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Infectious diseases: action on the ground needed rather than more research...

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01 February 2014, at 12:00am

Richard Gard reports on the Planning for Health and Profit conference where wide-ranging discussions were held on controlling infectious diseases and the need to maintain the effort

FARMERS and veterinary surgeons in the south-west of England are well aware of the Healthy Livestock initiative. The priority diseases are: Johne’s, BVD and respiratory disease for beef herds; Johne’s, mastitis, lameness and BVD for dairy; and lameness, parasite control and flock health management for sheep.

Since the autumn of 2010 there have been 8,500 farmer participants in the project, 85 veterinary practices have become partners of the initiative and 545 vets have received training to deliver the programme.

Underpinning all this activity has been a grant of £5.24 million but that money has now gone. The overwhelming view from delegates at the Planning for Health and Profit conference was that there should be a continuation of the effort with ongoing enthusiasm and support.

The county status of Johne’s disease in herds throughout the south- west ranges from 94% positive to 79% in dairy herds and 94% to 33% in beef herds. Gloucester has the highest incidence of Johne’s in beef herds and Devon and Cornwall the highest for dairy.

Plenty of detail

Considerable detail is available from the Duchy College Rural Business School with charts, percentages and disease maps. Over half of the dairy and the beef herds are shown to have inadequate disease control from outside the farm and inadequate limitation of spread within the herd.

Professor Soren Nielsen outlined the Danish experiences. He explained how important it is to protect calves from the manure of adults. The infection becomes established in the gut and initially the immune response of the cow controls the infection but the immune response is overwhelmed and destruction of the gut leads to a general bacteraemia.

Paratuberculosis infection then spreads via the faeces, milk and the uterus. The milk yield may not drop but the cow excretes bacteria for up to a year, representing a high risk to the herd.

Cows are categorised according to their test results as red, green and yellow. Whatever the test applied -faecal, blood or milk – the advice is to stick to one form of test and test frequently.

Cows who have positive results for the last two tests are red and these cows are not put in calf. Yellow identified cows represent a potential risk to the herd and calve onto clean bedding with good observance of biosecurity. Green cows have no history of the infection and the farmer can be more relaxed about calving conditions. 

In Denmark only 27% of the farmers provide a clean calving area and only 15% cull the red cows. Some of the farmers just test the cows but do not use the test results and make no management changes.

The term paratuberculosis is preferred to Johne’s disease and there is no such thing as categorising a herd as paratb free. A drop of 1% prevalence per year is the target for control with an anticipated green herd in 6-8 years.

The Danish experience has shown that farmers react better to the experiences of other farmers. On- farm meetings of 10 farmers and employees have been successful in developing control through farmer-to- farmer discussions of practical points, including colostrum management and reducing infection transfer.

Charles Harrison (a Nuffield scholar) has studied the disease in various countries. With 1,200 cows in milk in three herds, Charles now recognises that paddock block calving and colostrum pooling had contributed to years of financial loss from Johne’s disease.

New culture of co-operation

Professor Joe Brownlie welcomed the new culture of farmer co-operation being exhibited to control and eradicate bovine viral diarrhoea. Over 600 farmers are participating in the dairy initiative and over 1,000 beef farmers.

This is most encouraging but looking at the disease map shows just how dense the livestock farms are in the south-west and the risk of disease transfer is high. Regional tests indicate that over 20% of the herds have BVD although there may not be clinical cases.

The main reservoir of infection is persistently infected animals, usually a calf or adolescent. These are born as a PI and shed BVD virus for the whole of their life. PIs are unable to create an immune response, even if vaccinated, but individual ear tag samples enable tests for presence of the virus.

Bulk tank milk samples can be tested for antibody and virus. A positive antibody does not necessarily indicate the presence of the virus and whole herd milk tests will exclude dry cows, heifers, calves and bulls.

The culling of PIs, test and surveillance of herds and vaccination are successful tools for control of the virus. Where neighbouring farms carry out effective control at the same time, there can be greater confidence in the outcome.

Best investment

Anthony Rew indicated that the introduction of calf hutches was “the best investment on the farm”. His farm comprises both beef and dairy and an emphasis on disease control has proved financially beneficial.

Working in collaboration with the veterinary practice has improved welfare, reduced drug use and increased production. Making use of the gathering of animals for the TB test would be an improved additional step towards easier testing. 

Break-out discussion groups addressed mastitis, lameness, bovine respiratory disease, emerging diseases and risk- based health planning. The delegates selected two sessions and then came together for a final question and answer session. 

Dick Sibley is one of the advisers to the programme and he highlighted some of the realities of planning for health. Farmers who had purchased BVD vaccine have not been highly successful in its application. The wrong dose, or administering the product subcutaneously when it should be given intramuscularly, or vice versa, occurred with 21% of the herds.

One third of farmers never referred to the data sheet. It is difficult in practice to give the primary dose of vaccine prior to first service in heifers but 24% of farmers managed this targeted approach to control.

Knowing the risks and knowing the disease status of a herd are essential steps. Half of the cattle in the south-west have access to watercourses with run-off from other farms. One third of herds have no Johne’s and 80% no active BVD, but this makes them vulnerable and in need of protection.

Multipliers of disease within a herd need to be identified and it is important to manage and monitor progress. Farmers need to decide where they want to be in terms of disease with freedom from disease the top option, control of disease the second and tolerance of disease the third.

It is not always possible to aim for the top option, depending on the management and circumstance of the farm. It is important to have realistic aims, to invest in health and not pay for disease.

Richard Soffe and Paul Ward of the Rural Business School contributed to the final session and there were questions about maintaining the programme. Joe Brownlie appealed for continuing effort and other members of the panel reinforced the point that the success to date must not be wasted, as disease control is a long- term activity.

Duchy College is engaged in maintaining contact with the technical teams and there are ongoing discussions with potential supporters from the food industry. The role of the levy bodies, DairyCo and EBLEX, is unclear but it was felt that not only should the South West Healthy Livestock initiative be further extended and developed but that other areas of the country would benefit from learning the lessons from the programme.

It was strongly voiced that the tools are available to control infectious disease but it is action on the ground that is needed in 2014-15 and not more research.

  • Further information is available at www.duchy.co.uk or telephone Richard Soffe on 0845 4587485.