Diagnostics and vaccines - herd dynamics

Question 1

Diagnostic test options

Answer 1

• herd test vs individual
• parallel vs. serial testing
• same test, different application (bulk tank sample - any contagious dz, split bulk tank test - any contagious dz, young stock - typically BVD, individual cows - e.g. bTB or any eradication process)

Question 2

Diagnostic methods

Answer 2

• Ab ELISA
• Cell mediated response
• pathogen ELISA
• pathogen PCR
• pathogen culture
• slaighterhouse
• PME

Question 3

What blood tube to use for serology on blood?

Answer 3

plain tube, red top (allows blood to clot)

Question 4

What blood tube to use for PCR and Ag ELISA?

Answer 4

blood - heparin tube, green top (coagulation doesn’t happen because heparin/ EDTA)

Question 5

Which tube do you use for milk, serology and PCR?

Answer 5

tube WITH preservative (don’t dip into bulk tank)

Question 6

Which tube do you use for mil for culture?

Answer 6

milk sterile pot WITHOUT preservative

Question 7

What performance parameters should you ask the lab for?

Answer 7

sensitivity, specificity, NPV and PPV

Question 8

Outline diagnostics in dz eradication?

Answer 8

• know biology of dz
• know performance of test(s)
• know how test relates to biology of dz
• once eradication: monitor for absence or reintroduction

Question 9

Outline dz management

Answer 9

• know biology of dz
• eradicate
• manage (at point of entry)
• monitor
• treat
• vaccinate against/for (pathogen vs toxin, DIVA?)
• housing, hygiene, ventilation
• colostrum
• AIAO
• stocking density
• rotational grazing
• water trough management

Question 10

T/F: testing for Johne’s is highly sensitive?

Answer 10

false - not very sensitive

Question 11

Signs of poor dz management

Answer 11

• dry cow tube use
• mastitis cow tube use
• preventative tx with Halocur
• use of vaccine
• always look at dz, its behaviour, the farm and management before deciding on tx

Question 12

Outline vaccine use in dz management

Answer 12

• interacts with test performance
• cross reaction with other dz
• DIVA vaccines
• live vs iactivated vs subunit vs toxin
• ‘proper’ use of vaccine

Question 13

Outline specificity/sensitivity for parallel and serial testing

Answer 13

• PARALLEL: increases sensitivity, decreases specificity

- SERIAL: decreases specificity, increases sensitivity

Question 14

Aim - leptospirosis vaccination

Answer 14

reduce pathogen load

Question 15

Aim - BVD vaccination

Answer 15

protect herd from (re)introduction

Question 16

Aim - rotavirus/coronavirus vaccination

Answer 16

improve efficacy of current practice

Question 17

What is the sensitivity/ sepcificity of bTB skin test?

Answer 17

• 99.9% specific

- 80% sensitive

Question 18

Outline overall aim of dz management

Answer 18

typically raise herd immunity –> reduce pathogen load –> reduce infected animals –> infection dies out –> eradication of dz

Question 19

What are the different types of vaccine?

Answer 19

• LIVE: immunity v spread after innoculation
• ATTENUATED LIVE: local immunity developed
• DEAD: immunity response depends on adjuvant used
• SUBUNIT: FMD Ag presenting alfalfa
• TOXIN: clostridial dz
• BOOSTERS (ensure compatible if switch brands)

Question 20

Proper use of vaccines

Answer 20

• cold chain
• size of bottles
• used bottles
• always check farm fridge

Question 21

Use - halocur

Answer 21

Calf scour d/t cryptosporidium

Question 22

Outline creation of sentinel groups

Answer 22

• where farmer doesn’t vaccinate a subset of animals (e.g. 10 cows) to detect if infection is in herd (i.e. need to still vaccinate?)
• some farmers keen on trying this, others not

Question 23

If you open a vaccine bottle, when should you use if by?

Answer 23

same day