PID week 1 Intro to I.D. & Epi Flashcards
Principles of Infectious Diseases
infectious disease dependent on ?, ? and ?
environment, susceptible host and pathogen
Principles of Infectious Diseases
infectious disease dependent on pathogen, environment and susceptible host
susceptible host
1. ?, ?, ? and ?
2. ? and ?
3. ?
Environment
1. abiotic and biotic factors
2. ? management
3. population density
4. ?
5. nutrition
6. prevention
pathogen
1. pathogenicity
2. ? efficiency
3. ? efficiency
4. ? dose
Define infection, disease, and infectious diseases.
(define etiology)
infection: the invasion and multiplication of pathogens in an individual or population
“dis”ease: a “dis”order (s for structure) in the structure or function that causes adverse effects on the host and is not simply a result of physical injury
infectious diseases: diseases caused by pathogenic microbes. some are communicable i.e., can be spread directly or indirectly from one animal to another
etiology: study of cause of disease
[microorganisms or microbes are any organisms that are invisible to the ?
microbes first observed by whom?
microbes are ALL below ? micrometer and viruses ? ]
microorganisms or microbes are any organisms that are invisible to the naked eye
Antonie Van Leeuwenhoek
“micro”bes are ALL below 100 “micro”meter and flu virus = 100 nm
[smallest to largest:
prions (proteins so not rlly alive)
viruses (debate on whether alive or not)
bacteria
fungi
protozoa
multicellular parasites]
PVBFPM
Microbe - Host relationship
- Free-living
- Commensal
* A microorganism that is a ? inhabitant of the animal body
* In commensal relationships, either the microbe or host (or both) derives ?; neither is ? under normal circumstances - Pathogen
* A microorganism capable of causing ?
* Includes ? and non-commensals
Obligate pathogen
* A microorganism that must produce ?* to transmit and thereby survive evolutionarily.
* Obligate pathogens are not commensals, but they can produce ? infections (*In this context:damage to the organism at a ? level, with or without clinical signs)
Facultative pathogen
*Microorganism which can infect and multiply in hosts, occasionally or usually causing disease??, but also capable of multiplying in the ?
Microbe - Host relationship
- Free-living
- Commensal
* A microorganism that is a normal inhabitant of the animal body
* In commensal relationships, either the microbe or host (or both) derives benefit; neither is harmed under normal circumstances - Pathogen
* A microorganism capable of causing disease
* Includes commensals and non-commensals
(commensal so pathogens can be non-harming as well) - Obligate pathogen
* A microorganism that must produce disease* to transmit and thereby survive evolutionarily.
* Obligate pathogens are not commensals, but they can produce asymptomatic infections (*In this context: damage to the organism at a molecular level, with or without clinical signs) - Facultative pathogen
*Microorganism which can infect and multiply in hosts, occasionally causing disease, but also capable of multiplying in the enviroment
obligate in the sense obligate pathogen can only mulitply in the host and not in env.
- Commensal pathogen
- A microorganism that is commonly found within the ? microbiota that can cause disease in normal hosts with some ?.
- Example: Staphylococcus aureus, Streptococcus ?, ? albicans
- Not all manifest as pathogens with the same frequency, some may require significant impairment of the host’s ? to cause disease - known as ? pathogens
Environmental pathogen
* A microorganism capable of causing disease that is transmitted to the host from an ? source such as water or soil.
* Examples: ? and ?
Zoonotic pathogen
* A microorganism that is a ? or pathogen on animals and that can be transmitted to ? either through vectors (i.e. ticks) or direct contact with the animal or its products.
* Examples: ? abortus, ?
- Commensal pathogen
- A microorganism that is commonly found within the idigenous microbiota that can cause disease in normal hosts with some regularity.
- Example: Staphylococcus aureus, Streptococcus pneumoniae, Candida albicans
- Not all manifest as pathogens with the same frequency, some may require significant impairment of the host’s immunity to cause disease - known as oppurtunistic pathogens
Environmental pathogen
* A microorganism capable of causing disease that is transmitted to the host from an environmental source such as water or soil.
* Examples: clostridium tetani and clostridium botulinum
Zoonotic pathogen
* A microorganism that is a coloniser or pathogen on animals and that can be transmitted to humans either through vectors (i.e. ticks) or direct contact with the animal or its products.
* Examples: brucella abortus, rabies
- Describe the potential outcomes of the host’s exposure to infectious microbes
- Understand the importance of Koch’s postulates for the identification of pathogens causing diseases and its limitations
- Describe the stages of infectious diseases
- Define One Health and describe its importance
Attributes of Pathogens
Enter host
* Can occur through the skin, mucosa or body’s ?
* ? pathogens may skip this step, they’re “already there”
Establish a unique habitat within the host
* Usually requires crossing ? barriers and/or breaching the host’s ?
Multiply within host
* Typically what causes ?
Exit to infect new host
* Essential trait for ? pathogens
Attributes of Pathogens
Enter host
* Can occur through the skin, mucosa or body’s orifices
* commensal pathogens may skip this step, they’re “already there”
Establish a unique habitat within the host
* Usually requires crossing physical barriers and/or breaching the host’s defenses
Multiply within host
* Typically what causes disease
Exit to infect new host
* Essential trait for obligate pathogens
- Describe the potential outcomes of the host’s exposure to infectious microbes
- no infection
- infection
- ? (disease not severe enough)
- clinical
- subclinical
- ? elimination
- ?
- subclinical
- pathogen elimination
- immunity
- non-immunity
- pathogen elimination
- infection
- clinical- death
- carrier
- pathogen elimination
infection
- clinical (pathogen elimination, carrier, death)
- pathogen elimination
- immunity
- non-immunity
- Describe the potential outcomes of the host’s exposure to infectious microbes
- no infection
- infection
- subclinical (disease not severe enough)
- clinical
- subclinical
- pathogen elimination
- carrier (basically same as clinical but death not included)
- subclinical
- pathogen elimination
- immunity
- non-immunity
- pathogen elimination
- infection
- clinical- death
- carrier
- pathogen elimination
infection
- clinical
- pathogen elimination
- immunity
- non-immunity
immunity and non immunity for pathogen elimination for all
pathogen elimination and carrier both for clinical and subclinical // only difference for clinical is that it includes death
OUTCOMES OF EXPOSURE TO INFECTIOUS AGENTS
no exposure = no infection = no disease
- Understand the importance of Koch’s postulates for the identification of pathogens causing diseases and its limitations
KOCH’S POSTULATES
1. The suspected pathogen must be found in every case of ? and not be found in ? individuals.
2. The suspected pathogen can be ? and grown in ? culture.
3. A healthy test subject infected with the suspected ? must develop the same signs and symptoms of disease
4. The pathogen must be ? from the new host.
KOCH’S POSTULATES
1. The suspected pathogen must be found in every case of disease and not be found in healthy individuals.
2. The suspected pathogen can be isolated and grown in pure culture.
3. A healthy test subject infected with the suspected pathogen must develop the same signs and symptoms of disease
4. The pathogen must be re-isolated from the new host.
KOCH’S POSTULATES LIMITATIONS
- Inability to ? the organism in pure culture
- Inability to isolate the organism in cell-free culture (y a limitation??)
- Organisms for which a single species acts as host
- Subclinical infection (not severe enough)
- Organisms that cause ‘?’ infection
- Disease caused by toxins (why is it a limitation??)
- Diseases that require ?
- Organisms associated with tumors
KOCH’S POSTULATES LIMITATIONS
- Inability to isolate the organism in pure culture
- Inability to isolate the organism in cell-free culture
- Organisms for which a single species acts as host
- Subclinical infection (not severe enough)
- Organisms that cause ‘distant’ infection
- Disease caused by toxins (why is it a limitation??)
- Diseases that require coinfection
- Organisms associated with tumors.
Five stages of an infectious disease
- ? - Pathogen multiplies without clinical signs
- ? - General and unspecific signs
- ? - Signs and symptoms are more severe and specific
- ? - Number of pathogens and clinical signs begin to decline
- ? - Return to normalcy*
Five stages of an infectious disease
- Incubation - Pathogen multiplies without clinical signs
- prodromal - General and unspecific signs
- illness - Signs and symptoms are more severe and specific
- decline - The number of pathogens and clinical signs begin to decline
- convalescence - Return to normalcy*
LOs
* Understand what is epidemiology and its
application in veterinary science
- Understand the importance of epidemiology in veterinary practice
- Understand and know some concepts of epidemiology: study designs, measures of disease frequency, surveillance, compartment model, epidemic, causation
LOs
* Understand what is epidemiology and its
application in veterinary science
[vet epidemiologists are vets with advanced trainings in monitoring, controlling, and preventing disease in animal populations
most work regular hrs, a basic doctor of vet medicine (DVM) degree is needed
may find jobs at: research labs, academic institutions, private corporations]
Epidemiology: is the science of study and analysis of ? and ?
of ? and ? conditions in defined populations
Epidemiology: is the science of study and analysis of distribution and determinants
of health and disease conditions in defined populations
LOs
* Understand what is epidemiology and its
application in veterinary science
Epidemiology: is the science of study and analysis of ? and ?
of ? and ? conditions in defined populations
Epidemiology purposes
- ? : agent, host, and factors that affect health
- ? : relative importance of causes of illness, disability and death
- ?: a population at risk from specific causes
- ?: the effectiveness of health programs and services
Epidemiology: is the science of study and analysis of determination and distribution
of health and disease conditions in defined populations
Epidemiology purposes
- discover: agent, host, and factors that affect health
- determine: the relative importance of causes of illness, disability, and death (lead poisoning) - cancer
- identify: a population at risk from specific causes
- evaluate: the effectiveness of health programs and services
DDIE
Does epidemiology refer exclusively to the study of infectious diseases in a population?
infectious diseases
?
cardiovascular diseases
? - family line (genetics)
Does epidemiology refer exclusively to the study of infectious diseases in a population?
no as cardiovascular disease not infectious
infectious diseases
injuries
cardiovascular diseases
cancers (- family line (genetics) - mainly from smoking and drinking)
lead poisoning (- from pipes (classic example, human public health - old pipes makes from lead)
Individual approach
sheep -> diagnosis -> treatment
Anamnesis (u ask questions) -> (look at) clinical signs -> hypothesis=differntial diagnosis -> test (laboratory) -> diagnosis -> treatment and prevention
diff characteristics of WHO? so
1. breed
2. age
3. sex
WHERE, WHEN?
Environment
1. housing management
2. population density
3. nutrition
4. season
5. prevention
For each disease or condition, u will learn the epidemiology of it
- role of skin cancer in white cats (you’ll know the determinants)
- hip dysplasia prevalence higher in german sheperds
- spirocerca lupi in southern USA
- Transmission of ringworm by contact
- Risk of Lyme Disease in hunting dogs
- Bovine Respiratory Disease with peak in fall
what is the ? ? (outcome // surveillance) ->
what is the cause? (exposure // risk factor) ->
what works? (? Evaluation) ->
How do you do it? (?)
what is the prob? (outcome // surveillance) ->
what is the cause? (exposure // risk factor) ->
what works? (intervention Evaluation) ->
How do you do it? (Implementation) ->
BASIC CONCEPT OF PREVENTION AND CONTROL
imagine an outbreak of cholera so keep cholera out there and prevent the spread of cholera - the basic concept of prevention
once u see sheep below have cholera so the population already has the disease and that’s when you do CONTROL so control cholera and find out who has cholera and identify those and separate them and those are control measures to reduce the burden.
RECENT RESEARCH ON EPIDEMIOLOGY
- WHO world health organization was only focused on noncommunicable diseases earlier such as smoking, cancer, cardiovascular diseases, and obesity but now also focusing on COMMUNICABLE DISEASES (malaria vaccines - vector-borne diseases)
PART 2 principles of epidemiology and basic concepts
A LOT OF VARIABLES IN NATURE HAVE A ? DISTRIBUTION (bell-shaped distribution)
- study designs
- measures of disease frequency
- surveillance
- compartment model of infectious diseases
- epidemic and endemic
- causation in epidemiology
A LOT OF VARIABLES IN NATURE HAVE A normal DISTRIBUTION (bell-shaped distribution)
Study design
were groups compared:
e.g. you gather data of shoe size and not comparing anything, then it would be called ? study
e.g. now comparing shoe size of male vs females so now called ?
had the researcher any control on variables?
e.g. injected something, diet that might have affected shoe size? then called ? study
how many times were the individuals observed?
cross-sectional vs cohort
e.g. “at this time” i know the shoe size of this cohort then called ? study
e.g. after 4 years will be again taking shoe size so now called ? study (following up with it)
forward or backward timeline?
e.g. prospective (So we start today and it will go on in time and gather more data about this situation)
vs retrospective (today and shoe size was when you were a child)
Study design
were groups compared:
e.g. you gather data of shoe size and not comparing anything, then it would be called DESCRIPTIVE study
e.g. now comparing shoe size of male vs females so now called ANALYTICAL
had the researcher any control on variables?
e.g. injected something, diet that might have affected shoe size? then called EXPERIMENTAL study
how many times were the individuals observed?
cross-sectional vs cohort
e.g. “at this time” i know the shoe size of this cohort then called CROSS-SECTIONAL study
e.g. after 4 years will be again taking shoe size so now called COHORT study (following up with it)
forward or backward timeline?
e.g. PROSPECTIVE STUDY (So we start today and it will go on in time and gather more data about this situation)
vs RETROSPECTIVE STUDY (today and shoe size was when you were a child)
INTRODUCTION TO SURVEILLANCE
- ? systematic collection, analysis, and ? of health data
(surveillance system comprises of both COLLECTION and analyze so we interpret it and do something about it and NOT JUST COLLECTION of data)
- Ongoing systematic collection, analysis, and interpretation of health data
(surveillance system comprises of both COLLECTION and analyze, interpret it and do something about it and NOT JUST COLLECTION of data)
Compartment model of infectious diseases
(As I think I mentioned to you the other day, that all models are wrong for definition and these models are incomplete and wrong also)
IMP! will ask about definition of latent and infectious period
3 options
1. carrier
2. recovered
3. dead
Latent period: animals are NOT infectious
Infectious period: animals are infectious
based on clinical signs:
incubation period include both latent AND infectious period!
symptomatic period only includes the infectious period (no latent period i.e. not infectious)
BASED ON INFECTIOUSNESS
Latent period: time from infection to infectiousness. The pathogen ? in the host but is NOT ? yet.
Infectious period: the pathogen is ? by the individual
BASED ON CLINICAL SIGNS
incubation period: time from infection to ? of the disease. the pathogen ? but no clinical signs are observed
symptomatic period: observation of ? signs
Compartment model of infectious diseases
(As I think I mentioned to you the other day, that all models are wrong for definition and these models are incomplete and wrong also)
IMP! will ask about definition of latent and infectious period
3 options
1. carrier
2. recovered
3. dead
Latent period: animals are NOT infectious
Infectious period: animals are infectious
based on clinical signs:
incubation period include both latent AND infectious period!
symptomatic period only includes the infectious period (no latent period i.e. not infectious)
- notes: makes sense as symptoms..infectious period..spreading it to others
BASED ON INFECTIOUSNESS
Latent period: time from infection to infectiousness. The pathogen replicates in the host but is NOT SHED yet.
Infectious period: the pathogen is shed by the individual
BASED ON CLINICAL SIGNS
incubation period: time from infection to “onset of the disease” (= 2nd one, symptomatic period). the pathogen replicates but no clinical signs are observed
symptomatic period: observation of clinical signs
Epidemic: ? occurrence of a disease in a particular geographical region
EPIZOOTIC
Endemic: Disease that is ? present in a particular geographical region
ENZOOTIC
Pandemic: Epidemic at the ? scale
PANZOOTIC
Epidemic: excessive occurrence of a disease in a particular geographical region
EPIZOOTIC (used for animals but we say epidemic (for humans) anyway)
- note: take us longer to define if it’s really an epidemic because we cannot compare with anything and we have to define a time period.
Endemic: Disease that is regularly present in a particular geographical region
ENZOOTIC (at rosssU flu, lepto!! esp around hurricane bc of water as rods pee in water - lack of clean water so end up drinking pee - lepto!)
Pandemic: Epidemic at the worldwide scale
PANZOOTIC
Causation in Microbiology Four (Koch) postulates
- Must be found in abundance in all organisms suffering from the disease but should not be found in healthy organisms.
- Must be isolated from a diseased organism and grown in pure culture
- The cultured microorganism should cause disease when introduced into a healthy organism.
- Must be re-isolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.
Causation in Epidemiology
1. ? of the association
The “stronger the association between a risk factor and outcome”, the more likely the relationship is to be causal e.g the more u smoke the more likely u get cancer
- ? of findings
Have the “same findings” been observed among different populations, in different study designs and different times? - ? sequence of association
Exposure must precede (come before) outcome (did u get cancer before or after u started smoking - get a massive data set so outcome must come after exposure) - Biological plausibility
Presence of a potential ? mechanism - Experiment
Does the removal of the exposure alter the frequency of the outcome?
Causation in Epidemiology
1. strength of the association
The “stronger the association between a risk factor and outcome”, the more likely the relationship is to be causal e.g the more u smoke the more likely u get cancer
- consistency of findings
Have the “same findings” been observed among different populations, in different study designs and different times? - temporal sequence of association
Exposure must precede (come before) outcome (did u get cancer before or after u started smoking - get a massive data set so outcome must come after exposure) - Biological plausibility
Presence of a potential biological mechanism - Experiment
Does the removal of the exposure alter the frequency of the outcome?
