Impact of the shedding level on transmission of persistent infections in Mycobacterium avium subspecies paratuberculosis (MAP).

Super-shedders are infectious individuals that contribute a disproportionate amount of infectious pathogen load to the environment. A super-shedder host may produce up to 10,000 times more pathogens than other infectious hosts. Super-shedders have been reported for multiple human and animal diseases. If their contribution to infection dynamics was linear to the pathogen load, they would dominate infection dynamics. We here focus on quantifying the effect of super-shedders on the spread of infection in natural environments to test if such an effect actually occurs in Mycobacterium avium subspecies paratuberculosis (MAP). We study a case where the infection dynamics and the bacterial load shed by each host at every point in time are known. Using a maximum likelihood approach, we estimate the parameters of a model with multiple transmission routes, including direct contact, indirect contact and a background infection risk. We use longitudinal data from persistent infections (MAP), where infectious individuals have a wide distribution of infectious loads, ranging upward of three orders of magnitude. We show based on these parameters that the effect of super-shedders for MAP is limited and that the effect of the individual bacterial load is limited and the relationship between bacterial load and the infectiousness is highly concave. A 1000-fold increase in the bacterial contribution is equivalent to up to a 2-3 fold increase in infectiousness.

Longitudinal data collection of Mycobacterium avium subspecies Paratuberculosis infections in dairy herds: the value of precise field data.

Longitudinal infection data on Mycobacterium avium subspecies paratuberculosis (MAP) was collected on three dairy farms in Northeastern United States during approximately 10 years. Precise data on animal characteristics and animal location within farm were collected on these farms. Cows were followed over time with regard to MAP status during biannual fecal and serum sampling and quarterly serum sampling. Approximately 13 000 serum samples, 6500 fecal samples and 2000 tissue samples were collected during these years. Prevalence of positive samples was 1.4% for serological samples, 2.2% in fecal samples and 16.7% in tissue samples. Infection dynamics of MAP was studied and resulted in a number of potential changes in our understanding of MAP infection dynamics. First, a high prevalence of MAP infection was observed in these herds due to lifetime follow up of cows, including slaughter. Second, two distinctly different infection patterns were observed, so called non-progressors and progressors. Non-progressors were characterized by intermittent and low shedding of MAP bacteria and a virtual absence of a humoral immune response. Progressors were characterized by continuous and progressive shedding and a clearly detectable and progressive humoral immune response. Strain typing of MAP isolates on the three farms identified on two of three farms a dominant strain type, indicating that some strains are more successful in terms of transmission and infection progression. Continuous high quality longitudinal data collection turned out to be an essential tool in our understanding of pathobiology and epidemiology of MAP infections in dairy herds.

Differences in intermittent and continuous fecal shedding patterns between natural and experimental Mycobacterium avium subspecies paratuberculosis infections in cattle.

The objective of this paper is to study shedding patterns of cows infected with Mycobacterium avium subsp. paratuberculosis (MAP). While multiple single farm studies of MAP dynamics were reported, there is not large scale meta-analysis of both natural and experimental infections. Large difference in shedding patterns between experimentally and naturally infected cows were observed. Experimental infections are thus probably driven by different pathological mechanisms. For further evaluations of shedding patterns only natural infections were used. Within such infections, the transition to high shedding was studied as a proxy to the development of a clinical disease. The majority of studied cows never developed high shedding levels. Those that do, typically never reduced their shedding level to low or no shedding. Cows that eventually became high shedders showed a pattern of continuous shedding. In contrast, cows with an intermittent shedding pattern had a low probability to ever become high shedders. In addition, cows that start shedding at a younger age (less than three years of age) have a lower hazard of becoming high shedders compared to cows starting to shed at an older age. These data suggest the presence of three categories of immune control. Cows that are intermittent shedders have the infection process under control (no progressive infection). Cows that start shedding persistently at a young age partially control the infection, but eventually will be high shedders (slow progressive infection), while cows that start shedding persistently at an older age cannot effectively control the infection and become high shedders rapidly.

Persistence of Mycobacterium avium subsp. paratuberculosis in soil, crops, and ensiled feed following manure spreading on infected dairy farms.

The goal of this study was to determine the persistence of Mycobacterium avium subsp. paratuberculosis (MAP) in soil, crops, and ensiled feeds following manure spreading. This bacterium was often found in soil samples, but less frequently in harvested feeds and silage. Spreading of manure on fields used for crop harvest is preferred to spreading on grazing pastures.

Persistance deMycobacterium aviumssp.paratuberculosisdans le sol, les récoltes et l'ensilage après l'épandage de fumier dans des fermes laitières infectées. Le but de cette étude était de déterminer la persistance de Mycobacterium avium ssp. paratuberculosis (MAP) dans le sol, les récoltes et l'ensilage après l'épandage de fumier. Cette bactérie se trouvait souvent dans des échantillons de sol, mais moins fréquemment dans les récoltes d'aliments pour le bétail et l'ensilage. L'épandage de fumier dans les champs utilisés pour la récolte des cultures est préféré à l'épandage dans les pâturages.(Traduit par Isabelle Vallières).

Application of a peptide-mediated magnetic separation-phage assay for detection of viable Mycobacterium avium subsp. paratuberculosis to bovine bulk tank milk and feces samples.

Naturally contaminated bovine bulk tank milk (n = 44) and feces (n = 39) were tested for the presence of viable Mycobacterium avium subsp. paratuberculosis by a novel peptide-mediated magnetic separation-phage (PMS-phage) assay. Counts of viable M. avium subsp. paratuberculosis cells ranging from 1 to 110 PFU/50 ml of milk and 6 to 41,111 PFU/g of feces were indicated by the PMS-phage assay.

Culture phenotypes of genomically and geographically diverse Mycobacterium avium subsp. paratuberculosis isolates from different hosts.

Mycobacterium avium subsp. paratuberculosis causes paratuberculosis (Johne's disease) in ruminants in most countries. Historical data suggest substantial differences in culturability of M. avium subsp. paratuberculosis isolates from small ruminants and cattle; however, a systematic comparison of culture media and isolates from different countries and hosts has not been undertaken. Here, 35 field isolates from the United States, Spain, Northern Ireland, and Australia were propagated in Bactec 12B medium and Middlebrook 7H10 agar, genomically characterized, and subcultured to Lowenstein-Jensen (LJ), Herrold's egg yolk (HEY), modified Middlebrook 7H10, Middlebrook 7H11, and Watson-Reid (WR) agars, all with and without mycobactin J and some with sodium pyruvate. Fourteen genotypes of M. avium subsp. paratuberculosis were represented as determined by BstEII IS900 and IS1311 restriction fragment length polymorphism analysis. There was no correlation between genotype and overall culturability, although most S strains tended to grow poorly on HEY agar. Pyruvate was inhibitory to some isolates. All strains grew on modified Middlebrook 7H10 agar but more slowly and less prolifically on LJ agar. Mycobactin J was required for growth on all media except 7H11 agar, but growth was improved by the addition of mycobactin J to 7H11 agar. WR agar supported the growth of few isolates. The differences in growth of M. avium subsp. paratuberculosis that have historically been reported in diverse settings have been strongly influenced by the type of culture medium used. When an optimal culture medium, such as modified Middlebrook 7H10 agar, is used, very little difference between the growth phenotypes of diverse strains of M. avium subsp. paratuberculosis was observed. This optimal medium is recommended to remove bias in the isolation and cultivation of M. avium subsp. paratuberculosis.

Molecular epidemiology of Mycobacterium avium subsp. paratuberculosis in a longitudinal study of three dairy herds.

The objective of this study was to evaluate whether cows that were low shedders of Mycobacterium avium subsp. paratuberculosis were passively shedding or truly infected with M. avium subsp. paratuberculosis. We also investigated whether it is possible that these M. avium subsp. paratuberculosis-infected animals could have been infected as adults by contemporary high-shedding animals (supershedders). The M. avium subsp. paratuberculosis isolates were obtained from a longitudinal study of three dairy herds in the northeastern United States. Isolates were selected from fecal samples and tissues at slaughter from all animals that were culture positive at the same time that supershedders were present in the herds. Shedding levels (CFU of M. avium subsp. paratuberculosis/g of feces) for the animals at each culture-positive occasion were determined. Using a multilocus short-sequence-repeat technique, we found 15 different strains of M. avium subsp. paratuberculosis from a total of 142 isolates analyzed. Results indicated herd-specific infection patterns; there was a clonal infection in herd C, with 89% of isolates from animals sharing the same strain, whereas herds A and B showed several different strains infecting the animals at the same time. Tissues from 80% of cows with at least one positive fecal culture (other than supershedders) were culture positive, indicating a true M. avium subsp. paratuberculosis infection. The results of M. avium subsp. paratuberculosis strain typing and observed shedding levels showed that at least 50% of low shedders have the same strain as that of a contemporary supershedder. Results of this study suggest that in a dairy herd, more of the low-shedding cows are truly infected with M. avium subsp. paratuberculosis than are passively shedding M. avium subsp. paratuberculosis. The sharing of strains between low shedders and the contemporary supershedders suggests that low shedders may have been infected by environmental exposure of M. avium subsp. paratuberculosis.

GSEA-SNP identifies genes associated with Johne's disease in cattle.

SNP-based gene-set enrichment analysis from single nucleotide polymorphisms, or GSEA-SNP, is a tool to identify candidate genes based on enrichment analysis of sets of genes rather than single SNP associations. The objective of this study was to identify modest-effect genes associated with Mycobacterium avium subsp. paratuberculosis (Map) tissue infection or fecal shedding using GSEA-SNP applied to KEGG pathways or Gene Ontology (GO) gene sets. The Illumina Bovine SNP50 BeadChip was used to genotype 209 Holstein cows for the GSEA-SNP analyses. For each of 13,744 annotated genes genome-wide located within 50 kb of a Bovine SNP50 SNP, the single SNP with the highest Cochran-Armitage Max statistic was used as a proxy statistic for that gene's strength of affiliation with Map. Gene-set enrichment was tested using a weighted Kolmogorov-Smirnov-like running sum statistic with data permutation to adjust for multiple testing. For tissue infection and fecal shedding, no gene sets in KEGG pathways or in GO sets for molecular function or cellular component were enriched for signal. The GO biological process gene set for positive regulation of cell motion (GO:0051272, q = 0.039, 5/11 genes contributing to the core enrichment) was enriched for Map tissue infection, while no GO biological process gene sets were enriched for fecal shedding. GSEA-SNP complements traditional SNP association approaches to identify genes of modest effects as well as genes with larger effects as demonstrated by the identification of one locus that we previously found to be associated with Map tissue infection using a SNP-by-SNP genome-wide association study.

Type A botulism in horses in the United States: a review of the past ten years (1998-2008).

The objective of the current retrospective study was to describe naturally occurring type A botulism in horses in the United States. In the past 10 years, the Botulism Laboratory at the University of Pennsylvania's School of Veterinary Medicine has identified 3 isolated cases and 8 outbreaks of type A botulism in horses via samples positive for Clostridium botulinum type A toxin or spores using the mouse bioassay test. Additional information was obtained by review of submission forms and by telephone or email interviews. Almost all type A cases and outbreaks occurred in the western United States, with Oregon and Idaho overrepresented. Type A toxin was identified in only 1 outbreak; all other identified cases and outbreaks were positive for spores but not preformed toxin. Reported clinical signs included progressive muscle weakness, recumbency, decreased tail and/or tongue tone, dysphagia, respiratory distress, and death. Isolated cases involved foals < or =1 month of age; outbreaks involved horses > or =11 months. One hundred and nineteen horses were potentially exposed to the toxin source; 54 out of 119 showed signs of botulism, and 49 out of 54 affected horses were confirmed dead. The number of horses affected per outbreak ranged from 2 to 24. The source of infection was confirmed to be hay or silage in 6 out of 8 outbreaks and was unknown in 2 out of 8 outbreaks. The present report is the first description of outbreaks of type A botulism in horses and has important implications for prevention and treatment. Based on these findings, type A botulism should be considered in suspect cases of equine botulism in the western United States.

Correlation between Herrold egg yolk medium culture and real-time quantitative polymerase chain reaction results for Mycobacterium avium subspecies paratuberculosis in pooled fecal and environmental samples.

Real-time quantitative polymerase chain reaction (qPCR) testing for Mycobacterium avium subspecies paratuberculosis (MAP) in fecal samples is a rapid alternative to culture on Herrold egg yolk medium (HEYM), the traditional antemortem reference test for MAP. Although the sensitivity and specificity of these 2 tests have been estimated based on dichotomized test results, the correlation between real-time qPCR threshold cycle (Ct) values and colony-forming units (CFU) on HEYM for fresh and thawed samples has not been evaluated. The objectives of the present study were to estimate the correlation and association between Ct and CFU in fresh and thawed pooled fecal and environmental samples. Results of HEYM culture of 1,997 pooled fecal samples from cows in 14 herds, and 802 environmental samples from 109 dairies nationwide were negatively (inversely) correlated with their respective real-time qPCR results. The Spearman's rank correlation between Ct and CFU was good (-0.66) in fresh and thawed pooled fecal samples, and excellent (-0.76) and good (-0.61) in fresh and thawed environmental samples, respectively. The correlation varied from good (-0.53) to excellent (-0.90) depending on the number of samples in a fecal pool. Truncated regression models indicated a significant negative association between Ct and CFU in fecal pools and environmental samples. The use of real-time qPCR instead of HEYM can yield rapid, quantitative estimates of MAP load and allow for incorporation of real-time qPCR results of pooled and environmental samples in testing strategies to identify dairy cow groups with the highest MAP shedding.

Absorbed EVELISA: a diagnostic test with improved specificity for Johne's disease in cattle.

The use of enzyme-linked immunosorbent assays (ELISAs) is recommended for Johne's disease (JD) control in dairy herds. In 2006, we developed a novel ELISA test for JD, named EVELISA (ELISA using ethanol extract of Mycobacterium avium subsp. paratuberculosis), which showed higher sensitivity than commercial ELISA tests. To further investigate the performance of EVELISA, we obtained 38 serum samples from cattle in a JD-free herd with suspected cases of serological false-positive reactions. When these samples were tested using the EVELISA and a commercial ELISA test, more than 70% of the samples were falsely identified as JD positive. Antibodies in the serum samples reacted strongly with antigens of various environmental mycobacteria, suggesting the presence of cross-reactive antibodies in the samples. The possible cross reactions in the EVELISA were inhibited markedly by the use of Mycobacterium phlei antigens for antibody absorption. When these samples were tested, 8 samples were classified as positive for JD by the EVELISA with the antibody absorption, whereas 27 samples were classified as positive for JD by the commercial ELISA. For an estimation of tentative sensitivity and specificity, the ELISA tests were performed on 38 serum samples from JD-negative herds with no suspected cases of serological false-positive reaction and 68 samples from cattle diagnosed as positive for M. avium subsp. paratuberculosis infection by fecal culture test. Sensitivity and specificity of the EVELISA with preabsorption of serum with M. phlei ("ethanol vortex absorbed-ELISA" or EVA-ELISA) were estimated to be 97.1% and 100%, respectively, whereas those of the commercial ELISA were 48.5% and 97.4%, respectively. Further, in 85 fecal culture-negative cattle in JD-positive herds, higher sensitivity of the EVA-ELISA than the commercial ELISA was demonstrated by a Bayesian analysis. This study indicates that the EVA-ELISA may form a basis for a sensitive diagnostic test with a higher level of specificity than that of the current commercial ELISA test.

Exposure of young dairy cattle to Mycobacterium avium subsp. paratuberculosis (MAP) through intensive grazing of contaminated pastures in a herd positive for Johne's disease.

This study investigated the susceptibility of 1- to 2-year-old cattle to Mycobacterium avium subsp. paratuberculosis (MAP) on pasture previously grazed by infected cattle. The exposure of yearling cattle to pastures contaminated with MAP resulted in infection with MAP, showing that age resistance to infection can be overcome by pressure of infection.

Effect of subcutaneous administration of a killed Mycobacterium avium subsp paratuberculosis vaccine on colonization of tissues following oral exposure to the organism in calves.

OBJECTIVE-To evaluate the effect of vaccination of calves with a killed Mycobacterium avium subsp paratuberculosis (MAP) vaccine on colonization of tissues following oral MAP exposure. ANIMALS-12 healthy Holstein calves. PROCEDURES-At 14 days after birth, calves received the MAP vaccine (1.0 mL, SC) or saline (0.9% NaCl) solution (1.0 mL, SC [control treatment]). Each calf received 1.2 x 10(9) CFUs of live MAP orally 21 and 22 days after vaccination. Prior to vaccination and at subsequent intervals, a blood sample was collected for ELISA detection of antibodies against MAP and for whole blood, antigen-specific, interferon (IFN)-gamma-release assay. Nine weeks after MAP challenge, calves were euthanized and various tissue samples were collected for mycobacterial culture. Interferon-gamma production in prescapular lymph node cells was measured following in vitro stimulation with MAP antigens. RESULTS-Calves were seronegative for anti-MAP antibodies at all times. Compared with the findings in control calves, antigen-specific IFN-gamma production in circulating lymphocytes and prescapular lymph node cells from vaccinated calves was significantly higher. Culture of tissues from vaccinated calves yielded significantly fewer CFUs of MAP (2,417 CFUs/g), compared with tissues from control calves (15,709 CFUs/g). Furthermore, significantly fewer tissue samples from vaccinated calves yielded MAP in culture (21.8 tissues/calf), compared with findings in control calves (27.6 tissues/calf). CONCLUSIONS AND CLINICAL RELEVANCE-Inoculation of calves with a killed MAP vaccine was associated with reduced colonization of intestinal tissues following experimental exposure to MAP. Use of the vaccine could potentially reduce transmission of MAP to calves in infected herds.

Elucidating Transmission Patterns of Endemic Mycobacterium avium subsp. paratuberculosis Using Molecular Epidemiology.

Mycobacterial diseases are persistent and characterized by lengthy latent periods. Thus, epidemiological models require careful delineation of transmission routes. Understanding transmission routes will improve the quality and success of control programs. We aimed to study the infection dynamics of Mycobacterium avium subsp. paratuberculosis (MAP), the causal agent of ruminant Johne's disease, and to distinguish within-host mutation from individual transmission events in a longitudinally MAP-defined dairy herd in upstate New York. To this end, semi-annual fecal samples were obtained from a single dairy herd over the course of seven years, in addition to tissue samples from a selection of culled animals. All samples were cultured for MAP, and multi-locus short-sequence repeat (MLSSR) typing was used to determine MAP SSR types. We concluded from these precise MAP infection data that, when the tissue burden remains low, the majority of MAP infections are not detectable by routine fecal culture but will be identified when tissue culture is performed after slaughter. Additionally, we determined that in this herd vertical infection played only a minor role in MAP transmission. By means of extensive and precise longitudinal data from a single dairy herd, we have come to new insights regarding MAP co-infections and within-host evolution.

Experimental challenge models for Johne's disease: a review and proposed international guidelines.

An international committee of Johne's disease (JD) researchers was convened to develop guidelines for JD challenge studies in multiple animal species. The intent was to develop and propose international standard guidelines for models based on animal species that would gain acceptance worldwide. Parameters essential for the development of long-term and short-term infection models were outlined and harmonized to provide a "best fit" JD challenge model for cattle, goats, sheep, cervids, and mice. These models will be useful to study host-pathogen interactions, host immunity at the local and systemic level, and for evaluating vaccine candidates and therapeutics. The consensus guidelines herein list by animal species strains of Mycobacterium avium subsp. paratuberculosis used, challenge dose, dose frequency, age of challenge, route of challenge, preparation of inoculum, experimental animal selection, quality control, minimal experimental endpoints and other parameters.

Comparison of three DNA preparation methods for real-time polymerase chain reaction confirmation of Mycobacterium avium subsp. paratuberculosis growth in an automated broth culture system.

Three methods of harvesting DNA from broth culture tubes for quantitative real-time polymerase chain reaction (qrtPCR) confirmation of Mycobacterium avium subsp. paratuberculosis (MAP) were evaluated. A commercial DNA extraction kit, the boil method (boiling for 5 minutes), or direct addition of broth culture media to the PCR reaction mix were tested. Samples were evaluated at 8 or 11 days of incubation and at the time of instrument-signal culture-positive. In total, when tested at time to instrument signal positive, 10/10 (100%) of samples extracted by the commercial method were positive on qrtPCR, whereas 9/10 (90%) were positive after the boil method, and 6/10 (60%) were positive after the direct method. Increased volumes of egg-yolk emulsion added to the culture tubes prolonged the number of cycles to threshold positive for the samples that were not subjected to commercial extraction or boiling. Samples were not reliably positive when tested at 8 or 11 days of incubation. The boil method appears to represent a reasonable time- and money-saving method to harvest DNA for qrtPCR confirmation of MAP in broth culture at time to instrument signal positive.

Longitudinal study of ELISA seroreactivity to Mycobacterium avium subsp. paratuberculosis in infected cattle and culture-negative herd mates.

Two thousand nine hundred fifty-two serum samples, collected once or twice annually from 545 cows of known fecal culture status were tested for antibodies to Mycobacterium avium subsp. paratuberculosis using a commercially available enzyme-linked immunosorbent assay (ELISA) test. Overall, 13.5% of the samples from 282 infected cows had positive ELISA results, but when tested multiple times, 38.3% of the cows had at least 1 serum sample with positive results. Among 263 fecal culture-negative cows, 98.1% of the serum samples had negative ELISA results, but when tested multiple times, 7.8% of the cows had at least 1 positive ELISA sample. Fecal culture was positive on a test before the first positive ELISA in 50 cows, ELISA was positive before fecal culture in 12 cows, and in 38 cows, both tests became positive at the same testing time. An additional 174 cows were positive on fecal culture and always negative on ELISA until culled. For cows that had ELISA sample:positive (S/P) ratios below the cutoff point, the change in S/P between sequential tests was evaluated to determine whether a rise in S/P could predict infection status. In this study, change in S/P was not a useful predictor of infection status in seronegative cows.

Fecal shedding of Mycobacterium avium subsp. paratuberculosis by dairy cows.

Between 1982 and 2000, fecal samples were obtained from 786 cows that were shedding Mycobacterium avium subsp. paratuberculosis (Map). These cows were resident on 93 Pennsylvania dairies (mean herd size, 64 milk cows) that had no or minimal previous testing for Map. Feces were cultured on four tubes of Herrold's egg yolk medium and the distribution of mean Map colony forming units (CFU) was evaluated. Most cows were light (< 10 CFU/tube, 51.4%) or high (> 50 CFU/tube, 30.8%) fecal shedders with fewer cows in the moderate category (10-50 CFU/tube). Of the 786 cows, 192 (24.4%) had colonies in only one of four tubes. In the multivariable negative binomial model, there were significant associations between mean CFU/tube and prevalence, herd size, and season and an interaction between herd size and season. The linear mixed model of continuous tube counts with a random herd effect yielded similar findings with associations with herd size as a continuous variable, season, and an interaction between categorized prevalence and continuous herd size. Variability in CFU/tube was greatest among cows in the same herd, intermediate for replicate tubes from the same cow, and smallest among cows in different herds. Reduction in the number of replicate tubes from four would have reduced the sensitivity of fecal culture for Map by approximately 6% (for three tubes) to 12% (for two tubes).

Common variable immunodeficiency in three horses with presumptive bacterial meningitis.

Three adult horses were evaluated for signs of musculoskeletal pain, dullness, ataxia, and seizures. A diagnosis of bacterial meningitis was made on the basis of results of CSF analysis. Because primary bacterial meningitis is so rare in adult horses without any history of generalized sepsis or trauma, immune function testing was pursued. Flow cytometric phenotyping of peripheral blood lymphocytes was performed, and proliferation of peripheral blood lymphocytes in response to concanavalin A, phytohemagglutinin, pokeweed mitogen, and lipopolysaccharide was determined. Serum IgA, IgM, and IgG concentrations were measured by means of radial immunodiffusion, and serum concentrations of IgG isotypes were assessed with a capture antibody ELISA. Serum tetanus antibody concentrations were measured before and 1 month after tetanus toxoid administration. Phagocytosis and oxidative burst activity of isolated peripheral blood phagocytes were evaluated by means of simultaneous flow cytometric analysis. Persistent B-cell lymphopenia, hypogammaglobulinemia, and abnormal in vitro responses to mitogens were detected in all 3 horses, and a diagnosis of common variable immunodeficiency was made.

Back to the real world: connecting models with data.

Mathematical models for infectious disease are often used to improve our understanding of infection biology or to evaluate the potential efficacy of intervention programs. Here, we develop a mathematical model that aims to describe infection dynamics of Mycobacterium avium subspecies paratuberculosis (MAP). The model was developed using current knowledge of infection biology and also includes some components of MAP infection dynamics that are currently still hypothetical. The objective was to show methods for parameter estimation of state transition models and to connect simulation models with detailed real life data. Thereby making model predictions and results of simulations more reflective and predictive of real world situations. Longitudinal field data from a large observational study are used to estimate parameter values. It is shown that precise data, including molecular diagnostics on the obtained MAP strains, results in more precise and realistic parameter estimates. It is argued that modeling of infection disease dynamics is of great value to understand the patho-biology, epidemiology and control of infectious diseases. The quality of conclusions drawn from model studies depend on two key issues; first, the quality of biology that has gone in the process of developing the model structure; second the quality of the data that go into the estimation of the parameters and the quality and quantity of the data that go into model validation. The more real world data that are used in the model building process, the more likely that modeling studies will provide novel, innovative and valid results.