Ante mortem diagnosis of paratuberculosis: A review of accuracies of ELISA, interferon-γ assay and faecal culture techniques

High-throughput direct fecal PCR assay for detection of Mycobacterium avium subsp. paratuberculosis in sheep and cattle

Johne's disease (JD) is a chronic enteric disease caused by Mycobacterium avium subsp. paratuberculosis that affects ruminants. Transmission occurs by the fecal-oral route. A commonly used antemortem diagnostic test for the detection of M. avium subsp. paratuberculosis in feces is liquid culture; however, a major constraint is the 2- to 3-month incubation period needed for this method. Rapid methods for the detection of M. avium subsp. paratuberculosis based on PCR have been reported, but comprehensive validation data are lacking. We describe here a new test, the high-throughput-Johnes (HT-J), to detect M. avium subsp. paratuberculosis in feces. Its diagnostic accuracy was compared with that of liquid radiometric (Bactec) fecal culture using samples from cattle (1,330 samples from 23 herds) and sheep (596 samples from 16 flocks). The multistage protocol involves the recovery of M. avium subsp. paratuberculosis cells from a fecal suspension, cell rupture by bead beating, extraction of DNA using magnetic beads, and IS900 quantitative PCR. The limit of detection of the assay was 0.0005 pg, and the limit of quantification was 0.005 pg M. avium subsp. paratuberculosis genomic DNA. Only M. avium subsp. paratuberculosis was detected from a panel of 51 mycobacterial isolates, including 10 with IS900-like sequences. Of the 549 culture-negative fecal samples from unexposed herds and flocks, 99% were negative in the HT-J test, while 60% of the bovine- and 84% of the ovine-culture-positive samples were positive in the HT-J test. As similar total numbers of samples from M. avium subsp. paratuberculosis-exposed animals were positive in culture and HT-J tests in both species, and as the results of a McNemar's test were not significant, these methods probably have similar sensitivities, but the true diagnostic sensitivities of these tests are unknown. These validation data meet the consensus-based reporting standards for diagnostic test accuracy studies for paratuberculosis and the Minimum Information for Publication of Quantitative Real-Time PCR Experiments (MIQE) guidelines (S. A. Bustin et al., Clin. Chem. 55:611-622, 2009, doi:10.1373/clinchem.2008.112797). The HT-J assay has been approved for use in JD control programs in Australia and New Zealand.

A novel low-cost method for Mycobacterium avium subsp. paratuberculosis DNA extraction from an automated broth culture system for real-time PCR analysis

PCR is a highly accurate technique for confirming the presence of Mycobacterium avium subsp. paratuberculosis (Map) in broth culture. In this study, a simple, efficient, and low-cost method of harvesting DNA from Map cultured in liquid medium was developed. The proposed protocol (Universidad Austral de Chile [UACH]) was evaluated by comparing its performance to that of two traditional techniques (a QIAamp DNA Stool Mini Kit and cethyltrimethylammonium bromide [CTAB] method). The results were statistically assessed by agreement analysis for which differences in the number of cycles to positive (CP) were compared by Student's t-test for paired samples and regression analysis. Twelve out of 104 fecal pools cultured were positive. The final PCR results for 11 samples analyzed with the QIAamp and UACH methods or ones examined with the QIAamp and CTAB methods were in agreement. Complete (100%) agreement was observed between data from the CTAB and UACH methods. CP values for the UACH and CTAB techniques were not significantly different, while the UACH method yielded significantly lower CP values compared to the QIAamp kit. The proposed extraction method combines reliability and efficiency with simplicity and lower cost.

Antigenicity of recombinant maltose binding protein-Mycobacterium avium subsp. paratuberculosis fusion proteins with and without factor Xa cleaving

Mycobacterium avium subsp. paratuberculosis causes Johne's disease (JD) in ruminants. Proteomic studies have shown that M. avium subsp. paratuberculosis expresses certain proteins when exposed to in vitro physiological stress conditions similar to the conditions experienced within a host during natural infection. Such proteins are hypothesized to be expressed in vivo, are recognized by the host immune system, and may be of potential use in the diagnosis of JD. In this study, 50 recombinant maltose binding protein (MBP)-M. avium subsp. paratuberculosis fusion proteins were evaluated using serum samples from sheep infected with M. avium subsp. paratuberculosis, and 29 (58%) were found to be antigenic. Among 50 fusion proteins, 10 were evaluated in MBP fusion and factor Xa-cleaved forms. A total of 31 proteins (62%) were found to be antigenic in either MBP fusion or factor Xa-cleaved forms. Antigenicity after cleavage and removal of the MBP tag was marginally enhanced.

Bayesian estimation of the sensitivity and specificity of individual fecal culture and Paralisa to detect Mycobacterium avium subspecies paratuberculosis infection in young farmed deer

A Bayesian latent class model was used to estimate the sensitivity and specificity of an immunoglobulin G1 serum enzyme-linked immunosorbent assay (Paralisa) and individual fecal culture to detect young deer infected with Mycobacterium avium subsp. paratuberculosis. Paired fecal and serum samples were collected, between July 2009 and April 2010, from 20 individual yearling (12–24-month-old) deer in each of 20 South Island and 18 North Island herds in New Zealand and subjected to culture and Paralisa, respectively. Two fecal samples and 16 serum samples from 356 North Island deer, and 55 fecal and 37 serum samples from 401 South Island deer, were positive. The estimate of individual fecal culture sensitivity was 77% (95% credible interval [CI] = 61–92%) with specificity of 99% (95% CI = 98–99.7%). The Paralisa sensitivity estimate was 19% (95% CI = 10–30%), with specificity of 94% (95% CI = 93–96%). All estimates were robust to variation of priors and assumptions tested in a sensitivity analysis. The data informs the use of the tests in determining infection status at the individual and herd level.

Flow cytometric detection of Mycobacterium avium subsp. paratuberculosis-specific antibodies in experimentally infected and naturally exposed calves

A desirable test to diagnose infections with Mycobacterium avium subsp. paratuberculosis facilitates identification of infected cattle prior to the state of M. avium subsp. paratuberculosis shedding. This study aimed at adjusting a flow cytometry (FC)-based assay, using intact M. avium subsp. paratuberculosis bacteria as the antigen, for diagnosis of M. avium subsp. paratuberculosis infections in calves. Serum samples were collected from experimentally infected (n = 12) and naturally exposed (n = 32) calves. Samples from five calves from positive dams were analyzed to determine the dynamics of maternal antibodies. Samples from adult cattle with defined infection status served as the standard (18 M. avium subsp. paratuberculosis shedders, 22 M. avium subsp. paratuberculosis free). After preadsorption with Mycobacterium phlei, sera were incubated with M. avium subsp. paratuberculosis and M. avium subsp. avium bacterial suspensions, respectively, followed by the separate detection of bovine IgG, IgG1, IgG2, and IgM attached to the bacterial surface. M. avium subsp. paratuberculosis-specific sample/positive (S/P) ratios were compared to enzyme-linked immunosorbent assay (ELISA) S/P ratios. In adult cattle, the FC assay for IgG1 had a sensitivity of 78% at a specificity of 100%. Maternally acquired antibodies could be detected in calves up to 121 days of life. While all but two sera taken at day 100 ± 10 postnatum from naturally exposed calves tested negative, elevated S/P ratios (IgG and IgG1) became detectable from 44 and 46 weeks postinoculation onwards in two calves infected experimentally. Even with the optimized FC assay, M. avium subsp. paratuberculosis-specific antibodies can only occasionally be detected in infected calves less than 12 months of age. The failure to detect such antibodies apparently reflects the distinct immunobiology of M. avium subsp. paratuberculosis infections rather than methodological constraints.

Specific antibody and interferon-gamma responses associated with immunopathological forms of bovine paratuberculosis in slaughtered Friesian cattle

Mycobacterium avium subsp. paratuberculosis (MAP) infection causes a chronic granulomatous inflammatory regional enteritis in ruminants. Cell-mediated immune responses are assumed to be protective and therefore, to be associated with its more delimited lesion types, while humoral responses are mainly associated with diffuse histopathological lesions. However, this duality of immune responses has been recently questioned. The aim of this study was to assess the relationship between both types of immunological responses and the type and extension of intestinal lesions and the presence of MAP in bovine tissues. Standard histopathological examinations, two microbiological procedures (culture and real time PCR (rtPCR)), as well as MAP specific antibody and interferon gamma (IFN-γ) release assays (IGRA) were performed on tissues and blood of 333 slaughtered Holstein-Friesian animals. Paratuberculous lesions were observed in 176 (52.9%) of the animals and overall MAP detection rates were estimated at 13.5% and 28.5% for tissue culture and rtPCR, respectively. Unlike the relatively constant non-specific IFN-γ release, both the antibody levels and the specific IFN-γ release significantly increased with tissue damage. Delimited immunopathological forms, which accounted for 93.2% of all forms, were mostly related to positive testing in the IGRA (38.4%) whereas diffuse ones (6.8%) were associated with antibody seropositivity (91.7%). However, since the frequency of positive immune responses in both tests increased as the lesions severity increased, polarization of Th1/Th2 responses was less prominent than expected. MAP was detected in the majority of ELISA-positive animals (culture+: 90%, rtPCR+: 85%) but the bacteria was only confirmed in the 36.1% of IGRA-positive animals by any of the two microbiological tests. In terms of diagnosis, the antibody test was a good indicator of advanced tissue damage (diffuse forms), but the IGRA did not associate well with more delimited forms or with MAP detection.

Cellular and humoral immunogenicity of Mycobacterium avium subsp. paratuberculosis specific lipopentapeptide antigens

Paratuberculosis caused by Mycobacterium avium subsp. paratuberculosis (MAP) is a chronic infectious disease affecting domestic and wild ruminants. Antigens currently used for the diagnosis of paratuberculosis are whole-cell derived crude preparations. The identification of MAP-specific antigens for the specific and early diagnosis of this infection is strongly needed. This study assessed the ability of the MAP-specific synthetic lipopeptide antigen Para-LP-01 to invoke specific serum antibody (Ab) and cell-mediated immune (CMI) responses in sheep experimentally exposed to MAP S strain. Responses were compared to those elicited by the crude whole-cell derived MAP 316v antigen (316v). Para-LP-01 induced a significant serum Ab response in MAP-infected sheep in comparison with unexposed or uninfected sheep, but failed to induce detectable CMI responses including production of IFN-γ, IL-10 and lymphoproliferation, unlike 316v which invoked both CMI and serum Ab responses in MAP-exposed sheep. Para-LP-01 is a suitable antigen for serodiagnosis of MAP-infection in sheep. The differential induction of humoral and CMI responses by lipid based antigens could enhance current understanding of the role played by cell-wall associated lipid antigens in the pathogenesis of MAP-infection.

Using vaccination to prevent the invasion of Mycobacterium avium subsp. paratuberculosis in dairy herds: a stochastic simulation study

Paratuberculosis, or Johne's disease (JD), is a chronic enteric disease of ruminants infected by Mycobacterium avium subsp. paratuberculosis (MAP) that causes a significant financial loss in dairy industry. To reduce prevalence and transmission in dairy herds infected with MAP, control programs have been implemented, including test-based culling, improved calf rearing management, and vaccination. The important issue of preventing MAP invasion into a MAP-free herd has been less investigated, however. The objective of this study was to examine whether vaccination was able to prevent MAP invasion in dairy cattle using a stochastic simulation approach. We developed a MAP vaccination model in which calves were vaccinated with a vaccine that is both imperfect in reducing the susceptibility of the host ('leaky') and that does not successfully immunize all calves ('failure in take'). Probability of MAP persistence and the number of infected animals in herds were computed for both control and vaccinated herds over a ten-year period after introduction of an initial infected heifer. Global parameter sensitivity analyses were performed to find the most influential parameters for MAP invasion. Our results show that vaccination of calves is effective in preventing MAP invasion, provided that the vaccine is of high efficacy in both reduction of susceptibility and 'take' effects; however, there is still a small chance (<0.15) that MAP can be sustained in herds over a long time (>10 years) due to vertical transmission. This study indicates that reduction in the transmission rate of high shedders (>50 CFU), the number of infected heifers initially introduced to herds, and vertical transmission are important to further decrease the probability of MAP becoming endemic and the overall number of infected animals in endemic herds. The simulation work is useful for designing vaccination programs aimed at preventing MAP invasion in MAP-free herds.

Paratuberculose em ruminantes no Brasil

A paratuberculose ou doença de Johne é uma enterite granulomatosa causada por Mycobacterium avium subsp. paratuberculosis (Map) e comumente afeta ruminantes domésticos, no entanto, pode infectar várias espécies de mamíferos. Está presente nos cinco continentes e é considerada endêmica em algumas regiões pela Organização Internacional de Epizootias (OIE). Pertence à lista de enfermidades notificáveis, que compreende as doenças transmissíveis de importância sócio-econômica e/ou em saúde-pública, cujo controle é necessário para o comércio internacional de animais e alimentos de origem animal. A importância da doença de Johne não se restringe somente aos prejuízos econômicos causados à indústria animal, mas também na possível participação do Map na íleocolite granulomatosa que afeta seres humanos, conhecida como doença de Crohn. No Brasil, a paratuberculose já foi descrita em diversas espécies de ruminantes e em vários estados. Embora os relatos naturais da enfermidade sejam pontuais, acredita-se na possibilidade da transmissão interespecífica e na disseminação do agente através da compra e venda de animais infectados. O objetivo deste artigo foi reunir as informações disponíveis referentes aos aspectos epidemiológicos, clínico-patológicos e laboratoriais da paratuberculose em bovinos, bubalinos, caprinos e ovinos no Brasil, e salientar a necessidade de implementação de medidas de controle sanitário da enfermidade no país, o que possibilitaria a melhoria da qualidade e valorização dos produtos de origem animal no mercado internacional.

The modification and evaluation of an ELISA test for the surveillance of Mycobacterium avium subsp. paratuberculosis infection in wild ruminants

BACKGROUND

Enzyme-linked immunosorbent assay (ELISA) is often used to test wildlife samples for Mycobacterium avium subsp. paratuberculosis (MAP) infection. However, commercially available kits are only validated for use with domestic ruminant species. A literature review was performed to document the current use of MAP serum ELISA in wild and semi-domestic ruminants. We then modified and evaluated a commercial ELISA kit (IDEXX Mycobacterium paratuberculosis Antibody Test Kit) for use with species for which it was not originally developed: elk (Cervus elaphus), bison (Bison bison) and caribou (Rangifer tarandus). We tested the affinity of different conjugates for immunoglobulin G (IgG) isolated from these species, performed checkerboard tests to determine the optimal dilutions of samples and conjugates, and established cut-off values using two different methods: a Receiver Operational Curve on a panel of known samples for elk, and an alternate method involving a panel of unknown serum samples for the three species.

RESULTS

We found that the anti-bovine conjugate included in the IDEXX ELISA kit has limited affinity for elk, bison, and caribou IgG. Protein G showed good affinity for IgG of all three species, while anti-deer conjugate also bound elk and caribou IgG. Using Protein G with elk serum, a cut-off sample-to-positive (S/P) value of 0.22 was selected, resulting in a sensitivity and specificity of 73% and 90%, respectively, whereas, using an anti-deer conjugate with elk serum, an S/P cut-off value of 0.29 gave a sensitivity of 68%, with 100% specificity. Cut-off values for bison and caribou using the Protein G conjugate were 0.17 and 0.25 respectively.

CONCLUSIONS

Due to incomplete reporting and a lack of test validation, it is difficult to critically appraise results of many sero-surveys that have previously been done for MAP in wildlife. Commercial ELISA kits may have limited or no capacity to detect antibodies from species other than for which they were developed. In order to generate reliable test results, it is essential to evaluate the test and perform modifications if deemed necessary. Despite the challenges inherent to wildlife diagnostics, we have shown that several methods can be used to improve confidence in test results.

Rapid and sensitive method to identify Mycobacterium avium subsp. paratuberculosis in cow's milk by DNA methylase genotyping

Paratuberculosis is an infectious, chronic, and incurable disease that affects ruminants, caused by Mycobacterium avium subsp. paratuberculosis. This bacterium is shed primarily through feces of infected cows but can be also excreted in colostrum and milk and might survive pasteurization. Since an association of genomic sequences of M. avium subsp. paratuberculosis in patients with Crohn's disease has been described; it is of interest to rapidly detect M. avium subsp. paratuberculosis in milk for human consumption. IS900 insertion is used as a target for PCR amplification to identify the presence of M. avium subsp. paratuberculosis in biological samples. Two target sequences were selected: IS1 (155 bp) and IS2 (94 bp). These fragments have a 100% identity among all M. avium subsp. paratuberculosis strains sequenced. M. avium subsp. paratuberculosis was specifically concentrated from milk samples by immunomagnetic separation prior to performing PCR. The amplicons were characterized using DNA methylase Genotyping, i.e., the amplicons were methylated with 6-methyl-adenine and digested with restriction enzymes to confirm their identity. The methylated amplicons from 100 CFU of M. avium subsp. paratuberculosis can be visualized in a Western blot format using an anti-6-methyl-adenine monoclonal antibody. The use of DNA methyltransferase genotyping coupled to a scintillation proximity assay allows for the detection of up to 10 CFU of M. avium subsp. paratuberculosis per ml of milk. This test is rapid and sensitive and allows for automation and thus multiple samples can be tested at the same time.

Comparison of fecal DNA extraction kits for the detection of Mycobacterium avium subsp. paratuberculosis by polymerase chain reaction

Culture of Mycobacterium avium subsp. paratuberculosis (MAP) from feces has been considered the gold standard for the diagnosis of paratuberculosis for many years. However, direct fecal polymerase chain reaction (PCR) is becoming more widely used, demonstrating similar sensitivity and specificity to culture. To ensure efficient and reproducible PCR results from a difficult sample matrix such as feces, there are many obstacles that a DNA extraction method must overcome, including the presence of inhibitors and the thick waxy cell wall of MAP. In the current study, 6 commercial DNA extraction kits were evaluated using fecal samples from naturally infected cattle shedding various amounts of MAP. Upon extraction, DNA purity and yield were measured, and real-time PCR was performed for detection of the insertion sequence (IS)900 and ISMAP02 targets. The kits evaluated showed significant differences in the purity and yield of DNA obtained. The best results were observed with kits E and A, having identified 94% (16/17) and 76% (13/17) of the positive samples by IS900 PCR, respectively. Both of these kits utilized bead beating in a lysis solution for cell disruption, followed by spin column technology (kit E) or magnetic bead-based technology (kit A) for nucleic acid isolation and purification. Two kits (A and F) demonstrated improved performance when used in conjunction with the respective manufacturer's PCR test. The present study demonstrates the importance of choosing the correct methodology for the most accurate diagnosis of paratuberculosis through fecal PCR.

Comparison of prevalence estimation of Mycobacterium avium subsp. paratuberculosis infection by sampling slaughtered cattle with macroscopic lesions vs. systematic sampling

The objective of this study was to identify the most reliable approach for prevalence estimation of Mycobacterium avium ssp. paratuberculosis (MAP) infection in clinically healthy slaughtered cattle. Sampling of macroscopically suspect tissue was compared to systematic sampling. Specimens of ileum, jejunum, mesenteric and caecal lymph nodes were examined for MAP infection using bacterial microscopy, culture, histopathology and immunohistochemistry. MAP was found most frequently in caecal lymph nodes, but sampling more tissues optimized the detection rate. Examination by culture was most efficient while combination with histopathology increased the detection rate slightly. MAP was detected in 49/50 animals with macroscopic lesions representing 1.35% of the slaughtered cattle examined. Of 150 systematically sampled macroscopically non-suspect cows, 28.7% were infected with MAP. This indicates that the majority of MAP-positive cattle are slaughtered without evidence of macroscopic lesions and before clinical signs occur. For reliable prevalence estimation of MAP infection in slaughtered cattle, systematic random sampling is essential.

Paratuberculosis (Johne's disease) in cattle and other susceptible species

Paratuberculosis (Johne's disease) is a widespread and costly disease. This consensus statement will summarize recommendations regarding diagnosis, control, and treatment of Johne's disease in cattle and other species. Each section of recommendations is followed by a statement that subjectively characterizes the strength of the supporting evidence. The role played by Mycobacterium avium subsp. paratuberculosis (MAP) in the pathogenesis has been a matter of controversy for many years. This statement concludes with an assessment of the evidence in favor of MAP as a potential zoonotic pathogen.

Gamma-delta T-cell responses during subcutaneous Mycobacterium avium subspecies paratuberculosis challenge in sensitized or naive calves using matrix biopolymers

We have developed a model to explore the early immune response against Mycobacterium avium subspecies paratuberculosis (Map) infection in the bovine calf using subcutaneously placed liquid gel matrix biopolymer (matrigel) containing live Map. Matrigel rapidly polymerizes in vivo, retains recruited cellular infiltrates and soluble immune mediators, and can be rapidly removed 48 hours later and depolymerized for analysis. In this study, we examined early host immune events at matrigel/Map sites; recruited cells were evaluated by histopathology and flow cytometry, and cytokines were measured by flow cytometry, enzyme-linked immunosorbent assay, and Luminex bead immunoassay. Our results demonstrate earlier recruitment of gamma-delta (γδ) T cells to matrigel/Map challenge sites compared to CD4+ T cells. We also show that significantly more γδ T cells were recruited to matrigel/Map sites postinfection day 7 compared to postinfection day 30 and that these cells produced significant amounts of the cytokine interferon gamma. We also provide evidence that peripheral blood-derived γδ T-cell subsets in cattle differentially generate interferon gamma, suggesting distinct roles for these cells. These data provide unique insight into initial antimycobacterial host cellular immune responses following Map infection in calves.

Detection of antibody responses against Mycobacterium avium subsp. paratuberculosis stress-associated proteins within 30 weeks after infection in cattle

In this study, humoral immune responses in cattle against Mycobacterium avium subsp. paratuberculosis (MAP) stress-associated recombinant proteins were assessed longitudinally by ELISA during the first 30 weeks after MAP infection. A total of 11 MAP genes previously identified by proteomic analysis were selected for cloning and expression. These included possible general stress-associated proteins of MAP and proteins expressed in vivo in MAP-infected sheep at an early stage of infection. An increase in the antibody levels against 5 recombinant antigen preparations (MAP1027c, MAP1339, MAP1588c, MAP1589c and MAP2411) was seen in MAP-infected calves (n=16) but not in control calves (n=3) over the time examined. Antibody responses were recorded as early as two weeks post-inoculation, and 87.5% of the inoculated cattle responded to at least one of the five immunogenic antigen preparations within the first 30 weeks of infection, suggesting that these proteins identified in the in vitro models of stress were also expressed in vivo in MAP-infected cattle at a relatively early stage after infection and therefore stimulate the host's immune system. It has been assumed that the sensitivity of antibody ELISA tests is dependent on the stage of infection and the age of the animals. However, we have provided some evidence that humoral immunity occurs at an early stage of paratuberculosis and can be detected using appropriate antigens such as MAP stress-associated proteins.

Heritability estimates for Mycobacterium avium subspecies paratuberculosis status of German Holstein cows tested by fecal culture

The objective of this study was to estimate genetic manifestation of Mycobacterium avium ssp. paratuberculosis (MAP) infection in German Holstein cows. Incorporated into this study were 11,285 German Holstein herd book cows classified as MAP-positive and MAP-negative animals using fecal culture results and originating from 15 farms in Thuringia, Germany involved in a paratuberculosis voluntary control program from 2008 to 2009. The frequency of MAP-positive animals per farm ranged from 2.7 to 67.6%. The fixed effects of farm and lactation number had a highly significant effect on MAP status. An increase in the frequency of positive animals from the first to the third lactation could be observed. Threshold animal and sire models with sire relationship were used as statistical models to estimate genetic parameters. Heritability estimates of fecal culture varied from 0.157 to 0.228. To analyze the effect of prevalence on genetic parameter estimates, the total data set was divided into 2 subsets of data into farms with prevalence rates below 10% and those above 10%. The data set with prevalence above 10% show higher heritability estimates in both models compared with the data set with prevalence below 10%. For all data sets, the sire model shows higher heritabilities than the equivalent animal model. This study demonstrates that genetic variation exists in dairy cattle for paratuberculosis infection susceptibility and furthermore, leads to the conclusion that MAP detection by fecal culture shows a higher genetic background than ELISA test results. In conclusion, fecal culture seems to be a better trait to control the disease, as well as an appropriate feature for further genomic analyses to detect MAP-associated chromosome regions.

Paratuberculose em pequenos ruminantes domésticos

Mycobacterium avium subesp. paratuberculosis (MAP) é o agente etiológico da paratuberculose em ruminantes domésticos e silvestres. Em caprinos e ovinos causa uma enterite granulomatosa crônica com emagrecimento progressivo seguido de morte, raramente a diarreia é observada. Nesse aspecto, a doença é considerada uma ameaça mundial aos rebanhos, pois pode permanecer no estádio subclínico por anos, manifestando perdas indiretas na produção animal e na disseminação do agente. Além disso, existem relatos da possível relação de MAP com a doença de Crohn, determinando, assim, a sua relevância na saúde pública. O Brasil não dispõe de dados quantificando as reais perdas produtivas nos rebanhos acometidos pela doença, e poucas informações do comprometimento de caprinos e ovinos no país são relatadas. Assim, este artigo busca revisar a paratuberculose em pequenos ruminantes domésticos.

Depletion of CD4 T lymphocytes at the time of infection with M. avium subsp. paratuberculosis does not accelerate disease progression

A calf model was used to determine if the depletion of CD4 T cells prior to inoculation of Mycobacterium avium subsp. paratuberculosis (Map) would delay development of an immune response to Map and accelerate disease progression. Ileal cannulas were surgically implanted in 5 bull calves at 2 months of age. Two calves were depleted of CD4 T cells by intravenous injection of anti-bovine CD4 antibody administered 24h prior to inoculation with Map. The two CD4-depleted calves and one non-depleted calf were inoculated via ileal cannula with 1 × 10(8)cfu live Map every 3 days for a total of 4 inoculations. Two additional calves served as non-depleted and uninfected controls. Injection with the anti-CD4 mAb reduced the frequency of CD4 T cells from a pre-depletion average of 15% to less than 1% in PBMC at 24h. However, a consistent proliferative response dominated by CD4 T cells, developed in both treated and untreated calves over the course of the 6-month study period. Recovery of Map from serial biopsies obtained from the CD4-depleted and non-depleted calves after Map infection did not differ. In addition, CD4 depletion did not increase the level of Map shed in the feces over the non-depleted animal.

Detection of Bovine IgG Isotypes in a PPA-ELISA for Johne's Disease Diagnosis in Infected Herds

Johne's Disease or Paratuberculosis is a chronic granulomatous enteritis disease affecting ruminants. Detection of subclinically infected animals is difficult, hampering the control of this disease. The aim of this work was to evaluate the performance of detection of IgG isotypes in a PPA-ELISA to improve the recognition of cattle naturally infected with Map in different stages. A total of 108 animals from Tuberculosis-free herds were grouped as follows: exposed (n = 30), subclinically infected (n = 26), clinically infected (n = 14), and healthy controls (n = 38). Receiver-operating characteristic (ROC) curves of isotypes/PPA-ELISAs were constructed and areas under the curves were compared to evaluate the performance of each test. Our study demonstrated that the conventional PPA-ELISA (detecting IgG) is the best to identify clinically infected animals with high sensitivity (92.9%) and specificity (100%). Meanwhile, IgG2/PPA-ELISA improved the number of subclinically infected cattle detected as compared with conventional IgG/PPA-ELISA (53.8 versus 23.1%). In addition, it had the maximum sensitivity (65.0%, taking into account all Map-infected cattle). In conclusion, the combination of IgG and IgG2/PPA-ELISAs may improve the identification of Map-infected cattle in different stages of disease. The usefulness of IgG2 detection in serological tests for Johne's Disease diagnosis should be further evaluated.

MAP1272c encodes an NlpC/P60 protein, an antigen detected in cattle with Johne's disease

The protein encoded by MAP1272c has been shown to be an antigen of Mycobacterium avium subsp. paratuberculosis that contains an NlpC/P60 superfamily domain found in lipoproteins or integral membrane proteins. Proteins containing this domain have diverse enzymatic functions that include peptidases, amidases, and acetyltransferases. The NlpC protein was examined in comparison to over 100 recombinant proteins and showed the strongest antigenicity when analyzed with sera from cattle with Johne's disease. To further localize the immunogenicity of NlpC, recombinant proteins representing defined regions were expressed and evaluated with sera from cattle with Johne's disease. The region from amino acids 74 to 279 was shown to be the most immunogenic. This fragment was also evaluated against a commercially available enzyme-linked immunosorbent assay (ELISA). Two monoclonal antibodies were produced in mice immunized with the full-length protein, and each recognized a distinct epitope. These antibodies cross-reacted with proteins from other mycobacterial species and demonstrated variable sizes of the proteins expressed from these subspecies. Both antibodies were further analyzed, and their interaction with MAP1272c and MAP1204 was characterized by a solution-based, luminescent binding assay. These tools provide additional means to study a strong antigen of M. avium subsp. paratuberculosis.

Crohn's disease and the mycobacterioses: a quarter century later. Causation or simple association?

It has been more than 25 years since Mycobacterium paratuberculosis was first proposed as an etiologic agent in Crohn's disease based on the isolation of this organism from several patients. Since that time, a great deal of information has been accumulated that clearly establishes an association between M. paratuberculosis and Crohn's disease. However, data are conflicting and difficult to interpret and the field has become divided into committed advocates and confirmed skeptics. This review is an attempt to provide a thorough and objective summary of current knowledge from both basic and clinical research from the views and interpretations of both the antagonists and proponents. The reader is left to draw his or her own conclusions related to the validity of the issues and claims made by the opposing views and data interpretations. Whether M. paratuberculosis is a causative agent in some cases or simply represents an incidental association remains a controversial topic, but current evidence suggests that the notion should not be so readily dismissed. Remaining questions that need to be addressed in defining the role of M. paratuberculosis in Crohn's disease and future implications are discussed.

Clinical and pathological insights into Johne's disease in buffaloes

Alternative diagnostic tools and interesting epidemiological assumptions were associated with an outbreak of Johne's disease. In a buffalo herd infected with paratuberculosis, seven clinically affected animals and 21 animals with anti-Mycobacterium avium ELISA reactions were identified. Total herd included 203 buffaloes. Most lesions were comparable to those described in buffaloes and cattle affected by Johne's disease. Water buffalo behaviors such as communal nursing and allosuckling may be additional risk factors for this disease. Detection of positive Ziehl-Neelsen staining and anti-M. avium immunolabeling in rectal biopsies from one buffalo with paratuberculosis are highlighted as auxiliary diagnostic tools for Johne's disease in live animals.

Pan-genomic analysis of bovine monocyte-derived macrophage gene expression in response to in vitro infection with Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis is the causative agent of Johne's disease, an intestinal disease of ruminants with major economic consequences. Infectious bacilli are phagocytosed by host macrophages upon exposure where they persist, resulting in lengthy subclinical phases of infection that can lead to immunopathology and disease dissemination. Consequently, analysis of the macrophage transcriptome in response to M. avium subsp. paratuberculosis infection can provide valuable insights into the molecular mechanisms that underlie Johne's disease. Here, we investigate pan-genomic gene expression in bovine monocyte-derived macrophages (MDM) purified from seven age-matched females, in response to in vitro infection with M. avium subsp. paratuberculosis (multiplicity of infection 2:1) at intervals of 2 hours, 6 hours and 24 hours post-infection (hpi). Differentially expressed genes were identified by comparing the transcriptomes of the infected MDM to the non-infected control MDM at each time point (adjusted P-value threshold ≤ 0.10). 1050 differentially expressed unique genes were identified 2 hpi, with 974 and 78 differentially expressed unique genes detected 6 and 24 hpi, respectively. Furthermore, in the infected MDM the number of upregulated genes exceeded the number of downregulated genes at each time point, with the fold-change in expression for the upregulated genes markedly higher than that for the downregulated genes. Inspection and systems biology analysis of the differentially expressed genes revealed an enrichment of genes involved in the inflammatory response, cell signalling pathways and apoptosis. The transcriptional changes associated with cellular signalling and the inflammatory response may reflect different immuno-modulatory mechanisms that underlie host-pathogen interactions during infection.

Genetic evaluation of IS900 partial sequence of Mycobacterium avium subsp. paratuberculosis Brazilian isolates from bovine milk

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis. Insertion sequence IS900 is used for the identification of MAP. The objective of this study was to verify the genetic conservation of IS900 sequences in raw milk samples. To evaluate genetic conservation, 206 quarter milk samples and 16 bulk-tank milk samples were collected. DNA extraction and IS900 PCR were performed in all samples. Six samples amplified the expected fragment. To confirm the identity of the amplified fragments, PCR products were cloned and sequenced. The resulting sequences were compared with other MAP sequences from GenBank, and it was possible to identify eight polymorphic regions and to form five distinct haplotypes. The number of mutations in each haplotype was verified. IS900 sequence is a very well-conserved sequence that could be used as tool for the molecular detection of this agent and epidemiological purposes. The results showed the first genetic analysis on Brazilian isolates of MAP.

The collection of lymphatic fluid from the bovine udder and its use for the detection of Mycobacterium avium subsp. paratuberculosis in the cow

The objective of the current study was to evaluate the feasibility of lymph collection from the bovine udder and to investigate if the lymphatic fluid might be of diagnostic value in cows infected with Mycobacterium avium subsp. paratuberculosis (MAP), the etiologic agent of paratuberculosis. Lymph fluid collection was attempted from 58 cows, and the reactions of the cows as well as the level of difficulty of the procedure were recorded in 56 animals. Lymph samples (51 in total) were tested for the presence of MAP by nested polymerase chain reaction. Collection of the lymphatic fluid caused no or mild signs of discomfort in 94.6% of the cows; in 51.8% of cows, lymphatic fluid was attained on the first attempt, while sample collection was unsuccessful in 12.1%. Mycobacterium avium subsp. paratuberculosis was detected in 43.1% of all lymph samples. The bacterium was present in 66.7% of cows with clinical Johne’s disease, in 42.8% of asymptomatic cows with a positive or suspicious enzyme-linked immunosorbent assay (ELISA) result in blood, and in 38.7% of cows with a negative ELISA result in blood. The present study shows that the procedure was well tolerated by most cows and can easily be performed on farm. The current report of the isolation of MAP from lymph fluid suggests that the present approach could be used for the early detection of Johne’s disease in cattle.

Bovine IFNGR2, IL12RB1, IL12RB2, and IL23R polymorphisms and MAP infection status

Mycobacterium avium ssp. paratuberculosis (MAP) infection causes a chronic granulomatous inflammatory condition of the bovine gut that is characterized by diarrhea, progressive weight loss, and emaciation, and ultimately leads to loss in productivity and profitability of dairy operations. The host cytokine machinery is known to play an important role in protecting against MAP infection. Therefore, the goal of the present study was to assess whether polymorphisms in candidate genes encoding important cytokines and cytokine receptors are associated with MAP infection status of dairy cattle. MAP infection status was evaluated based on serum and milk enzyme-linked immunosorbent assays (ELISAs) for MAP-specific antibodies. Twenty previously reported polymorphisms in genes encoding bovine interferon gamma (IFNG), IFNGR1, IFNGR2, IL22, IL22RA1, IL12RB1, IL12RB2, and IL23R were genotyped in a resource population of 446 dairy Holsteins with known MAP infection status, and logistic regression was used to assess the statistical association with a binomial MAP infection status phenotype. Four SNPs in IFNGR2, IL12RB1, IL12RB2, and IL23R were found to be associated with the MAP infection status of the resource population. These results underscore the importance of cytokines and their receptors in conferring protection against MAP infection and warrant further functional characterization of these associations.

Bayesian analysis of longitudinal Johne's disease diagnostic data without a gold standard test

A Bayesian methodology was developed based on a latent change-point model to evaluate the performance of milk ELISA and fecal culture tests for longitudinal Johne's disease diagnostic data. The situation of no perfect reference test was considered; that is, no "gold standard." A change-point process with a Weibull survival hazard function was used to model the progression of the hidden disease status. The model adjusted for the fixed effects of covariate variables and random effects of subject on the diagnostic testing procedure. Markov chain Monte Carlo methods were used to compute the posterior estimates of the model parameters that provide the basis for inference concerning the accuracy of the diagnostic procedure. Based on the Bayesian approach, the posterior probability distribution of the change-point onset time can be obtained and used as a criterion for infection diagnosis. An application is presented to an analysis of ELISA and fecal culture test outcomes in the diagnostic testing of paratuberculosis (Johne's disease) for a Danish longitudinal study from January 2000 to March 2003. The posterior probability criterion based on the Bayesian model with 4 repeated observations has an area under the receiver operating characteristic curve (AUC) of 0.984, and is superior to the raw ELISA (AUC=0.911) and fecal culture (sensitivity=0.358, specificity=0.980) tests for Johne's disease diagnosis.

Modeling the occurrence of Mycobacterium avium subsp. paratuberculosis in bulk raw milk and the impact of management options for exposure mitigation

Mycobacterium avium subsp. paratuberculosis (MAP) is the causal agent of paratuberculosis (Johne's disease) in cattle and other farm ruminants. The potential role of MAP in Crohn's disease in humans and the contribution of dairy products to human exposure to MAP continue to be the subject of scientific debate. The occurrence of MAP in bulk raw milk from dairy herds was assessed using a stochastic modeling approach. Raw milk samples were collected from bulk tanks in dairy plants and tested for the presence of MAP. Results from this analytical screening were used in a Bayesian network to update the model prediction. Of the 83 raw milk samples tested, 4 were positive for MAP by culture and PCR. We estimated that the level of MAP in bulk tanks ranged from 0 CFU/ml for the 2.5th percentile to 65 CFU/ml for the 97.5th percentile, with 95% credibility intervals of [0, 0] and [16, 326], respectively. The model was used to evaluate the effect of measures aimed at reducing the occurrence of MAP in raw milk. Reducing the prevalence of paratuberculosis has less of an effect on the occurrence of MAP in bulk raw milk than does managing clinically infected animals through good farming practices.

Use of information on disease diagnoses from databases for animal health economic, welfare and food safety purposes: strengths and limitations of recordings

Many animal health, welfare and food safety databases include data on clinical and test-based disease diagnoses. However, the circumstances and constraints for establishing the diagnoses vary considerably among databases. Therefore results based on different databases are difficult to compare and compilation of data in order to perform meta-analysis is almost impossible. Nevertheless, diagnostic information collected either routinely or in research projects is valuable in cross comparisons between databases, but there is a need for improved transparency and documentation of the data and the performance characteristics of tests used to establish diagnoses. The objective of this paper is to outline the circumstances and constraints for recording of disease diagnoses in different types of databases, and to discuss these in the context of disease diagnoses when using them for additional purposes, including research. Finally some limitations and recommendations for use of data and for recording of diagnostic information in the future are given. It is concluded that many research questions have such a specific objective that investigators need to collect their own data. However, there are also examples, where a minimal amount of extra information or continued validation could make sufficient improvement of secondary data to be used for other purposes. Regardless, researchers should always carefully evaluate the opportunities and constraints when they decide to use secondary data. If the data in the existing databases are not sufficiently valid, researchers may have to collect their own data, but improved recording of diagnostic data may improve the usefulness of secondary diagnostic data in the future.