Human Health and Disease

What is Health & Disease?

This chapter focuses on understanding Human health and disease, common human diseases, immunity mechanisms, AIDS, cancer, drug and alcohol abuse, and methods for prevention and control.

What is Health?

• Old Beliefs:
  • Early Greeks like Hippocrates and Indian Ayurveda thought health was about balancing ‘humors’ (body fluids).
  • People with ‘blackbile’ were thought to have hot personalities and fevers.
• Modern Understanding:
  • William Harvey discovered blood circulation and proved the ‘good humor’ hypothesis wrong.
  • Health is now seen as influenced by the mind, neural system, endocrine system, and immune system.

Factors Affecting Health

• Genetic Disorders: Issues inherited from parents or present at birth.
• Infections: Diseases caused by pathogens.
• Lifestyle: Food, water, rest, exercise, and habits.

Definition of Health

• Health is not just ‘absence of disease’ or ‘physical fitness’.
• It means complete physical, mental, and social well-being.
• Healthy people are more efficient and productive.
• Health increases lifespan and reduces infant and maternal deaths.

Maintaining Good Health

• Balanced diet, personal hygiene, and exercise are crucial.
• Yoga promotes physical and mental health.
• Awareness about Vaccination, diseases and their prevention is important.
• Proper waste disposal, vector (disease-carrying organisms) control, and clean food/water are needed.

What is Disease?

• Disease: when body organs/systems don’t function properly, showing signs and symptoms.
• Two types of diseases:
  • Infectious Diseases: Spread from person to person (e.g., AIDS).
  • Non-Infectious Diseases: Not spread from person to person (e.g., cancer).

Common Diseases in Humans

Pathogens

• Disease-causing organisms like bacteria, viruses, fungi, protozoans, and helminths.
• Enter the body, multiply, and interfere with normal functions.

1. Bacterial Diseases

• Typhoid Fever:
  • Pathogen (Caused by): Salmonella typhi.
  • Symptoms & Effects: High fever, weakness, stomach pain, constipation, headache, loss of appetite.
    • Intestinal perforation and death possible in severe cases.
  • Transmission: Spread through contaminated food and water.
  • Confirmatory test: Widal test confirms the disease.
  • Famous Cook Case: Mary Mallon (Typhoid Mary) was a typhoid carrier, spread typhoid through the food she prepared.
• Pneumonia:
  • Caused by: Streptococcus pneumoniae and Haemophilus influenzae.
  • Symptoms & Effects: Fever, chills, cough, headache, respiratory problems.
    • It infects lung alveoli. Alveoli get filled with fluid, causing breathing issues.
    • In severe cases, lips and nails turn grey-blue.
  • Transmission: Spread by inhaling droplets or sharing utensils with an infected person.
• Other bacterial diseases: Dysentery, plague, diphtheria, etc.

2. Viral Diseases

• Common Cold:
  • Caused by: Rhinoviruses.
  • Symptoms & Effects: Nasal congestion, discharge, sore throat, cough, headache, tiredness.
    • It infects the nose & respiratory tract but not the lungs
  • Transmission: Spread by inhaling droplets or touching contaminated objects.

3. Protozoan Diseases

• Amoebiasis (Amoebic Dysentery)
  • Caused by: Entamoeba histolytica
  • Symptoms: Constipation, abdominal pain, cramps, stools with mucus and blood clots.
  • Transmission: Houseflies transmit parasites from infected feces to food.

• Malaria:
  • Caused by: Plasmodium.
  • Symptoms: chills and high fever every 3-4 days.
  • Hosts: Humans and mosquitoes.
  • Vector: Female Anopheles mosquito.
• Types of Plasmodium:
  • Plasmodium vivax
  • Plasmodium malariae
  • Plasmodium falciparum (causes the most serious form, malignant malaria)

Life Cycle of Plasmodium

• Entry into Human Body:
  • Plasmodium enters as sporozoites (infectious form) through the bite of an infected female Anopheles mosquito.
• Multiplication in Liver:
  • Parasites multiply in liver cells.
• Attack on RBCs:
  • Parasites then attack red blood cells (RBCs), causing them to rupture.
  • The rupture releases haemozoin, a toxic substance, leading to chills and high fever every 3-4 days.
• Transmission to Mosquito:
  • When a mosquito bites an infected person, parasites enter the mosquito and develop further.
  • Parasites form sporozoites in the mosquito’s salivary glands.
• Re-infection of Humans:
  • When the mosquito bites another human, sporozoites are transferred, restarting the cycle.

Key Points

• Hosts:
  • Plasmodium requires two hosts to complete its life cycle: humans and mosquitoes.
• Vector:
  • The female Anopheles mosquito is both the host and the vector (transmitting agent).

4. Helminthic Diseases

• Ascariasis:
  • Caused by: Ascaris (roundworm).
  • Symptoms: Internal bleeding, muscle pain, fever, anemia, intestinal blockage.
  • Transmission: Spread through contaminated food and water.
• Filariasis (Elephantiasis):
  • Caused by: Filarial worms or Wuchereria (W. bancrofti, W. malayi)
  • Symptoms: Chronic inflammation, swollen lower limbs, genital deformities.
  • Transmission: Female mosquito (Culex) bites.

5. Fungal Diseases

• Ringworm:
  • Caused by: Fungi (Microsporum, Trichophyton, Epidermophyton)
  • Symptoms: Dry, scaly lesions on skin, nails, scalp with intense itching.
  • Transmission: Soil, towels, clothes, combs (personal items) of infected persons.

Prevention and Control

• Personal hygiene:
  • clean body, food, and water.
• Public hygiene:
  • proper waste disposal, cleaning water sources.
• Avoid close contact with infected persons.
• Vector Control:
  • Avoid water stagnation.
  • Clean household coolers.
  • Use mosquito nets and wire mesh on windows.
  • Introduce mosquito-eating fish like Gambusia in ponds.
  • Spray insecticides.
  • These precautions can prevent vector-borne diseases like Malaria, Filariasis, Dengue, and Chikungunya.

Advancements in Disease Control

• Vaccines:
  • Eradicated diseases like smallpox.
  • Controlled polio, diphtheria, pneumonia, tetanus.
  • New & safer vaccines being developed through biotechnology.
• Antibiotics & drugs:
  • Effective treatment for many infectious (bacterial) diseases.

Immunity

What is Immunity?

• Immunity is the body’s ability to fight/defend against disease-causing organisms.
• There are two types of immunity:
  • Innate (inborn) Immunity
  • Acquired (adaptive) Immunity

Innate Immunity

• Innate immunity is present at birth and is non-specific (defends against all pathogens equally).
• It provides barriers to prevent the entry of foreign agents:
  • Physical Barriers: Skin prevents entry of microbes. Mucus in the respiratory, gastrointestinal, and urogenital tracts traps microbes.
  • Physiological Barriers: Acid in the stomach, saliva in the mouth, and tears from eyes prevent microbial growth.
  • Cellular Barriers: White blood cells like neutrophils, monocytes, and natural killer cells destroy microbes. Macrophages in tissues also help.
  • Cytokine Barriers: Virus-infected cells release interferons (a cytokine protein) that protect other cells from viral infection.

Acquired Immunity

• Acquired immunity is pathogen-specific, developed during lifetime and has memory.
• Memory Response: The body remembers the first encounter with a pathogen and responds more strongly the next time.
  • Primary Response: The first response to a pathogen, which is weak (low intensity).
  • Secondary (Anamnestic) Response: The response to subsequent encounters, which is much stronger.
• Memory-based acquired immunity evolved to differentiate foreign organisms from self-cells.
• Primary and secondary immune responses involve B-lymphocytes (B-cells) and T-lymphocytes (T-cells).

Types of Lymphocytes

• B-Lymphocytes: Produce antibodies to fight pathogens. Antibodies are proteins that help destroy pathogens.
  • Different types of antibodies: IgA, IgM, IgE, IgG.
  • Four peptide chains (H2L2 structure): Two light chains, two heavy chains.
  • The response involving Antibodies is called Humoral (Bodily fluids) immune response/ Antibody mediated immunity (AMI).
• T-Lymphocytes: Help B-cells produce antibodies and mediate cell-mediated immune response (CMI).

Transplantation and Immune Response

• When organs fail, transplantation is needed.
• Organs cannot be taken from just anyone because the body may reject them.
• Tissue matching and blood group matching are necessary.
• Even with a match, patients must take immuno-suppressants to prevent rejection.
• The body differentiates between ‘self’ and ‘non-self’, leading to graft rejection if not matched.

Summary

Type	Description	Examples
Innate Immunity	Non-specific defense present at birth	Skin barrier, stomach acid, WBCs
Acquired Immunity	Pathogen-specific, memory-based	Antibodies from B-cells, T-cell response

Innate Immunity Barriers

Barrier Type	Examples
Physical Barriers	Skin, mucus lining
Physiological Barriers	Stomach acid, saliva, tears
Cellular Barriers	Neutrophils, monocytes, macrophages
Cytokine Barriers	Interferons

Acquired Immunity Responses

Response Type	Description	Cells Involved
Primary Response	First encounter with pathogen, low intensity	B-lymphocytes, T-cells
Secondary Response	Subsequent encounters, highly intensified	Memory B-cells, T-cells

Types of Acquired immunity

Active Immunity

• Produced when the body is exposed to antigens (like living or dead microbes or proteins).
• The body produces antibodies in response.
• It is slow and takes time to be fully effective.
• Examples: It is produced in two ways:
  1. Natural Active Immunity: Developed during natural infection (unintentional exposure) by microbes.
  2. Artificial Active Immunity: Developed by injecting microbes deliberately during immunization. e.g. Getting a vaccine (deliberate exposure).

Passive Immunity

• Ready-made antibodies or antitoxin are directly given to the body.
• Provides immediate protection.
• Examples: It is of 2 types.
  1. Natural Passive Immunity: E.g. Mother’s milk (colostrum) contains antibodies (IgA) that protect newborns.
     • Antibodies (IgG) are also passed from mother to fetus through the placenta.
  2. Artificial Passive Immunity: E.g. Anti-tetanus serum (ATS), Anti-venom serum.

Summary

Type	Description	Examples
Active Immunity	Host produces antibodies in response to antigens	Vaccination, natural infection
Passive Immunity	Ready-made antibodies are introduced into the body	Antitoxins, maternal antibodies (colostrum)

Vaccination and Immunisation

Principle of Vaccination

• Principle: Based on the immune system’s memory.
• Vaccination:
  • Vaccines contain weakened or inactivated pathogens or their antigenic proteins.
  • The body produces antibodies against these antigens.
  • Memory cells (B and T cells) recognize the pathogen quickly in the future when actual infection occurs, and then antibodies neutralize antigens.
  • E.g. Polio vaccine, Hepatitis B vaccine, DPT vaccine etc.

Examples of Immunisation

• Passive Immunisation:
  • Tetanus: Preformed (readymade) antibodies or antitoxins are injected for quick response.
  • Snakebites: Injection contains preformed antibodies against the venom.
• Recombinant DNA Technology
  • Produces vaccines by creating antigenic polypeptides in bacteria or yeast.
  • Allows large-scale production.
  • Example: Hepatitis B vaccine made from yeast.

Summary

Type	Description	Examples
Vaccination	Introduction of antigenic proteins/weakened pathogens to generate memory cells	Polio vaccine, measles vaccine
Passive Immunisation	Injection of preformed antibodies or antitoxins	Tetanus antitoxin, snakebite antivenom
Recombinant DNA Vaccine	Vaccines produced using genetically engineered antigens	Hepatitis B vaccine

Allergies

• What are allergies?
  • An exaggerated response of the immune system to certain substances called allergens (like Dust mites, pollen, animal dander, etc).
• Symptoms:
  • Sneezing, watery eyes, runny nose, difficulty in breathing.
• Cause:
  • The antibodies produced against allergens are of the IgE type.
  • Allergens & IgE trigger the release of chemicals like histamine and serotonin from mast cells.
• Common allergens:
  • Dust mites, pollen, animal dander.
• Treatment:
  • Drugs like anti-histamines, adrenaline, and steroids reduce symptoms.
• Modern Lifestyle:
  • Lower immunity and more sensitivity to allergens, especially in children in metro cities.

Summary

Cause	Description	Examples
Environmental Allergens	Exaggerated immune response to environmental antigens	Pollen, dust mites, animal dander
Symptoms	Physical reactions to allergens	Sneezing, watery eyes, runny nose
Treatment	Medications to reduce symptoms	Anti-histamines, adrenaline, steroids

Auto Immunity

• What is auto immunity?
  • When the body’s immune system attacks its own cells.
• Example:
  • Rheumatoid arthritis.
• Cause:
  • Due to genetic and other unknown reasons.

Immune System in the Body

• Components:
  • Lymphoid organs, tissues, cells, and soluble molecules like antibodies.
• Functions:
  • Recognizes and responds to foreign antigens, remembers them.
  • Plays a role in allergic reactions, auto-immune diseases, and organ transplantation.

Lymphoid Organs

Organs where lymphocytes are produced, mature, and proliferate.

• Primary lymphoid organs: Organs where lymphocytes are formed and mature.
  • Bone marrow:
    • Produces all blood cells including lymphocytes.
  • Thymus:
    • A bilobed structure located near the heart, helps in the maturation of T-lymphocytes.
    • Large at birth but shrinks with age.
• Secondary lymphoid organs: Organs where mature lymphocytes interact with antigens and then proliferate to become effector cells.
  • Spleen:
    • Bean-shaped, contains lymphocytes and phagocytes, filters blood, traps blood-borne microorganisms.
    • Large reservoir of erythrocytes.
  • Lymph nodes:
    • Small solid structures along the lymphatic system, trap microorganisms and antigens, activate lymphocytes.
  • Mucosa-associated lymphoid tissue (MALT):
    • Located in the lining of respiratory, digestive, and urogenital tracts.
    • Constitutes about 50% of the lymphoid tissue in the body.

Summary

Type	Organs	Function
Primary Lymphoid Organs	Bone marrow, thymus	Production and maturation of lymphocytes
Secondary Lymphoid Organs	Spleen, lymph nodes, tonsils, Peyer’s patches, appendix	Interaction with antigens, proliferation of lymphocytes
Mucosa-Associated Lymphoid Tissue (MALT)	Located in respiratory, digestive, and urogenital tracts	Constitutes 50% of lymphoid tissue in the body

Complete Summary

Concept	Key Points
Types of Immunity	Innate (non-specific, present at birth), Acquired (specific, memory-based)
Innate Immunity Barriers	Physical (skin, mucus), Physiological (stomach acid, saliva), Cellular (WBCs), Cytokine (interferons)
Acquired Immunity Responses	Primary (first encounter, low intensity), Secondary (subsequent encounters, high intensity)
Types of Acquired Immunity	Active (host-produced antibodies), Passive (introduced antibodies)
Vaccination and Immunisation	Vaccination (antigen introduction), Passive Immunisation (preformed antibodies), Recombinant DNA Vaccine (genetically engineered antigens)
Allergies	Cause (environmental allergens), Symptoms (sneezing, watery eyes), Treatment (anti-histamines, adrenaline, steroids)
Auto Immunity	Immune system attacks self-cells, Example: Rheumatoid arthritis
Lymphoid Organs	Primary (bone marrow, thymus), Secondary (spleen, lymph nodes, tonsils, Peyer’s patches, appendix), MALT (respiratory, digestive, urogenital tracts)

AIDS

What is AIDS?

• Stands for Acquired Immuno Deficiency Syndrome.
• It is a deficiency/weakening of the immune system acquired during a person’s lifetime.
• It is not a congenital disease (not present at birth).
• A “syndrome” means a group of symptoms.
• History:
  • First reported in 1981 in America.
  • In 25 years, it has spread globally, killing over 25 million people.

Cause:

• Caused by the Human Immuno Deficiency Virus (HIV).
• HIV is a retrovirus with an envelope enclosing the RNA genome.

How HIV Spreads (Transmission) :

• Sexual contact with an infected person.
• Transfusion of contaminated blood.
• Sharing infected needles (common among drug users).
• From an infected mother to her child through the placenta.

High-Risk Groups:

• Individuals with multiple sexual partners.
• Intravenous drug users/addicts.
• Individuals needing repeated blood transfusions.
• Children born to HIV-infected mothers.

Important Note (Non-Transmission):

• HIV/AIDS is not spread by touch or physical contact.
• Only spreads through body fluids.

How HIV Affects the Body:

• Enters macrophages and helper T-lymphocytes (TH cells).
• Replicates and destroys helper T-lymphocytes, reducing their number.
• Leads to frequent infections and diseases due to weakened immunity.

Symptoms:

• Initial symptoms: Bouts of fever, diarrhea, weight loss.
• Severe symptoms: Increased susceptibility to infections by bacteria (Mycobacterium), viruses, fungi, and parasites (Toxoplasma) due to immune system failure.
• The time lag (incubation period) between HIV infection and the onset of AIDS symptoms can be 5-10 years.

Diagnosis:

• Enzyme-linked immuno-sorbent assay (ELISA) test is commonly used.

Treatment:

• Anti-retroviral drugs: partially effective, can prolong life but can not cure the disease completely.

Prevention:

• No cure, so prevention is crucial.
• Preventive measures include:
  • Safe blood transfusions.
  • Use of disposable needles and syringes and avoid sharing needles..
  • Free distribution of condoms.
  • Controlling drug abuse.
  • Avoid unprotected sex and advocating safe sex.
  • Regular HIV check-ups for at-risk populations.
• Education and awareness are key; “Don’t die of ignorance.”

Efforts to Prevent HIV/AIDS:

• National AIDS Control Organisation (NACO) and NGOs educate people about AIDS..
• WHO programs to prevent HIV spread.
• Safe blood practices, disposable needles, free condoms, and safe sex advocacy.
• Regular check-ups for high-risk groups.

Social Support:

• Society must help and support HIV/AIDS-infected people instead of isolation.
• Collective action is needed to tackle and prevent the spread of AIDS.

Chapter Summary:

• Health is not just about being free from illness; it includes being physically, mentally, socially, and psychologically well.
• Diseases such as typhoid, cholera, pneumonia, fungal skin infections, malaria, and others cause distress to people.
• Vector-borne diseases like malaria, especially the one caused by Plasmodium falciparum, can be fatal if not treated.
• Personal cleanliness, hygiene, and public health measures like proper waste disposal, clean drinking water, and mosquito control help prevent these diseases.
• Our immune system plays a crucial role in defending against pathogens.
• Innate defenses like skin, mucous membranes, antimicrobial substances in tears and saliva, and phagocytic cells block pathogens from entering our body.
• Specific antibodies and cells kill pathogens if they enter our body, providing protection.
• The immune system remembers pathogens, leading to rapid and intense responses on subsequent exposures, a basis for vaccination.
• AIDS caused by HIV and cancer are major causes of death globally.
• AIDS is preventable with precautions, and many cancers are curable if detected early and treated appropriately.
• Drug and alcohol abuse among youth is concerning due to their addictive nature and perceived benefits.
• Education about their harmful effects, counseling, and seeking professional help are crucial to overcome addiction.