Infectious Diseases- the basics Flashcards
describe the 4 parts of the circle of disease transmission
- entry
- replication
- exit
- environmental persistence
at what point in the circle of disease transmission does spread occur?
exit
how does infection occur in entry through the respiratory tract?
through inhalation of infectious agents
what protective mechanisms does the respiratory tract have against infectious agents? (3)
- mucous from goblet cells
- cilia in epithelium
- specific (IgA) and nonspecific (macrophage and neutrophil) immune defenses
what type of barrier is the mucous secreted by goblet cells in the respiratory tract?
physical barrier
how do cilia in the epithelium of the respiratory tract protect against disease?
do the wave! move bad shit away
what does IgA stand for? what is it produced by?
immunoglobulin Type A, produced by lymphocytes
list 3 factors that help facilitate spread of disease through the respiratory route?
- concurrent infections
- aerosols
- poor ventilation and irritants
describe concurrent infections as a factor facilitating spread of disease through the respiratory route
some microbes stop cilia movement so other microbes can become more pathogenic, basically microbes work together to take you down
describe aerosols as a factor facilitating spread of disease through the respiratory route
sneezing in close proximity = bad news bears
give an example of poor ventilation as a factor facilitating spread of disease through the respiratory route
in pig farms poor ventilation leads to a build up ammonia, which irritates mucosa and leads to more infection
describe transmission of disease through the gastrointestinal tract (2)
- transmission via ingestion of pathogens
2. contamination of feed
list 4 protective mechanisms of the GI tract to prevent disease transmission through this route
- peritalsis: stay right the fuck there
- low pH, bile, secretions: i kill you
- mucus layer: physical barrier
- IgA and non-specific immune defenses
what are 4 factors facilitating spread of disease through the GI tract?
- high contamination of environment
- poor cleaning
- dysbiosis: change in microbiome
- high density of animals
how do pathogens enter through the skin route?
enter through the barrier
what are the protective mechanisms of skin against disease? (2)
- cornified (keratinized) epithelium)
2. skin microbiome
what are the factors facilitating spread of disease through the skin route? (3)
- skin abrasion/rupture/barrier break
- wounds
- animal/insect bites
what are the 3 mechanisms of entry through the reproductive tract for infectious diseases?
- sexually transmitted diseases
- natural mating
- AI!!!!!
what are the 3 protective mechanisms of the reproductive tract against infectious diseases?
- mucous
- innate and acquired immunity
- microbiota
what are the 4 factors facilitating disease transmission through the reproductive route?
- AI is a great way to get em sick if you dont follow proper sanitation protocol
- conjunctive: diseased male
- placenta: vertical transmission of mom to fetus
- horizontal transmission: individual to individual
what are the 9 steps of microbial infection
- acquire access to portal of entry
- encounter “targets” in mucosa
- colonize targets to sustain and/or amplify the encounter
- spread locally in EC matrix to encounter and colonize new populations of target cells
- enter blood and/or lymphatic cells
6-8 (yay): spread to regional lymphnodes and/or then systematically within the circulatory system to encounter, colonize, and invade new populations of target cells that are unique to a specific organ system - cause dysfunction and/or lysis of target cells and disease
what is incubation period?
the time between entry of the pathogen and the development of clinical signs
how long can an incubation period be?
from 24-30 hours up to years
why is there an incubation period?
an organism needs to replicate inside a host enough to be able to cause damage
describe lentiviruses in terms of incubation period
reproduce very slowly and fight with the host immune system constantly in waves
describe the general incubation period for pathogens that cause immunodeficiencies
years
why is knowledge of incubation period useful? (2)
- helps establish quarantine guidelines
2. helps backtrack contacts (contact tracing)
what is infectivity period?
the period of time that an animal is contagious to others
what does infectivity period coincide with?
the shedding of infectious pathogens
when can the infectivity period start?
at any point of the transmission cycle
does showing symptoms mean an individual is shedding infectious pathogens?
nope
what is an individual called when they are shedding infectious pathogens (infectivity period) but not showing symptoms?
an asymptomatic carrier
what are the 4 levels of infectious diseases?
- severe disease
- disease
- subclinical
- exposure with no infection
what level of infectious diseases should you not really look for and why?
severe disease, they won’t rly make it before you can get involved
what level of infectious diseases should you look for and why?
- disease, will have symptoms but a chance at recovery
what causes level 4: exposure without infection of infectious diseases?
host not right for microbe, immune system too strong
what is the route of exit in most infectious disease cases link to?
route of entry
what does route of exit in infectious disease cases depend on?
if agents stay localized or spread systemically throughout the host
list 6 types of exit of infectious diseases
- oronasal secretions
- conjunctival secretions
- urine
- feces
- semen
- blood
what kind of infectious diseases choose airborne exit routes/transmission?
respiratory diseases mainly (also foot and mouth diseases and PRRS)
describe airborne transmission
dispered in small particles in the air
describe the 2 sizes of particles in airborne transmission
- smaller particles: smaller than 5um, suspended in the air for longer time and travel longer distances, can be inhaled directly into the lungs, called aerosols
- larger particles: larger than 10 um, get trapped in the ciliary epithelium, can be aerosolized by coughing, sneezing, or breathing, remain infectious for a long time
when a particle is larger than 5 um, what is its airborne transmission name?
droplets
what are the 2 types of transmission of infectious pathogens?
- airborne
2. contact
list the 7 types of contact transmission in infectious diseases and one disease for each
- fecal-oral: parvovirus
- fomite: salmonella
- water-borne: E. coli, Leptospirosis
- sexual: mycoplasma agalactiae
- vector-borne: West Nile Virus
- vertical: ruminant lentiviruses
- iatrogenic: scrapies
what 3 things need to be in perfect harmony for infection to occur?
- host susceptible
- pathogen ready
- environment
list the 7 aspects relating to the pathogen that contribute to its ability to infect a host
- pathogenicity and virulence
- survival in environment
- ability to persist in host
- strength and duration of the host immune reaction
- broad host vs. species specific
- mutagenesis, antigenic drift
- latency
what is virulence?
degree of disease
discuss survival in environment as a pathogen trait
especially important in airborne, waterborne, and feedborne diseases
give an example of a pathogen’s ability ti survive in the environment
clostridium tetani forms spores to protect from dessication and UV light
give an example of a pathogen’s ability to persist in host environment
Herpes virus hides in cells from immune response
give an example of a pathogen evading strength and duration of host immune reaction
enevelope proteins on pathogen make pathogen unrecognizable to immune system
give an example of pathogen latency
like lentiviruses, can hang out until immune system leaves are or is down
give an example of mutagenesis of a pathogen
mutate or change proteins to avoid recognition by immune system, like influenza or COVID
list the 6 aspects of the host that relate to infection
- nutritional status
- age
- presence or concurrence of other pathogens
- level of immunity
- genetic predisposition
- carriers
describe how nutritional status of host relates to infection
lower status = more likely to get infection
describe how age of host relates to infection
younger or older hosts generally weaker
describe how presence or concurrence of other pathogens in the host relates to infection
infectious agents can team up to take you down, if host is fighting a previous infection they are more likely to contract another infection, as in the case of a cow fighting ketosis can be more likely to get mastitis
describe how genetic predisposition of host can relate to infection
microbes can be specific, different degrees of infection/disease due to genetics, and hosts can have different levels of innagte immunity
list the 5 aspects of the environment that relate to infections
- temperature
- humidity
- presence of vectors
- housing density
- hygiene protocols
describe how temperature of environment and housing density can relate to infection (3)
- if keep animals inside to avoid fluctuations in temperature, you create housing density;
- if temperature too hot, immune system stressed
- animals not as affected by cold temps, but excessive cold can damage epithelium in respiratory tract and other places
give an example of vectors as relates to infection
flies are a big disease vector, around animals a lot
describe how hygiene of environment can relate to infection
poor hygiene increases liklihood of infection
what are the 5 cardinal signs of inflammation?
- pain
- heat
- redness
- swelling
- loss of function
describe how inflammation occurs
injury or death of cells caused by infectious microbes can initiate a well-organized cascade of fluid and cellular changes within living tissue vascularized tissue called inflammation
define inflammation
protective mechanisms whose biologic prupose is to dilute, isolate, and eliminate the cause of injury and to repair rissue damage resulting from the injury
what are the 3 phases of inflammation?
- exudative (fluidic) phase
- cellular phase (leukocyte activation cascade)
- reparative phase
what 3 things happen in the exudative (fluidic) phase of inflammation?
- increased bloow flow (active hyperemia) to the site of injury
- increased permeability of capillaries
- emigration of leukocytes
what is the order of leukocytes in the luekocyte activation cascade?
- neutrophils
- macrophages
- lymphocytes
what are the humoral components of the luekocyte activation cascade?
- histamine and seratonin
- prostaglandins and leukotrienes
- cytokines
what does the reparative phase of inflammation depend on?
depends on the cell damage and the persistency of the harmful agent
what are the 3 paths of the reparative phase of inflammation?
- healing by fibrosis
- abscess formation
- progression to chronic inflammation
