AHEAD IN ANIMAL HEALTH
Twenty-five topics to be considered in the design of paratuberculosis control programmes for dairy herds Maarten F. Weber1,2, Thomas Dijkstra1, Marian Aalberts1 and Ynte H. Schukken1,2,3 1 Royal GD, Deventer, the Netherlands, m.weber@gdanimalhealth.com, 2 Dept. of Population Health Sciences, Faculty of Veterinary Medicine, Utrecht University, the Netherlands, 3 Quantitative Veterinary Epidemiology, Dept. of Animal Sciences, Wageningen University, the Netherlands
Introduction
The MQAP
Optimal design of control programmes for Mycobacterium avium subsp. paratuberculosis (Map) depends on population characteristics (e.g., distribution of herd sizes, contacts between herds and prevalences of infection) and the aims of the programme at the herd level and metapopulation level. The Dutch Milk Quality Assurance Programme (MQAP) for paratuberculosis aims to control Map in participating herds and reduce the concentration of Map in bulk milk. Although results achieved to date are promising, an internal review of the MQAP was performed to identify potential areas of improvement to further increase its efficacy. The identified topics may be relevant to other Map control programmes as well.
Initial assessment ELISA once
Materials and Methods Literature on control programmes, epidemiology, diagnostics, zoonotic aspects and on-farm impact of Map published since the initiation of the MQAP in 2006 was reviewed. The design of the MQAP was compared with programmes in other European countries. Identified topics were grouped into nine domains.
Results
Suveillance
Control
Status A ELISA once / 2 yr
Status B or C ELISA once / yr
Herd examination by ELISA: individual milk samples of all lactating cattle with optional confirmatory faecal qPCR
• Be explicit about the aims of the programme; • Include ‘low-risk’ trade of cattle between herds in the aims of the programme; • Implement criteria for ’certification areas’ in IAP guidelines on livestock movements; • Evaluate programme performance in a 5-year Plan-Do-Check-Act cycle; • Predefine performance indicators (e.g., time-to-cull of test-positives, Map concentration in bulk milk, faecal contamination of bulk milk, results of environmental samples).
• Provide ELISA results to cattle breeding organisations to calculate estimated breeding values for ELISA response.
Aim of the programme 5
Breeding for resistance agains Map
4
• Develop a certification scheme for specialised young stock herds.
Knowledge, attitude, behaviour
3 2
• Post-movement testing by faecal PCR (rather than serum ELISA); • Post-movement testing if the herd of origin does not have the preferred status herd, irrespective of age; • If the status of the herd of origin is lower than status of the herd of destination, the herd of destination is assigned the status of the herd of origin. • Require test-positive herds to submit a risk assessment and management plan at least once per five years; • Evaluate the use of environmental samples to quantify exposure (dust samples) of and shedding (slurry samples) in young stock; • Study the role of lagomorphs in the epidemiology of Map in Dutch cattle.
Certification of specialised young stock herds
1
Surveillance of status A herds
0
Cattle movements between herds
Control in status B/C herds
Preventive management measures
Transition status B
A
• Increase the number of fully negative herd examinations required to progress to the preferred herd status;
• Incentives by stakeholders to farmers to improve the status of their herd; • Develop a bench mark system to compare progress of control in infected herds; • Provide training and extension activities to farmers and veterinarians. • Report low- and high positive ELISA results as separate categories to enable selective confirmatory PCR testing; • Risk-based variation of the interval between herd examinations based on prior test results, introduction of cattle from other herds, testing of bulk milk and environmental samples; • Identify a subset of status A herds with a high probability of freedom of infection as a source of low risk trade of cattle. • In addition to lactating cattle, compulsory testing of dry cows; • Evaluate the beneficial effect of biannual instead of annual herd examinations; • Evaluate the effect of including young stock 12 - 24 months of age in herd examinations; • Report low- and high positive ELISA results as separate categories to enable selective confirmatory PCR testing; • Develop a benchmark system based on the distribution of S/P ratio’s in various age groups.
Fig. 1 Identified topics that may need to be considered in the design of any paratuberculosis control programme, grouped into nine domains
Discussion The review has been presented to decision makers of the Dutch dairy industry, who concluded that the identified topics in the design of the MQAP were valuable for future consideration. The identified topics may be considered in the design of any paratuberculosis control programme.
m.weber@gdanimalhealth.com www.gdanimalhealth.com
GD2613/06-22