Infectious Disease Dairy

Question 1

infectious disease impacts

Answer 1

-direct impacts: drop in milk production (infected mammary gland)
-indirect impacts: ill health on young animals which makes them poop producers as an adult or an insult to an organ or body structure that is distant from the mammary gland

Question 2

most important aspect of dairy operations

Answer 2

profitability!!!
- dairy operations are the most controlled because of the thin profit margins

Question 3

Mammary Gland

Answer 3

-inflammation of the mammary gland= mastitis
-can be caused by infections and not infections
-infection the most common cause of mastitis

Question 4

clinical mastitis effects

Answer 4

-can cause major economic losses
-clinical mastitis: 1-7% in lactation yield ( 72-527 kg loss per cow)
-loss of production for one infected quarter = 730kg milk per infected quarter per year
-economic losses in USA $185/cow or 1.8bill dolla annually

Question 5

subclinical mastitis effects:

Answer 5

• diminish milk prodcution but not as much as clinical
  -subclinical can cause marked reduction in the overall milk yield if many cows are affected
  -for every case of clinical mastitis there’s 40 subclinical cases (ONE TO FORTY REMEMBER)
  -80%economic loss

Question 6

mastitis routes of infection

Answer 6

-hematogenous: brucella, mycobacterium
-percutaneuos: skin wound or any organism
-teat canal: main route (ascending infection)

Question 7

epidimiological triad

Answer 7

pathogenesis dependent on: agent (pathogen), microbial ecology (environment) and host health (animal)

Question 8

what does mastitis transmission depend on

Answer 8

• amount of infectious agent in evironment
  -efficiency of milking personnel, machine and milking parlor hygiene
  -susceptibility of cow is related to epidemiological traingle

Question 9

susceptibility of cow depends on…

Answer 9

1. stage of lactation: 1st two months is most susceptible
   - occur readily during dry seasons
2. age of cow: more than 4 lactations most susceptible
   - also affects shape of teat canal
3. lesions on skin and orifice
4. immune status of cow- especially leukocytes in quarter

Question 10

3 phases of infection development

Answer 10

1. invasive phase
   2.infection phase
   3.inflammation phase

Question 11

invasive phase factors

Answer 11

• presence of bacteria in barn or environment
• the amnt of contamination in the apices of the teat
• injury to teat sphincter and tone of teat sphincter
• presence of antibacterial substances in teat canal

Question 12

infection phase factors

Answer 12

• type of bacteria (virulence) = ability to adhere to mammary epithelium and ability to multiply in milk
• susceptibility to commonly used antibiotics
• previous injury to teat or concurrent infection
• stage of lactation: first two months is most susceptible
• infections appear readily in dry period

Question 13

inflammation phase factors

Answer 13

-pathogenicity of bacteria (streptococci = very little tissue injury, staphylococci = marked tissue injury)
-reactivity of tissue (previous or concurrent infections cause more tissue reaction)

Question 14

types of mastitis

Answer 14

-subclinical: no obvious sign of infection
-clinical: obvious signs of infection

Question 15

types of clinical mastitis

Answer 15

1. peracute: minimal signs and can be deadly
2. acute: swelling of udder and purulent discharge in milk
3. chronic: long term drop in milk production and hard udder from concurrent scarring
   -allows for more infections

Question 16

chronic active mastitis

Answer 16

• can affect other parts of body other than mammary gland
  -ex. decreased blood flow = edema

Question 17

acute mastitis cause

Answer 17

• caused by strep. uberis from enviro

Question 18

contagious mastitis

Answer 18

• cow to cow mastitis
• most often causes subclinical and chronic infections

Question 19

contgious mastitis transmission

Answer 19

• contaminated fomites ( wipes, sponges, milking machines, milekrs hands)

Question 20

common organisms for contagious mastitis

Answer 20

1. streptococcus agalactiae
   2.staphylococcus aureus
2. mycoplasma
   1 and 2 most serious

Question 21

strep. agalactiae

Answer 21

-was major cause of mastitis but phased out by staph aureus
-can induce losses of 25% production per cow and 10-15% loss of production per herd

Question 22

staph aureus

Answer 22

-cause heavy loss of production ( drop in milking and culling) and peracute death (gangrene)
-most common forms = clinical and subclinical mastitis

Question 23

staph aureus peracute form

Answer 23

• most common during first several days following calving

Question 24

staph aureus chronic form

Answer 24

-most economically important: 50% of a herd can be affected but most of the infection can be hard to recognize

Question 25

problem with mastitis

Answer 25

-milking cows w mastitis can break abscesses and structure of mammary gland allows it to reinfect other parts bc it can go into the milk or mil kmachine

Question 26

environmental mastitis

Answer 26

- environment to cow: bacteria survives in environment (oil, feces, bedding water etc) - most common pathogens: e. coli, enviro. streptococcus, Pseudomonas -any organism found in enviro can cause enviro mastitis

Question 27

mastitis treatment

Answer 27

-clean envrio and equipment - for acute cases- strip the milk: milk infected udder every 2 hrs for the first 24-72 hrs - intrammamary infusion of antibiotics - treat during dry period

Question 28

pododdermatitis

Answer 28

- foot rot -contagious diseases that can cause both severe acute and chronic lameness in dairy and beef cattle

Question 29

pododermatitis causes

Answer 29

-initial infection with fusobacterium necrophorum (foot scald) and followed w other species like bacteirus nodosus -other species: spirochete and ctinomycetes pyogenes

Question 30

pododermatitis clinical signs

Answer 30

- characterized by moist dermatitis that is around coronary band and interdigital space - infection in joints of hood = chronic arthritis, tendonitis, desmitis (ligaments) and lameness -cattle becomes inappetent and drop in milk production

Question 31

pododermatitis transmission

Answer 31

- spread via contact w contaminated cattle or environment -once mcrb is seeded into enviro, its hard to remove -transmission occurs around high traffic areas ex. feed trough, gates, barn exits

Question 32

pododermatitis occurence (enviro)

Answer 32

- occurs when theres alot of moisture (humidity) - standing in mud or manure for extended periods of time -occurs when cattle are exposed to har surfaces for long periods of time (dairy barn floors) -stony ground and sharp gravel

Question 33

pododermatitis treatment

Answer 33

-clean up environemnt and remove source of infection -systemic antibiotics (oxytetracycline) -surgical removal of infected tissue -foot baths: 5% copper sulfate or 5% formalin (careful) -Zn supplement to diet to help neutrophils -vaccine for F. necrophorum (reduce incidence in large operations)

Question 34

foot rot beef economics

Answer 34

-75% of all lameness diagnosed in beef cattle -weight gain loss: infected cattle lose 0.5 lbs per day -economic impact: losses in weight gain and treatment costs, decreased breeding efficiency (lame bulls = poor breeders) and culled animals -prevention > treatment