Distribution of Mycobacterium avium subsp. paratuberculosis in organs of naturally infected bull-calves and breeding bulls

Mycobacterium avium subsp. paratuberculosis in Wild Boar (Sus scrofa) in Portugal

Paratuberculosis, or Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic granulomatous enteritis affecting both domestic and wild ruminants. The agent was also found in wild mammals such as wild boar (Sus scrofa); however, the role of wild mammals in the epidemiology of MAP is unclear. During the research period, 941 free-ranging wild boar (S. scrofa) legally hunted in two locations in the central-eastern region of Portugal were examined. Ninety-seven wild boars exhibited one or more gross lesions and were tested for the presence of Mycobacterium avium subsp. paratuberculosis using acid-fast staining, mycobacterial culture, polymerase chain reaction (PCR), and histopathological examination. Forty-five animals (46.4%, 95% CI: 36.5-56.3%) were identified as infected, as indicated by positive results in culture and/or PCR. The findings revealed that the most significant risk factor was being a juvenile compared to yearlings and adults (OR = 10.2, 95% CI: 2.2-48.0). Based on our results, 37.9% (n = 11) of the infected animals were considered suitable for human consumption. Our findings offer novel insights into mycobacterial infections in wild boar populations in Portugal and suggest that wild boar could be a source of human infection if zoonotic potential is considered.

Diagnostic performance of faecal and tissue multiplex qPCR IS900/F57 for the detection of Mycobacterium avium subspecies paratuberculosis in cattle

Mycobacterium avium subspecies paratuberculosis (MAP) is responsible for bovine-paratuberculosis (bPTB), which causes high production losses in cattle. A cross-sectional study was conducted in 228 cattle to evaluate the validity and diagnostic utility of a multiplex real-time PCR (qPCR) on faecal and intestinal samples [ileocaecal valve (ICV) and ileocaecal lymph nodes (ICLN)], using intestinal tissue culture as a reference test. Based on the sensitivity, specificity, and likelihood ratios (LR) obtained, the diagnostic value of faecal qPCR for confirming MAP infection was moderate (sensitivity 50.3%, specificity 93.5%, positive LR 7.8), and low to rule it out (negative LR 0.5). In areas with a prevalence of >23% the credibility of positive results was higher than 70%. In the case of negative results, their credibility was higher than 90% in herds with an infection rate below 19%, so faecal qPCR would be very useful in these areas to certify the absence of infection. For post-mortem diagnosis, qPCR on ICV samples showed good diagnostic accuracy to confirm the disease (sensitivity 71.7%, specificity 93.3%, positive LR 10.8), with a credibility higher than 70% in animals from areas or herds with a prevalence of infection greater than or equal to 18%. The best strategy to rule out the disease was the parallel combination of both tissues (ICV + ICLN) (sensitivity 81.3%, specificity 89.5%, negative LR 0.2) with a credibility of over 95% in animals from areas with an infection prevalence of 0-20%. Faecal and tissues qPCR techniques can be used to monitor bPTB, the interpretation of results, according to epidemiological situation of the herd or area, are shown.

Early-stage findings in an experimental calf model infected with Argentinean isolates of Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium subsp. paratuberculosis (MAP) is an important pathogen that causes granulomatous enteritis known as Johne's disease or paratuberculosis (PTB). In this study an experimental model of calves infected with Argentinean isolates of MAP for 180 days was used to provide more data of the early PTB stages. Calves were challenged by oral route with MAP strain _IS900-RFLPA (MA; n = 3), MAP strain _IS900-RFLPC (MC; n = 2) or mock infected (MI; n = 2), and response to infection was evaluated through peripheral cytokine expression, MAP tissue distribution and histopathological early-stage findings. Specific and varied levels of IFN-γ were only detected at 80 days post-infection in infected calves. These data indicate that specific IFN-γ is not a useful indicator for early detection of MAP infection in our calf model. At 110 days post-infection, TNF-α expression was higher than IL-10 in 4 of the 5 infected animals and a significant decrease of TNF-α expression was detected in infected vs. non-infected calves. All calves challenged were identified as infected by mesenteric lymph node tissue culture and real time IS900 PCR. In addition, for lymph nodes samples, the agreement between these techniques was almost perfect (κ = 0.86). Colonization of tissues and levels of tissue infection varied between individuals. Evidence of early MAP dissemination to extraintestinal tissues such as the liver was detected by culture in one animal (MAP strain _IS900-RFLPA). In both groups microgranulomatous lesions were observed predominantly in the lymph nodes, with giant cells present only in the MA group. In summary, the findings described herein may indicate that local MAP strains induced specific immune responses with particularities that could suggest differences in their biological behavior. Further studies should be carried out in order to obtain an in-depth understanding of the influence of MAP strains in host-pathogen interactions and the outcome of disease.

Interaction of Mycobacterium avium subsp. paratuberculosis with bovine sperm

Mycobacterium avium subsp. paratuberculosis (MAP) is responsible for Paratuberculosis mainly affecting domestic ruminants. The interaction between MAP and sperm and/or germ cells has not yet been established, however the adherence between MAP and the host cell surface is associated to the 85 complex proteins that bind to the host cell's fibronectin. Therefore, this study aimed to evaluate the binding of MAP to bovine sperm and to verify changes in these cells by the presence of MAP before and after sperm cryopreservation. Polyclonal antibodies to MAP 85 complex proteins were produced and utilized in the analyzes. Two Nelore bulls were used for semen collection and MAP dilutions (10³-10⁸ CFU/mL) were inoculated in the samples; sperm motility and vigor were evaluated using light microscopy at different times before and after cryopreservation and in the presence and absence of the antibodies 85A and 85B. Interaction of MAP and sperm, interaction of MAP and sperm in the presence of Ab 85A and in the presence of Ab 85B were analyzed by scanning electron microscopy. The viability of MAP after sperm cryopreservation were evaluated by plating the samples after thawing. It was observed that sperm in the presence of MAP shows a decrease in motility and vigor, and that the higher the MAP concentration, the lower the sperm performance. It was possible to determine the viability of MAP after cryopreservation in samples of higher concentrations, which demonstrates the potential of transmission of this pathogen through artificial insemination. The interaction of MAP with bovine sperm occurs mainly in the midpiece and may be linked to the proteins 85A and 85B present in the MAP membrane.

A Bovine Enteric Mycobacterium Infection Model to Analyze Parenteral Vaccine-Induced Mucosal Immunity and Accelerate Vaccine Discovery

Mycobacterial diseases of cattle are responsible for considerable production losses worldwide. In addition to their importance in animals, these infections offer a nuanced approach to understanding persistent mycobacterial infection in native host species. Mycobacteriumavium ssp. paratuberculosis (MAP) is an enteric pathogen that establishes a persistent, asymptomatic infection in the small intestine. Difficulty in reproducing infection in surrogate animal models and limited understanding of mucosal immune responses that control enteric infection in the natural host have been major barriers to MAP vaccine development. We previously developed a reproducible challenge model to establish a consistent MAP infection using surgically isolated intestinal segments prepared in neonatal calves. In the current study, we evaluated whether intestinal segments could be used to screen parenteral vaccines that alter mucosal immune responses to MAP infection. Using Silirum^® – a commercial MAP bacterin – we demonstrate that intestinal segments provide a platform for assessing vaccine efficacy within a relatively rapid period of 28 days post-infection. Significant differences between vaccinates and non-vaccinates could be detected using quantitative metrics including bacterial burden in intestinal tissue, MAP shedding into the intestinal lumen, and vaccine-induced mucosal immune responses. Comparing vaccine-induced responses in mucosal leukocytes isolated from the site of enteric infection versus blood leukocytes revealed substantial inconsistences between these immune compartments. Moreover, parenteral vaccination with Silirum did not induce equal levels of protection throughout the small intestine. Significant control of MAP infection was observed in the continuous but not the discrete Peyer’s patches. Analysis of these regional mucosal immune responses revealed novel correlates of immune protection associated with reduced infection that included an increased frequency of CD335⁺ innate lymphoid cells, and increased expression of IL21 and IL27. Thus, intestinal segments provide a novel model to accelerate vaccine screening and discovery by testing vaccines directly in the natural host and provides a unique opportunity to interrogate mucosal immune responses to mycobacterial infections.

Identification of Mycobacterium avium subsp. paratuberculosis (MAP) in Sheep Milk, a Zoonotic Problem

Johne’s disease (JD) is a life-threatening gastrointestinal disease affecting ruminants, which causes crucial economical losses globally. This ailment is caused by Mycobacterium avium subsp. paratuberculosis (MAP), a fastidious intracellular pathogen that belongs to the Mycobacteriaceae family. This acid-fast, hard-to-detect bacterium can resist milk pasteurization and be conveyed to dairy product consumers. Many studies have emphasized the zoonotic nature of MAP, suggesting an association between MAP and some gastroenteric conditions such as Crohn’s disease in humans. This underlines the importance of utilizing efficient pasteurization alongside a state-of-the-art diagnostic system in order to minimize the possible ways this pathogen can be conveyed to humans. Until now, no confirmatory MAP screening technique has been developed that can reveal the stages of JD in infected animals. This is partially due to the lack of an efficient gold-standard reference method that can properly evaluate the performance of diagnostic assays. Therefore, the following research aimed to compare the merits of qPCR and ELISA assessments of milk for the detection of MAP in a total of 201 Sardinian unpasteurized sheep milk samples including 73 bulk tank milk (BTM) and 128 individual samples from a MAP-infected flock (MIF) applying various reference models. Accordingly, milk qPCR and ELISA assessments, together and individually, were used as reference models in the herd-level study, while serum ELISA and fecal PCR were similarly (together and in isolation) considered as the gold standards in the individual-level diagnosis. This study showed that the type of gold-standard test affects the sensitivity and specificity of milk qPCR and ELISA significantly. At the individual level in the MAP-infected flock, serum ELISA in isolation and together with fecal PCR were recognized as the best references; however, the best correlation was seen between milk and serum ELISA (p < 0.0001). Regarding the detection of MAP in BTM, qPCR IS900 was recognized as the most sensitive and specific diagnostic test (p < 0.0001) for monitoring the MAP shedders and animals with clinically developed symptoms within herds, under the condition that both milk qPCR and milk ELISA tests formed a binary reference model. The BTM analyses (qPCR and ELISA) revealed that MAP positivity has a seasonal pattern. This hypothesis was proven through a longitudinal study on 14 sheep herds.

General Overview of Nontuberculous Mycobacteria Opportunistic Pathogens: Mycobacterium avium and Mycobacterium abscessus

Nontuberculous mycobacteria (NTM) are emerging human pathogens, causing a wide range of clinical diseases affecting individuals who are immunocompromised and who have underlying health conditions. NTM are ubiquitous in the environment, with certain species causing opportunistic infection in humans, including Mycobacterium avium and Mycobacterium abscessus. The incidence and prevalence of NTM infections are rising globally, especially in developed countries with declining incidence rates of M. tuberculosis infection. Mycobacterium avium, a slow-growing mycobacterium, is associated with Mycobacterium avium complex (MAC) infections that can cause chronic pulmonary disease, disseminated disease, as well as lymphadenitis. M. abscessus infections are considered one of the most antibiotic-resistant mycobacteria and are associated with pulmonary disease, especially cystic fibrosis, as well as contaminated traumatic skin wounds, postsurgical soft tissue infections, and healthcare-associated infections (HAI). Clinical manifestations of diseases depend on the interaction of the host's immune response and the specific mycobacterial species. This review will give a general overview of the general characteristics, vulnerable populations most at risk, pathogenesis, treatment, and prevention for infections caused by Mycobacterium avium, in the context of MAC, and M. abscessus.

Regional Dichotomy in Enteric Mucosal Immune Responses to a Persistent Mycobacterium avium ssp. paratuberculosis Infection

Chronic enteric Mycobacterium avium ssp. paratuberculosis (MAP) infections are endemic in ruminants globally resulting in significant production losses. The mucosal immune responses occurring at the site of infection, specifically in Peyer's patches (PP), are not well-understood. The ruminant small intestine possesses two functionally distinct PPs. Discrete PPs function as mucosal immune induction sites and a single continuous PP, in the terminal small intestine, functions as a primary lymphoid tissue for B cell repertoire diversification. We investigated whether MAP infection of discrete vs. continuous PPs resulted in the induction of significantly different pathogen-specific immune responses and persistence of MAP infection. Surgically isolated intestinal segments in neonatal calves were used to target MAP infection to individual PPs. At 12 months post-infection, MAP persisted in continuous PP (n = 4), but was significantly reduced (p = 0.046) in discrete PP (n = 5). RNA-seq analysis revealed control of MAP infection in discrete PP was associated with extensive transcriptomic changes (1,707 differentially expressed genes) but MAP persistent in continuous PP elicited few host responses (4 differentially expressed genes). Cytokine gene expression in tissue and MAP-specific recall responses by mucosal immune cells isolated from PP, lamina propria and mesenteric lymph node revealed interleukin (IL)22 and IL27 as unique correlates of protection associated with decreased MAP infection in discrete PP. This study provides the first description of mucosal immune responses occurring in bovine discrete jejunal PPs and reveals that a significant reduction in MAP infection is associated with specific cytokine responses. Conversely, MAP infection persists in the continuous ileal PP with minimal perturbation of host immune responses. These data reveal a marked dichotomy in host-MAP interactions within the two functionally distinct PPs of the small intestine and identifies mucosal immune responses associated with the control of a mycobacterial infection in the natural host.

Detection of Mycobacterium avium subsp. paratuberculosis in reproductive tissue and semen of naturally infected rams

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of paratuberculosis (PTB), disease that causes a syndrome of bad nutrient absorption, weight loss and eventually death. The intestine is the main target organ where the infection develops; however, there is evidence of infection by MAP in extra-intestine sites of sheep, including mesenteric nodes and semen. The aim of the study was to identify the presence of MAP in reproductive tissue and semen of infected Pelibuey rams in clinical state of PTB. Seven rams were used in clinical PTB state and a non-infected ram by MAP of the Pelibuey breed, confirmed by serology, nPCR and bacteriological culture, with average weight and age of 57.23 ± 1.73 kg and 2.91 ± 0.17 years, respectively. The presence of MAP was identified in different tissue samples: spleen (1/7, 14.3% and 2/7, 28.6%), small intestine (3/7, 42.9% and 4/7, 57.1%) and mesenteric lymph nodes (3/7, 42.9% and 3/7, 42.9%), with nPCR and culture, respectively. It was also identified in epididymis tissue (1/7, 14.3%), Cowper gland (2/7, 28.6%) and prostate (1/7, 14.3%), using nPCR, although without detection in culture. It was identified in testicular tissue in 42.8% (3/7; culture or nPCR technique), but in 28.6% (2/7) with both techniques. Finally, the presence of MAP was identified in 42.9% (3/7) of semen samples with nPCR; however, it was not detected through culture. In conclusion, the presence of MAP was identified in lymphatic, digestive tissue, and semen; the presence of MAP was reported for the first time in epididymis, Cowper gland, prostate and testicles of infected Pelibuey rams.

Management of Mycobacterium avium subsp. paratuberculosis in dairy farms: Selection and evaluation of different DNA extraction methods from bovine and buffaloes milk and colostrum for the establishment of a safe colostrum farm bank

The aim of this study was to develop and validate different innovative DNA extraction methods to detect Mycobacterium avium subsp. paratuberculosis (MAP) DNA from bovine and buffalo colostrum. Paratuberculosis is a chronic inflammatory infection of domestic and wild animals, especially ruminants, caused by MAP. The primary route of disease transmission is feces, but MAP can also be excreted in milk and colostrum. In 2015, the Italian Ministry of Health has issued a voluntary control plan of MAP in order to allow risk‐based certification of bovine and buffaloes farms. In addition to the annual diagnostic screening and to the clinical surveillance of animals the plan includes the adoption of biosecurity and management measures to progressively mitigate the incidence of MAP. To achieve this goal it is crucial to ensure the accuracy of the methods used to detect the presence of MAP in bovine and buffaloes milk and colostrum, in order to: (1) support a "safe colostrum farm‐bank" set‐up and thus prevent the main within‐farm MAP transmission route and (2) to allow the MAP‐free certification of milk products for export purposes. To achieve these goals, seven different DNA extraction protocols were identified from bibliography, out of which three methods were finally selected after the adoption of an evaluation procedure aimed at assessing the efficiency of extraction of DNA, the purity of DNA and the adaptability of the DNA amplification: NucleoSpin^® Food Kit (Macherey‐Nagel), NucleoSpin^® Food Kit (Macherey‐Nagel) combined with the magnetic beads, and QIAamp Cador Pathogen Mini kit (QIAGEN). In particular, the NucleoSpin^® Food Kit (Macherey‐Nagel) and the QIAamp Cador Pathogen Mini kit (QIAGEN) were tested on bovine and buffalo colostrum, showing a LOD between 4 × 10⁴ (2.6 × 10⁶ cfu/ml) and 4.08 (26.7 cfu/ml) IS900 target copies and a LOD between 5.3 × 10⁵ (4.1 × 10⁶ cfu/ml) and 53 (4.1 × 10³ cfu/ml) IS900 target copies, respectively.

A nested compartmental model to assess the efficacy of paratuberculosis control measures on U.S. dairy farms

Paratuberculosis, also known as Johne's disease (JD), is a chronic contagious disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP). The disease is incurable, fatal and causes economic losses estimated to exceed 200 million dollars to the U.S. dairy industry annually. Several preventive and control measures have been recommended; however, only a few of these measures have been validated empirically. Using a nested compartmental (NC) modeling approach, the main objective of this research was to identify the best combination of control and preventive measures that minimizes the prevalence and incidence of JD and the risk of MAP occurrence in a dairy herd. The NC model employs both MAP transmission estimates and data on pen movement of cattle on a dairy to quantify the effectiveness of control and preventive measures. To obtain reasonable ranges of parameter values for between-pen movements, the NC model was fitted to the movement data of four typical California dairy farms. Using the estimated ranges of the movement parameters and those of JD from previous research, the basic reproduction number was calculated to measure the risk of MAP occurrence in each pen environment as well as the entire dairy. Although the interventions evaluated by the NC model were shown to reduce the infection, no single measure alone was capable of eradicating the infection. The numerical simulations suggest that a combination of test and cull with more frequent manure removal is the most effective method in reducing incidence, prevalence and the risk of MAP occurrence. Other control measures such as limiting calf-adult cow contacts, raising calves in a disease-free herd or colostrum management were less effective.

Review: Risks of disease transmission through semen in cattle

The purpose of this paper is to review scientific evidence concerning pathogens that could potentially be transmitted via bovine semen. As a result of a careful analysis of the characteristics of infections that may cause transmission of disease through semen, effective control procedures can be identified that provide minimal constraint to the introduction of new bulls into herds for natural breeding and importation of valuable novel genetics through artificial insemination. The potential for transmission through bovine semen and corresponding effective control procedures are described for bovine herpesvirus 1, bovine viral diarrhea virus, bovine leukemia virus, lumpy skin disease virus, bluetongue virus, foot-and-mouth disease virus, and Schmallenberg virus. Brief consideration is also provided regarding the potential for transmission via semen of Tritrichomonas foetus, Campylobacter fetus venerealis, Brucella abortus, Leptospira spp., Histophilus somni, Ureaplasma diversum, Mycobacterium avium subsp. paratuberculosis, Chlamydiaceae, Mycobacterium bovis, Coxiella burnetii, Mycoplasma mycoides ssp. mycoides and Neospora caninum. Thoughtful and systematic control procedures can ensure the safety of introducing new bulls and cryopreserved semen into cattle production systems.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): paratuberculosis

Paratuberculosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of paratuberculosis to be listed, Article 9 for the categorisation of paratuberculosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to paratuberculosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, paratuberculosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria in Sections 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (c), (d) and (e) of Article 9(1). The animal species to be listed for paratuberculosis according to Article 8(3) criteria are several species of mammals and birds as susceptible species and some species of the families Bovidae, Cervidae and Leporidae as reservoirs.

Early Foetal Loss Correlates Positively with Seroconversion against Mycobacterium avium paratuberculosis in High-Producing Dairy Cows

This study was designed to examine (i) the seroprevalence of Mycobacterium avium subs paratuberculosis (MAP) in a high-producing dairy herd with clinical symptoms of bovine paratuberculosis, (ii) MAP seroconversion and seronegativation dynamics in the herd and (iii) possible relationships between MAP infection status and herd reproductive performance. One single blood test per cow was performed early post-partum on a monthly basis from day 10-40 post-partum during the first year of the study in 519 cows belonging to a commercial dairy herd. A subset of 111 cows that became pregnant during the study was tested again 60-200 days later during the early foetal period, immediately after the first confirmation of gestation at 58-64 days post-AI. Logistic regression analysis indicated no effect of any independent variable on MAP seropositivity and conception rate 28-34 days post-AI. MAP seropositivity was not a factor affecting the anoestrous, subfertility and early foetal loss rates. In the subset of 111 cows, animals that seroconverted had a 3.9 times greater risk of suffering from early foetal loss (30.3%, 10/33) than the remaining pregnant animals (10.3%, 8/78), (95% confidence interval: 1.11-13.4; p = 0.003). In conclusion, early foetal loss was positively correlated with seroconversion to MAP. Reproductive performance was not impaired by MAP infection.

Distribution of Mycobacterium avium subsp. paratuberculosis in a Subclinical Naturally Infected German Fleckvieh Bull

Although it has been known for years that Mycobacterium avium subsp. paratuberculosis (MAP) is detectable in the reproductive organs and semen of infected bulls, only few studies have been conducted on this topic worldwide. This study surveyed the MAP status of a bull, naturally infected due to close contact with its subclinically infected parents over a period of 4 years. From the age of 7 weeks to necropsy, faecal, blood and, after sexual maturity, semen samples were drawn repeatedly. Already at the first sampling day, MAP-DNA was detected in faeces by semi-nested PCR. True infection was confirmed by the detection of MAP-DNA in blood at the age of 40 weeks. In total, MAP-DNA was present in 25% faecal (34/139), 16% blood (23/140) and 5% semen (4/89) samples, including MAP-free intervals of up to 9 weeks. MAP genome equivalents (MAP-GE) of up to 6.3 × 10⁶ /g faeces and 1.8 × 10⁵ /ml blood were determined. Cultivation of MAP occurred only in three of 137 faecal and two of 109 blood, but never in semen samples. Over the whole period, the bull was a serological negative MAP shedder. During necropsy, 42 tissue samples were collected. Neither macroscopic nor histological lesions characteristic of a MAP infection were observed. Cultivation of MAP in tissue sections failed. However, MAP-DNA was spread widely in the host, including in tissues of the lymphatic system (7/15), digestive tract (5/14) and the urogenital tract (5/9) with concentrations of up to 3.9 × 10⁶ MAP-GE/g tissue. The study highlighted the detection of MAP in male reproductive organs and semen. It supports the hypothesis that bulls may probably transmit MAP, at least under natural mating conditions. In artificial insemination, this might not be relevant, due to antibiotics included currently in semen extenders. However, the survivability of MAP in this microenvironment should be investigated in detail.

Survey on the presence of Mycobacterium avium subsp. paratuberculosis in ground beef from an industrial meat plant

Paratuberculosis of ruminants is characterised by chronic enteritis but, at advanced stages of the disease, a systemic dissemination of Mycobacterium avium subsp. paratuberculosis (MAP) in tissues and organs can occur. MAP has been recovered from lymph nodes and muscles of clinical and sub-clinical cows. In most countries, dairy and beef cattle infected with paratuberculosis are routinely sent to slaughter and the consumption of their meat could be a possible route of human exposure to MAP. However, few studies on MAP in ground beef are currently available. During the period November 2013-March 2014 we carried out a survey on the ground beef produced in an industrial meat processing plant. One-hundred and forty samples of ground meat were analysed by IS900-qPCR and culture (VersaTrek System). The limit of detection (LOD) of qPCR was 630 MAP cells/g (107 CFU/g) while the LOD for culture was 170-230 MAP cells/g (62-115 CFU/g). No samples were positive by direct IS900 qPCR, while two samples were positive by liquid culture. Our data suggest that the presence of live MAP in raw minced meat is possible. In order to avoid exposure for humans through the consumption of contaminated meat, proper cooking of meat is recommended.

Clinical disease and stage of lactation influence shedding of Mycobacterium avium subspecies paratuberculosis into milk and colostrum of naturally infected dairy cows

Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of Johne's disease (JD). One mode of transmission of MAP is through ingestion of contaminated milk and colostrum by susceptible calves. The objective of this study was to determine if the amount of MAP shed into the milk and colostrum of infected cows was affected by severity of infection as well as the number of days in milk (DIM). Milk was collected over the 305-d lactation period from naturally infected cows in the asymptomatic subclinical (n=39) and symptomatic clinical (n=29) stages of disease, as well as 8 noninfected control cows. All milk samples were assayed for MAP by culture on Herrold's egg yolk medium and either BACTEC 12B (Becton Dickinson, Franklin Lakes, NJ) or para-JEM (Thermo Fisher Scientific, Trek Diagnostic Systems Inc., Cleveland, OH) liquid medium, and by direct PCR for the IS900 target gene. Mycobacterium avium ssp. paratuberculosis was detected in 3.8, 4.1, and 12.6% of milk samples collected from cows with subclinical JD after culture in Herrold's egg yolk medium, liquid medium, and direct PCR, respectively. The frequency of MAP positivity increased to 12.9, 18.4, and 49.2% of milk samples collected from cows with clinical JD by these same methods, respectively. None of the milk samples collected from control cows was positive for MAP by any detection method. Viable MAP was primarily isolated from milk and colostrum of subclinically and clinically infected cows collected in early lactation (DIM 0-60), with negligible positive samples observed in mid (DIM 60-240) and late (DIM 240-305) lactation. This study demonstrates that shedding of MAP into milk is affected by infection status of the cow as well as stage of lactation, providing useful information to producers to help break the cycle of infection within a herd.

Short communication: Viable Mycobacterium avium subspecies paratuberculosis in retail artisanal Coalho cheese from Northeastern Brazil

Mycobacterium avium ssp. paratuberculosis (MAP) is the etiologic agent of paratuberculosis and it potentially plays a role in Crohn's disease. In humans, the main route of transmission of MAP might be the intake of contaminated milk and dairy products. Considering that MAP has already been detected in many types of cheese in different counties, and that Coalho cheese is an important dairy product in northeastern Brazil, the aim of this study was to report the first detection of MAP in retail Coalho cheese in Brazil by PCR and culture. Of 30 retail Coalho cheese samples, 3 (10%) amplified fragments of a similar size to that expected (626 bp) were obtained and viable MAP was recovered by culture from 1 (3.3%) sample. The DNA from the positive culture sample was sequenced and showed 99% identity with the insertion sequence IS900 deposited in GenBank. It was possible to identify the presence of MAP-specific DNA in the analyzed samples for the first time in Brazil, and to recover viable cells from retail Coalho cheese.

Genetic diversity and phylogeny of Mycobacterium avium

Mycobacterium avium, one of the species of the M. avium complex (MAC), includes 4 subspecies, i.e., M. avium subsp. hominissuis (MAH), M. avium subsp. avium (MAA), M. avium subsp. silvaticum (MAS) and M. avium subsp. paratuberculosis (MAP), in turn classified into the S (sheep) and C (cattle) types. These subspecies, although closely related, represent distinct organisms, each endowed with specific pathogenetic and host range characteristics, ranging from environmental opportunistic bacteria that cause infections in swine and immunocompromised patients to pathogens of birds and ruminants. The present review summarizes the basic epidemiological and pathological features of the M. avium subspecies, describes the major genomic events responsible of M. avium subspecies diversity (insertion sequences, sequence variations in specific chromosome loci or genes, deletions, duplications and insertions of large genomic regions) and then reconstructs the phylogenetic relationships among the M. avium subspecies.

Inactivation of Mycobacterium avium subsp. paratuberculosis during cooking of hamburger patties

The role of Mycobacterium avium subsp. paratuberculosis (MAP) in Crohn's disease in humans has been debated for many years. Milk and milk products have been suggested as possible vectors for transmission since the beginning of this debate, whereas recent publications show that slaughtered cattle and their carcasses, meat, and organs can also serve as reservoirs for MAP transmission. The objective of this study was to generate heat-inactivation data for MAP during the cooking of hamburger patties. Hamburger patties of lean ground beef weighing 70 and 50 g were cooked for 6, 5, 4, 3, and 2 min, which were sterilized by irradiation and spiked with three different MAP strains at levels between 10² and 10⁶ CFU/ml. Single-sided cooking with one flip was applied, and the temperatures within the patties were recorded by seven thermocouples. Counting of the surviving bacteria was performed by direct plating onto Herrold's egg yolk medium and a three-vial most-probable-number method by using modified Dubos medium. There was considerable variability in temperature throughout the patties during frying. In addition, the log reduction in MAP numbers showed strong variations. In patties weighing 70 g, considerable bacterial reduction of 4 log or larger could only be achieved after 6 min of cooking. For all other cooking times, the bacterial reduction was less than 2 log. Patties weighing 50 g showed a 5-log or larger reduction after cooking times of 5 and 6 min. To determine the inactivation kinetics, a log-linear regression model was used, showing a constant decrease of MAP numbers over cooking time.

Mycobacterium avium subsp. paratuberculosis detected in the reproductive tract of cows from an infected herd

Mycobacterium avium subspecies paratuberculosis (MAP), the causal agent of paratuberculosis, was detected by quantitative real-time IS900 PCR in the follicular fluid from the reproductive tracts of cows originating from one infected herd. As well as being detected in follicular fluid of cows shedding bacteria in their faeces, MAP was also detected in the follicular fluid of one apparently healthy, non-shedding individual cow. The finding of MAP in follicular fluid is unexpected and could contribute to the lower viability of embryos and resultant lower pregnancy rate. In addition to finding contaminated follicular fluid, vaginal and uterine flush fluids were determined to be positive for the presence of MAP in 75% and 56.3% of the time of the cattle currently shedding MAP in their faeces, respectively. The presence of MAP in different parts of the reproductive tract was seen in clinically as well as subclinically infected cows. These findings extend our currently scant and contradictory knowledge about the dissemination of MAP in the reproductive tract of female cattle.

A longitudinal study to characterize the distribution patterns of Mycobacterium avium ssp. paratuberculosis in semen, blood and faeces of a naturally infected bull by IS 900 semi-nested and quantitative real-time PCR

Johne's disease is caused by Mycobacterium avium ssp. paratuberculosis (MAP) and has been recognized as an important bacterial infection in ruminants. Although MAP has been detected in semen and within the reproductive organs of bulls, the bacterial distribution and shedding patterns are currently not well characterized. Our investigation was performed to detect and quantify MAP in faeces, semen and blood samples repeatedly drawn from a naturally infected but asymptomatic 18-month-old German Simmental breeding bull candidate over a period of 3 years (June 2007-November 2010). Qualitative and quantitative polymerase chain reaction (PCR) techniques were used to correlate the presence and matrix-specific amounts of MAP. In total, 65 sampling dates were selected. Mycobacterium avium ssp. paratuberculosis was detected intermittently in all matrices with MAP-free intervals of up to 18 weeks by an IS900 semi-nested PCR. The number of MAP-positive results from semen and blood samples was higher than from faecal samples. A quantitative polymerase chain reaction detected the highest MAP contents in faeces (10(3) -10(6) MAP/g), while lower amounts were found in semen and blood samples (10(2) -10(5) MAP/ml). Although no significant agreement was calculated between the presence of MAP in faeces and blood, a statistically significant positive correlation between its occurrence in semen and blood was determined (r = 0.38, P < 0.05, n = 29). The present study contributes to a more detailed understanding of MAP distribution patterns in faeces, semen and blood of a subclinically infected breeding bull candidate. It highlights the possible role of breeding bulls as a source of MAP transmission and indicates the need for further monitoring and hygienic measures to prevent the spread of the infection via semen.

Detection of paratuberculosis in breeding bulls at pakistani semen production units: a continuous source of threat

Paratuberculosis is a chronic bowel disease of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Its secretion through semen highlights the importance of paratuberculosis-free breeding bulls. The breeding and teaser bulls at three semen production units (SPUs) located in Punjab, Pakistan, were screened for the presence of antibodies against MAP. A total of 253 samples were collected from SPUs and a commercially available indirect screen ELISA (Is-ELISA) was applied. Is-ELISA detected antibodies in 20 (24.6%), 16 (22.8%), and 17 (16.6%) samples from SPU-I, SPU-II, and SPU-III, respectively. Collectively, seroprevalence of 20.0% (47/235) in breeding bulls and 33.3% (6/18) in teaser bulls was observed, and thus it poses a potential threat of disease spread to a high number of heifers and cows through artificial insemination. Therefore, this paper highlights the presence of the disease for the first time at SPUs and triggers attempts to ascertain the prevalence of paratuberculosis throughout the country.

Intestinal infection following aerosol challenge of calves with Mycobacterium avium subspecies paratuberculosis

A challenge experiment was performed to investigate whether administration of Mycobacterium avium subsp. paratuberculosis (MAP) via the respiratory route leads to MAP infection in calves. Eighteen calves from test negative dams were randomly allocated to four groups. Six calves were challenged with MAP nasally and six calves were challenged by transtracheal injection; three orally challenged calves served as positive controls, and three non challenged calves as negative controls. The challenge was performed as a nine-fold trickle dose, 10⁷ CFU in total. Blood and faecal samples were collected frequently. Calves were euthanized three months post-challenge and extensively sampled. Blood samples were tested for the presence of antibodies and interferon gamma producing cells by ELISA. Faecal and tissue samples were cultured in a liquid culture system and the presence of MAP was confirmed by IS900 realtime PCR. Fourteen out of fifteen calves had no MAP antibody response. The negative controls remained negative; all positive controls became infected. Two nasally challenged calves showed a Purified Protein Derivative Avian (PPDA) specific interferon gamma response. In all nasally challenged calves, MAP positive intestinal samples were detected. In three calves of the nasal group MAP positive retropharyngeal lymph nodes or tonsils were detected. In all calves of the transtracheal group MAP positive intestinal tissues were detected as well and three had a MAP positive tracheobronchial lymph node. These findings indicate that inhalation of MAP aerosols can result in infection. These experimental results may be relevant for transmission under field conditions since viable MAP has been detected in dust on commercial dairy farms.

Temporal patterns of genetic and phenotypic variation in the epidemiologically important drone fly, Eristalis tenax

Eristalis tenax L. (Diptera: Syrphidae) is commonly known as the drone fly (adult) or rat-tailed maggot (immature). Both adults and immature stages are identified as potential mechanical vectors of mycobacterial pathogens, and early-stage maggots cause accidental myiasis. We compared four samples from Mount Fruška Gora, Serbia, with the aim of obtaining insights into the temporal variations and sexual dimorphism in the species. This integrative approach was based on allozyme loci, morphometric wing parameters (shape and size) and abdominal colour patterns. Consistent sexual dimorphism was observed, indicating that male specimens had lighter abdomens and smaller and narrower wings than females. The distribution of genetic diversity at polymorphic loci indicated genetic divergence among collection dates. Landmark-based geometric morphometrics revealed, contrary to the lack of divergence in wing size, significant wing shape variation throughout the year. In addition, temporal changes in the frequencies of the abdominal patterns observed are likely to relate to the biology of the species and ecological factors in the locality. Hence, the present study expands our knowledge of the genetic diversity and phenotypic plasticity of E. tenax. The quantification of such variability represents a step towards the evaluation of the adaptive potential of this species of medical and epidemiological importance.

Apparent Prevalence of Beef Carcasses Contaminated with Mycobacterium avium subsp. paratuberculosis Sampled from Danish Slaughter Cattle

Presence of Mycobacterium avium subsp. paratuberculosis (MAP) in beef has been reported as a public health concern because asymptomatically infected cattle may contain MAP in tissues that are used for human consumption. Associations between MAP carcasses contamination and animal characteristics such as age, breed, production type, and carcass classification were assessed. Cheek muscles from 501 carcasses were sampled cross-sectionally at a Danish abattoir and tested for presence of viable MAP and MAP DNA by bacterial culture and IS900 realtime PCR, respectively. Cheek muscle tissues from carcasses of two dairy cows were positive by culture whereas 4% of the animals were estimated with ≥10 CFU/gram muscle based on realtime PCR. Age was found to be associated with carcass contamination with MAP. The observed viable MAP prevalence in beef carcasses was low. However, detection of MAP and MAP DNA in muscle tissues suggested that bacteremia occurred in slaughtered cattle.

Mycobacterium avium subsp. paratuberculosis in dairy products, meat, and drinking water

Mycobacterium avium subsp. paratuberculosis (Map) is the cause of Johne's disease, a chronic infection of the gut, in ruminant animals that provide milk and/or meat for human consumption. Map also may be involved in Crohn's disease and type 1 diabetes in humans. Although the role of Map in human diseases has not been established, minimizing the exposure of humans to the organism is considered desirable as a precautionary measure. Infected animals can shed Map in feces and milk, and the organism can become disseminated in tissues remote from the gut and its associated lymph nodes. The presence of at least some Map in raw milk and meat and in natural waters is likely, but the numbers of Map in those foods and waters should be reduced through cooking or purification. The available information relating to Map in milk and dairy products, meats, and drinking water is reviewed here for assessment of the risks of exposure to Map from consumption of such foods and water.

Comparative evaluation of nested PCR and conventional smear methods for the detection of Mycobacterium tuberculosis in sputum samples

BACKGROUND

With 1.8 million new cases each year, India carries 20% of the global burden of tuberculosis, a situation that is now further exacerbated with the emergence of drug resistance. The current diagnostic technique suggested by the Government of India's Revised National Tuberculosis Control Programme is Ziehl-Neelsen staining of a sputum smear. This technique is known to be inadequate.

OBJECTIVE

The aim of this study was to evaluate nested PCR (nPCR) in the detection of pulmonary tuberculosis in sputum samples in comparison with conventional smear findings, in an effort to improve detection rates from those obtained by the smear-alone approach.

STUDY DESIGN

Patients attending a tertiary-care hospital (situated in a rural area of Vellore district) with clinical suspicion of pulmonary tuberculosis were prospectively recruited from mid-April 2009 to mid-December 2009 and investigated. The sputum samples were stained by Ziehl-Neelsen staining for smear examination. DNA extracted from concentrated sputum was tested by nPCR, targeting the IS6110 sequence in the Mycobacterium tuberculosis genome.

RESULTS

Among 84 patients tested (median age 45.5 years), 80.95% were from the rural community and 19.05% were from the peri-urban community. Seventeen patients (20.24%; mid-p 95% CI 31.5, 52.4) tested positive by the smear examination and 35 (41.67%; mid-p 95% CI 12.7, 29.8) tested positive by nPCR. The difference in detection rates was statistically significant (chi(2) = 9.02; p = 0.002). The kappa coefficient between smear findings and nPCR findings was 0.47, which was a statistically significant agreement (Z = 4.91; p < 0.0001).

CONCLUSION

This report describes the molecular detection of M. tuberculosis in patients' sputum samples tested by the nPCR format, using IS6110 as a target sequence. A high prevalence of pulmonary tuberculosis was identified by the nPCR assay, which was shown to have a significantly higher detection rate than conventional smear staining.

Culture of Mycobacterium avium subspecies paratuberculosis (MAP) from blood and extra-intestinal tissues in experimentally infected sheep

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's disease or paratuberculosis, a chronic enteritis of ruminants, and has been suggested to play a role in Crohn's disease in humans. While Johne's disease is primarily expressed in the gastrointestinal tract, isolation of MAP from extra-intestinal tissues indicates that microbial dissemination via the haematogenous route may occur during the infection. Consequently, the occurrence of mycobacteraemia and dissemination to the liver and hepatic lymph node was investigated in 111 sheep. Disseminated infection was detected in 18 of the 53 sheep that were confirmed to be infected following oral exposure to MAP while the bacterium was isolated from the blood of only 4 of these animals. Disseminated infection was detected more frequently from animals with a positive compared to a negative faecal culture result, multibacillary compared to paucibacillary lesions, and clinical compared to subclinical disease. Detection of MAP in blood by culture was significantly associated with increased time post-exposure and clinical disease, with trends for increased detection in animals with multibacillary lesions and positive faecal culture results. Isolation of MAP from blood was difficult in the early stages of the disease and in paucibacillary animals as the bacteraemia may be intermittent, below the limit of detection or MAP may be present in a dormant non-culturable form. Prolonged incubation periods prior to growth in BACTEC were consistent with inhibition of growth or dormancy in some blood cultures.

Consecutive excretion of Mycobacterium avium subspecies paratuberculosis in semen of a breeding bull compared to the distribution in feces, tissue and blood by IS900 and F57 quantitative real-time PCR and culture examinations

Paratuberculosis (Johne's disease) has emerged as one of the most important diseases in cattle. The role of infected bull semen in the spread of infection remains unclear, as the correlation between the amount of excreted Mycobacterium avium subsp. paratuberculosis (semen and feces) and the infection load (blood and tissues) has not been defined. The aim of the present study was to study by culture, and a quantitative real-time polymerase chain reaction, the presence of bacteria in consecutive semen, blood, and fecal samples collected from one infected Piedmont breeding bull during a 380-day period. Five out of seven blood samples and all nine semen samples were positive in the real-time quantitative polymerase chain reaction with 10¹ to 10² and 10² to 10⁴ copies of IS900/F57 per ml, respectively. In all, there were 9 fecal culture positive samples with too numerous to count colony forming units and positive real-time quantitative polymerase chain reactions ranging from 10⁵ to 10⁷ copies of IS900/F57. After the bull was euthanized, Mycobacterium avium subsp. paratuberculosis was cultured from various parts of the small and large intestines, liver tissue and lymph nodes and from the epididymis and vesicular glands. The results demonstrate a wide extraintestinal distribution of the bacterium and that breeding bulls should be considered a source of paratuberculosis infection due to their contact with other breeding bulls and a high number of heifers and cows through the natural mating process.

Isolation of Mycobacterium avium subsp. paratuberculosis from muscle tissue of naturally infected cattle

Johne's disease or paratuberculosis is a chronic granulomatous inflammation of the small intestine of ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Recent studies suggest an association between MAP and Crohn's disease in humans. MAP can become widely distributed within the tissues of infected animals, and meat may be a possible route of exposure of MAP to humans. In this study, 47 dairy and beef cattle were examined for the occurrence of viable MAP in diaphragm muscle. At the slaughterhouse, gut tissues, diaphragm muscle, blood, and feces of the 47 animals were collected for bacteriological culture, as well as gut samples for histopathological analysis. MAP was detected by bacteriological culture and conventional and real-time IS900 polymerase chain reaction in the diaphragm muscle of six infected cattle at slaughter (13%). The six animals showing evidence of MAP in diaphragm muscle had diffuse lesions and severe granulomatous inflammation in ileocecal lymph nodes, jejunal lymph nodes, ileocecal valve, and ileum. All six had heavy bacterial load in mesenteric lymph nodes, ileocecal valve, ileum, and jejunum, and four showed clinical signs of paratuberculosis. Two animals did not show clinical signs but had viable MAP in intestinal tissues and in diaphragm muscle as well. MAP was found in blood of only one of the six animals showing evidence of MAP in diaphragm muscle and in feces of three of them. In general, there was a positive association between enteric lesion severity, clinical signs of paratuberculosis, heavy bacterial load in intestinal tissues, fecal shedding of MAP, and the presence of disseminated MAP infection in diaphragm muscle. The results of this study demonstrated that MAP can be detected and cultured from muscle of MAP-infected cattle destined for human consumption and suggest a possible risk of exposure of humans to MAP via contaminated meat.

Contamination of food products with Mycobacterium avium paratuberculosis: a systematic review

Although a causal link between Mycobacterium avium subspecies paratuberculosis (MAP) and Crohn's disease has not been proved, previous studies suggest that the potential routes of human exposure to MAP should be investigated. We conducted a systematic review of literature concerning the likelihood of contamination of food products with MAP and the likely changes in the quantity of MAP in dairy and meat products along their respective production chains. Relevant data were extracted from 65 research papers and synthesized qualitatively. Although estimates of the prevalence of Johne's disease are scarce, particularly for non-dairy herds, the available data suggest that the likelihood of contamination of raw milk with MAP in most studied regions is substantial. The presence of MAP in raw and pasteurized milk has been the subject of several studies which show that pasteurized milk is not always MAP-free and that the effectiveness of pasteurization in inactivating MAP depends on the initial concentration of the agent in raw milk. The most recent studies indicated that beef can be contaminated with MAP via dissemination of the pathogen in the tissues of infected animals. Currently available data suggests that the likelihood of dairy and meat products being contaminated with MAP on retail sale should not be ignored.

A robust method for bacterial lysis and DNA purification to be used with real-time PCR for detection of Mycobacterium avium subsp. paratuberculosis in milk

A possible mode of transmission for the ruminant pathogen Mycobacterium avium subsp. paratuberculosis (MAP) from cattle to humans is via milk and dairy products. Although controversially, MAP has been suggested as the causative agent of Crohn's disease and its presence in consumers' milk might be of concern. A method to detect MAP in milk with real-time PCR was developed for screening of bulk tank milk. Pellet and cream fractions of milk were pooled and subjected to enzymatic digestion and mechanical disruption and the DNA was extracted by automated magnetic bead separation. The analytical sensitivity was assessed to 100 organisms per ml milk (corresponding to 1-10 CFU per ml) for samples of 10 ml. The method was applied in a study of 56 dairy herds to compare PCR of farm bulk tank milk to culture of environmental faecal samples for detection of MAP in the herds. In this study, 68% of the herds were positive by environmental culture, while 30% were positive by milk PCR. Results indicate that although MAP may be shed into milk or transferred to milk by faecal contamination, it will probably occur in low numbers in the bulk tank milk due to dilution as well as general milking hygiene measures. The concentration of MAP can therefore be assumed to often fall below the detection limit. Thus, PCR detection of MAP in milk would be more useful for control of MAP presence in milk, in order to avoid transfer to humans, than for herd prevalence testing. It could also be of value in assessing human exposure to MAP via milk consumption. Quantification results also suggest that the level of MAP in the bulk tank milk of the studied Danish dairy herds was low, despite environmental isolation of MAP from the herds.

Invasion and persistence of Mycobacterium avium subsp. paratuberculosis during early stages of Johne's disease in calves

Infection with Mycobacterium avium subsp. paratuberculosis causes Johne's disease in cattle and is a serious problem for the dairy industry worldwide. Development of models to mimic aspects of Johne's disease remains an elusive goal because of the chronic nature of the disease. In this report, we describe a surgical approach employed to characterize the very early stages of infection of calves with M. avium subsp. paratuberculosis. To our surprise, strains of M. avium subsp. paratuberculosis were able to traverse the intestinal tissues within 1 h of infection in order to colonize distant organs, such as the liver and lymph nodes. Both the ileum and the mesenteric lymph nodes were persistently infected for months following intestinal deposition of M. avium subsp. paratuberculosis despite a lack of fecal shedding of mycobacteria. During the first 9 months of infection, humoral immune responses were not detected. Nonetheless, using flow cytometric analysis, we detected a significant change in the cells participating in the inflammatory responses of infected calves compared to cells in a control animal. Additionally, the levels of cytokines detected in both the ileum and the lymph nodes indicated that there were TH1-type-associated cellular responses but not TH2-type-associated humoral responses. Finally, surgical inoculation of a wild-type strain and a mutant M. avium subsp. paratuberculosis strain (with an inactivated gcpE gene) demonstrated the ability of the model which we developed to differentiate between the wild-type strain and a mutant strain of M. avium subsp. paratuberculosis deficient in tissue colonization and invasion. Overall, novel insights into the early stages of Johne's disease were obtained, and a practical model of mycobacterial invasiveness was developed. A similar approach can be used for other enteric bacteria.

Sensitive detection of Mycobacterium avium subsp. paratuberculosis in bovine semen by real-time PCR

AIMS

To develop a fast and sensitive protocol for detection of Mycobacterium avium subsp. paratuberculosis (MAP) in bovine semen and to make a critical evaluation of the analytical sensitivity.

METHODS AND RESULTS

Processed semen was spiked with known amounts of MAP. Semen from different bulls as well as semen of different dilutions was tested. The samples were treated with lysing agents and beadbeating and the DNA was extracted with phenol and chloroform. Real-time PCR with a fluorescent probe targeting the insertion element IS900 detected as few as 10 organisms per sample of 100 mul semen. PCR-inhibition was monitored by inclusion of an internal control. Pre-treatment with immunomagnetic separation was also evaluated, but was not shown to improve the overall sensitivity.

CONCLUSIONS

Real-time PCR is a sensitive method for detection of MAP in bovine semen. Lysis by mechanical disruption followed by phenol and chloroform extraction efficiently isolated DNA and removed PCR-inhibitors.

SIGNIFICANCE AND IMPACT OF THE STUDY

The high sensitivity of the applied method allows reliable testing of bovine semen used for artificial insemination to prevent the spread of Johne's disease, caused by MAP.

No evidence of Mycobacterium avium subsp. paratuberculosis in in vitro produced cryopreserved embryos derived from subclinically infected cows

The aim of the project was to ascertain if Mycobacterium avium subsp. paratuberculosis (Map) could be cultured from frozen-thawed in vitro produced (IVP) embryos derived from cows with subclinical Johne's disease (JD). Straws of 109 IVP embryos were obtained from 267 cumulus-oocyte-complexes (COCs) collected from 12 clinically normal cows in which antibodies against Map were detected in blood by an enzyme-linked immunosorbent assay (ELISA). These embryos were processed, washed using the standard protocol as described by the International Embryo Transfer Society (IETS) and frozen in a commercial IVP embryo laboratory. Of the 12 donor cows, 11 had histopathological or bacteriological evidence of infection at post-mortem inspection. The frozen embryos were thawed and the contents of the straws were cultured using the radiometric mycobacterial culture method. No Map was detected in any of the 109 embryos or freezing media. This suggests that the use of in vitro produced and cryopreserved embryos derived from cows with subclinical JD poses very low, if any, risk of spreading infection to susceptible animals.