LA Diagnostics and Vaccines

Question 1

What are the sample options on farm and when are these relevant?

Answer 1

• bulk milk sample or split bulk tank test : any contagious disease
• young stock check : BVD, if Ab+ then a carrier (if PI then will not have AB)
• individual cows: TB or any eradication programme

Question 2

Diagnostic options for identifying pathogen presence/exposure/disease?

Answer 2

• antibody ELISA (with DIVA vax)
• cell mediated response (g-INF test, skin test for TB)
• pathogen ELISA or PCR (IBR)
• pathogen culture
• slaughterhouse
• PM

Question 3

What can you infer about a disease if older cows are AB+ but younger cows are AB-?

Answer 3

• previous exposure to pathogen
• active spreading nt likely or all cows would be affected
• or different timing of a vax schedule

Question 4

What pots should be used for serology samples?

Answer 4

• serum pots (clots)

- RED or PLAIN

Question 5

What pots should be used for PCR and Ag ELISA samples?

Answer 5

• heparinised

- GREEN or PURPLE

Question 6

What pots should be used for serology and PCR on milk?

Answer 6

Tube iwth preservative : DONT DIP IN BULK TANK! Contamination poss.

Question 7

What pots should be used for culture of milk?

Answer 7

Sterile pot without preservative

Question 8

What should be checked with the lab when interpretting test results?

Answer 8

• sensitivty
• specificity
• NPV
• PPV (predicting values)

Question 9

IS the johnes test sensitive?

Answer 9

• not very

- milk more sensitive than blood ?

Question 10

What are the 2 types of prevalence of a disease that can be reported?

Answer 10

• individual prevalence

- herd prevalence

Question 11

What 2 types of testing can be used to identify disease in a herd? Which is more sensitive/specific?

Answer 11

• Parallel (v spec, ^ sense)

- Series (^ spec, v sense) = confirmation testing. eg. skin test followed by g-IFN test for TB

Question 12

What is the sense/spec of IBR testing?

Answer 12

Good

- generally good for viral, less good for bacterial

Question 13

What 3 reasons may we be testing a herd?

Answer 13

• testing for presence/prevalence (random samples)
• testing ot eradicate (must test all individuals)
• testing for abscnece ( eg. FMD so contagious that only few samples needed to prove not likely present)

Question 14

How sense/spec is the TB test?

Answer 14

• 99.9% spec
• 80% sense
  > parallel testing so spec v and sesne^ ??

Question 15

Give an eg of a disease you would want to eradicate? monitor? Tx? Vaccinate against the disease?

Answer 15

• eradicate FMD
• monitor BVDV
• tx Leptospriosis to v excretion (zoonotic)
• vax for
  > pathogen or toxin (eg. clostridium)
  > DIVA for dz

Question 16

What must be remembered when thinking about treating a dz?

Answer 16

no point treating unless you can manage it at point of entry

• GI worms, liver luke, claf scours, bTB, lepto, IBR
• No vaccine for bad management!

Question 17

Outline concepts of disease management and which diseases are relevant to each

Answer 17

• housing, hygiene, ventilation
• colostrum management
• all in all out concept (poultry)
• stocking density (resp disease, environmental mastitis)
• rotational grazing (GI worms)
• Water trough management (IBR)

Question 18

How can poor disease management be identified from hx or records?

Answer 18

• dry cow tube use
• mastitis cow tube use
• preventative tx with Halocur (Crypto scouring calf tx)
• use of vax
  > always look at disease, farm management etc. before jumping to a quick fix

Question 19

Which diseases can cross react tests and vaccines?

Answer 19

• TB test and Johnes vax

Question 20

How can vax be sued as part of disease management?

Answer 20

• v pathogen load (lepto)
• protect herd from reintroduction (BVD/IBR)
• improve efficacy of current practice (rota/corona) eg . colostrum
  > typically raise herd immunity -> v pathogen load -> v infected animals -> infection dies out -> eradication

Question 21

Which type of infections are vaccines more effective for?

Answer 21

• viral good

- bacterial less good

Question 22

How can vax interfere with testing? How can this be overcome?

Answer 22

• most common testing based on serology
• vaccines -> immune response
• consider MDA
  > create sentinel groups that are not vaccinatede
• if these test + for disese then it is naturally occouring in the herd
• if consistently testing -ve may be able to stop vaccinating at some point

Question 23

What are DIVA vax?

Answer 23

• differentiating infected from vaccinated animals
• sensivity/specificity of the differentiating test
  > available for IBR, AI, FMD, bTB in development

Question 24

How do differing types of vaccine impact the response?

Answer 24

• live: immunity v spread after inoculation
• attenuated live: local immunity developee
• deadL immunity response depends on adjuvant used
• subunit vax eg. FMD AG presenting alfalfa (genetically modified)
• toxin based for clostridial disease
• boosters

Question 25

How long shuld a vaccine be used after opening?

Answer 25

within 24hours

- always check farm fridge