Proceedings of the 10th International Colloquium on Paratuberculosis

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Table 1. Posterior median (CrIs) <strong>of</strong> model parameters from (I) a standard Weibull model that ignored <strong>the</strong> latent infection period (ui) <strong>of</strong> Mycobacterium avium subsp. paratuberculosis (MAP) infection and (II) <strong>the</strong> proposed Weibull model that adjusted for ui. Estimations were based on 1912 cows from 8 Danish dairy herds naturally infected with MAP. Variable Level Model (I) Median (CrIs) Model (II) Intercept -21.42 (-22.67; -20.28) - 4.53 (-4.89; -4.19) MAP FCLow 0.91 ( 0.70; 1.11) 0.88 ( 0.67; 1.09) shedding FCHigh 1.14 ( 0.90; 1.36) 1.13 ( 0.89; 1.37) level FCNeg Ref. Ref. Shape parameter � 2.67 ( 2.52; 2.83) 0.56 (0.51; 0.61) 000 1a � 1a 1 1b HR 4.0E -03 3.5E -03 3.0E -03 2.5E -03 2 0E 03 HR 1.8E -03 1.6E -03 1.4E -03 1.2E -03 1.0E -03 8.0E -04 6.0E -04 4.0E -04 2.0E -04 0.0E+00 0 Non-shedders Low shedders Heavy shedders Non-shedders Low shedders Heavy shedders Figure 1. Posterior median (CrIs) <strong>of</strong> <strong>the</strong> hazard function (HF) – <strong>the</strong> age-specific seroconversion rate (1a) and infection rate (1b) – for heavy-, low- and non-shedders <strong>of</strong> MAP. DISCUSSION The proposed model allowed us to assess association between time to infection and shedding level by <strong>the</strong> analysis <strong>of</strong> available time-to-seropositivity data. Estimated median infection times demonstrated that animals getting infected earlier in <strong>the</strong>ir lives were more likely to become shedders in <strong>the</strong> future, fur<strong>the</strong>r contributing to <strong>the</strong> vicious cycle <strong>of</strong> MAP 153 3
persistence in an infected herd. The latter findings are consistent with <strong>the</strong> well established need for control strategies that will, among o<strong>the</strong>r things, prioritize <strong>the</strong> interruption <strong>of</strong> MAP transmission during early calfhood. Importantly, we captured <strong>the</strong> inverse relationship between <strong>the</strong> incidence rate <strong>of</strong> seroconversion and infection with time: <strong>the</strong> incidence rate <strong>of</strong> milk seroconversion increases, while that <strong>of</strong> infection decreases with age (Figure 1). Young calves are more susceptible to MAP infection and susceptibility to infection decreases with aging (Taylor, 1953), while highparity dairy cattle are more likely to become seropositive than low-parity dairy cattle (Nielsen et al., 2002). Our model heavily depends on correct prior specification for ui. We, <strong>the</strong>refore, had to base our priors on adequate, relevant and scientifically justified information. Within an infected herd most animals acquire MAP early in <strong>the</strong>ir life. In natural infections, <strong>the</strong> immunological and infectious properties <strong>of</strong> MAP infection are not fully characterized. Susceptibility to infection decreases over time, while environmental (Tiwari et al., 2009) and genetic (Koets et al., 2000) factors, not fully conceptualized yet, play a critical role on whe<strong>the</strong>r initial entrance and persistence <strong>of</strong> MAP will lead to clinical manifestations, be restrained during <strong>the</strong> productive life <strong>of</strong> infected animals or even be cleared out. Most clinical cases occur between 3 to 5 years (Chiodini et al., 1984). In experimental infections, <strong>the</strong> latent period is generally shorter (Lepper et al., 1989) but can only be indicative for natural infections because <strong>of</strong> <strong>the</strong> variation in infective doses occurring during natural infections (Nielsen and Ersbøll, 2006). Specified priors captured both our prior belief and <strong>the</strong> variation <strong>of</strong> latent period occurring at natural infections. The proposed model adjusts for <strong>the</strong> latent period <strong>of</strong> infection and can be quite useful for <strong>the</strong> analysis <strong>of</strong> chronic infections – like MAP – with a long latent period, which, if ignored, will have a severe impact on estimations. REFERENCES Augustin T, Wolff J, 2004. A bias analysis <strong>of</strong> Weibull models under heaped data. Statistical Papers 45, 211-229. Chiodini RJ, van Kruiningen HJ, Merkal RS, 1984. Ruminant paratuberculosis (Johne’s disease): The current status and future prospects. Cornell Vet. 74, 218–262. Koets AP, Adugna G, Janss LLG, Van Weering HJ, Kalis CHJ, Wenting GH, Rutten VPMG, Schukken YH, 2000. Genetic variation <strong>of</strong> susceptibility to Mycobacterium avium subsp. paratuberculosis infection in dairy cattle. J. Dairy Sci., 83, 2702–2708. Lepper AWD, Wilks CR, Kotiw M, Whitehead JT, Swart KS, 1989. Sequential bacteriologic observations in relation to cell-mediated and humoral antibody responses <strong>of</strong> cattle infected with Mycobacterium paratuberculosis and maintained on normal or high iron intake. Aust. Vet. J. 66,50–55. Nielsen SS, T<strong>of</strong>t N, 2006. Age-specific characteristics <strong>of</strong> ELISA and fecal culture for purposespecific testing for paratuberculosis. J. Dairy Sci. 89:569–579. Nielsen SS, Enevoldsen C, Gröhn YT, 2002. The Mycobacterium avium subsp. paratuberculosis ELISA response by parity and stage <strong>of</strong> lactation. Prev Vet Med. 54:1- 10. Nielsen SS, Ersbøll AK, 2006. Age at occurrence <strong>of</strong> Mycobacterium avium subspecies paratuberculosis in naturally infected dairy cows. J Dairy Sci. 89, 4557-66. Skinner CJ, Humphreys K,1999. Weibull regression for lifetimes measured with error. Lifetime Data Analysis 5, 23-37. Taylor AW, 1953. Experimental Johne’s disease in cattle. J Comp Pathol Therapeutics. 63, 355-373. Tiwari A, VanLeeuwen JA, Dohoo IR, Keefe GP, Haddad JP, Scott HM, Whiting T, 2009. Risk factors associated with Mycobacterium avium subspecies paratuberculosis seropositivity in Canadian dairy cows and herds. Preventive Veterinary Medicine. 88, 32- 41. 154 4
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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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• MIRU (3 loci); • VNTR-MIRU (7
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indexes, compared to each single an
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#108 Evaluation of
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#110 Detection and molecular confir
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endoscopic criteria and histopathol
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Bull TJ, McMinn EJ, Sidi-Boumedine
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#131 Seroprevalence of</str
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could be partly attributed to a sma
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#146 Analysis of v
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#162 Comparison of
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#187 Comparison of
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#191 Potentiating day-old blood sam
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samples from the s
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(MAA) (MAP87 and MAP3776) and 1 fro
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#196 Inter- and intra-subtype genot
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RESULTS In 601 (29%) of</st
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#211 Culture of my
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#242 Application and field validati
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#251 Diagnosis of
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Table 2. Paratuberculosis PCR resul
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#254 Programmes on Paratuberculosis
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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
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Page 124 and 125: #23 Role of Mycoba
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Page 128 and 129: #28 Intestinal MAP Infection via Pe
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Page 146 and 147: Table 1 UK and Cyprus MAP survey Re
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Page 168 and 169: CONCLUSION IS1311-based nested Ma/M
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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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#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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