Lecture 6 - Infectious Dz & Pathogenesis

Question 1

What are saprophytes

Answer 1

microbes that feed off of dead/decaying tissues
not a true ‘pathogen’ since host/tissue already deadWh

Question 2

What are pathogenic heterotrophs?

Answer 2

feed off of living cells/tissues
feeding will cause host damage (to cells so they release nutr.)
pathogen lives in/on host - can be outside/inside host cell
Intracellular pathogens exist inside the host cell - all viruses are intracellular pathogens, only some bacteria are IC pathogens

Question 3

How much damage can a pathogen cause?

Answer 3

pathogens have a neg relationship with their hose - host is being damaged while pathogen benefits
most successful pathogens evolved to cause limited amount of damage to host - if host dies, it no benefits
exception is pathogens can easily spread/infect other hosts - kill current host and move on

Question 4

What are primary pathogens

Answer 4

disease-causing microbes w/ means to breach defences of healthy host
can survive natural defense barriers and initial immune attack and begin replicating

Question 5

What are oppertunistic pathogens?

Answer 5

only cause dz in immunocomp host
have ability to cause dz but req,
1. lrg # of bact
2. immunocomp system

Part of normal flora - immunocomp cannot regular microbes
Also acquired thru enviro/others

Question 6

What are the steps to microbial dz?

Answer 6

1. transmission
2. infection - entry, attachment colonization
   3, replication
3. tissue damage
4. spread within host
5. spread outside host

Question 7

Explain transmission in steps of microbial dz

Answer 7

SPREAD OF DISEASE
- normal flora no need to be transmitted
all others are acquired via transmission

Question 8

What is direct transmission?

Answer 8

anim-anim
req physical contact btw infect-suspectible
microbe does not spend significant time in enviro
same household, herdWha

Question 9

tWhat are types of direct transmission

Answer 9

touching, kissing, sex, contact with body lesions/fluids
Aerosol transmission - respiratory droplets

Question 10

What is indirect transmission

Answer 10

microbe acquired from surface/enviro
microbe spent time in enviro
types:
fomites, waterborn, airborne, vectorborn

Question 11

What are fomites? examples?

Answer 11

inanimate objects

Household - water/food bowls, bedding
clinic/vet - stethoscopes, weigh scales
enviro - dirt, wood, straw bedding

Question 12

What are airborn trasmissions

Answer 12

pathogens carried in evaporated droplets or dust from one loc to another
can travel far, land on fomite, very sm, very resist to drying

ex anthrax

Question 13

What are vector-borne transmission

Answer 13

vector = sml anim capable of transmit dz
usually insects - mosquito, ticks, fleas, flies
vector no pathology, but carries to susceptible animal

Question 14

What is fecal-oral transmission

Answer 14

organisms in feces are ingested
direct or indirect (grooming, eat contam food/water/soil)
Parvovirus, salmonella

Question 15

How to reduce fecal-oral transmission

Answer 15

cook ur food, handwashing, protect water supplies, feed away from feces, pick up dog poop

Question 16

What is verticle transmission

Answer 16

Mother-child

ex FIV, hepatitis B

In utero - from mom blood to placenta to fetus
Trans-vaginally - neonate exposed in birthing canals, enters via swallowing thru MM
Via nursing - pathogens enter mam glands into colostrum - drank by neonate

Question 17

What is horizontal transmission

Answer 17

other routes than mom-child
indirect/direct

EX. feedlot

Question 18

What are nosocomial infection/

Answer 18

dz acquired in hospital/clinic
direct/indirect
aerosols from another patients, fomites, contam fluid (saline squirt bottle, reuse IV fluids)
Always concerning bc microbes have inc change of drug resist + inc chance that suspectible animal is immunocomp

Question 19

Zoonosis

Answer 19

anim-human
indirect or direct
contact w/ blood, urine, feces, bitten by tick/mosquito(vector), eat/drink unsafely - unpasteruized milk

Question 20

What are some important zoonoses?

Answer 20

rabies, salmonella, e. coli, campylobacter

Question 21

What is endemic dz?

Answer 21

always present in popul. at expected, low lvl

Seasonal flu, common cold

Question 22

What is an epidemic dz

Answer 22

sudden inc in # of cases in period of time within a popul.

rapid spreading, stays WITHIN community

ex ebola

Question 23

What is a pandemic dz?

Answer 23

widespread epidemic
more cases/short period, spread within community - adjacent communities

due to new infectious dz (new strain/species), popul lack prior exposure

Ex. covid 19

Question 24

Explain infection in steps of microbial dz

Answer 24

3 parts
Entry - disruption of barriers in entry/adhesion. minimum # must enter to cause DZ (Minimun infectious dose)
attachment - attach to cells before replication, attach vai fimbriae, pilli, lipopolysacc, slime layers, receptors on surface of bact recognize and bind to specific host cell receptors
establishment - multiply, if immune attacks/eliminate faster than replication rate, animal no sick. If received MID, immune not quick enough

Question 25

What is the minimum infectious dose?

Answer 25

minimum # of microbes to enter to cause dz

inhale 5 cold virus no work but 10,000 will

MID req; pathogenicity + immune state of host

Question 26

What is pathogenicity?

Answer 26

measure of how much dissue damage a microbe can cause

Question 27

What is direct damage?

Answer 27

due to an action of the microbe
bact/fungi prod damaging toxins to release nutr. + spread to other tissues (hemolysin causes RBC break down)
Virus’ use host cells as “factories for multiplication” and will kill cell to release new viruses

Question 28

What is indirect damage?

Answer 28

occures when immune reacts to presences of infectious microbe
activates - some degree of inflamm
inflame always non-specific and damages host tissues in process of destroying bact

Question 29

Describe the disease course

Answer 29

specific to pathogen/host

follow same pattern
infection (entry, attach, multi)
incubation
prodromal
Clinical (symptomatic)
resolution -> convalescence

Question 30

What does the ability to cause dz depend on?

Answer 30

infectiouse dose
pathogenicity of microbe
immune status of anim

Question 31

Describe the incubation period

Answer 31

time btw exposure to pathogen when clinical signs first appear
hrs, dys, wks, mo, yrs
NO clinical signs
pathogen is establishing/multiplying
microbes shed during incube

Question 32

What is the prodromal period

Answer 32

when there are non-specific signs

pathogen established, numbers still low

Question 33

What is the clinical period

Answer 33

symptomatic period
highst #’s of infectious organisms
clin signs specific to pathogen
easiest diagnosable stage

Question 34

What is resolutiong in dz?

Answer 34

period of dec #’s of pathogen + dec of severity of clin signs

Question 35

What is convalescnece?

Answer 35

period when specific symptoms are Gone - infectious organisms still present at low numbers

body return to normal state - inc risk of other dz/re-infection
infectious organisms still present so anim can shed infectious organisms

Question 36

What is reinfection, reccurent and resistant alt endings?

Answer 36

Reinfect - infection completely resolves but started again from transmission stage. Underlying issue
Reccurent
Resistant - issue never completely resolves, still present

Question 37

What are chronic infections - chronic symptomatic/asymp?

Answer 37

chronic symp - persists with continued sympto dz

chronic asymp - infection @ low lvls, low lvls of replication, no clin signs, may/may not transmit

Question 38

What is latent infection

Answer 38

chronic asymp infection

organisms remians in host, not actively repli or prod pathogenic factors, no transmission

IF its reactivated, returns to clin stage and transmissable

Question 39

What is remission/relapse?

Answer 39

remission - clin signs temporaryily absent, stay in remission for long/short period, was never cured

Relapse - when clin signs present
infectious organism start to replicate again if latent or prod pathogenic factors