Weight loss in adult cows

Question 1

what causes Johne’s disease

Answer 1

Mycobacterium avium subsp. paratuberculosis (MAP)

Question 2

what is Johne’s characterised by

Answer 2

wasting and diarrhoea

Question 3

T/F pasteurisation effectively kills MAP in milk

Answer 3

False

Question 4

When does infection with Johne’s occur

Answer 4

<60 days of life

Question 4

How is Johne’s shed

Answer 4

In faeces intermittently
increases as the cow develops clinical disease

Question 5

List 5 sources of Johne’s infection

Answer 5

Faeces from shedding cattle
Colostrum/ milk from infected cattle
Faeces from shedding goats/sheep
Environment and fomite spread
Wildlife reservoirs

Question 6

T/F susceptibility to Johne’s decreases as the cow gets older

Answer 6

True

Question 7

List the clinical signs of Johne’s

Answer 7

diarrhoea - intermittent becoming chronic
decreased production
weight loss/ emaciation
+/- oedema (‘bottle jaw’)

Question 8

at what age do clinical signs of Johne’s tend to occur at

Answer 8

2-6 years of age

Question 9

List 8 possible Differentials for weight loss and diarrhoea in cows

Answer 9

Liver fluke
Johne’s
Peritonitis
displaced abomasum
abdominal neoplasia
chronic salmonellosis
parasitic gastroenteritis
copper deficiency

Question 10

List the 2 approaches to diagnosing Johne’s

Answer 10

Detect MAP in faeces
Detect immune response to MAP

Question 11

what is the problem with diagnosing Johne’s through decting in faeces

Answer 11

MAP only intermittently shed in faeces so sensitivity quite poor

Question 12

Describe how to diagnose Johne’s

Answer 12

PCR on faeces
ELISA to detect Ab in milk or blood

Question 13

what is faecal PCR used for when diagnosing Johne’s

Answer 13

mostly used as confirmatory test

Question 14

what is the sen and spec of faecal PCR

Answer 14

20-65% sensitivity (lots of false neg)
>99% spec (not many false positives)

Question 15

Why is detecting Ab to johnes better than faecal PCR

Answer 15

cheaper and quicker than faecal testing
more sensitive

Question 16

what are blood and milk Ab tests used for when testing for Johnes

Answer 16

blood- mostly for indivual cases and beef herd screening
milk- used for dairy herd screening

Question 17

Can we treat Johnes

Answer 17

No

Question 18

How long can MAP survive on pastue

Answer 18

over a year in the right environment

Question 19

List 6 ways to reduce likelihood of calves getting infected with Johne’s

Answer 19

reduce stocking density in calving pens
keep Johne’s positive cows separate
Buy Johne’s free accredited animals
Clean calving pen after every calving
don’t allow new born calves to suckle from johne’s positive cows
keep calving pens clean

Question 20

what disease has Johnes disease been linked to in humans

Answer 20

Crohn’s disease

Question 21

how can we differentiate Johnes from liver fluke

Answer 21

Lab work

Question 22

describe how to differentiate TRP from Johnes

Answer 22

TRP will have other signs such as pyrexia or abdominal pain

Question 23

how to differentiate Johnes from a displaced abomasum

Answer 23

a displaced abomasum can be identified on clinical exam and will usally be more acute

Question 24

why is it difficult to diagnose Johnes antibodies or antigens early in the disease

Answer 24

because the cell mediated immune response is high and this keep the antigens low, and the antibodies have not had time to build up yet