A potential model for assessing and managing herd risks as part of a TB control programme

Transcription

1 A potential model for assessing and managing herd risks as part of a TB control programme Dick Sibley BVSc HonFRCVS Pete Orpin BVSc MRCVS Myhealthyherd.com dicksibley@aol.com Help! Is anyone listening? (with apologies to Edvard Munch)

2 Take home Herd level disease control requires the urgent identification and management of high risk herds that may or may not be already infected Herds at risk are opportunities: biosecurity works Predict and prevent is a more efficient and effective use of resources than test and treat Flexible surveillance, protection and control strategies are required with options and choices based on herd risks, engaging farmer and vet Knowing is not enough we must apply (thanks, Goette)

3 The Healthy Livestock Initiative A funded health programme for cattle and sheep farmers throughout the South West Specific work strands for BVD and Johnes disease in dairy and beef herds involved a risk based approach

4 Johne s disease-what is it? A contagious bacterial disease of the intestine Caused by mycobacterium avium subspecies paratuberculosis (MAP). Most infections contracted in first week of life Slow growing bacteria. Disease has long incubation period 3-7 years typically Diagnosis of the incubator, carrier and subclinical case very difficult Show clinical signs as adult cattle but clinical cases are rare most infected animals never show obvious clinical signs No treatment & No recovery Johne s - also called ParaTB, MAP, JD, Johns Johnes can be prevented and controlled at the herd level copyright myhealthyherd.com 2010

5 The four pillars supporting the Health status of a herd Health status of the herd Biocontainment Risk of spread Resilience & immunity Surveillance Biosecurity Risk of entry Making herds healthier

6 The Johnes Disease work strand 1) Educate and train participating vetscreate Johnes Champions 2) Engage farmer participants enthuse and transfer knowledge 3) Individual risk assessment and surveillance plan to determine disease status 4) Farm specific prevention and control plan with assessment of robustness agreed with the farmer Example Johnes Biosecurity Plan Valued Effective Specific Practical Achievable

7 The Healthy Livestock Initiative 168 vets from 78 South West veterinary practices attended Johnes training at their own expense 1757 dairy farmers and 564 beef farmers attended Johnes engagement meetings Approximately 1000 herds went on to undertake testing and control through the initiative Most are now continuing at their own expense Johne's 1 Beef Actual Johnes Participants 347 Johne's 2 Beef 264 Johne's 3 Beef 56 Johne's 4 Beef 1757 Johne's 1 Dairy 630 Johne's 2 Dairy 540 Johne's 3 Dairy 98 Johne's 4 Dairy

8 Creating a risk profile for the herd Biosecurity risks = risks of disease entry into the herd Cattle People Environment General and disease specific risks Specific to herd type: beef and dairy Biosecurity in the beef herd Sibley In Practice 2014;36: doi: /inp.g2829 Biosecurity in the dairy herd Sibley In Practice 2010;32: doi: /inp.c3913

9 Creating a risk profile for the herd Bio-containment risks = the risk of disease spread within the herd General and disease specific risks The multiplier of disease within the herd (and may influence persistence)

10 The risk assessment and assignment Risk data collected on farm by trained vets Entered into web based database and algorithm applied according to specific risks and disease Risk report, with categorisation. Beware the Red-Red herd = high risk of entry and high risk of spread

11 Dairy Herd Biosecurity Risks General biosecurity risks relevant to Jones Disease n = 2993 dairy herds Frequently Occasionally Never The herd introduces cattle on to the farm 13.7% 62.1% 24.2% Cattle share grazing or buildings with cattle of unknown disease status 2.9% 8.2% 88.9% Slurry or farm yard manure is from another farm is spread on land 0.6% 4.9% 94.5% Cattle have access to waterways that have passed through another 14.5% 38.7% 46.8% livestock farm Cattle are fed with feeds that could have had contact with other animals 1.8% 16.1% 82.2% Johnes Disease specific biosecurity risks n=2296 dairy herds Herd has introduced groups of animals of unknown Johnes status in last 13.4% 39.6% 47.0% ten years Introduced individual animals of unknown Johnes status over last ten 11.0% 57.8% 31.2% years Slurry of farm yard manure from another farm is spread onto youngstock 0.4% 4.2% 95.4% pastures Calves have access to streams or watercourses that have passed through 6.6% 28.2% 65.2% another livestock farm Youngstock graze pastures that are heavily infected with rabbits 13.8% 48.9% 37.3% Youngstock co-graze pastures with sheep of unknown disease status 8.0% 21.9% 72.1%

12 Dairy Herd Biosecurity Risks for Johnes Disease General biosecurity risks relevant to Jones Disease n = 2993 dairy herds Frequently Occasionally Never The herd introduces cattle on to the farm 13.7% 62.1% 24.2% Cattle share grazing or buildings with cattle of unknown disease status 2.9% 8.2% 88.9% Slurry or farm yard manure is from another farm is spread on land 0.6% 4.9% 94.5% Cattle have access to waterways that have passed through another livestock farm 14.5% 38.7% 46.8% Cattle are fed with feeds that could have had contact with other animals 1.8% 16.1% 82.2% Johnes Disease specific biosecurity risks n=2296 dairy herds Herd has introduced groups of animals of unknown Johnes status in last ten years Introduced individual animals of unknown Johnes status over last ten years Slurry of farm yard manure from another farm is spread onto youngstock pastures Calves have access to streams or watercourses that have passed through another livestock farm 13.4% 39.6% 47.0% 11.0% 57.8% 31.2% 0.4% 4.2% 95.4% 6.6% 28.2% 65.2% Youngstock graze pastures that are heavily infected with rabbits 13.8% 48.9% 37.3% Youngstock co-graze pastures with sheep of unknown disease status 8.0% 21.9% 72.1%

13 Dairy herd Bio-containment risks for Johnes Disease Bio-containment Risks for the Spread of Johne s Disease (n=1860 dairy herds) Calving areas are used for more than one calving Calving area / maternity pen has more than five cows in it at any one time Cows have legs and udders that are soiled with faeces Calving areas are used to accommodate sick cows New born calves stay in maternity pen with mother for more than six hours New born cows are allowed to suckle from a cow The calving pen / maternity area is cleaned after every calving Heifer replacement calves are fed with pooled, untreated colostrum Heifer replacement calves are fed with pooled untreated surplus milk from healthy cows Heifer replacement calves are fed with pooled waste milk from sick cows or cows with mastitis Colostrum is collected from cows without teat disinfection Calves have contact with cows or their faeces prior to weaning Milk and feed areas used for calves is contaminated with cow faeces Calves access pasture that has had cow slurry of farm yard manure applied in the same season Growing heifers have direct contact with cattle or their faeces prior to entering the milking herd Water and feed areas used by growing heifers are contaminated with cow faeces Growing heifers have access to pastures which has had cow slurry or farmyard manure applied in the same season Frequently Occasionally Never 70.2% 26.1% 3.8% 22.8% 33.2% 43.9% 7.3% 68.1% 24.5% 8.8% 55.0% 36.2% 56.3% 33.8% 9.9% 68.2% 26.1% 5.8% 15.1% 40.1% 44.8% 33.6% 26.7% 39.5% 47.1% 22.5% 30.4% 28.9% 26.8% 44.3% 23.3% 25.8% 50.9% 12.4% 21.3% 66.4% 2.6% 16.1% 81.3% 9.8% 37.9% 52.2% 31.8% 43.8% 24.4% 6.1% 20.2% 64.8% 17% 49.7% 33.4%

14 Risk of spread report Key document that will determine the future Johnes management of the herd Identifies and quantifies the multiplier of disease in the herd Used to predict future prevalence

15 Identifying the high risk herd Beware of the Red Red herd This herd is at high risk of entry and high risk of spread The herd may not yet be infected, or may not be detected as infected! Infection in this herd is likely, and will spread rapidly These herds will become high prevalence herds and will be a problem to vet and farmer

16 53.5% of dairy herds are at high risk of Johnes disease entering their herds Only 18.6% can consider themselves reasonably secure against this disease entering their herd.

17 66% of beef herds are at high risk of Johnes disease entering their herd Only 8% of beef herds are reasonable secure from Johnes entry

18 Biocontainment = the multiplier Nearly 78% of dairy herds are at high risk of Johnes disease spreading within their herds if the herd becomes infected. These herds are likely to become problem, high prevalence herds (>10% infected prevalence)

19 Bio-containment risks = the multiplier 32 % of beef herds re at high risk of Johnes disease spreading within their herds Nearly 20% of beef herds have low risks of spread, and although many of these herds will be infected, the disease is unlikely to reach a high prevalence within them

20 The high risk herds: red, amber and green risks Some of these herds will test negative: does that make them low risk herds? Which herds would you source safe cows from?

21 Managing risks at herd level: Strategies and tasks

22 Prevention and Control Strategy Options Prevention and control options to fit any farm, according to: Aspiration Current status Current risk Resources Selection of a strategy creates a task list: risk management requires commitment and action!

23 Selection of control options for Johnes Disease in dairy herds Control Strategy Number Percent Risk based control programme, identifying infected cows by milk antibody testing four times per year, and managing infectious cows to prevent disease spread Improve farm management for the whole herd in order to minimise the risks of disease spread without identifying infected cows, but monitoring herd prevalence by targeted screens Improve farm management to minimise the risks of disease spread, and identify infected cows with single annual milk antibody or blood tests and apply special risk management procedures to those cows with positive tests. Traditional test and cull strategy where all adult animals are tested once a year, using a combination of blood or milk antibody, faecal PCR and faecal culture and animals with positive tests are immediately culled Breed all cows to a beef sire and rear all the offspring as beef animals, replacing breeding stock with low prevalence dairy replacements purchased from other herds Vaccinate to control Johnes in the herd and reduce clinical prevalence Combination of the above, or specific control strategy created by the farm veterinary surgeon to suit the aspirations and resources. No specific controls within the herd, but protect the herd by good biosecurity and monitor for any change in prevalence

24 Lessons learnt and potential for TB Farmer engagement essential farmer based decisions with expert advice Vets and farmers engage with risk management One size will not fit all: control and surveillance strategies will depend on: Aspirations Farming systems Risks Status Resources Pump priming required, but once benefits are evident, programme become self financing Programmes

25 A potential herd level TB Engagement and Control Programme 40% of herds in the high risk areas have not had btb in the last 10 years they need protection Engagement + Risk management issue Biggest spend is on the chronically infected herds they need special help for control but would have best been prevented Assess risks and status of all farms at the time of the TB test a clear test may not indicate freedom from infection! Use trained vets to offer farm specific prevention and control plans with agreement of the farmer Use market mechanisms to incentivise engagement; risk based trading Predict and Prevent V - Test and Treat Farm Animal Practice: Use of diagnostics for risk-based control of paratuberculosis in dairy herds Søren Saxmose Nielsen In Practice 2009;31: doi: /inpract Editorial: Predict and prevent versus test and treat Peter Orpin, Dick Sibley Veterinary Record 2014;174: doi: /vr.g2749