Health, nutrition, and disease form an intricate web that profoundly influences human well-being. Nutrition, encompassing the intake of essential nutrients, serves as the cornerstone of health, with both organic and inorganic substances playing pivotal roles in bodily functions. While proper nutrition fosters vitality, diseases, whether communicable or non-communicable, pose significant threats to human health. Among them, genetic diseases stand as poignant reminders of the intricate interplay between genes and health outcomes. Immunity, the body’s defense mechanism, offers protection against pathogens through immunization while grappling with the complexities of autoimmunity. Additionally, zoonotic diseases underline the interconnectedness between human and animal health, urging a holistic approach to disease prevention and management. This intricate tapestry of health, nutrition, and disease underscores the importance of comprehensive understanding and proactive measures to safeguard individual and public health.
Nutrients and Nutrition
Nutrients and nutrition are often used interchangeably, yet they carry distinct meanings. Here’s a breakdown:
Nutrients: These are vital substances necessary for the body’s proper functioning. They encompass six categories:
- Carbohydrates: Provide energy.
- Proteins: Aid in tissue growth and repair.
- Fats: Serve as energy sources and aid in vitamin absorption.
- Vitamins: Essential for various bodily functions.
- Minerals: Important for bone health, nerve function, etc.
- Water: Essential for hydration and bodily functions.
Nutrition: Refers to the process of acquiring and utilizing nutrients to maintain a healthy body. This process includes:
- Ingestion: Consuming food and drink.
- Digestion: Breaking down food into nutrients.
- Absorption: Assimilating nutrients into the body.
- Metabolism: Utilizing nutrients for bodily functions and energy.
- Elimination: Disposing of waste products from the body.
Key Differences:
- Nutrients serve as the foundation of nutrition, which is the process of acquiring and utilizing those nutrients.
- Nutrients are classified into six categories, while nutrition encompasses various bodily processes.
- Nutrients can be obtained from food or supplements, whereas nutrition relies solely on the ingestion, digestion, absorption, metabolism, and elimination of food.
- Nutrients are crucial for bodily function, while nutrition is essential for overall health and well-being.
Nutritional Deficiencies and Associated Disorders
Prolonged inadequacy of specific nutrients in our diet can lead to various diseases or disorders. Here’s an overview of common nutrient-related deficiencies and their associated symptoms:
Vitamin A: Night blindness Reduced vision, difficulty seeing in low light conditions, potential loss of vision.
Vitamin B1: Beriberi Weakness in muscles, fatigue, impaired energy levels.
Vitamin C: Scurvy Bleeding gums, delayed wound healing, fatigue.
Vitamin D: Rickets Softening and deformation of bones, skeletal deformities.
Calcium Osteoporosis: Weak and brittle bones, tooth decay, increased risk of fractures.
Components of Food
Food encompasses a spectrum of essential components crucial for our well-being. Here are the key elements:
- Carbohydrates: These serve as the primary energy source for the body and are present in grains, fruits, vegetables, and legumes. They come in two forms: simple (found in candy, fruits) and complex (found in bread, pasta).
- Proteins: Vital for tissue growth and repair, proteins are abundant in meat, fish, eggs, dairy, and legumes. They consist of amino acids and can be complete (containing all essential amino acids) or incomplete.
- Fats: Acting as energy reservoirs, fats are found in oils, nuts, seeds, and meats. They come in saturated (found in animal products) and unsaturated forms (found in plant-based foods).
- Vitamins: Essential for overall health, vitamins are present in various foods. They are classified as water-soluble (easily absorbed, found in fruits and vegetables) and fat-soluble (stored in fat cells, found in meat, eggs, dairy).
- Minerals: Crucial for cellular function, minerals like iron, calcium, and zinc are found in diverse food sources.
- Water: An indispensable component found in all foods, water is vital for bodily functions and hydration.
Diseases
Diseases are abnormal conditions characterized by specific signs and symptoms. They can stem from external causes, such as infections, or internal factors like autoimmune disorders.
Communicable Diseases:
Communicable diseases are those that spread from one person to another through various means, including: Contact with blood and bodily fluids. Inhalation of airborne viruses. Bites from infected insects. Examples include HIV, TB, and Malaria.
Modes of Transmission:
Communicable diseases spread through several routes: Direct physical contact with an infected individual, such as through skin contact (staphylococcus), sexual activity (gonorrhea, HIV), or oral/fecal transmission (hepatitis A). Indirect contact with contaminated surfaces or objects (Norwalk virus), food (salmonella, E. coli), blood (HIV, hepatitis B), or water (cholera). Insect or animal bites capable of transmitting diseases (mosquitoes: malaria and yellow fever; fleas: plague). Airborne transmission, as seen in diseases like tuberculosis or measles.
Communicable Disease Caused by Bacteria
Tuberculosis (TB):
Tuberculosis (TB) is recognized by the World Health Organization (WHO) as one of the top 10 causes of global mortality, ranking higher than HIV/AIDS as the leading cause of death from a single infectious agent. The disease is instigated by the bacterium Mycobacterium tuberculosis. While TB primarily affects the lungs (pulmonary TB), it can also manifest in other body parts (extrapulmonary TB). India bears the highest burden of TB cases worldwide, followed by Indonesia and China. TB is often linked with poverty, leading to economic hardships, vulnerability, marginalization, and societal stigma for those affected (WHO).
Treatment for Tuberculosis:
TB is both curable and preventable. Approximately 85% of TB patients can be effectively treated with a 6-month regimen of drugs. Vaccination/Drug Therapy: BCG (Bacillus Calmette-Guérin) vaccine, Antibiotics such as streptomycin. Drug-Resistant TB:
Multidrug-Resistant TB (MDR-TB): Resistant to at least isoniazid and rifampicin, two potent first-line drugs. Extensively Drug-Resistant Tuberculosis (XDR-TB): Resistant to at least four core anti-TB drugs, including additional resistance to fluoroquinolones and injectable second-line drugs.
Totally Drug-Resistant Tuberculosis (TDR-TB): Shows resistance to all first- and second-line TB drugs.
WHO’s End TB Strategy: Vision: Achieving a world free from TB, aiming for zero deaths, disease, and suffering due to TB. Targets for 2035: A 95% reduction in TB deaths, a 90% decrease in TB incidence compared to 2015, and eliminating catastrophic costs for TB-affected families.
Initiatives:
- Nikshay: India’s web-based TB case monitoring system.
- True Nat: A novel molecular test capable of diagnosing TB within an hour and detecting rifampicin resistance, endorsed by the WHO and developed by Indian firm MolBio Diagnostics Pvt Ltd.
- Incorporating TB vaccination into the Universal Immunization Programme. Implementation of the Revised National TB Control Programme (RNTCP), which released the ‘National Strategic Plan to end TB’ framework in 2017, aiming to control and eliminate TB in India by 2025 under the National Health Mission.
- Ministry of Health’s ‘TB Harega Desh Jeetega Campaign’ to expand and enhance TB care services nationwide by 2022.
Diarrhea:
Diarrhea is characterized by loose, watery stools that occur more frequently than usual. It often results from reduced fluid absorption in the intestines or increased fluid secretion, leading to the rapid passage of stool through the intestines.
Types of Diarrhea:
- Acute Diarrhea: Typically lasts for 2 or 3 days, rarely exceeding a week. It is not life-threatening and can be managed with appropriate medications.
- Chronic Diarrhea: May persist for 1 or 2 weeks or even longer, often indicating underlying gastrointestinal issues.
Symptoms:
- Loose stools
- Vomiting
- Nausea
- Abdominal cramps
- Urgency for bowel movement
- Abdominal pain
- Fever
- Bloody stools (in rare cases)
Treatment: Acute diarrhea usually resolves within 2 to 3 days without treatment. However, consulting a physician is advisable.
Anthrax:
Anthrax is a serious infectious disease caused by gram-positive, rod-shaped bacteria called Bacillus anthracis. It is commonly found in soil and affects domestic and wild animals worldwide, particularly cattle, sheep, and goats.
Transmission: Anthrax is not transmitted directly from infected animals or people but through spores, which can be carried on clothing or shoes.
Symptoms:
- Chest or muscle pain
- Skin blisters and dark scabs
- Ulcers
- Fever or malaise
- Respiratory distress or shortness of breath
- Coughing
- Headache
- Itching
- Nausea
- Sore throat
- Swollen lymph nodes
Treatment: The standard treatment for anthrax involves a 60-day course of antibiotics such as ciprofloxacin (Cipro) or doxycycline (Doryx, Monodox).
Prevention: Anti-anthrax vaccines available in the market trigger an immune response against a Bacillus protein-protective antigen, which assists in transporting bacillus toxins inside cells.
Leprosy:
Leprosy, also known as Hansen’s Disease, is a chronic, yet curable infectious disease characterized by skin lesions and nerve damage. It primarily affects the skin, eyes, nose, and peripheral nerves.
Causes and Symptoms: Leprosy is caused by the bacterium Mycobacterium leprae. Symptoms often include light-colored or red skin patches with reduced sensation, as well as numbness and weakness in the hands and feet.
Transmission: The disease is mainly transmitted through breathing airborne droplets from affected individuals and can be contracted at any age.
Treatment: Leprosy can be effectively cured with 6-12 months of Multi-Drug Therapy (MDT). Early diagnosis and treatment help prevent disability. The treatment regimen for multi-bacillary leprosy now combines rifampicin and clofazimine with dapsone.
Communicable Diseases Caused By Viruses:
AIDS (Acquired Immunodeficiency Syndrome):
AIDS is caused by the Human Immunodeficiency Virus (HIV), a type of lentivirus belonging to the retrovirus class. HIV infection progresses over time to AIDS. HIV targets and destroys White Blood Cells (WBCs) and T-helper (CD4) cells, weakening the immune system. There is currently no cure for HIV, as the virus cannot be completely eliminated from the body even with treatment.
ELISA Test: The Enzyme-Linked Immunosorbent Assay (ELISA) test detects and measures antibodies in the blood, aiding in the diagnosis of various infectious conditions. Antibodies, produced by the body in response to harmful substances called antigens, are detected by the ELISA test.
HAART (Highly Active Antiretroviral Therapy): HAART involves a combination of three or more antiretroviral drugs to treat HIV-1 infected patients, inhibiting viral replication by different mechanisms. HAART helps reduce HIV transmission and is also used for HIV Type-2 treatment, although specific guidelines for HIV-2 management are lacking.
Polio:
Polio is a highly infectious viral disease that affects the nervous system, potentially causing irreversible paralysis. Three wild poliovirus strains exist: Wild Poliovirus Type 1 (WPV1), Wild Poliovirus Type 2 (WPV2), and Wild Poliovirus Type 3 (WPV3).
Vaccines: Oral Polio Vaccine (OPV) contains live attenuated strains of polioviruses and is administered orally. Inactivated Poliovirus Vaccine (IPV) provides protection against all three poliovirus types without containing a live virus, preventing viral shedding and transmission.
Polio Status in India:
India’s Pulse Polio Immunization Programme, initiated in 1995, significantly reduced polio cases from tens of thousands annually to zero by 2012. In 2014, India was declared polio-free after three consecutive years without reported cases. The introduction of injectable polio vaccine in India’s Universal Immunization Programme aims to mitigate Vaccine-Derived Polio Virus (VDPV) occurrences.
Global Polio Eradication Initiative: A public-private partnership, comprising WHO, Rotary International, US CDC, UNICEF, Bill & Melinda Gates Foundation, and GAVI, aims to eradicate polio worldwide.
Zika Virus:
Zika, transmitted by Aedes aegypti mosquitoes, typically manifests without symptoms, though it can lead to paralysis (Guillain-Barré Syndrome) in rare cases. In pregnant women, Zika may result in birth defects. Symptoms, when present, include mild fever, rash, joint pain, and red eyes. No specific vaccine or treatment exists. Focus remains on symptom relief through rest, hydration, and acetaminophen. Avoid aspirin and NSAIDs.
Dengue Fever:
Dengue, transmitted by female Aedes Aegypti mosquitoes in tropical regions, presents with high fever, headache, rash, and muscle/joint pain. Severe cases may progress to dengue hemorrhagic fever, characterized by bleeding and plasma leakage. Recent cases suggest sexual transmission of dengue. Treatment includes fluids, pain relievers, and hospital care for severe cases.
Japanese Encephalitis (JE):
JE, spread by infected mosquitoes in rural areas, is caused by a Flavi Virus affecting the brain’s membranes. A leading cause of Acute Encephalitis Syndrome (AES) in India, JE is transmitted by Culex mosquitoes. Supportive care and vaccination are essential. JE vaccination is part of the Universal Immunization Program.
Influenza (Flu):
An often-deadly viral infection, especially risky for high-risk groups, including young children, elderly, pregnant women, and those with chronic illnesses. Flu symptoms affect the lungs, nose, and throat, including fever, chills, muscle aches, cough, congestion, headaches, and fatigue. Treatment focuses on rest and hydration. Influenza A and B viruses cause seasonal epidemics, while Influenza C primarily induces mild illness. Influenza D affects cattle. Common influenza strains like H1N1 (Swine Flu), H5N1, H5N8, and H2N9 (Bird Flu) pose significant health risks during outbreaks.
Nipah Virus:
A zoonotic virus, transmitted from animals to humans, often through bats or pigs, and contaminated foods. It can also spread directly between humans. Symptoms resemble influenza, including fever, muscle pain, respiratory issues, and brain inflammation. No specific drugs or vaccines are available for Nipah virus.
Coronaviruses:
Coronaviruses, found in various animals like bats, cats, and birds, cause respiratory and gastrointestinal symptoms in humans. Noteworthy strains include Severe Acute Respiratory Syndrome (SARS), Middle East Respiratory Syndrome (MERS), and the recent COVID-19 outbreak.
COVID-19:
A newly discovered coronavirus causing COVID-19, initially identified in Wuhan, China, in 2019. It’s zoonotic in origin. Symptoms range from mild to severe respiratory illness, particularly impacting older adults and individuals with underlying health issues. Several vaccines are under development, with approved options like Pfizer (USA), Covaxin, and Covishield (India).
Hepatitis:
An inflammatory liver condition, often viral in origin, but can also stem from autoimmune reactions, medications, toxins, and alcohol. Hepatitis B and C are major causes of chronic hepatitis, with vaccines available for A, B, and E. Nobel Prize in Medicine 2020 awarded for Hepatitis C virus discovery. National Viral Hepatitis Control Program aims to combat hepatitis, targeting its eradication as a public health threat by 2030.
Ebola:
Ebola Hemorrhagic Fever, caused by the Ebola virus, leads to severe bleeding, organ failure, and death. Human-to-human transmission occurs through bodily fluids. Initial symptoms include fever, headache, and muscle pain, progressing to internal bleeding. Supportive hospital care, including oxygen therapy and IV fluids, forms the mainstay of treatment. Blood transfusion may be necessary.
Communicable Diseases Caused By Parasite
Malaria:
Malaria, caused by Plasmodium parasites, is transmitted through the bite of infected female Anopheles mosquitoes. Symptoms include chills, fever, and sweating, typically appearing a few weeks after being bitten. Treatment involves antimalarial drugs. The world’s first vaccine against a parasitic disease, Mosquirix, has been developed. Algeria and Argentina have recently been officially recognized by the WHO as malaria-free countries. The WHO’s E-2020 initiative, part of the Global Technical Strategy for Malaria 2016-2030, aims to significantly reduce or eliminate the global malaria burden within 15 years.
Kala Azar/Black Fever:
Kala Azar, or Black Fever, is a neglected tropical disease affecting nearly 100 countries, including India, caused by Leishmania parasites. Transmitted through sandfly bites, it is also known as Dumdum fever. Symptoms vary; some individuals may be asymptomatic, while others may experience fever, weight loss, and spleen or liver enlargement. There are three types of leishmaniasis: Visceral, Cutaneous, and Mucocutaneous, with visceral leishmaniasis being the most severe. Visceral leishmaniasis, commonly known as Kala Azar in India, is fatal in over 95% of untreated cases, affecting internal organs like the spleen, liver, and bone marrow. Treatment options are available to eliminate the parasites; however, severe cases left untreated can be fatal.
Non-Communicable Diseases (NCDs)
Non-Communicable Diseases (NCDs) are predominantly chronic conditions such as cardiovascular diseases, cancers, and diabetes. Non-infectious diseases, or non-communicable diseases (NCDs), have a variety of causes, including genetics, poor nutrition, age, sex, and other factors.
The four major NCDs include:
- Cardiovascular diseases (heart disease and stroke)
- Cancer- It causes one in six deaths – 9.3 million people a year, a further 44% of cancer deaths could have been prevented or delayed by eliminating risks to health.
- Diabetes- One in 28 deaths – 2.0 million people a year – is due to diabetes. More than 95% of diabetes cases globally are of type 2 diabetes.
- Chronic respiratory diseases- It indicated that 70% of deaths due to chronic respiratory diseases could have been prevented or delayed by eliminating risks to health.
Only 6% of countries are currently on track to achieve the related SDG target 3.4.
Non-Communicable Diseases pose hindrances to social and economic development and can significantly threaten international health security, as evidenced by increased case fatalities and disruptions in health systems during the COVID-19 pandemic.
Non-communicable diseases in India
According to the WHO, over 60.46 lakh individuals in India died in 2019 due to NCDs.
In the country, cardiovascular diseases accounted for over 25.66 lakh fatalities in 2019, while chronic respiratory disorders caused 11.46 lakh deaths.
Additionally, 20 lakh people succumbed to cancer, and 3.49 lakh individuals in the nation lost their lives to diabetes.
Government Initiatives:
- The National Programme for Prevention and Control of Cancer, Diabetes, Cardiovascular Diseases, and Stroke (NPCDCS) is being implemented under the National Health Mission (NHM).
- The Strengthening of Tertiary Care Cancer Facilities scheme supports the establishment of State Cancer Institutes (SCI) and Tertiary Care Centers (TCCC) across the country.
- Screening for common NCDs, including oral, breast, and cervical cancers, is integral to service delivery under Ayushman Bharat – Health and Wellness Centers.
- Cancer treatment is also available under Ayushman Bharat – Pradhan Mantri Jan Arogya Yojana (PMJAY).
- The Affordable Medicines and Reliable Implants for Treatment (AMRIT) Deendayal outlets offer cancer and cardiovascular disease drugs and implants at discounted prices to patients.
- Financial assistance for treatment, including cancer treatment, is provided to families living below the poverty line under the Rashtriya Arogya Nidhi scheme in Government hospitals.
Genetic Disorders
Genetic disorders arise from alterations or abnormalities in the genome of an organism. These disorders can result from mutations in single genes or multiple genes, as well as changes in the number or structure of chromosomes.
To comprehend genetic disorders fully, it’s essential to grasp the concept of genes. Genes serve as the fundamental unit of heredity, carrying genetic information encoded in DNA. They facilitate life processes by encoding proteins, which play crucial roles in various biological functions. In most living organisms, DNA serves as the stable genetic material, while RNA assumes this role in select instances. RNA, however, tends to be less stable compared to DNA, making DNA the predominant genetic component across most organisms.
In certain circumstances, genes may undergo mutations, disrupting the genetic code. Mutated genes can produce malfunctioning proteins that fail to perform their intended functions, thereby contributing to genetic disorders. These disorders manifest as abnormalities in various physiological processes, leading to health complications and disorders.
Types of Genetic Disorders
- Mendelian Disorders:
Mendelian disorders result from mutations in a single gene and can manifest as autosomal dominant, autosomal recessive, sex-linked dominant, sex-linked recessive, or mitochondrial disorders. Detection of Mendelian disorders often involves pedigree analysis. These disorders may originate from mutations on either sex chromosomes or autosomes, presenting in recessive or dominant modes. Autosomal recessive diseases emerge when the mutant gene is present in a homozygous state, typically when both parents carry one copy of the mutant gene and one copy of a normal functional gene. In autosomal traits, both males and females have equal chances of being affected. Examples of Mendelian disorders include:
- Sex-Linked Disorders like Hemophilia.
- Autosomal Recessive Disorders such as Cystic Fibrosis, Albinism, and Sickle Cell Anemia.
- Chromosomal Disorders
Chromosomal disorders arise from mutations affecting the structure or number of chromosomes. These disorders can impact numerous genes simultaneously and may lead to severe health consequences. Chromosomal disorders may result from the loss or gain of whole chromosomes. Examples of Chromosomal Disorders include:
- Down Syndrome, characterized by an extra chromosome 21 (trisomy).
- Turner Syndrome, marked by the absence of an X chromosome (XO).
- Klinefelter Syndrome, identified by the addition of an X chromosome (XXY).
- Multifactorial Genetic Inheritance
Also known as polygenic inheritance, multifactorial genetic disorders result from interactions between environmental factors and gene mutations. Examples of Multifactorial Diseases encompass:
- Heart Disease
- High Blood Pressure
- Alzheimer’s Disease
- Cancer
- Arthritis
- Mitochondrial Inheritance
These genetic disorders stem from mutations in non-nuclear mitochondrial DNA and are inherited exclusively from the mother. Each mitochondrion typically contains 5 to 10 pieces of DNA. Examples of Mitochondrial Diseases include:
- Leber’s Hereditary Optic Atrophy (LHON)
- Myoclonic Epilepsy with Ragged Red Fibers
- Mitochondrial Encephalopathy
- Lactic Acidosis
Genetic Disorders in India:
In India, several genetic disorders pose significant health challenges. Among the commonly observed genetic disorders are Beta-Thalassemia, Cystic Fibrosis, Sickle Cell Anemia, Spinal Muscular Atrophy, and Hemophilia.
- Beta-Thalassemia: Beta-Thalassemia is a blood disorder characterized by reduced haemoglobin production.
- Cystic Fibrosis: Cystic Fibrosis is a disorder that adversely affects the lungs, digestive system, and other organs in the body.
- Sickle Cell Anemia: Sickle Cell Anemia, or sickle cell disease (SCD), is a genetic condition impacting the red blood cells (RBCs).
- Spinal Muscular Atrophy: Spinal Muscular Atrophy presents as a disorder marked by weakness and wasting in muscles crucial for movement (skeletal muscles).
- Hemophilia: Hemophilia is a genetic disorder characterized by impaired blood clotting.
Symptoms of Genetic Disorders:
Symptoms of genetic disorders vary depending on the specific disorder and the affected organs. Common indicators include:
- Breathing difficulties
- Behavioral changes or disturbances
- Cognitive deficits affecting information processing
- Developmental challenges, particularly in social skills
- Digestive issues impeding nutrient processing
- Muscle stiffness, weakness, and movement disorders
- Poor growth, vision impairment, and hearing loss
Identification of Genetic Disorders:
Individuals with a family history of genetic disorders can take proactive steps to understand and manage their genetic risks. Key approaches include:
- Genetic Counselling: Genetic counselling involves comprehensive communication to help individuals and families comprehend and adapt to the medical implications of genetic disorders. It aids in identifying potential genetic diseases and understanding their implications.
- Carrier Testing: Carrier testing is a blood test designed to determine whether parents carry mutations linked to genetic disorders.
- Prenatal Diagnostic Testing: Prenatal diagnostic testing allows parents to assess whether their unborn child faces a risk of genetic disorders. This testing involves analyzing fluid samples from the womb.
- Prenatal Screening: Prenatal screening is conducted in pregnant women to identify common chromosome conditions in unborn children.
- Newborn Screening: Newborn screening involves analyzing a sample of newborn blood to detect genetic disorders early in life. Early detection facilitates timely intervention and treatment, improving outcomes for affected children.
Immunity
Immunity is the body’s remarkable ability to shield itself from harmful pathogens and microorganisms that can cause diseases. Despite encountering numerous microorganisms daily, only a small fraction actually lead to illness. This is because our bodies possess the remarkable capacity to produce antibodies that combat these harmful invaders, thus safeguarding us from diseases. Immunity encompasses a complex defense mechanism that plays a crucial role in maintaining overall health and well-being.
Types of Immunity:
- Innate Immunity or Natural or Non-specific Immunity: Innate immunity is inherent from birth and provides immediate protection against pathogens upon exposure. It encompasses various barriers and defense systems that prevent the entry of foreign substances into the body. These natural defenses, including salivary enzymes, natural killer cells, intact skin, neutrophils, and others, enable the body to fend off diseases even before encountering specific pathogens or antigens.
Cells Involved in Innate Immunity:
- Phagocytes
- Macrophages
- Mast Cells
- Neutrophils
- Eosinophils
- Basophils
- Natural Killer Cells
- Dendritic Cells
- Acquired Immunity or Adaptive Immunity: Acquired immunity, also known as adaptive immunity, develops over time and is not present at birth. It refers to the immune system’s ability to respond to specific pathogens and produce pathogen-specific immunity. This type of immunity is characterized by the production of lymphocytes or antibodies that neutralize antigens, rendering them harmless. Acquired immunity plays a crucial role in treating ongoing infections and providing protection against future encounters with the same pathogen.
Acquired immunity involves a sophisticated lymphatic defense system that recognizes and targets specific pathogens while ignoring the body’s own cells. When exposed to a virus or its antigen, the immune system initiates a response by producing antibodies to envelop and eliminate the infection. This initial encounter with the pathogen triggers a primary response, while subsequent exposures lead to a secondary response characterized by the rapid and efficient targeting of pathogens.
Cells Involved in Acquired Immunity
Acquired immunity relies on the coordinated efforts of two types of cells: B-cells and T-cells.
B-cells: B-cells undergo maturation in the bone marrow. Upon encountering foreign substances, known as antigens, B-cells become activated. Activated B-cells undergo differentiation into plasma cells, which produce antibodies specific to the encountered antigen. These antibodies bind to the surface of the antigen, marking it for destruction. B-cells play a crucial role in humoral immunity, which relies on antibody-mediated responses.
T-cells: T-cells undergo maturation in the thymus following their origin in the bone marrow. T-cells can differentiate into various subtypes, including helper, cytotoxic, and regulatory T-cells, and are released into the bloodstream. Helper T-cells secrete cytokines upon activation by antigens, initiating the differentiation of B-cells into plasma cells. Cytotoxic T lymphocytes target and destroy cancer cells, infected cells, and foreign invaders. Regulatory T cells help modulate immune responses to prevent overactivation.
Types of Acquired Immune Response:
Humoral Immune Response: The humoral immune response involves the production and circulation of antibodies produced by B-lymphocytes throughout the body. When an antigen interacts with an antibody on a B-cell surface, the humoral immune response is triggered. Activated B-cells differentiate into plasma cells, which release antibodies into the bloodstream. Memory B cells retain information about the pathogen to mount a rapid response upon subsequent exposure.
Cell-mediated Immune Response: The cell-mediated immune response is initiated by T-helper cells. Cytotoxic T cells target and eliminate infected cells by releasing toxins and inducing programmed cell death (apoptosis). T-helper cells also stimulate other immune cells, particularly evident in transplant recipients. In cases of organ transplantation, T-lymphocytes distinguish between self and foreign tissues, leading to rejection if the tissue is perceived as foreign. Immunosuppressant medication is often necessary to prevent rejection reactions in transplant recipients, with T-lymphocytes playing a pivotal role in regulating this response.
The Immune System in the Body
- Lymphoid Organs: Lymphoid organs serve as sites for the genesis, maturation, and proliferation of lymphocytes. Primary lymphoid organs include the thymus and bone marrow, where immature lymphocytes develop into antigen-sensitive cells. Following maturation, lymphocytes migrate to secondary lymphoid organs such as the appendix, spleen, lymph nodes, tonsils, and Peyer’s patches in the small intestine. Secondary lymphoid organs provide the locations for lymphocytes to encounter antigens and undergo proliferation to become effector cells. The bone marrow serves as the primary lymphoid organ, generating all blood cells, including lymphocytes. The thymus, situated beneath the breastbone near the heart, undergoes size reduction with age, playing a crucial role in T-lymphocyte formation and maturation. The
- Spleen: The spleen, resembling a bean in shape, is a substantial organ rich in lymphocytes and phagocytes. It functions to filter blood by capturing microorganisms and serves as a reservoir for erythrocytes.
- Lymph Nodes: Lymph nodes are small, solid structures distributed throughout the lymphatic system. They capture microorganisms or antigens present in lymph and tissue fluid, initiating immunological responses. Antigens lodged in lymph nodes activate resident lymphocytes, triggering immune responses.
- Mucosal-Associated Lymphoid Tissue (MALT): MALT is lymphoid tissue found in the linings of the respiratory, digestive, and urogenital tracts. It constitutes approximately 50% of the body’s lymphoid tissue and plays a crucial role in mucosal immunity.
Immunization from Immunity
Immunity refers to the overall capability of the body to detect and eliminate foreign substances or organisms. On the other hand, immunization specifically pertains to the body’s capacity to recognize and counteract a particular pathogen, thereby preventing it from causing severe harm. Immunization may occur naturally as a result of exposure to the pathogen or through vaccination.
Understanding Immunization
Immunization refers to the process by which your body learns to identify and counteract a specific pathogen, thereby either preventing the disease from occurring or reducing its severity. It serves as a shield against infectious diseases, often caused by viruses or bacteria, which can lead to illness or even death.
Upon immunization against a particular antigen, your body is equipped to mount a secondary immune response that is both quicker and more efficient. This secondary response can either prevent the onset of illness altogether or mitigate its severity.
Immunization can take place either through vaccination or exposure to the specific antigen.
There are two main types of immunization:
Active Immunization:
Active immunization involves the body’s adaptive immune system generating a targeted response to a specific pathogen. While full protection may take some time to develop, it is generally long-lasting.
Passive Immunization:
Passive immunization occurs when immunity is transferred from one individual to another. For instance, when mothers breastfeed, antibodies are transferred from mother to baby through breast milk. Additionally, in certain cases, purified antibodies from blood donations are administered to provide immediate protection against disease. This type of immunization typically lasts for a few weeks or months.
How does vaccination create immunization?
- Vaccination involves administering a vaccine into the body or taking a vaccine dose, aiming to provide immunization safely without causing disease and with minimal risk of complications.
- The vaccine triggers active immunization by stimulating both the innate and adaptive immune responses. Within approximately two weeks, the immune system becomes capable of specifically responding to the targeted disease.
- Some vaccines require multiple doses to establish a stronger “immune memory” of the specific antigen. The frequency of vaccination varies depending on the pathogen, as many viruses or bacteria mutate over time to evade immune responses. For instance, the flu vaccine is administered annually due to rapid mutations in the influenza virus.
- The development of immune memory can be influenced by age.
- If an individual is exposed to the pathogen before completing the vaccination schedule, they may still contract the illness as their immune system is only partially prepared to respond.
- Generally, the risk associated with vaccination is significantly lower compared to the risk of infection by the pathogen itself. Moreover, vaccinations may offer more robust and longer-lasting protection compared to natural immunization through infection.
Autoimmunity
Autoimmunity is the presence of antibodies (which are made by B lymphocytes) and T lymphocytes directed against normal components of a person (autoantigens). These components are called autoantigens or self-antigens and typically consist of proteins (or proteins complexed to nucleic acids). The antibodies and T lymphocytes that recognize autoantigens are called “autoantibodies” and “autoreactive T cells”.
Autoimmune Diseases:
Autoimmune diseases are conditions characterized by the immune system mistakenly attacking the body’s own tissues and organs. Typically, the immune system serves to protect the body against viruses and pathogens by deploying specialized cells to combat these invaders upon detection.
The immune system is adept at distinguishing between self and non-self cells, recognizing and targeting foreign entities while sparing the body’s own tissues. In autoimmune disorders, however, the immune system malfunctions, identifying certain parts of the body, such as joints or skin, as foreign. This leads to the production of autoantibodies, proteins that attack healthy cells.
Some autoimmune conditions affect specific organs, like the pancreas in type 1 diabetes, while others, such as lupus (or systemic lupus erythematosus), can have systemic effects impacting multiple organs throughout the body. The exact cause of immune system dysregulation in autoimmune diseases remains unclear, confounding medical experts.
Common autoimmune diseases
- Type 1 diabetes: The immune system attacks and destroys insulin-producing cells in the pancreas.
- Rheumatoid arthritis: The immune system attacks the joints.
- Psoriasis: The causes skin cells to multiply too quickly. The extra cells build up and form inflamed, red patches, commonly with silver-white scales of plaque.
- Multiple sclerosis: It damages the myelin sheath, the protective coating surrounding nerve cells in your central nervous system.
- Systemic lupus erythematosus (SLE): It is a skin disease because of the rash it commonly produces, but it affects many organs, including the joints, kidneys, brain, and heart.
- Inflammatory bowel disease: It describes conditions that cause inflammation in the lining of the intestinal wall.
- Addison’s disease: It affects the adrenal glands, which produce the hormones cortisol and aldosterone as well as androgen hormones.
- Hashimoto’s thyroiditis: The thyroid hormone production slows to a deficiency.
- Myasthenia gravis: It affects nerve impulses that help the brain control the muscles.
- Autoimmune vasculitis: This happens when the immune system attacks blood vessels.
- Pernicious anemia: This condition causes a deficiency of a protein made by stomach lining cells, which is an intrinsic factor needed for the small intestine to absorb vitamin B12 from food.
- Celiac disease: People with celiac disease can’t eat foods containing gluten, a protein found in wheat, rye, and other grain products.
Zoonotic Disease
The term ‘Zoonosis’ (plural: Zoonoses) was coined by Rudolf Virchow in 1880 to encompass diseases shared by both humans and animals in nature. Later, in 1959, the World Health Organization (WHO) defined Zoonoses as diseases and infections naturally transmitted between vertebrate animals and humans. Zoonotic diseases can be bacterial, viral, parasitic, or caused by unconventional agents. Apart from being a public health concern, many major zoonotic diseases also hinder efficient food production from animals and create barriers to international trade in animal products.
How do germs spread between animals and people?
Zoonotic transmission can occur in various contexts, including companionship (pets), economic activities (farming), predatory behaviors (hunting, butchering, or consuming wild game), or research involving animals. Germs can spread through:
- Contaminated food or water supply: Consuming contaminated food or water can lead to various diseases in humans.
- Direct contact: Touching or petting animals, as well as bites or scratches from them, can transmit germs.
- Indirect contact: Contacting areas where animals live and roam can also lead to the spread of germs.
- Vector-borne transmission: Germs can be transmitted through bites from ticks, insects like mosquitoes or fleas, and contaminated food.
Types of Zoonotic Diseases
Zoonotic diseases encompass a broad array of illnesses originating from various pathogens. These diseases can be categorized based on their underlying causes:
- Bacterial Zoonoses: Pathogens like anthrax, salmonellosis, tuberculosis, Lyme disease, brucellosis, and plague are examples of bacterial zoonoses.
- Viral Zoonoses: Diseases such as rabies, acquired immune deficiency syndrome (AIDS), Ebola, and avian influenza stem from viral infections.
- Parasitic Zoonoses: Conditions like trichinosis, toxoplasmosis, trematodosis, giardiasis, malaria, and echinococcosis result from parasitic infections.
- Fungal Zoonoses: Ringworm and similar fungal infections contribute to fungal zoonoses.
Additional categories include:
- Rickettsial Zoonoses: For instance, Q-fever.
- Chlamydial Zoonoses: Examples include psittacosis.
- Diseases caused by acellular non-viral pathogenic agents.
Based on the mode of transmission, zoonotic diseases can be categorized into different types:
- Direct zoonoses: These diseases are transmitted directly from an infected vertebrate host to a susceptible host (such as humans) through direct contact, contact with contaminated objects (fomites), or by mechanical vectors. Examples include rabies, anthrax, and brucellosis.
- Cyclozoonoses: These diseases require more than one vertebrate host species to complete the life cycle of the agent, but they do not involve an invertebrate host. Examples include echinococcosis and taeniasis.
- Metazoonoses: These diseases are biologically transmitted by invertebrate vectors, where the agent multiplies and/or develops. There is always an extrinsic incubation (prepatent) period before transmission to another vertebrate host. An example is plague.
- Saprozoonoses: These diseases require a vertebrate host and a non-animal developmental site, such as soil, plant material, or pigeon droppings, for the infectious agent to develop. An example is aspergillosis.
Factors Responsible For Zoonotic Diseases:
- Ecological Changes in Human Environments:
- Human activities such as exploiting new territories, harnessing rivers, constructing roads, and clearing land for agriculture can disrupt natural ecosystems. This disruption exposes humans to potential pathogens that are part of the natural environment.
- Large-Scale Agricultural and Engineering Projects:
- Activities like expanding agriculture, building dams, and clearing forests can alter the habitats of disease-carrying vectors and reservoir animals. This alteration in habitats can contribute to the spread of zoonotic diseases.
- Occupational Hazards from Handling Animal By-Products and Wastes:
- Workers in industries like carpet weaving, livestock raising, and textile production may be exposed to zoonotic diseases like anthrax and leptospirosis through contact with animal products and wastes.
- Increased Human Movement:
- Human activities such as land development, engineering projects, pilgrimages, and tourism can expose people to contaminated food and water, increasing the risk of zoonotic disease transmission.
- Increased Trade in Animal Products:
- Trade in animal products such as wool, bone meal, and meat can introduce zoonotic diseases from endemic areas into new territories.
- Transportation of Virus-Infected Mosquitoes:
- Modes of transportation like aircraft, ships, trains, and vehicles can facilitate the movement of virus-infected mosquitoes, leading to the spread of diseases like yellow fever, Chikungunya fever, and dengue fever.
- Cultural and Anthropological Practices:
- Certain cultural practices, such as allowing dogs and hyenas to consume human bodies infected with diseases like hydatidosis in some regions like Kenya, can perpetuate the transmission cycle of zoonotic diseases.
List of Zoonotic Diseases:
- Bacterial zoonoses: anthrax, brucellosis, plague, leptospirosis, salmonellosis, lyme disease
- Viral zoonoses: rabies, arbovirus infections, KFD, yellow fever, influenza, CCHF
- Rickettsial zoonoses: murine typhus, tick typhus, scrub typhus, Q-fever
- Protozoal zoonoses: toxoplasmosis, trypanosomiasis, leishmaniasis
- Helminthic zoonoses: echinococcosis (hydatid disease), taeniasis, schistosomiasis, dracunculiasis
- Fungal zoonoses: deep mycosis – histoplasmosis, cryptococcosis, superficial dermatophytes
- Ectoparasites: scabies, myiasis
FAQs
Q: What are essential nutrients and why are they important for health?
Essential nutrients are substances that the body cannot produce on its own, so they must be obtained through diet. These include vitamins, minerals, essential fatty acids, and essential amino acids. They are vital for various bodily functions such as metabolism, growth, repair of tissues, and immune function.
Q: What is the difference between organic and inorganic substances in nutrition?
Organic substances in nutrition refer to compounds that contain carbon, usually derived from living organisms, such as carbohydrates, proteins, lipids, and vitamins. Inorganic substances, on the other hand, do not contain carbon and are typically minerals like calcium, iron, zinc, and electrolytes. While both are essential for health, they serve different roles in the body’s functioning.
Q: How do communicable diseases differ from non-communicable diseases?
Communicable diseases, also known as infectious diseases, are caused by pathogenic microorganisms such as bacteria, viruses, fungi, and parasites, and can be transmitted from person to person or from animals to humans. Non-communicable diseases (NCDs), on the other hand, are not infectious and typically develop over time due to genetic, environmental, and lifestyle factors. Examples of NCDs include heart disease, diabetes, cancer, and chronic respiratory diseases.
Q: What are genetic diseases and how do they impact health?
Genetic diseases are disorders caused by abnormalities in an individual’s genetic material (DNA). These abnormalities can be inherited from one or both parents or can occur spontaneously due to mutations. Genetic diseases can affect various aspects of health, including physical development, metabolism, immune function, and neurological function. Examples include cystic fibrosis, sickle cell anemia, Huntington’s disease, and Down syndrome.
Q: What is the role of immunity in preventing diseases, and how does immunization contribute to this?
Immunity is the body’s ability to defend itself against harmful pathogens and other foreign substances. It involves both innate immunity, which provides immediate, nonspecific defense against pathogens, and adaptive immunity, which develops over time in response to specific pathogens. Immunization, also known as vaccination, helps to stimulate the immune system to produce antibodies against specific diseases, providing protection against future infections. It is a crucial public health intervention for preventing the spread of infectious diseases and reducing morbidity and mortality rates. Additionally, autoimmune diseases occur when the immune system mistakenly attacks healthy cells and tissues in the body, leading to conditions such as rheumatoid arthritis, lupus, and multiple sclerosis. Zoonotic diseases are infectious diseases that can be transmitted between animals and humans, such as rabies, Ebola, and avian influenza.
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