Welsh Black Cattle Society - Johne's Disease

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Main factors in the spread of infection

1. Calves born to an infected mother - not only are the cows teats likely to be soiled by faeces containing large numbers of the infective organism, the organism can also be found in colostrum, milk and even pass directly to the calf before birth through the placenta. This is impossible to control in suckler herds and so these calves should not be retained for breeding.

2. At housing - calves are at risk when loose housed in a large group of cows and calves which has had a scouring infected cow in it.

3. Cows and calves grazing wet/marshy land with pools of water from which they can drink, or fields where the water source is a shallow pond, ditch or slow flowing stream (often fast flowing streams have a shallow, slow flowing area from which the cattle drink). An infected cow can contaminate all these water sources.

4. Water troughs or feed sources that are contaminated by an infected cow.

Preventing spread

1. Isolate a suspicious animal immediately and test e.g. one with symptoms of scouring and/or loss of weight.

2. Isolate and test any bought-in animals unless from a certified 'Monitored Free Herd'.

3. Good isolation premises are essential and isolated animals should be kept there until the test results are known.

4. Cull all animals positive to the ELISA blood test.

5. Cull or do not retain in the breeding herd any offspring of positive cows.

6. Clean out all water troughs regularly and fence off any potentially dangerous sources of water - provide piped water where possible.

7. Do not graze suckling calves in areas/fields where there is stagnant or slow moving water, which could be used by them as a drinking source.

8. Winter housing should be looked at to reduce risk of manure contamination of water or food sources.

9. Lying area for cows should be as clean as possible i.e. well bedded. Cows that will not use cubicles will have very dirty udders and should be housed elsewhere.

10. Calving pens should be cleaned or well bedded with fresh straw between occupants.

11. Do not graze suckling calves for 12 months on land which has had cattle manure spread on it (important if there is a risk of infected animals having been in the shed).

12. If possible change calving period so that cows calve outside, otherwise turn calves out as soon as possible after calving.

13. Manure from isolation premises should not be spread on land if it has contained a confirmed case of Johne's disease (should be burnt etc.).

14. Of lesser risk is possible infection from sheep, goats, rabbits, deer etc. - it is more likely for them to become infected from cattle than vice-versa.

15. Where possible avoid grazing cattle, especially cows suckling calves, and sheep together.

16. Cattle should not be housed in the same shed as sheep.

17. Manure from the sheep shed should not be spread on land to be grazed by suckling calves during the next 12 months.

18. Finally work closely with your veterinary surgeon seeking his advice in relation to the above measures and any other steps he may consider appropriate in your case.

Johne's Disease - The Facts

Symptoms

Johne’s disease in cattle is a chronic wasting disease with long lasting diarrhoea and weight loss despite good appetite, which results in eventual death. It is usually seen in cattle aged 3-5 years and often older, but rarely in younger cattle.

Incubation

The incubation period is long (from one to many years). This means that some cattle can be infected and never develop symptoms of the disease, but they are still capable of spreading infection through the herd. Johne’s disease can therefore be present and spreading within the herd long before the farmer is aware of it. Often cattle develop symptoms after a period of stress such as calving, or movement to another farm, or a period of work in the case of bulls.

Susceptible animals

Calves up to 30 days old are extremely susceptible and then they slowly develop a resistance as they get older. After 12 months they become increasingly resistant so it is rare for adult cattle to pick up the infection.

Introduction of infection to a herd

Buying an infected animal that is not yet showing signs of disease is the usual way infection is introduced to a herd.

Herds Affected

Because of the long incubation period and the fact that young cattle are the most susceptible to infection, the impact of the disease in beef herds is greatest in those which breed their own replacements. Once infection is introduced to such a herd, the disease will become more firmly established as years go by with an increasing number of losses, unless control measures are taken.

Spread of infection within the herd

Cattle are infected by ingestion (taking in by mouth) of the organism which is present in the faeces (dung) of an infected animal. One gram of faeces from a clinically affected cow can sometimes contain over 5 million Johne’s bacteria and less than 1000 of these bacteria are necessary to infect a young calf. Calves are at risk when sucking contaminated udders and when exposed to contaminated water or food sources. Modern husbandry methods of loose housing large numbers of cows and calves together can increase the spread of the disease. The bacteria can survive on pasture for up to 12 months and in water up to 17 months. Some infected cows shed the bacteria in their colostrum and milk and sometimes calves can be infected through the uterus prior to birth. Therefore an infected cow is highly likely to pass the infection on to her calf.

To prevent introduction of infection to a herd

It is most important to avoid buying in infected cattle. This means cattle of unknown status should be isolated and tested before being introduced to the herd. However because the tests will not pick up every animal in the early stages of incubation, knowing the disease status of a herd is of more value than the test results of an individual animal. Therefore the safest cattle to buy are those from herds which are ‘Accredited Monitored Free of Johne’s disease’.

Control of Johne's disease

The basics of control are to identify and cull infected cattle, (any offspring of infected cows should not be retained for breeding either) and new infections must be prevented. Therefore elimination of Johne’s disease from a herd requires a thorough understanding of the disease by the farmer, close co-operation with his veterinary surgeon and regular blood testing of the herd. Half-hearted attempts at control will generally fail.

Identifying infected animals

All animals 2 years of age and older are blood-sampled and the samples are laboratory tested (ELISA test) for Johne’s disease. All animals that test positive should be culled or separated from the rest of the herd until they can be culled.

The blood test will not always pick every animal in the earlier stages of incubation, but as they become nearer to showing signs of the disease the detection rate increases up to 90%. So, after culling positive animals there can still be infected animals in the herd. However these animals in the early stages of disease are not shedding such large numbers of organism and are a lower risk, as a source of infection to other cattle.

Nevertheless it is important to understand the risk that these infected test negative animals present in prolonging the infection in a herd. Because of this it is essential to introduce measures to prevent new infections. It also means that a test and cull programme will of necessity take several years.

Prevention of new infections within the herd

This is based on reducing the risk as far as possible of calves under 1 year old, especially the youngest calves, being exposed to Johne’s disease organisms which are being shed in the faeces of an infected animal.

Isolate immediately any animal showing symptoms suspicious of Johne’s disease (scouring and weight loss) and test.

Isolate and test bought in animals unless they come from an accredited monitored free herd.

Good isolation premises are essential and animals should be kept there until all results of tests are known.

Cull or separate from the rest of the herd all animals positive to the ELISA test.

Cull or do not retain in the breeding herd any offspring of positive cows.

Fence off any areas of stagnant or slow moving water which can become fouled and is used as a drinking source and provide piped water. If this is not possible avoid grazing any suckling calves which are potential breeding stock in areas where such water is to be found.

All water troughs should be checked for signs of fouling by adult cattle and cleaned out regularly.

Winter housing should be looked at to reduce the risk of calves’ water or food sources becoming fouled by adult cattle. Water troughs can be raised to a level which will prevent access by young caves and reduce the risk of fouling and the calves can be given a separate water trough in their creep area.

Lying areas for cows should be as clean/well bedded as possible. Cows that will not lie in cubicles will have very dirty udders and should be housed elsewhere.

Calving pens should be cleaned or well bedded with fresh straw between occupants.

If possible change calving period so that cows calve outside, otherwise turn calves out as soon as possible after calving.

Suckling calves should not be grazed on land which has recently had cattle manure spread on it.

Manure from isolation premises which have contained a confirmed case of Johne’s disease should never be spread on the land (should be burnt etc.).

Of lesser risk is possible infection from sheep, goats, rabbits, deer etc. – it is more likely for them to become infected from cattle than vice-versa.

Avoid grazing sheep and suckling calves together.

Do not house cattle and sheep together in the same shed.

Do not spread manure from the sheep shed on pastures to be grazed by suckling calves.

Work closely with your veterinary surgeon seeking his advice in relation to the above measures and any other steps he/she may consider appropriate in your case.

Vaccination

Advice must be sought from your veterinary surgeon regarding the use of vaccine.

In heavily infected herds vaccination is a useful method of reducing the number of clinical cases and therefore reducing the amount of infection in the environment.

Calves should be vaccinated in the first week of life and vaccination should continue until no clinical Johne’s disease has occurred for at least 2 years. When combined with good husbandry and hygiene measures (ie. care in preventing spread of infection as outlined above) it can be an effective method of control. Vaccinated animals are less likely to develop clinical symptoms of Johne’s disease but they can still become infected and shed the infective organisms and therefore there is a danger of the disease remaining in the herd albeit at a lower level.

Salvage of genetic material

Serious attempts to control or eliminate Johne’s disease can involve the culling of valuable breeding stock. Genetic material can be saved by the use of artificial breeding. Both semen and embryos are considered to be low risk of spreading infection. Clean recipients are obviously necessary for this approach.

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