Unit 6 Flashcards
What are sprophytes
AKA saprobes
Microbes that feed off dead/decaying tissues (not a true pathogen since the tissue is already dead/damaged)
Decomposers
What are pathogenic heterotrophs
Pathogens that feed of living cells/tissues -causes damage in the process of feeding which releases more nutrients
Live in or on the host
True or false
All viruses are intracellular pathogens, and only some bacteria are
True
Why do pathogens have a negative relationship with their host
Because the host is being damaged while the pathogen is benefiting
Why are the most successful pathogens the ones that cause a limited amount of damage to the host
Because if the host dies the pathogen no longer benefits
What is the exception for the commonly most successful pathogens
Pathogens that can easily spread to and infect other hosts which kill their host and movebon to another one
What are primary pathogens
Disease causing microbes with the means to breach the defences of a host, and can survive past the natural defensive barriers and initial attack by the immune system
What are opprotunistic pathogens
Pathogens that can only cause disease to a host with a compromised immune system or if they are in very large numbers
Can also be acquired from the environment or from others
What are some examples of a host with a compromised immune system
Very sick Malnourished Internal parasites Immunosuppresive drugs (steroids, chemotherapy) Poor hygiene Pregnant Neonates
True or false
There is often opprotunistic pathogens in normal flora
True
If the host is immune suppressed, the numbers of microbes cannot be suppressed, so opprotunistic pathogens
Can easily overwhelm and start disease
What are the 6 steps of microbial disease
Transmission Infection(entry-attachment-colonization) Replication Tissue damage Spread within the host Spread outside the host
What is transmission
The spread of the disease (first step in infectious disease process)
Normal flora that can cause disease does not need to be transmitted (already in host, but all other pathogens
Must be acquired through transmission
What is direct transmission
From animal to animal, requires physical contact between the infected and susceptible animals
Pathogens that need direct contact ____ when away from the host
Readily die in the environment when away from the host, often from drying
What are some examples of direct transmission
Touching Kissing Sexual contact Contact with body lesions Contact with bodily fluid (blood, saliva) Aerosal transmission
What is aerosal transmission what is it considered
Respiratory or nasal secretions, droplets, that can travel short distances, usually inhaled or land on mucus membranes
Not always considered direct transmission, some consider it air borne transmission
What is indirect transmission
Microbe is aquired from a contaminated surface/environment
These microbes are usually more resistant and can survive in the environment
What are some ways of indirect transmission
Fomites
Water borne transmission
Air borne transmission
Vector borne transmission
What are fomites
Any inanimate object that conveys a pathogen from one individual to another
What is air borne transmission
Pathogens carried in evaporated droplets or dust through the air
Usually land on a fomite
Very small and resistant to drying
What are some examples of air borne diseases
Anthrax
Influenza
Foot and mouth disease
What is vector borne transmission
Small animals capable of transmitting disease
Ex. Mosquitos (most common, carry westnile), ticks, fleas, flies
Vector itself does not undergo pathology, carries pathogen from infected animal to susceptible animal
Called vector borne diseases
What is fecal oral transmission
Organisms in feces accidentally ingested by contamination
Can be direct or indirect (grooming, contaminated food, water and soil)
Most common reason for spread of pathogens from animal feces to people
Salmonella, parvovirus, E. coli
How can fecal-oral transmission be reduced
Cooking food Hand washing Protection of water supply Keeping feed away from feces Picking up dog feces
What is vertical transmission
Spread of disease from mother to child
3 ways:
In utero: from mothers blood via the placenta to the fetus
Trans-vaginally: exposed in birthing canal (pathogens from urogenital tract and feces) enters via swallowing
Nursing: pathogens in mammary glands and secreted in colostrum/milk and ingested by neonates
What decreases chances of trans vaginal transmission
C sections
What is horizontal transmission
Pathogens that are spread by routes other than mother to child , includes direct and indirect transmission
What are nosocomial infections
Diseases acquired while in the hospital/Clinc
Can be direct or indirect (aerosals, fomites, contaminated fluids (squirt bottles and water baths))
Always a concern
Why are nosocomial infections harder to treat
Microbe had a greater chance of having antimicrobial drug resistance (previously exposed to antibiotics and survived while in hospital)
Greater chance of being exposed to an immunocompromised patient, more likely to get infected, and more dependent on drugs
What is zoonosis
Disease that are passed from animal to people or vise versa
Direct or indirect ( saliva, blood, urine, feces, bites, ingestion)
According to the centers for disease control (CDC) ___% of human infectious diseases are potential zoonoses
60%
According to the centers for disease control (CDC) ___% of new emerging diseases are zoonotic
75%
What are some important zoonoses
Rabies
Salmonella, E. coli, campylobacter
Toxoplasma gondii, Giardia
Roundworms
What is endemic
An infectious disease always present in a population at a low level
Common cold, seasonal flu, radies, distemper
What is Epidemic
When there is a sudden increase in the numbers of cases in a period of time with a population (stays within a community, rapidly spreading)
What is pandemic
Widespread epidemic, more cases in a short amount of time and moves to adjacent communities
Pandemic and epidemics are usually due to
New infectious diseases
New species that has entered a diff host
New strain that the immune system doesnt recognize
New strain with increased pathogenicity
Population lacks prior exposure and does not have immunity to fight it
What is infection and the 3 steps of it
The second step in infectious disease process
Entry
Attachment
Establishment/colonization
All 3 must occur in order for disease to occur
What is entry In the first part of infection
Infection depends on the number of pathogens that enter the host
What are some protective barriers of the body that prevent entry
Skin Tears Gastrointestinal mucosa Stomach acid Normal GI flora
What are some examples of distuptions to the protective barriers and what does it cause
Scratches Wounds Inflammation of the respiratory/urogenital tracts Injections Disruption of GI flora
Increases the chance of entry and adhesion of pathogens
What is the minumum infectious dose
The minimum number of microbes that must enter the host in order for disease to occur
What does the minumum infectious dose depend on
Pathogenicity of the microbe
Immune state of the host
What is attachement in the infection process
After entry, the microbe must attach to cells and body surfaces before replication can occur
Any bacteria that do not adhere can be washed out (urination, peristalsis, tears)
How do bacteria attach
Fimbriae Pilli Lipopolysaccharides Slime layers Receptors on the surface of bacteria bind to specific receptors on the surface of host cells
What is establishment/colonization in the infection process
Once the microbe is attached, it can start to multiply
If the immune system can attack and eliminate the infection faster than the bacteria can replicate, the animals will___
Not become sick
In most causes the animal recieves the ____ and the immune system will not be able to clear the infection and itnwill become sick
Minimum infectious dose
What is pathogenicity
Meausre if how much damage a microbe causes
What is a pathogen
A microbe that causes damage
Why are primary pathogens the most virulent
Minimum infectious dose: 3-100,000
Disease produced: distinct
Source of infection: transmitted
Host state: can be healthy
Why are opprotunistic kind of virulent
Minumum infectious dose: 100,00+
Disease produced: non specific
Source if infection: normal flora
Host state: mild-moderate immune suppression
Why are non pathogens the least virulent
Minimum infectious dose: 1,000,000+
Disease produced: non specific
Source of infection: normal flora
Host state: severe immune suppression
What is direct damage
Damage due to the action of the microbe
Bacteria and fungi produce toxins that damage surrounding tissues to
Release nutrients
Enable spread to other tissues
What are some examples of toxins that cause damage and what do they do
Hemolysin: breakdown RBCs
Collagenase: breaks down connective tissue
Enterotoxins: damage GI barrier so nutrients arent absorbed
Viruses use host cells as “factories for multiplication” and often kill the cell in order to
Release newly formed viruses
What is indirect damage
From when the immune sustem reacts to the presence of an infectious organisms
Causes Inflammation which damages tissues in the process of destroying bacteria
What si the course of a disease/the clinical pattern
1: infection (entry, attachment, start to multiply)
2: incubation
3: prodromal period
4: clinical/symptomatic period
5: resolution
6: convalesence
What is exposure
When aniamls come into contact with potential pathogens
Dose not always mean there will be disease (must enter attach and establish)
It isnpossible for the immune system to clear the microbe before it can attach
The ability to cause disease depends on
Infectious dose
Pathogenicity of microbe
Immune status of the animal
What is the incubation oeriod
Time between exposure to the pathogen and when clinical signs first appear
There are not clinical signs or symptoms in this time
Pathogen is establishing itself and multiplying (damage is minimal)
Microbes can be shed during this time
True or false
The incubation period is the same for all microbes
FALSE
it is specific to the microbe
Parvovirus: 4-7 days
Rabies: up to 6 months
What is the prodromal period
Following incubation when there are non-specific clinical signs
Ex. Lethargy, fever, decreased appetite
Animal is sick but signs do not indicate a specific disease or where it may be occuring
Pathigen is established but numbers are still low
What is the clinical period
AKA symptomatic period
Period with the highest number of infectious organism
Clinical signs are specific to colonization of a specific tissue and/or specific pathogenic factor specific to that organism
Easiest stage to diagnose
What are some specific signs of radies and bordetella
Rabies: neurological symptoms
Bordetella: rhinotracheitis
What is the resolution period
Decreasing numbers of pathogen with a corresponding decrease in secerity if clinical signs
By activation of the immune system or treatment
What is convalescence period
When specific symptoms are GONE
Infectious organisms are still Present in very low numbers (not enough to cause disease)
Body is returning to normal
Can still shed the pathogens
During the convalescence period there is an increased
Risk of re-infection
Risk of getting other diseases
What is shedding
Transmitting disease or pathogen to others
What is reinfection
Previous infection was resolved but same infection has started again from the transmission stage
Usually a sign of an underlying issue (hygiene, immune system, stress)
What is a reccurent disease
Reinfection at weekly to monthly intervals
What is a resistant disease
The original infection was never completely resolved, so it is still present due to failure to treat it
What are chronic symptomatic infections
Infection persists with continued symtoms, occurs if the host immune response is unable to clear the infection
What is a chronic asymptomatic infection
Infection persists at low levels, low levels of replication, no clinical signs,
May or may not be able to shed disease
What is a latent infection
A form if chrinic asymptomatic infection when the organism remains in the host but is not actively replication or producing pathogenic factors (no clinical signs)
No risk of tansmission
What happens in a latent infection if the infectious organism is reactivated
Start to replicate again and produce pathogenic factors, and will return to clinical stage and transmit to others
What is remission
When clinical signs are temporarily absent
Can stay in remission for long or short periods of time
Means the infection was never cured
What us relapse
Periods when clinical signs are present
When infectious organism starts to replicate again and produce pathogenic factors
What happens when an infection causes death
When the severity of clinical signs go above the clinical threshold
