Johne's disease DEFRA - reading

Question 1

Which species does Johne’s affect?

Answer 1

cattle and other ruminants

Question 2

How does this cause disease?

Answer 2

The disease progressively damages the intestines of
affected animals, and in cattle this results in profuse and persistent diarrhoea, severe weight loss,
loss of condition and infertility. Affected animals eventually and inevitably die. In dairy herds, the
presence of Johne’s disease will significantly reduce milk yields well before other signs of the
disease can be found.

Question 3

Is it notifiable?

Answer 3

Johne’s disease is not a notifiable disease in Great Britain (England,
Scotland and Wales), but it is notifiable in Northern Ireland

Question 4

How is Map spread?

Answer 4

Diseased animals in general pass large numbers of Map in their faeces (dung). A single diseased
animal can therefore pose a high risk to susceptible animals, in particular young calves in the
herd. Diseased animals may also excrete Map in milk and colostrum

Question 5

How do calves become infected?

Answer 5

Calves may be infected in the womb but are more commonly infected through:
• drinking contaminated colostrum;
• ingesting dung that may be present on unclean teats;
• contaminated feed; and
• contaminated environment or water supplies.

Question 6

Can Map survive in the environment?

Answer 6

The organism is extremely tough and may survive for up to a year on pasture, in slurry and in
water. Other animals, particularly deer, sheep, goats and South American camelids such as llamas
and alpaca, can carry Map and pass it in their dung. They can therefore be sources of infection
where there is co-grazing or sequential grazing in the same pasture. Rabbits and other wildlife
can be infected with Map. Although their role in the spread of disease in livestock has not been
established, rabbits are currently believed to be less significant as a source of disease than
infected cattle.

Question 7

When are clinical signs rarely seen? Commonly?

Answer 7

Rarely = Between the ages of 2-3years
commonly = 2-5 years

Question 8

How can you spot Johne’s?

Answer 8

Takes several years for clinical signs to become apparent. After it has been developed it can usually be confirmed microscopically from a dung sample or blood test.

Question 9

Why does it usually take a long time to significantly reduce the level of Johne’s infection in a herd?

Answer 9

Because of the high persistence
of Map in the environment and the long “silent” period between infection and the first signs of
disease becoming apparent, it takes a long time to significantly reduce the level of infection in a
dairy herd.

Question 10

Why is Johne’s an expensive disease?

Answer 10

Infected cattle are more susceptible to other diseases such as mastitis and, because they
have difficulty maintaining body condition, their fertility is poor. Treatment of these
conditions is expensive, and you will have to consider the costs of replacing culled stock.

Question 11

Why might it be beneficial to eradicate Johne’s?

Answer 11

To increase the value of your breeding stock if your herd is certified as free of the disease.

Question 12

How long may it take for a diagnosis to be made of Johne’s?

Answer 12

The Map organism can
be cultured and identified from the dung, but it takes up to six months to obtain the result – too
long for this to be useful for the routine diagnosis of disease. There is a blood test that detects the antibody to Map produced by infected cattle. However, cattle
tend to produce the antibody to Map relatively late in the infection.

Question 13

How to control Johne’s?

Answer 13

• Biosecurity
• maintain a closed herd - if you have to bring animals in, try and obtain from a herd that is routinely tested and free from disease. The longer the herd has tested negative, the lower the chance of buying in an infected animal.
• embryo transfer may be the safest way to introduce new gene to the herd.
• clean water
• You should avoid grazing young animals on land for at least three months and ideally a year after application in order to minimise the likelihood of infection, where practical.
• avoid co-grazing with other potential reservoirs of infection.
• sequential grazing within the same grazing season should be avoided.
• minimise exposure of young animals to dung or slurry from adult animals

Question 14

What should you consider if a calf if born to an infected dam?

Answer 14

consider removing the calf from its dam earlier than the recommended 12-24 hours after birth (dairy) and rear in a clean, disinfected environment, free of adult faecal contamination.

• receive adequate colostrum (ideally own dam, if not from a SINGLE repeatedly negative cow)
• if kept with actual dam, ensure teats are clean and pen is kept as clean as possible from adult faeces.

Question 15

Can you pool colostrum?

Answer 15

No -even if it is from animals that have tested negative as the tests aren’t 100% accurate.

Question 16

Can you breed from the offspring of infected animals?

Answer 16

You shouldn’t, they should in fact be removed from the herd.

Question 17

What might be an option with infected but valuable cow in terms of breeding?

Answer 17

one option is to collect ‘clean’ embryos and transfer them into clean recipients.

Question 18

When can you can you vaccinate against Johne’s?

Answer 18

Options are limited as the vaccine causes a positive reaction to the avian part of the TB test and because it doesn’t remove infection from the herd. It must be given to calves in the first month of life and will reduce the number of animals that develop the later stages of the disease.

Question 19

What is the only (not recommended) time that you can feed calves pooled milk?

Answer 19

if it has been boiled first