevent specific diseases (e.g., malaria, cholera, common cold) at home and in school. They share their lists with the class. The class compiles a comprehensive list of prevention strategies on the board.
Conclusion (10 minutes)
Teacher Activity: Reviews the key concepts of causes, factors, and prevention methods. Addresses any lingering questions. Assigns independent practice.
Student Activity: Ask clarifying questions. Prepare for independent practice.
Materials: Whiteboard/Chalkboard and markers/chalk Charts or diagrams illustrating microorganisms, disease transmission, or prevention methods (if available). Handouts (optional) Pictures or examples of good hygiene practices (e.g., handwashing steps).
Community Health Campaigns: The knowledge from this lesson directly relates to public health campaigns conducted by the Nigerian government and NGOs. Students can participate in or initiate awareness campaigns in their communities on topics like handwashing, proper waste disposal, and the importance of immunization, especially during disease outbreaks (e.g., cholera, Lassa fever). They can design posters or simple jingles to educate others.
Household Practices and Family Health: Students can apply prevention strategies directly in their homes. For instance, ensuring family members wash hands before meals, proper storage and preparation of food, use of insecticide-treated nets, and timely seeking of medical attention for symptoms of illness. This reduces the burden of disease within their families, saving healthcare costs and improving productivity.
Environmental Stewardship: Understanding the role of the environment in disease spread motivates students to take responsibility for their surroundings. This includes participating in community clean-up exercises, advocating for better sanitation facilities, and understanding the impact of climate change on vector-borne diseases (e.g., increased rainfall leading to more mosquito breeding sites). This fosters a sense of civic responsibility and promotes sustainable health practices.