The importance of culling in Johne's disease control

Johne's disease is caused by Mycobacterium avium subsp. paratuberculosis (MAP) infection and results in economic losses in the dairy industry. To control MAP transmission in herds, test-based culling has been recommended and immediate culling of high shedding animals is typically implemented. I...

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Bibliographic Details
Published in:Journal of theoretical biology 2008-09, Vol.254 (1), p.135-146
Main Authors: Lu, Z., Mitchell, R.M., Smith, R.L., Van Kessel, J.S., Chapagain, P.P., Schukken, Y.H., Grohn, Y.T.
Format: Article
Language:English
Subjects:
Animal Husbandry
Animals
Basic reproduction ratio
Cattle
Culling
Enzyme-Linked Immunosorbent Assay
Euthanasia, Animal
Feces - microbiology
Female
Genes, Bacterial
Johne's disease
Models, Biological
Mycobacterium avium subsp. paratuberculosis - genetics
Paratuberculosis - diagnosis
Paratuberculosis - microbiology
Paratuberculosis - prevention & control
Phase diagram
Polymerase Chain Reaction
Test sensitivity
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Summary:Johne's disease is caused by Mycobacterium avium subsp. paratuberculosis (MAP) infection and results in economic losses in the dairy industry. To control MAP transmission in herds, test-based culling has been recommended and immediate culling of high shedding animals is typically implemented. In this study, we quantified the effects of MAP control in US dairy herds, using the basic reproduction ratio R 0 . The effectiveness of culling strategies was evaluated for good and poor herd management (low- and high-transmission rates, respectively) by a phase diagram approach. To establish a quantitative relationship between culling rates and test properties, we defined the average detection times for low and high shedding animals. The effects of various culling strategies and test characteristics, such as test sensitivity, test turnaround time, and testing interval, were analyzed. To understand the overall effect of model parameters on R 0 , we performed global uncertainty and sensitivity analyses. We also evaluated the effectiveness of culling only high shedding animals by comparing three test methods (fecal culture, fecal polymerase chain reaction, PCR, and enzyme-linked immunosorbent assay, ELISA). Our study shows that, in the case of good herd management, culling of only high shedding animals may be effective in controlling MAP transmission. However, in the case of poor management, in addition to immediate culling of high shedding animals, culling of low shedding animals (based on the fecal culture test) will be necessary. Culling of low shedding animals may be delayed 6–12 months, however, if a shorter testing interval is applied. This study suggests that if farmers prefer culling only high shedding animals, faster MAP detection tests (such as the fecal PCR and ELISA) of higher sensitivity should be applied with high testing frequency, particularly on farms with poor management. Culling of infectious animals with a longer testing interval is generally not effective to control MAP.
ISSN:0022-5193
1095-8541
DOI:10.1016/j.jtbi.2008.05.008