Proceedings of the 10th International Colloquium on Paratuberculosis

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o<strong>the</strong>r projects and investigators, <strong>the</strong> much higher prevalence <strong>of</strong> infection in dairy herds would explain <strong>the</strong> inability <strong>of</strong> current control programs to eliminate MAP from dairy farms. Recent economic models and economic data obtained from observational studies (Groenendaal and Wolf 2008) show that control programs for MAP on dairy farms are generally only cost effective when best management practices particularly with regard to calf raising were practiced. Extensive test-and-cull strategies alone were shown to be ineffective and costly for producers (Groenendaal and Wolf 2008). Milk production loss linked to MAP infection was studied across a number <strong>of</strong> longitudinally followed populations (Nielsen et al. 2009, Smith et al. 2009). In both <strong>of</strong> <strong>the</strong>se studies, animals known to be infected with MAP but shedding low bacterial numbers, did not show an important milk production loss relative to uninfected controls. Only when cows started to shed larger numbers <strong>of</strong> bacteria or when MAP ELISA values were increased for a prolonged period <strong>of</strong> time was a discernable effect on milk production present (Smith et al. 2009, Nielsen et al. 2009). These data would also indicate that test-and-cull strategies maybe costly when applied across all MAP infected animals. Infection Prevalence C R 0=1 R 0 or <strong>the</strong> lack <strong>of</strong> control measures Fig 3. The relationship between R0 and <strong>the</strong> prevalence <strong>of</strong> infection in a herd. In this graph a backward bifurcation is presented. Ma<strong>the</strong>matical modeling to study MAP infections in dairy herds has been proposed (Lu et al. 2008). With <strong>the</strong>se ma<strong>the</strong>matical infection models, MAP infections in herds can be simulated and studied. These models try to reflect <strong>the</strong> biology and epidemiology <strong>of</strong> MAP as realistic as possible, but <strong>of</strong>ten relatively simple models are used to study simulated infections. Despite <strong>the</strong>ir simplicity, ma<strong>the</strong>matical models have shown to be useful in obtaining a better understanding <strong>of</strong> MAP transmission on dairy farms. Some important results include <strong>the</strong> prediction that calf-to-calf transmission may play an important role in infection maintenance, <strong>the</strong> quantification <strong>of</strong> <strong>the</strong> importance <strong>of</strong> super shedders in herds and a full understanding <strong>of</strong> <strong>the</strong> value <strong>of</strong> test-and-cull control programs in dairy herds (Lu et al. 2008). These ma<strong>the</strong>matical models also provide a more generic insight into MAP infection dynamics in dairy herds. The basic reproduction ratio or R0 <strong>of</strong> an contagious disease is defined as <strong>the</strong> number <strong>of</strong> secondary infections after <strong>the</strong> introduction <strong>of</strong> a single infectious individual in a susceptible population (herd). A threshold value <strong>of</strong> 1 for R0 distinguishes successful control measures (R0 < 1) from non-successful or a lack <strong>of</strong> control measures (R0>1). In figure 3, <strong>the</strong> relationship between <strong>the</strong> R0 value and <strong>the</strong> endemic infection prevalence is shown. When <strong>the</strong> R0 value is below 1, <strong>the</strong> endemic prevalence is stable at zero. With increasing R0, or a lack <strong>of</strong> control measures, <strong>the</strong> endemic infection prevalence increases in a sigmoid fashion (line A). Under normal circumstances, prevalence would decrease again along <strong>the</strong> same sigmoid curve (line A) when infection control measures are implemented (R0 will be smaller). However, with some endemic infections prevalence will initially not, but remain high despite <strong>the</strong> reduction in R0 value to values below <strong>the</strong> threshold value <strong>of</strong> 1 (Line B). Under <strong>the</strong>se circumstances <strong>the</strong>re is a situation possible where <strong>the</strong>re is a high prevalence <strong>of</strong> infection in a management situation where no introduction <strong>of</strong> infection would be successful (Line C). This 111 B A
phenomenon is defined as backward bifurcation (Figure 3). There are a number <strong>of</strong> reasons to believe that <strong>the</strong> backward bifurcation phenomenon is present in <strong>the</strong> case <strong>of</strong> MAP infections in dairy herds. First, environmental contamination and MAP survival in <strong>the</strong> environment may lead to a backward bifurcation; second, <strong>the</strong> presence <strong>of</strong> dose dependency in <strong>the</strong> likelihood <strong>of</strong> calfhood shedding status and <strong>the</strong> subsequent increased rate <strong>of</strong> development into a super shedder will also result in a backward bifurcation. These findings would imply that in endemically MAP infected herds, <strong>the</strong> effort to control <strong>the</strong> infection will be much more elaborate than what may have been predicted based on introduction <strong>of</strong> <strong>the</strong> infection in a dairy herd. This appears to be <strong>the</strong> case in many dairy herds in virtually all countries with reported MAP prevalence data. DISCUSSION Is elimination <strong>of</strong> MAP from dairy herds fact or fiction ? To answer this question we need to consider a number <strong>of</strong> arguments. The key arguments are that 1) within herd prevalence is much higher than measured using current diagnostic tools, 2) several currently underestimated transmission routes <strong>of</strong> infection appear to be important for infection maintenance on dairy farms, 3) aggressive test-and-cull based control programs are not economically feasible in modern dairy farms and 4) endemically infected dairy herds will need to employ extensive MAP control programs to overcome <strong>the</strong> impact <strong>of</strong> backward bifurcation in MAP infection dynamics. Based on <strong>the</strong>se arguments, combined with observed data across all dairy herd populations it appears that MAP elimination from dairy farms is more fiction than fact. ACKNOWLEDGEMENTS The authors are supported in part by <strong>the</strong> USDA-Agricultural Research Service (Agreements. 58-1265-3-155, 58-1265-3-156, 58-1265-3-158, 58-1265-4-020, and 58-1265-8-064) for <strong>the</strong> Regional Dairy Quality Management Alliance (RDQMA) and <strong>the</strong> Johne’s Disease Integrated Program (JDIP, USDA contract 45105). REFERENCES Benedictus A, Mitchell RM, Linde-Widmann M, Sweeney R, Fyock T, Schukken YH, Whitlock RH, 2008. Transmission parameters <strong>of</strong> Mycobacterium avium subspecies paratuberculosis infections in a dairy herd going through a control program. Prev Vet Med 83:215-227. Groenendaal H, Wolf CA, 2008. Farm-level economic analysis <strong>of</strong> <strong>the</strong> US National Johne's Disease Demonstration Herd Project. J Am Vet Med Assoc. 233:1852-1858. Lu Z, Mitchell RM, Smith RL, Van Kessel JS, Chapagain PP, Schukken YH, Grohn YT, 2008. The importance <strong>of</strong> culling in Johne's disease control. J Theor Biol. 254:135-146. Nielsen SS, Krogh MA, Enevoldsen C. 2009. Time to <strong>the</strong> occurrence <strong>of</strong> a decline in milk production in cows with various paratuberculosis antibody pr<strong>of</strong>iles. J Dairy Sci. 92:149- 55. Pradhan AK, Van Kessel JS, Karns JS, Wolfgang DR, Hovingh E, Nelen KA, Smith JM, Whitlock RH, Fyock T, Ladely S, Fedorka-Cray PJ, Schukken YH, 2009. Dynamics <strong>of</strong> endemic infectious diseases <strong>of</strong> animal and human importance on three dairy herds in <strong>the</strong> nor<strong>the</strong>astern United States. J Dairy Sci. 92:1811-1825. Smith RL, Grohn YT, Pradhan AK, Whitlock RH, Van Kessel JS, Smith JM, Wolfgang DR, Schukken YH, 2009. A longitudinal study on <strong>the</strong> impact <strong>of</strong> Johne's disease status on milk production in individual cows. J Dairy Sci. 92:2653-2661. van Roermund HJ, Bakker D, Willemsen PT, de Jong MC, 2007. Horizontal transmission <strong>of</strong> Mycobacterium avium subsp. paratuberculosis in cattle in an experimental setting: calves can transmit <strong>the</strong> infection to o<strong>the</strong>r calves. Vet Microbiol. 122:270-279. van Schaik G, Schukken YH, Crainiceanu C, Muskens J, VanLeeuwen JA, 2003. Prevalence estimates for paratuberculosis adjusted for test variability using Bayesian analysis. Prev Vet Med. 60:281-295. 112
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Book of Abstracts
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Proceedings <stron
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Grant Support and Sponsorship <stro
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Scott Wells - Planning Committee Ch
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Monday, August 10, 2009 - All sessi
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Kari Røste Lybeck, Anne Kristine S
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1120-1140 #88: Influence of
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Concurrent Session B - Rm 175 Wille
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Thursday, August 13 Thursday, Augus
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Diagnostics and Genotyping Convenor
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#229 Detecting Johne’s Disease he
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Kalis CHJ, Hesselink JW, Barkema HW
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MATERIALS AND METHODS Sampling For
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To better determine the</st
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#107 Multilocus Short Sequence Repe
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Fig. 1. Dendogram (showing genetic
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#105 MIRU-VNTR genotyping o
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Diagnostics and Genotyping Poster A
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Missouri). Serum from a cow with do
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#7 Significance of
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RESULTS Of the 327
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Direct fecal nested Map PCR testing
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#16 Histopathological and immunohis
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#19 Development of
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#36 Genetic diversity of</s
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#60 Evaluation of
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#66 Comparison of
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(b) IS900 Nested PCR, using p90-p91
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(d) f57 Real Time PCR. The figure o
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Page 64 and 65: indexes, compared to each single an
Page 66 and 67: #108 Evaluation of
Page 68 and 69: #110 Detection and molecular confir
Page 70 and 71: endoscopic criteria and histopathol
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Page 74 and 75: #131 Seroprevalence of</str
Page 76 and 77: could be partly attributed to a sma
Page 78 and 79: #146 Analysis of v
Page 80 and 81: #162 Comparison of
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Page 84 and 85: #191 Potentiating day-old blood sam
Page 86 and 87: samples from the s
Page 88 and 89: (MAA) (MAP87 and MAP3776) and 1 fro
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Page 94 and 95: #211 Culture of my
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Page 100 and 101: Table 2. Paratuberculosis PCR resul
Page 102 and 103: #254 Programmes on Paratuberculosis
Page 104 and 105: Fig. 1. European countries specifyi
Page 106 and 107: A bulk milk quality assurance progr
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Page 110 and 111: #276 Elimination of</strong
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Page 116 and 117: Host Response and Immunology Keynot
Page 118 and 119: #33 MERKAL AWARD LECTURE No interfe
Page 120 and 121: #75 Interleukin 17 and interleukin
Page 122 and 123: #173 Local and systemic roles for b
Page 124 and 125: #23 Role of Mycoba
Page 126 and 127: Host Response and Immunology Poster
Page 128 and 129: #28 Intestinal MAP Infection via Pe
Page 130 and 131: #73 Age susceptibility of</
Page 132 and 133: #95 Role of nitric
Page 134 and 135: #134 Analysis of <
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Page 138 and 139: #163 Immunohistochemical expression
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Page 146 and 147: Table 1 UK and Cyprus MAP survey Re
Page 148 and 149: #228 Mycobacterium avium ssp. parat
Page 150 and 151: #145 MERKAL AWARD LECTURE Multinomi
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Page 154 and 155: Table 1. Posterior median (CrIs) <s
Page 156 and 157: #55 Birth clusters of</stro
Page 158 and 159: from their dam, se
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#104 Relation between faecal shedde
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Epidemiology Poster Abstracts 109 1
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#22 The Prevalence of</stro
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CONCLUSION IS1311-based nested Ma/M
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#42 Seroprevalence survey o
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#77 Characterisation of</st
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Environmental samples were collecte
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REFERENCES 1) Chiodini RJ, Van Krui
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#113 Effect of soi
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#136 Error-adjusted, variance parti
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Latium Region Viterbo districts RES
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#144 The suitability of</st
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#178 Age structure of</stro
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A statistically significant lower f
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#183 Sero-prevalence of</st
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#218 Johne’s disease in t
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#244 A survey to estimate t
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Control Programs Keynote Lecture Re
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#202 Milk quality assurance for par
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#141 Control of pa
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#198 Use of small
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Control Programs Poster Abstracts 1
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RESULTS Loss of al
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#40 Managing Bovine Johnes Disease
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#74 Economic analysis of</s
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#87 Evaluation of
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separately for each existing herd <
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#98 An inter-laboratory ring-trial
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#120 Paratuberculosis vaccine inter
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The statement provides: • A stand
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COMPLEMENTARY ASPECTS On-Farm Disea
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#168 Paratuberculosis in Iran: past
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#180 Behavioural change in owners <
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the fact that <str
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#182 An integrated risk based appro
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etween 0 to 10, depending on <stron
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#203 Milk quality assurance for par
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#234 Johne’s disease vaccine: a c
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Pathogenomics and MAP Biology Conve
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#45 Identification of</stro
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#117 Adsorption of
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#222 Atypical structural features <
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Pathogenomics and MAP Biology Persp
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#52 Is ‘Indian Bison Type’ Myco
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#69 In vitro susceptibility <strong
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#118 Cloning, expression and purifi
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#176 A reference proteomic pr<stron
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#213 Construction the</stro
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#230 Iron concentration dependent s
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Abstract not available at press tim
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#174 Sharing of
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#177 Associations between CARD15 po
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Perspectives Talk: Public Health My
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A total of 206 qua
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Feller, M., K. Huwiler, R. Stephan,
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In 2008, the Ameri
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#115 Crohn’s disease and ruminant
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International John
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#76 Towards improved reporting stan
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#97 The EU ParaTBTools Project - Th
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#241 US Vaccine Initiative through
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Paratuberculosis ELISA Reliable, si
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PRIONICS AG WAGISTRASSE 27A PHONE +
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