The Presentation explains basic models of disease causation, to understand the etiology or causes of disease & altered production and helps to understand the applicability of causal criteria applied to epidemiological studies.
Measurements of morbidity and mortality
At the end of the session, the students shall be able to
List the basic measurements in epidemiology
Select an appropriate tools of measurement
Measure morbidity & mortality
Perform standardization of rates
Development over the centuries of Human Civilization concepts of disease causation remained transforming and still not reached the perfection.
Pre-modern era theories of Disease causation: Religions often attributed disease outbreaks or other misfortunes to divine retribution - punishment for mankind's sins.
and imbalance among four vital "humors“ within us. Hippocrates; Yellow Bile, Black Bile, Phlegm and Blood
Miasma Theory: 500 BC Miasmas are poisonous emanations from putrefying carcasses, vegetables, molds and also the invisible particles. This theory led to explanation of several outbreaks of cholera, plague and malaria (Mal-aria= bad air).
Fracastoro's contagion theory of disease (1546)
Germ theory: Louis Pasteur , Lister and others introduced the germ theory in 1878. In 1890 Robert Koch proposed specific criteria that should be met before concluding that a disease was caused by a particular bacterium. Only single germ is responsible for causation of a specific disease.
Webs of Causation: Epidemiological concept
As per John M. Last (1988) Epidemiology is the study of the distribution and determinants of health related states or events in specified populations, and the application of this study to the control of health problems.
Measurements of morbidity and mortality
At the end of the session, the students shall be able to
List the basic measurements in epidemiology
Select an appropriate tools of measurement
Measure morbidity & mortality
Perform standardization of rates
Development over the centuries of Human Civilization concepts of disease causation remained transforming and still not reached the perfection.
Pre-modern era theories of Disease causation: Religions often attributed disease outbreaks or other misfortunes to divine retribution - punishment for mankind's sins.
and imbalance among four vital "humors“ within us. Hippocrates; Yellow Bile, Black Bile, Phlegm and Blood
Miasma Theory: 500 BC Miasmas are poisonous emanations from putrefying carcasses, vegetables, molds and also the invisible particles. This theory led to explanation of several outbreaks of cholera, plague and malaria (Mal-aria= bad air).
Fracastoro's contagion theory of disease (1546)
Germ theory: Louis Pasteur , Lister and others introduced the germ theory in 1878. In 1890 Robert Koch proposed specific criteria that should be met before concluding that a disease was caused by a particular bacterium. Only single germ is responsible for causation of a specific disease.
Webs of Causation: Epidemiological concept
As per John M. Last (1988) Epidemiology is the study of the distribution and determinants of health related states or events in specified populations, and the application of this study to the control of health problems.
Observingthedistributionofdiseaseorhealth related events in human population.
• Identify the characteristics with which the disease is associated.
• Basically 3 questions are asked who, when and where.
• Who means the person affected, where means the place and when is the time distribution.
This presentation will help to get an insight into Epidemiological methods and describes details of Descriptive epidemiology. It will be useful to medical researcher as an initial input.
Causation. A number of models of disease causation have been proposed. Among the simplest of these is the epidemiologic triad or triangle, the traditional model for infectious disease. The triad consists of an external agent, a susceptible host, and an environment that brings the host and agent together.
Observingthedistributionofdiseaseorhealth related events in human population.
• Identify the characteristics with which the disease is associated.
• Basically 3 questions are asked who, when and where.
• Who means the person affected, where means the place and when is the time distribution.
This presentation will help to get an insight into Epidemiological methods and describes details of Descriptive epidemiology. It will be useful to medical researcher as an initial input.
Causation. A number of models of disease causation have been proposed. Among the simplest of these is the epidemiologic triad or triangle, the traditional model for infectious disease. The triad consists of an external agent, a susceptible host, and an environment that brings the host and agent together.
Introduction to Epidemiology
History of Epidemiology.
Definition of Epidemiology and its components.
Epidemiological Basic concepts.
Aims of Epidemiology.
Ten Uses of Epidemiology.
Scope or The Areas of Application .
Types of Epidemiological Studies.
Disease Control is the term used to describe operation or activities with the aims;
1.
2.
3.
4.
To reduce incidences of diseases.
To reduce duration of diseases.
To reduce chances of transmission of diseases from one person to another.
To reduce negative effects of disease which include both the physical &
psychological complications.
5. To reduce financial burden to the community in case of any disability.
Issues in Veterinary Disease Diagnosis.pptxBhoj Raj Singh
Diagnosis of a disease or a problem is the first step towards solution/ treatment/ control/ prevention.
Diagnosis is successfully. important to determine Prevalence (True prevalence, apparent prevalence) and Incidence of the disease to estimate the disease burden so that prevention and control measures can be planned and implemented.
However, in few years with the invasion of pharmaco-politics in disease control the term got vitiated.
Epidemiological Approaches for Evaluation of diagnostic tests.pptxBhoj Raj Singh
Diagnosis of a disease or a problem is the first step towards solution/ treatment. Clinical Diagnosis or Provisional Diagnosis is the first step in diagnosis and is done after a physical examination of the patient by a clinician. Clinical diagnosis may or may not be true and to reach Final diagnosis Laboratory Investigations using gross and microscopic pathological observations and determining the disease indicators are required. The diagnostic tests may be Non-dichotomous Diagnostic Tests (when continuous values are given by the test in a range starting from sub-normal to above-normal range) and Dichotomous Diagnostic Tests (when results are given either plus or minus, disease or no-disease). To make non- Dichotomous diagnostic test a Dichotomous one you need to establish the cut-off values based on reference values or Gold Standard test readings or with the use of Receiver operator characteristic (ROC) curves, Precision-Recall Curves, Likelihood Ratios, etc., and finally establishing statistical agreement (using Kappa values, Level of Agreement, χ2 Statistics) between the true diagnosis and laboratory diagnosis. Thereafter, the Accuracy, Precision, Bias, Sensitivity, Specificity, Positive Predictive value, and Negative Predictive value, of a diagnostic test are established for use in clinical practice. Diagnostic tests are also used to determine Prevalence (True prevalence, apparent prevalence) and Incidence of the disease to estimate the disease burden so that control measures can be implemented. There are several Phases in the development and use of a diagnostic assay starting from conceptualization of the diagnostic test, development and evaluation to determine flaws in diagnostic test use and Interpretation influencers. This presentation mainly deals with the epidemiological evaluation procedures for diagnostic tests.
Types of Trials in Medicine, vaccine efficacy or effectiveness trials and rel...Bhoj Raj Singh
The importance of learning about medicines’ and vaccines’ efficacy or effectiveness trials is not only necessary to those who are developing, producing or marketing these pharmaceutical products but to the users also because: The Emergency approval of Covid-19 vaccines and many other medicines in last few years has created so much fuss to understand the reality. The lesson learnt from Covid-19 vaccine(s) by vaccine production, marketing, vaccination and finally the revenue earned by vaccine developers and producers, and political gain by politicians, is proving deleterious to the society as several vaccine(s), useless or scarcely proven safe and useful, are going to infest and some have already infested the market (the health industry). So reading this presentation may be useful to you so that you may question the authorities if any is engaged in bluffing you. The presentation talks briefly about Prevention trials, Screening trials, Treatment trials, Feasibility studies, Pilot studies, Phases in clinical trial, Multi-arm multi-stage (MAMS) trials, Global Clinical Trials, Vaccine efficacy, Vaccine safety, Emergency Use Authorization (EUA), Serious Adverse Events (SAE), SEA rules, The Vaccine Adverse Event Reporting System (VAERS), Vaccine Safety Datalink (VSD), The Advisory Committee on Immunization Practices (ACIP), Clinical Immunization Safety Assessment (CISA), CDSCO Rules Governing Clinical Trials, Schedule Y, The Ethics Committee, Empowered Committee on Animal Health, Tracking Vaccine Quality, Pre-clinical and Clinical data, Proof of Concept, Biological License Application (BLA) and Clinical hold.
Detection and Characterization of Pathotypes, Serotypes, Biotypes, Phenotypes...Bhoj Raj Singh
This presentation of my lecture, to Epidemiology students, briefs about different methods for differentiating or finding similarities among isolates of pathogens required establishing causal associations in epidemiological disease diagnosis.
Epidemiology of antigenic, genetic and biological diversity amongst pathogens...Bhoj Raj Singh
This presentation briefly describes the Antigenic, genetic and biological diversity amongst pathogens, and their origin and emergence. It also discusses with their association with different forms associated with a disease/ outbreak. The presentation also enlists diversity in strains causing some common diseases of livestock in India.
Differentiation of field isolates (wild) from vaccine strains (Marker, DIVA &...Bhoj Raj Singh
Nowadays vaccination is often reported as the cause of disease outbreaks. To ward off this misconception (vaccines are made to save the masses not to risk their lives)or to understand vaccination failures, it is necessary to understand the difference between a field strain causing the disease and a vaccine strain having attenuated virulence. This presentation talks about DIVA and DISA vaccines too.
Lumpy skin disease (LSD) Globally and in India.pptxBhoj Raj Singh
LSD has emerged as a dairy industry devastating disease in India in the last four years. First noticed in Orrisa and is now present all over India. Recurring outbreaks are now noticed in Rajasthan, Uttarakhand and other states indicating that the disease is becoming endemic in India.
Molecular determinants of pathogenicity and virulence among pathogens.pptxBhoj Raj Singh
The presentation discusses the pathogenicity and virulence of pathogens, their determinants and their interaction with the host. It talks briefly about pathogenicity, virulence, adhesions, invasions, toxins, disease, pathogenesis, pathogenicity islands (PAIs), intracellular, extracellular, bacteria, virus, fungi, prion, metazoan worms, protozoa, tuberculosis, E. coli, Salmonella, Yersinia, Mycobacterium, cytotoxins, enterotoxins, exotoxins, neurotoxins, endotoxins, in-silico, in-Vitro, in-vivo, immunohistology, haemagglutinins, spike proteins, integrins, and phagolysosomes.
Molecular epidemiology and Disease causation.pptxBhoj Raj Singh
This short presentation describes molecular epidemiology, differentiate it from genetic epidemiology, and also deals with ascertaining the cause of disease.
My research proposals, to porotect holy cow, rejected by the ICAR-IVRI in the...Bhoj Raj Singh
The presentation relates to my three research proposals, aimed at Protection of Holy cow, rejected at ICAR-ICAR-Indian Veterinary Research Institute, Izatnagar-243 122, India, in last five years
Clinical evaluation of newly advocated therapies for brucellosis in cattle and buffaloes. Duration: September 2019 to August 2021
A cross-sectional survey of Holy Cow Infectious Problems in Gaushalas (Gaushalas are protective shelters for stray cows in India). Duration: September 2022-August 2024
Explorative study on Epidemiological determinants associated with a drastic reduction in Milk Production of Dairy Animals with reference to communicable diseases. Duration: September 2022-August 2024
Animal Disease Control and Antimicrobial Resistance-A Message to Veterinary S...Bhoj Raj Singh
This presentation is for
• Introspection by all authorities before criticizing Veterinarians for an increase in AMR & to Doyens of Veterinary Science sitting mum when Vets are criticized!
• To realize that DAHD and State Animal/ Livestock Departments are:
– Fake data masters!
A realization to Doyens of Veterinary Science that they are:
– Spineless when their voice is the most needed!
– Don’t understand epidemiology to the least and make minimal attempts to improve Epidemiological understanding in veterinarians!
– The real negative thinkers!
– Suffering from an inferiority complex!
– Real killers of the holy cow!
– Interested to develop the best vet doctors but creating butchers!
– Real anti-nationals!
They talk of one health without understanding it!
– Much more!!!
Causes of Disease and Preserving Health in Different systems of Medicine.pptxBhoj Raj Singh
This presentation deals with concepts of disease causation and methods used for the alleviation of those causes to ensure health. It has briefed the causes of diseases according to Ayurvedic medicine, Unani medicine, Siddham medicine, Naturopathy, Homeopathy, Chinese medicine, Touch therapy- Reiki, Mantra therapy, and Allopathy. It also summarizes the treatments and practices in different systems of medicine. DOI: 10.13140/RG.2.2.30883.22569
AMR challenges in human from animal foods- Facts and Myths.pptxBhoj Raj Singh
This presentation talks about ÄMR: A public health threat, a “silent pandemic”.
Infections caused by Antimicrobial-drug-resistant (AMR) pathogens caused >1.27 million deaths worldwide in 2019 (low level or no surveillance) and increasing year after year which may be > million in coming decades. Covid-19 caused ~6.8 million deaths in >3 years but now the pandemic is ending but the AMR pandemic has no timeline for its ending. Many deaths are also attributed to AMR pathogens.
More antibiotic use (irrespective of the sector) = More AMR.
This presentation also talks about ways and means to mitigate the AMR pandemic. 1. Stopping the blame game. All are equally responsible for the emergence of AMR, the share of developed and educated communities is much more than poor and un-educated communities.
2. Working together: On-Line Real-Time AST Data Sharing Platform for different diagnostic and research laboratories doing AST routinely.
3. Implementing not only antibiotic veterinary and medical stewardship but antimicrobial production and distribution stewardship too.
4. Educating for Environmental health not only human, plant, and animal health.
5. AMR's solution is not in searching for alternatives to antibiotics but in establishing environmental harmony.
6. More emphasis on AMR epidemiology than on AMR microbiology and pharmacology.
7. Development of understanding that bacteria and other microbes are more essential for life on earth than the human race. Microbes can live without humans, but humans can’t without microbes.
Global-Health is of prime importance than economic growth/ greediness.
Herbal antimicrobials are considered as an important alternative to antibiotic and probable tools to mitigate emerging antimicrobial-drug-resistance (AMR). However, it is difficult to accept that microbes may not adapt to herbal antimicrobials as rapidly as to antibiotics. This is now well documented that herbal antimicrobial resistance is also common among common pathogenic microbes and genes are now known to encode herbal drug-resistance too. This lecture gives description how resistance to conventional antimicrobials impacts susceptibility of microbes for herbal antimicrobials. Lecture Scheduled on 21st February 2023, In: Antimicrobial Resistance (AMR) in Foodborne pathogens” sponsored under the ICAR-NAHEP-CAAST project by the MAFSU, Mumbai Veterinary College, at the Division of Veterinary Public Health, ICAR-IVRI from 20th February to 25th February, 2023.
Epidemiological characterisation of Burkholderia cepacia complex (Bcc) from c...Bhoj Raj Singh
The presentation is extracted from the thesis talking about
1. The presence of Bcc organisms in the clinical infections of animals.
2. Ultrasound gels as a potential source of pathogens, especially Bcc.
3. Multidrug resistance in BCCs.
4. Lack of regulatory guidelines in Indian Pharmacopeia as existing in USP.
There are hundreds of diseases of livestock and pet animals that can be printed through properly used quality vaccines. This presentation summarises different types of vaccines used by veterinarians to control/ prevent diseases. The presentation enlists the vaccine-preventable diseases of pets and livestock, and also the different vaccines used.
Major flaws in Animal Disease Control Leading to Partial Success or Failure.pptxBhoj Raj Singh
This presentation summarises major problems of Animal Disease Control Programs ongoing in India. India is a hyperendemic country for many animal diseases and zoonotic diseases. Every year billions of rupees are spent on disease control, surveillance, monitoring, and vaccination against vaccine-preventable diseases. However, due to the failure of most animal disease control programs for one or other reasons India directly losses about 20 and 25 thousand crores annually due to endemicity of FMD & brucellosis, respectively. The presentation identifies problems at different levels of different ongoing disease control programs in India. The non-availability of authentic disease data and flaws in vaccine quality control are the biggest problems.
Animal Disease Control Programs in India.pptBhoj Raj Singh
India is a hyperendemic country for many animal diseases and zoonotic diseases. Every year billions of rupees are spent on disease control, surveillance, monitoring, and vaccination against vaccine-preventable diseases. However, due to the failure of most animal disease control programs for one or other reasons India directly losses about 20 and 25 thousand crores annually due to endemicity of FMD & brucellosis, respectively. The presentation describes the pros and cons of different ongoing disease control programs going on in India.
Control and Eradication of Animal diseases.pptxBhoj Raj Singh
The presentation details different methods and terminologies used in disease management. It briefs about different types of disease control programs run at global, regional, and national levels. It also tells about the success and failure of different disease control programs. The presentation also briefed about methods of disease control.
The presentation summarises important methods and protocols of Clinical Microbiology. It may be useful to learners of Clinical microbiology at the undergraduate label. The presentation describes the procedures for collecting clinical samples, transport, and testing. It also describes the different methods of antimicrobial susceptibility testing and standards.
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
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Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
Anti ulcer drugs and their Advance pharmacology ||
Anti-ulcer drugs are medications used to prevent and treat ulcers in the stomach and upper part of the small intestine (duodenal ulcers). These ulcers are often caused by an imbalance between stomach acid and the mucosal lining, which protects the stomach lining.
||Scope: Overview of various classes of anti-ulcer drugs, their mechanisms of action, indications, side effects, and clinical considerations.
Flu Vaccine Alert in Bangalore Karnatakaaddon Scans
As flu season approaches, health officials in Bangalore, Karnataka, are urging residents to get their flu vaccinations. The seasonal flu, while common, can lead to severe health complications, particularly for vulnerable populations such as young children, the elderly, and those with underlying health conditions.
Dr. Vidisha Kumari, a leading epidemiologist in Bangalore, emphasizes the importance of getting vaccinated. "The flu vaccine is our best defense against the influenza virus. It not only protects individuals but also helps prevent the spread of the virus in our communities," he says.
This year, the flu season is expected to coincide with a potential increase in other respiratory illnesses. The Karnataka Health Department has launched an awareness campaign highlighting the significance of flu vaccinations. They have set up multiple vaccination centers across Bangalore, making it convenient for residents to receive their shots.
To encourage widespread vaccination, the government is also collaborating with local schools, workplaces, and community centers to facilitate vaccination drives. Special attention is being given to ensuring that the vaccine is accessible to all, including marginalized communities who may have limited access to healthcare.
Residents are reminded that the flu vaccine is safe and effective. Common side effects are mild and may include soreness at the injection site, mild fever, or muscle aches. These side effects are generally short-lived and far less severe than the flu itself.
Healthcare providers are also stressing the importance of continuing COVID-19 precautions. Wearing masks, practicing good hand hygiene, and maintaining social distancing are still crucial, especially in crowded places.
Protect yourself and your loved ones by getting vaccinated. Together, we can help keep Bangalore healthy and safe this flu season. For more information on vaccination centers and schedules, residents can visit the Karnataka Health Department’s official website or follow their social media pages.
Stay informed, stay safe, and get your flu shot today!
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
1. Triad , Wheel, Web
and Pie concepts of
disease causation
By
Dr. Bhoj R Singh
Principal Scientist & Head Division of Epidemiology,
ICAR-Indian Veterinary Research Institute, Izatnagar-
243122, Bareilly, UP, India.
Email: brs1762@gmail.com
2. Objectives
To explain basic models of disease
causation.
To understand the etiology or causes of
disease & altered production.
To understand the applicability of causal
criteria as applied to epidemiological
studies
3. A cause?
Webster’s dictionary defines a cause as
‘something which has an effect’.
In epidemiology a cause can be considered
to be something that alters the frequency of
disease, health & production status or
associated factors in a population.
4. CONCEPT OF DISEASE
A condition of the body or some part
or organ of the body in which its
functions are deranged.
It is a mal-adjustment of an
organism to the environment.
It is deviation from normal function &
purpose.
5. 5
In epidemiology, there are several models of disease
causation that help understand disease process.
The most widely applied models are:
The epidemiological triad (triangle),
the wheel, and
the web. And
The sufficient cause and component causes models
(Rothman’s component causes model)
General Models of Causation
6. The epidemiologic triad Model
The epidemiologic triangle or triad is the traditional
model of infectious disease causation.
It has three components: an external agent, a
susceptible host, and environmental factors that
interrelate in a variety of complex ways to produce
disease & alter production & utility in animals.
7. 7
The Epidemiological Triad
HOST
AGENT ENVIRONMENT
Genetic make up (breed,
strain, variety.
Nutritional status
Immunological status etc.
Virulence
Pathovar
Biovar
ID50,LD50
Climate
Radiations
Rainfall
Winds
8. Agent factors
•Infectious agents: agent might be microorganism—virus,
bacterium, parasite, prions, other microbes and others
(poisonous creatures). Generally, these agents must be present
for disease to occur as essential causal factor.
•Nutritive: Excesses or deficiencies (Cholesterol, vitamins,
proteins)
•Chemical agents: (carbon monoxide, drugs, medications)
•Physical agents (Ionizing radiation,…
8
9. More about agent factors
Living organisms:
Adaptability
Host range
Virulence
Pathogenicity
Dose: ID50, LD50
etc.
Chemical agents (Toxins and pollutants)
Toxicity dose,
Pnetrability,
Stability
Half-life etc.
Physical agents (Radiations, sound, winds, floods, draughts, soil etc)
Compositions
Magnitude,
Exposure time
10. Host factors
•Host factors are intrinsic factors that influence an individual’s
exposure, susceptibility, or response to a causative agent.
•Host factors that affect a individual's risk of exposure to an
agent:
•Age, race, sex, breed, strain, purpose of domestication, feed
and feeding habits, breeding practices sociological status, etc..
•Host factors which affect susceptibility & response to an agent:
•Genetic composition, nutritional and immunologic status,
anatomic structure, presence of other disease or medications,
purpose & use of domestication, method of rearing & husbandry
practices and psychological makeup.10
11. Environmental factors
Environmental factors are extrinsic factors which affect the agent
as well as the host and the opportunity for exposure.
Environmental factors include:
Physical factors such as geology, climate,..
Biologic factors such as insects that transmit an agent; and
Socioeconomic factors such as crowding, sanitation, and the
availability of health services.
11
12. Web of Causation
Web of Causation is devised to address chronic
disease – can also be applied to communicable
disease) due to multi-factorial/ multi-etiologic nature
of causation in many diseases
There is no single cause / multi-factorial causes
Causes of disease are interacting in various pathways
Illustrates the interconnectedness of possible causes
Here the disease is usually well-defined from a clinical point
of view (e.g. lung cancer, Mastitis) but the etiologic
perspective is more complex.
14. 14
The Wheel of Disease Causation
Mausner & Kramer,1985
The Wheel of Causation de-emphasizes the
agent as the sole cause of disease,
It emphasizes the interplay of physical, biological
and social (production) environments. It also
brings genetics into the mix.
A disease model which discriminates between
'necessary' and 'sufficient' factors.
15. 15
Necessary and sufficient causes
A necessary cause is a causal factor whose presence is
required for the occurrence of the effect. If disease does
not develop without the factor being present, then we term
the causative factor “necessary”.
Sufficient cause is a “minimum set of conditions, factors or
events needed to produce a given outcome.
The factors or conditions that form a sufficient cause are
called component causes.
16. 16
Example
The tubercle bacillus is required to cause
tuberculosis but, alone, does not always
cause it.
Thus tubercle bacillus is a necessary,
not a sufficient cause.
This true for most the infectious causes.
17. 17
Rothman's model has emphasised that the causes of disease
comprise a collection of factors.
These factors represent pieces of a pie, the whole pie
(combinations of factors) is the sufficient cause for a
disease. May be several pies for a disease or syndrome.
It shows that a disease may have more that one sufficient
cause, with each sufficient cause being composed of several
factors.
Rothman’s Component Causes and
Causal Pies Model
18. 18
The factors represented by the pieces of the pie in this model
are called component causes.
Each single component cause is rarely a sufficient cause by
itself, but may be necessary for causation of the disease.
Control of the disease could be achieved by removing one of
the components in each "pie" and if there were a factor
common to all "pies“ (necessary cause) the disease would be
eliminated by removing that alone.
Rothman’s
Component Causes and Causal Pies
19. 19
Causal Complement
(Causal Pie)
Causal complement ≡
the set of factors that
completes a sufficient
causal mechanism
Example: Typhoid
Necessary agent
Salmonella enterica ser
Typhi
Causal complement
“Susceptibility”
20. Causal pies representing all sufficient causes of a
particular disease
20 A given disease can have multiple sufficient mechanisms
Necessary
cause =
found in all
cases (B)
Contributing
cause =
needed in
some cases
(A, C, D, E,
F) but not in
all cases.
Sufficient
cause = the
set of
necessary &
contributing
causes that
make disease
inevitable in
an individual
21. Applications
Epidemiologic Triad (devised to enhance
search for understanding communicable
disease). Model works with both infectious or
non-infectious diseases.
Web of Causation (devised to address chronic
disease – can also be applied to communicable
disease)
22. Applications
The purpose of studying cause and effect
in epidemiology is to generate knowledge
to prevent and control disease.
Distinguishing natural from other causes of
death & loss or reduced production/ utility.
Establishing modes of transmission &
spread.
23. Quiz
1. Define the cause and disease.
2. Name the different models to explain the
causation of disease.
3. Give Trriad factors of HS and FMD.
4. Define sufficient and necessary & component
causes.
5. Differentiate between Mausner & Kramer’s Wheel
and Rothman’s causal Pie Model.
6. Construct Pies for Mastitis & Infertility in cows.
7. Construct web model for repeat breeding in
buffaloes.