Mycobacterium avium subsp. paratuberculosis in Veterinary Medicine

Genomic insights into the plasmidome of non-tuberculous mycobacteria

BACKGROUND

Non-tuberculous mycobacteria (NTM) are a diverse group of environmental bacteria that are increasingly associated with human infections and difficult to treat. Plasmids, which might carry resistance and virulence factors, remain largely unexplored in NTM.

METHODS

We used publicly available complete genome sequence data of 328 NTM isolates belonging to 125 species to study gene content, genomic diversity, and clusters of 196 annotated NTM plasmids. Furthermore, we analyzed 3755 draft genome assemblies from over 200 NTM species and 5415 short-read sequence datasets from six clinically relevant NTM species or complexes including M. abscessus, M. avium complex, M. ulcerans complex and M. kansasii complex, for the presence of these plasmids.

RESULTS

Between one and five plasmids were present in approximately one-third of the complete NTM genomes. The annotated plasmids varied widely in length (most between 10 and 400 kbp) and gene content, with many genes having an unknown function. Predicted gene functions primarily involved plasmid replication, segregation, maintenance, and mobility. Only a few plasmids contained predicted genes that are known to confer resistance to antibiotics commonly used to treat NTM infections. Out of 196 annotated plasmid sequences, 116 could be grouped into 31 clusters of closely related sequences, and about one-third were found across multiple NTM species. Among clinically relevant NTM, the presence of NTM plasmids showed significant variation between species, within (sub)species, and even among strains within (sub)lineages, such as dominant circulating clones of Mycobacterium abscessus.

CONCLUSIONS

Our analysis demonstrates that plasmids are a diverse and heterogeneously distributed feature in NTM bacteria. The frequent occurrence of closely related putative plasmid sequences across different NTM species suggests they may play a significant role in NTM evolution through horizontal gene transfer at least in some groups of NTM. However, further in vitro investigations and access to more complete genomes are necessary to validate our findings, elucidate gene functions, identify novel plasmids, and comprehensively assess the role of plasmids in NTM.

Bayesian estimation of diagnostic accuracy of fecal smears, fecal PCR and serum ELISA for detecting Mycobacterium avium subsp. paratuberculosis infections in four domestic ruminant species in Saudi Arabia

Paratuberculosis, a chronic wasting disease affecting domestic and wild ruminants worldwide, is caused by Mycobacterium avium subsp. paratuberculosis (MAP). Various diagnostic tests exist for detecting MAP infection; however, none of them possess perfect accuracy to be qualified as a reference standard test, particularly due to their notably low sensitivity. Therefore, we used Bayesian latent class models (BLCMs) to estimate diagnostic accuracy of fecal smears (FS), fecal PCR and serum ELISA for detecting MAP infections in sheep, goats, cattle, and camels older than 2 years in Saudi Arabia. Data from a cross-sectional study conducted in the Eastern Province of Saudi Arabia on 31 different farms with a history of MAP infection were analyzed. Fecal and blood samples from all animals older than 2 years in each farm were collected, resulting in a total of 220 sheep, 123 goats, 66 cattle, and 240 camels sampled. FS and IS900-PCR were performed on fecal samples to detect acid-fast bacilli and MAP DNA, respectively. The IDEXX ELISA kit was used to detect MAP antibodies in serum samples. For each ruminant species population, a BLCM was fitted to obtain posterior estimates [medians and 95 % Bayesian credible intervals (95 % BCI)] for sensitivity (Se) and specificity (Sp) of the three tests. We assumed FS and PCR to be conditionally dependent on the true animal MAP status. Prior distributions for test accuracy were used if available. FS had the highest Se among all tests and across all species with median values around 80 % in sheep, goats and camels, and near 50 % in cattle. Median Sp estimates of ELISA and PCR were higher than 90 % for all species. FS yielded the lowest Sp of the study when applied in camels, sheep, and goats. Using the prevalence observed in this study, median positive predictive value (PPV) was higher for PCR and ELISA than FS for camels, sheep, and goats. In cattle, PPV of all tests was similar with median estimates > 95 %. In camels, sheep, and goats, median negative predicative value (NPV) of all tests were > 60 %. The lowest median NPV for all tests were observed in cattle (< 30 %). Our results suggest that ELISA is a suitable option to identify MAP infected animals in farms with previous history of MAP in the Eastern region of Saudi Arabia.

Clinical insights on paratuberculosis in Arabian camels (Camelus dromedarius): A review

Paratuberculosis (PTB) is a long-standing granulomatous infectious disease of both domesticated and wild ruminants. It is caused by Mycobacterium avium subsp. paratuberculosis (MAP). This review emphasizes the clinical, hematobiochemical, sonographic, and pathologic findings as well as therapeutic and control measures in dromedary camels infected with PTB. The clinical signs include intermittent and/or chronic diarrhea, decreased milk yield, emaciation, submandibular edema, dehydration, irregular and weak rumen contractions, and abdominal pain. Hematological changes include leukocytosis, neutrophilia, and decreased erythrocytes, hematocrit percent, and hemoglobin concentration. Biochemical alterations included hypoalbuminemia, hypoproteinemia, hyperglobulinemia, hypomagnesemia, hypoglycemia, increased alanine aminotransferase and aspartate aminotransferase activity, and increased concentration of magnesium and calcium. Sonographically, the intestinal wall is either mildly, moderately, or severely thickened along with mesenteric lymph nodes (LNs) enlargement. The LN capsule is either anechoic or echoic and the contents are either echogenic, anechoic, or heterogenous. Other sonographic findings include bright hepatic parenchyma, aggregation of echogenic materials separated with fluids among the intestines, and pleural and pericardial effusions. The typical pathological lesions are corrugation of the small intestinal mucosa, especially that of the ileum, and the colonic mucosa is folded. Mesenteric and ileocecal LNs are edematous, congested, and granular. Other necropsy findings include fatty liver and peritoneal, pericardial, and pleural effusions. Histologically, proliferative enteritis and lepromatous granulomas are detected. Clusters of acid-fast bacilli are usually found in the intestinal mucosa and lamina propria. Accurate diagnosis of PTB depends on the culture and identification of the causative organism MAP from tissue or feces. Herd screening is also performed through complement fixation, agar gel immunodiffusion, competitive-enzyme linked immunosorbent assay, Ziehl-Neelsen staining of tissue or feces, histologic pattern of a granulomatous reaction, DNA probes, and polymerase chain reaction. A trial for the treatment of PTB in dromedary camels was carried out through IM injection of rifampin and streptomycin for 10 weeks. The diarrhea resolved within 1 week of treatment, and MAP disappeared from rectal scraping 5-9 weeks after treatment. In conclusion, early detection and eradication procedures of PTB should be more implemented for the control and prevention of PTB in dromedary camels. More research should be directed toward vaccination programs in those species.

Clinical insights on paratuberculosis in Arabian camels (Camelus dromedarius): A review

Paratuberculosis (PTB) is a long-standing granulomatous infectious disease of both domesticated and wild ruminants. It is caused by Mycobacterium avium subsp. paratuberculosis (MAP). This review emphasizes the clinical, hematobiochemical, sonographic, and pathologic findings as well as therapeutic and control measures in dromedary camels infected with PTB. The clinical signs include intermittent and/or chronic diarrhea, decreased milk yield, emaciation, submandibular edema, dehydration, irregular and weak rumen contractions, and abdominal pain. Hematological changes include leukocytosis, neutrophilia, and decreased erythrocytes, hematocrit percent, and hemoglobin concentration. Biochemical alterations included hypoalbuminemia, hypoproteinemia, hyperglobulinemia, hypomagnesemia, hypoglycemia, increased alanine aminotransferase and aspartate aminotransferase activity, and increased concentration of magnesium and calcium. Sonographically, the intestinal wall is either mildly, moderately, or severely thickened along with mesenteric lymph nodes (LNs) enlargement. The LN capsule is either anechoic or echoic and the contents are either echogenic, anechoic, or heterogenous. Other sonographic findings include bright hepatic parenchyma, aggregation of echogenic materials separated with fluids among the intestines, and pleural and pericardial effusions. The typical pathological lesions are corrugation of the small intestinal mucosa, especially that of the ileum, and the colonic mucosa is folded. Mesenteric and ileocecal LNs are edematous, congested, and granular. Other necropsy findings include fatty liver and peritoneal, pericardial, and pleural effusions. Histologically, proliferative enteritis and lepromatous granulomas are detected. Clusters of acid-fast bacilli are usually found in the intestinal mucosa and lamina propria. Accurate diagnosis of PTB depends on the culture and identification of the causative organism MAP from tissue or feces. Herd screening is also performed through complement fixation, agar gel immunodiffusion, competitive-enzyme linked immunosorbent assay, Ziehl-Neelsen staining of tissue or feces, histologic pattern of a granulomatous reaction, DNA probes, and polymerase chain reaction. A trial for the treatment of PTB in dromedary camels was carried out through IM injection of rifampin and streptomycin for 10 weeks. The diarrhea resolved within 1 week of treatment, and MAP disappeared from rectal scraping 5-9 weeks after treatment. In conclusion, early detection and eradication procedures of PTB should be more implemented for the control and prevention of PTB in dromedary camels. More research should be directed toward vaccination programs in those species.

Comparative analysis of WC1.1+ and WC1.2+ γδ T cell subset responses from cattle naturally infected with Mycobacterium bovis to repeat stimulation with mycobacterial antigens

Mycobacterium bovis (M. bovis) causes bovine tuberculosis (bTB). The challenges in controlling and eradicating this zoonotic disease are compounded by our incomplete understanding of the host immune response. In this study, we used high-throughput bulk RNA sequencing (RNA-seq) to characterise the response profiles of γδ T cells to antigenic stimulation using purified protein derivate from M. bovis (PPDb). γδ T cells are a subgroup of T cells that bridge innate and adaptive immunity and have known anti-mycobacterial response mechanisms. These cells are usually classified based on the expression of a pathogen-recognition receptor, Workshop Cluster 1 (WC1), into two main subsets: WC1.1+ and WC1.2+. Previous studies have identified a preferential transcriptomic response in WC1.1+ cells during natural bTB infection, suggesting a subset-specific response to mycobacterial antigens. This follow on study tested the hypothesis that a subset specific response would also be apparent from γδ T cells from infected cattle after repeat stimulation. Peripheral blood was collected from Holstein-Friesian cattle naturally infected with M. bovis, confirmed by a single intradermal comparative tuberculin test (SICTT) and IFN-γ ELISA and stimulated with 10 μg/ml PPDb for 6 hours. After whole blood stimulation, WC1.1+ and WC1.2+ γδ T cell subsets were isolated using magnetic cell sorting (n = 5 per group). High-quality RNA was extracted from each purified lymphocyte subset (WC1.1+ and WC1.2+) to generate transcriptomes using bulk RNA sequencing, resulting in 20 RNA-seq libraries. Transcriptomic analysis revealed 111 differentially expressed genes (DEGs) common to both WC1.1+ and WC1.2+ γδ T cell compartments, including upregulation of IL1A, IL1B, IL6, IL17A, IL17F, and IFNG genes (FDR-Padj. < 0.1). Interestingly, the WC1.2+ cells showed upregulation of IL10, CCL22, and GZMA (log2FC ≥ 1.5, and FDR-Padj. < 0.1). In conclusion, while WC1.1+ and WC1.2+ γδ T cells exhibit a conserved inflammatory response to PPDb, differences in anti-inflammatory and antimicrobial gene expression between these cell subsets provide new insights into their effector functions in response to mycobacterial antigens.

Response of Mycobacterium avium subsp. paratuberculosis isolates to reactive oxygen stress generated by treatment with copper ions

Copper (Cu) ions have been recognized for their efficacy in inactivating bacteria, including Mycobacterium avium subsp. paratuberculosis (MAP), the causative agent of Johne's disease (JD) known for its resilience to unfavorable conditions. However, the response of MAP isolates isolated from cows to Cu exposure remains inadequately understood, as their responses may differ from those of laboratory-adapted reference strains. In this study, we examined the response of MAP isolates obtained from MAP-infected and affected cows to Cu ion treatment, comparing that with the response of the reference strain ATCC 19698 to the same treatment. Three MAP field isolates and the MAP reference strain were exposed to Cu ions, and their viability, protein/lipid damage, ROS production, and gene expression were evaluated in triplicate. Survival differed among isolates, with an isolate from a cow with clinical JD exhibiting increased tolerance to Cu exposure. While Cu treatment induced lipid peroxidation and ROS production across all isolates, genes associated with Cu detoxification and virulence were upregulated, particularly in the reference strain. Whole genome sequencing analysis revealed that, despite genomic similarities between field isolates and the reference strain ATCC 19698, there were differences regarding the presence/absence of genes related with certain virulence factors. Further research on Cu exposure with larger numbers of MAP isolates is needed to explain the stress-induced responses that influence MAP survival during natural infections and in challenging environments.

Discovery of Mycobacterium avium subsp. paratuberculosis Lytic Phages with Extensive Host Range Across Rapid- and Slow-Growing Pathogenic Mycobacterial Species

BACKGROUND/OBJECTIVES

Developing interventions for Johne's disease, which focuses on controlling Mycobacterium avium subsp. paratuberculosis (MAP) in contaminated environments by treating infected cows and preventing transmission from diseased animals, is a critical priority. Bacteriophage (phage) therapy, an emerging biological intervention, offers a promising alternative for the treatment and management of MAP infections.

METHODS

In this study, we generated an MAP-specific lytic phage library aimed at characterizing the therapeutic potential of phages under environmental and biological conditions that mimic those encountered in infected cattle such as ruminal fluid, milk, colostrum, and the bovine intestinal epithelium, a key site of MAP colonization and, later, transmission.

RESULTS

Our library contains a diverse collection of phages that have demonstrated robust lytic activity against MAP. The host range of these phages was thoroughly assessed, revealing that several isolates produce clear plaques on a range of MAP strains, as well as other pathogenic non-tuberculous mycobacterial (NTM) species and M. tuberculosis strains. This broad host range expands the therapeutic potential of the phage collection, positioning it as a potential cross-species antimicrobial tool. In vitro tests under conditions replicating the rumen, milk, and colostrum environments show that selected phages maintain stability and lytic efficacy, even in the presence of complex biological fluids. Furthermore, a subset of these phages was capable of preventing MAP colonization and invasion in cultured bovine epithelial cells, suggesting their potential for direct prophylactic application in cattle.

CONCLUSIONS

Our collection of MAP phages represents a valuable source that can be developed into probiotic-like preparations, offering a cost-effective solution for prophylaxis and control of Johne's disease.

Mycobacterium avium subspecies paratuberculosis (MAP) infection, and its impact on gut microbiome of individuals with multiple sclerosis

The microbial ecology of Mycobacterium avium subspecies paratuberculosis infections (MAP) within the context of Multiple Sclerosis (MS) is largely an unexplored topic in the literature. Thus, we have characterized the compositional and predicted functional differences of the gut microbiome between MS patients with MAP (MAP+) and without (MAP-) infection. This was done in the context of exposome differences (through self-reported filled questionnaires), principally in anthropometric and sociodemographic patterns to gain an understanding of the gut microbiome dynamics. 16S rRNA microbiome profiling of faecal samples (n = 69) was performed for four groups, which differed by disease and MAP infection: healthy cohort (HC) MAP-; HC MAP+ ; MS MAP-; and MS MAP+ . Using a dynamic strategy, with MAP infection and time of sampling as occupancy models, we have recovered the core microbiome for both HC and MS individuals. Additional application of neutral modeling suggests key genera that are under selection pressure by the hosts. These include members of the phyla Actinobacteriota, Bacteroidota, and Firmicutes. As several subjects provided multiple samples, a Quasi Conditional Association Test that incorporates paired-nature of samples found major differences in Archaea. To consolidate treatment groups, confounders, microbiome, and the disease outcome parameters, a mediation analysis is performed for MS cohort. This highlighted certain genera i.e., Sutterella, Akkermansia, Bacteriodes, Gastranaerophilales, Alistipes, Balutia, Faecalibacterium, Lachnospiraceae, Anaerostipes, Ruminococcaceae, Eggerthellaceae and Clostridia-UCG-014 having mediatory effect using disease duration as an outcome and MAP infection as a treatment group. Our analyses indicate that the gut microbiome may be an important target for dietary and lifestyle intervention in MS patients with and without MAP infection.

Superior protection against paratuberculosis by a heterologous prime-boost immunization in a murine model

Vaccination is the best strategy to control Paratuberculosis (PTB), which is a significant disease in cattle and sheep. Previously we showed the humoral and cellular immune response induced by a novel vaccine candidate against PTB based on the Argentinian Mycobacterium avium subspecies paratuberculosis (Map) 6611 strain. To improve 6611 immunogenicity and efficacy, we evaluated this vaccine candidate in mice with two different adjuvants and a heterologous boost with a recombinant modified vaccinia Ankara virus (MVA) expressing the antigen 85A (MVA85A). We observed that boosting with MVA85A did not improve total IgG or specific isotypes in serum induced by one or two doses of 6611 formulated with incomplete Freund's adjuvant (IFA). However, when 6611 was formulated with ISA201 adjuvant, MVA85A boost enhanced the production of IFNγ, Th1/Th17 cytokines (IL-2, TNF, IL-17A) and IL-6, IL-4 and IL-10. Also, this group showed the highest levels of IgG2b and IgG3 isotypes, both important for better protection against Map infection in the murine model. Finally, the heterologous scheme elicited the highest levels of protection after Map challenge (lowest CFU count and liver lesion score). In conclusion, our results encourage further evaluation of 6611 strain + ISA201 prime and MVA85A boost in bovines.

Differential role of M cells in enteroid infection by Mycobacterium avium subsp. paratuberculosis and Salmonella enterica serovar Typhimurium

Infection of ruminants such as cattle with Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease, a disease characterized by chronic inflammation of the small intestine and diarrhoea. Infection with MAP is acquired via the faecal-to-oral route and the pathogen initially invades the epithelial lining of the small intestine. In this study we used an in vitro 3D mouse enteroid model to determine the influence of M cells in infection of the gut epithelia by MAP, in comparison with another bacterial intestinal pathogen of veterinary importance, Salmonella enterica serovar Typhimurium. The differentiation of M cells in the enteroid cultures was induced by stimulation with the cytokine receptor activator of nuclear factor-κB ligand (RANKL), and the effects on MAP and Salmonella uptake and intracellular survival were determined. The presence of M cells in the cultures correlated with increased uptake and intracellular survival of Salmonella, but had no effect on MAP. Interestingly neither pathogen was observed to preferentially accumulate within GP2-positive M cells.

Interferon-gamma producing CD4+ T cells quantified by flow cytometry as early markers for Mycobacterium avium ssp. paratuberculosis infection in cattle

Current diagnostic methods for Johne's disease in cattle allow reliable detection of infections with Mycobacterium avium ssp. paratuberculosis (MAP) not before animals are 2 years of age. Applying a flow cytometry-based approach (FCA) to quantify a MAP-specific interferon-gamma (IFN-γ) response in T cell subsets, the present study sought to monitor the kinetics of the cell-mediated immune response in experimentally infected calves. Six MAP-negative calves and six calves, orally inoculated with MAP at 10 days of age, were sampled every 4 weeks for 52 weeks post-inoculation (wpi). Peripheral blood mononuclear cells (PBMC) were stimulated with either purified protein derivatives (PPD) or whole cell sonicates derived from MAP (WCSj), M. avium ssp. avium or M. phlei for 6 days followed by labeling of intracellular IFN-γ in CD4+ and CD8+ T cells. No antigen-specific IFN-γ production was detectable in CD8+ cells throughout and the responses of CD4+ cells of MAP-infected and control calves were similar up to 12 wpi. However, the mean fluorescence intensity (MFI) for the detection of IFN-γ in CD4+ cells after WCSj antigen stimulation allowed for a differentiation of animal groups from 16 wpi onwards. This approach had a superior sensitivity (87.8%) and specificity (86.8%) to detect infected animals from 16 wpi onwards, i.e., in an early infection stage, as compared to the IFN-γ release assay (IGRA). Quantification of specific IFN-γ production at the level of individual CD4+ cells may serve, therefore, as a valuable tool to identify MAP-infected juvenile cattle.

Development and evaluation of genomics informed real-time PCR assays for the detection and strain typing of Mycobacterium avium subsp. paratuberculosis

AIMS

This study aimed to identify specific genomic targets for the detection and strain typing of Map and analyse their sensitivity and specificity, and detect Map directly from faeces.

METHODS AND RESULTS

A comparative genomics approach was used to identify specific genomic targets for the detection and strain typing of Map. A Map specific qPCR using the primer pair 7132 that targets a DNA segregation ATPase protein was able to detect all strains of Map and is more sensitive than the current Johne's disease PCR assays with a sensitivity of 0.0002 fg µl-1. A strain specific qPCR using the Atsa primer pair that targets the arylsulfase gene was able to differentiate between Type S and Type C strains of Map and was more sensitive than the IS1311 PCR and REA with a sensitivity of 40 fg µl-1 and was specific for Type S Map. Both assays successfully detected Map directly from faeces.

CONCLUSION

This study developed and validated two genomics informed qPCR assays, 7132B Map and Atsa Type S and found both assays to be highly specific and sensitive for the detection of Map from culture and directly from faeces. This is the first time that a probe-based qPCR has been designed and developed for Map strain typing, which will greatly improve the response time during outbreak investigations.

Graduate Student Literature Review: Developmental adaptations of immune function in calves and the influence of the intestinal microbiota in health and disease

This graduate student literature review provides an examination of the ontological adaptations of the calf's immune system and how the intestinal microbiota influences calf immune function in health and disease. Within dairy rearing systems, various nutritional and management factors have emerged as critical determinants of development influencing multiple physiological axes in the calf. Furthermore, we discuss how multiple pre- and postnatal maternal factors influence the trajectory of immune development in favor of establishing regulatory networks to successfully cope with the new environment, while providing early immune protection via immune passive transfer from colostrum. Additionally, our review provides insights into the current understanding of how the intestinal microbiota contributes to the development of the intestinal and systemic immune system in calves. Lastly, we address potential concerns related to the use of prophylactic antimicrobials and waste milk, specifically examining their adverse effects on intestinal health and metabolic function. By examining these factors, we aim to better understand the intricate relationship between current management practices and their long-term effect on animal health.

Susceptibility, Immunity, and Persistent Infection Drive Endemic Cycles of Coxiellosis on Dairy Farms

Coxiella (C.) burnetii, a zoonotic bacterium, is prevalent in dairy farms. Some cows develop a persistent infection and shed C. burnetii into milk and occasionally by amniotic fluid at calving. Serological diagnosis of Q fever in humans is performed by phase (Ph)-specific antibody tests; PhII antibodies usually indicate an acute infection, while the development of a chronic infection is characterised by elevated PhI antibody titres. Phase-specific tests have now been established for diagnosis of coxiellosis in cattle. Additionally, an interferon-γ (IFN-γ) recall assay has been implemented to assess cellular immunity to C. burnetii in cattle. Milk samples from all lactating cows (n = 2718) of 49 Bavarian dairy farms were collected through a convenience sample and analysed for phase-specific antibodies. Antibody profiles were evaluated by age. Based on the seropositivity of first-lactation cows, three distinct herd profiles were observed: an 'acute' state of herd infection was characterised by a PhI-/PhII+ pattern. The detection of PhI antibodies (PhI+/PhII+) characterised the 'chronic' state, and seronegative results defined the 'silent' state of herd infection. If antibodies had not been detected in multiparous cows, the herd was considered as probably free of coxiellosis. The analysed cattle herds were noted to have an 'acute' (n = 12, 24.5%), 'chronic' (n = 18, 36.8%), or 'silent' state of herd infection (n = 16, 32.6%). Only three farms (6.1%) were classified as 'free' of C. burnetii. The detection of these herd states over a time period of 4 years in one farm indicated that the described states occur in a cyclical manner. Frequently, a wave-like profile was seen, i.e., a circumscribed seronegative age group was flanked by seropositive age groups. In seronegative animals, IFN-γ reactivity was demonstrated. Seroconversion after vaccination was observed by day 7 post-vaccination in chronically infected herds, whereas in the case of silent infection, it started by day 14. These data indicated a pre-existing immunity in seronegative animals in chronically infected herds. Additionally, IFN-γ reactivity was detected in seronegative calves (>3 months) and heifers from chronically infected farms compared to a negative farm. An infection prior to 3 months of age resulted in cellular immunity in the absence of detectable antibodies. An infection around calving would explain this. The aforementioned circumscribed seronegative age groups are, therefore, explained by an infection early in life during active shedding at calving. Based on these results, an endemic cycle of coxiellosis is proposed: Susceptible young heifers get infected by persistently infected cows. Subsequently, shedding of C. burnetii at calving results in infection and then in cellular immunity in offspring. When these calves enter the cow herd two years later, a maximum of herd immunity is achieved, shedding ceases, and new susceptible animals are raised. In an acutely infected dairy farm, the PhI+/PhII+ serological pattern prevailed in second-lactation cows. In this study, stored sera collected since birth were analysed retrospectively. From the earliest seroconversion, the peak of seroconversion took about 33 months. These data suggested a slow spread of infection within herds. The classification of dairy cow herds is a promising basis for further analysis of the clinical impact of coxiellosis.

Developmental adaptations of γδ T cells and B cells in blood and intestinal mucosa from birth until weaning in Holstein bull calves

This study aimed to characterize the development of systemic and colon tissue resident B and γδ T cells in newborn calves from birth until weaning. At birth, calves have limited capacity to initiate immune responses, and the immune system gradually matures over time. Gamma delta (γδ) T cells are an important lymphocyte subset in neonatal calves that confer protection and promote immune tolerance. A total of 36 newborn calves were enrolled in a longitudinal study to characterize how systemic and colon tissue resident B and γδ T cells develop from birth until weaning. Blood and colon biopsy samples were collected on d 2, 28, and 42 to determine the proportions of various B and γδ T cell subsets by flow cytometry. We classified γδ T cells into different functional subsets according to the level of expression intensity of the coreceptors WC1.1 (effector function) and WC1.2 (regulatory function). Furthermore, naive B cells were classified based on the expression IgM receptor, and activation state was determined based on expression of CD21 and CD32, 2 receptors with opposing signals involved in B cell activation in early life. Additional colon biopsy samples were used for 16S sequencing, and microbial diversity data are reported. At birth, γδ T cells were the most abundant lymphocyte population in blood, accounting for 58.5% of the lymphocyte pool, after which the proportions of these cells declined to 38.2% after weaning. The proportion of γδ T cells expressing WC1.1 decreased by 50% from d 2 to d 28, whereas no change was observed in the expression of WC1.2. In the colon, there was a 50% increase of γδ T cells after weaning and the proportion of WC1.2+ γδ T cells doubled from d 28 to 42. The proportion of IgM+ B lymphocytes in blood increased from 23.6% at birth to 30% after weaning, were the proportion of B cells expressing CD21 increased by 25%, while the proportion of B cells expressing CD32 decreased by 30%. While no changes were observed for the overall proportion of IgM+ B lymphocytes in the colon, there was a 6-fold increase in the proportion of CD21+ B cells from pre- (d 28) to postweaning (d 42). Microbial diversity increased from d 2 of life to 28 and declined abruptly after weaning. The reduction in microbial diversity during weaning was negatively correlated with the increase in all γδ T cell subsets and CD21+ B cells. These data suggest that developmental adaptations after birth coordinate expansion of γδ T cells to provide early systemic protection, as well as to steer immune tolerance, while B cells mature over time. Additionally, the increase of colonic γδ T cells on d 42 suggests a protective role of these cells during weaning.

Comparative Study of Mycobacterium bovis and Mycobacterium avium subsp. paratuberculosis In Vitro Infection in Bovine Bone Marrow Derived Macrophages: Preliminary Results

Bovine tuberculosis and paratuberculosis are endemic in many areas worldwide. This work aims to study cytokines production and gene expression profiles of bovine macrophages infected with Mycobacterium bovis and Mycobacterium paratuberculosis subsp. avium (MAP) strains to identify potential diagnostic biomarkers. Bovine bone marrow stem cells were differentiated into macrophages and subsequently infected in vitro with different spoligotypes of M. bovis and MAP field strains (as single infections and coinfections), using different multiplicity of infection. Supernatant and cell pellets were collected 24 h, 48 h, and one week post-infection. Preliminarily, gene expression on cell pellets of IL-1β, IL-2, INFγ, IL-6, IL-10, IL-12, and TNFα was assessed by qRT-PCR one week p.i. Subsequently, IL-1β and IL-6 were measured by ELISA and qRT-PCR to investigated their production retrospectively 24 h and 48 h p.i. A variability in macrophages response related to the concentration of mycobacteria, the coinfection with MAP, and M. bovis spoligotypes was identified. An early and constant IL-6 increase was observed in the M. bovis infection. A lower increase in IL-1β was also detected at the highest concentration of the two M. bovis spoligotypes one week post-infection. IL-6 and IL-1 β production was reduced and differently expressed in the MAP infection. IL-6 appeared to be the earliest cytokines produced by bovine macrophages infected with M. bovis.

Adjuvants influence the immune cell populations present at the injection site granuloma induced by whole-cell inactivated paratuberculosis vaccines in sheep

Vaccination is the most effective tool for paratuberculosis control. Currently, available vaccines prevent the progression of clinical disease in most animals but do not fully protect them against infection and induce the formation of an injection site granuloma. The precise mechanisms that operate in response to vaccination and granuloma development, as well as the effect that adjuvants could trigger, have not been fully investigated. Therefore, this study aimed to investigate the injection site granulomas induced by two inactivated paratuberculosis vaccines, which differ in the adjuvant employed. Two groups of 45-day-old lambs were immunized with two commercially available vaccines-one (n = 4) with Gudair® and the other (n = 4) with Silirum®. A third group (n = 4) was not vaccinated and served as control. The peripheral humoral response was assessed throughout the study by a commercial anti-Mycobacterium avium subspecies paratuberculosis (Map) antibody indirect ELISA, and the cellular immune response was assessed similarly by the IFN-γ release and comparative intradermal tests. The injection site granulomas were measured during the experiment and sampled at 75 days post-vaccination (dpv) when the animals were euthanized. The tissue damage, antigen and adjuvant distribution, and the presence and amount of immune cells were then determined and assessed by immunohistochemical methods. Antibodies against Map antigens; a general macrophage marker (Iba1), M1 (iNOS), and M2 (CD204) macrophages; T (CD3), B (CD20), and γδ T lymphocytes, proteins MHC-II and NRAMP1, and cytokines IL-4, IL-10, TNF, and IFN-γ were employed. Silirum® elicited a stronger peripheral cellular immune response than Gudair®, while the latter induced larger granulomas and more tissue damage at the site of injection. Additionally, adjuvant and Map antigen distribution throughout the granulomatous inflammatory infiltrate, as well as the NRAMP1 cell expression, which is linked to antigen phagocytosis, were highly irregular. In Silirum® induced granulomas, a higher number of MHC-II and TNF-expressing cells and a lower number of M2 macrophages suggested an improved antigen presentation, which could be due to the better antigen distribution and reduced tissue damage induced by this vaccine.

Lateral-flow assays for bovine paratuberculosis diagnosis

Mycobacterium avium subsp. paratuberculosis (MAP) causes bovine paratuberculosis (PTB). PTB is responsible for significant economic losses in dairy herds around the word. PTB control programs that rely on testing and culling of test-positive cows have been developed. Current diagnostics, such as ELISA for detecting MAP antibodies in serum samples and PCR detecting MAP DNA in feces, have inadequate sensitivity for detecting subclinical animals. Innovative "omics" technologies such as next-generation sequencing (NGS) technology-based RNA-sequencing (RNA-Seq), proteomics and metabolomics can be used to find host biomarkers. The discovered biomarkers (RNA, microRNAs, proteins, metabolites) can then be used to develop new and more sensitive approaches for PTB diagnosis. Traditional approaches for measuring host antibodies and biomarkers, such as ELISAs, northern blotting, quantitative reverse-transcriptase polymerase chain reaction (RT-qPCR), cDNA microarrays, and mass spectrometry are time-consuming, expensive, and sometimes exhibit poor sensitivity. With the rapid development of nanotechnology, low-cost monitoring devices for measuring antibodies against MAP proteins in point-of-care (POC) settings have been developed. Lateral flow assays (LFAs), in particular, are thought to be appropriate for the on-site detection of antibodies to MAP antigens and/or host biomarkers. This review aims to summarize LFAs that have recently been developed to accurately detect antibodies against MAP antigens, as well as the benefits that host biomarkers linked with MAP infection give to PTB diagnosis. The identification of these novel biomarkers could be the basis for the development of new LFAs. The dairy industry and producers are likely to benefit from reliable and rapid technologies capable of detecting MAP infection in situ to establish a quick and sensitive PTB diagnosis.

Rapid detection of Mycobacterium bovis in bovine cytological smears and tissue sections by peptide nucleic acid fluorescence in-situ hybridization

BACKGROUND

Bovine tuberculosis is the leading cause of death in cattle and other species worldwide. Quick and precise identification of mycobacteria is critical to control the occurrence of tuberculosis in cattle.

METHODS

We developed a fluorescent peptide nucleic acid fluorescence in situ hybridization (PNA-FISH) approach to detect Mycobacterium bovis and Mycobacterium avium in cytological smears and tissue sections of bovines suspected of having tuberculosis. PNA-FISH was conducted on smears of lung and lymph node tissues. Standard bovine mycobacterial cultures were used to standardize the probes using 50 % formamide for M. bovis and 30 % formamide for M. avium. M. bovis probe (MTBCcy3), which was standardized at hybridization conditions of (55 °C and 40 % formamide) concentrations, was positive in all cytological smears.

RESULTS

Four out of twenty five samples tested positive in tissue sections observed as a bright red fluorescence with a cy3 filter (MTBC probe). No results were observed with (MAVTAMRA) probe for M. avium which was standardized at hybridization conditions of (55 °C and 30 % formamide). No fluorescence was observed in the control tissue sections. Additionally, the results were juxtaposed with those of other commonly used detection methods such as immunohistochemistry and Polymerase Chain Reaction (PCR) by targeting the esxA gene. None of the samples tested positive for M. avium infection.

CONCLUSION

PNA-FISH can be used to obtain cytological impression smears and tissue sections. When compared to PCR it consumes less time in the diagnosis of bovine tuberculosis in post mortem cases.

Mycobacterium avium subsp. paratuberculosis Candidate Vaccine Strains Are Pro-apoptotic in RAW 264.7 Murine Macrophages

Mycobacterium avium subsp. paratuberculosis (MAP) is the etiological agent of Johne's disease, a severe gastroenteritis of ruminants. This study developed a model cell culture system to rapidly screen MAP mutants with vaccine potential for apoptosis. Two wild-type strains, a transposon mutant, and two deletion mutant MAP strains (MOI of 10 with 1.2 × 10⁶ CFU) were tested in murine RAW 264.7 macrophages to determine if they induce apoptosis and/or necrosis. Both deletion mutants were previously shown to be attenuated and immunogenic in primary bovine macrophages. All strains had similar growth rates, but cell morphology indicated that both deletion mutants were elongated with cell wall bulging. Cell death kinetics were followed by a real-time cellular assay to measure luminescence (apoptosis) and fluorescence (necrosis). A 6 h infection period was the appropriate time to assess apoptosis that was followed by secondary necrosis. Apoptosis was also quantified via DAPI-stained nuclear morphology and validated via flow cytometry. The combined analysis confirmed the hypothesis that candidate vaccine deletion mutants are pro-apoptotic in RAW 264.7 cells. In conclusion, the increased apoptosis seen in the deletion mutants correlates with the attenuated phenotype and immunogenicity observed in bovine macrophages, a property associated with good vaccine candidates.

Alternatives to antibiotics in veterinary medicine: considerations for the management of Johne's disease

Antibiotic resistance has become a major health concern globally, with current predictions expecting deaths related to resistant infections to surpass those of cancer by 2050. Major efforts are being undertaken to develop derivative and novel alternatives to current antibiotic therapies in human medicine. What appears to be lacking however, are similar efforts into researching the application of those alternatives, such as (bacterio)phage therapy, in veterinary contexts. Agriculture is still undoubtedly the most prominent consumer of antibiotics, with up to 70% of annual antibiotic usage attributed to this sector, despite policies to reduce their use in food animals. This not only increases the risk of resistant infections spreading from farm to community but also the risk that animals may acquire species-specific infections that subvert treatment. While these diseases may not directly affect human welfare, they greatly affect the profit margin of industries reliant on livestock due to the cost of treatments and (more frequently) the losses associated with animal death. This means actively combatting animal infection not only benefits animal welfare but also global economies. In particular, targeting recurring or chronic conditions associated with certain livestock has the potential to greatly reduce financial losses. This can be achieved by developing novel diagnostics to quickly identify ill animals alongside the design of novel therapies. To explore this concept further, this review employs Johne's disease, a chronic gastroenteritis condition that affects ruminants, as a case study to exemplify the benefits of rapid diagnostics and effective treatment of chronic disease, with particular regard to the diagnostic and therapeutic potential of phage.

Bioprospective Role of Ocimum sanctum and Solanum xanthocarpum against Emerging Pathogen: Mycobacterium avium Subspecies paratuberculosis: A Review

Mycobacterium avium subspecies paratuberculosis (MAP) is a chronic, contagious, and typically life-threatening enteric disease of ruminants caused by a bacterium of the genus Mycobacterium, but it can also affect non-ruminant animals. MAP transmission occurs through the fecal-oral pathway in neonates and young animals. After infection, animals generate IL-4, IL-5, and IL-10, resulting in a Th2 response. Early detection of the disease is necessary to avoid its spread. Many detection methods, viz., staining, culture, and molecular methods, are available, and numerous vaccines and anti-tuberculosis drugs are used to control the disease. However, the prolonged use of anti-tuberculosis drugs leads to the development of resistance. Whereas vaccines hamper the differentiation between infected and vaccinated animals in an endemic herd. This leads to the identification of plant-based bioactive compounds to treat the disease. Bioactive compounds of Ocimum sanctum and Solanum xanthocarpum have been evaluated for their anti-MAP activity. Based on the MIC50 values, Ursolic acid (12 µg/mL) and Solasodine (60 µg/mL) were found to be suitable for anti-MAP activity.

Evidence of Homeostatic Regulation in Mycobacterium avium Subspecies paratuberculosis as an Adaptive Response to Copper Stress

Background: Bacteria are capable of responding to various stressors, something which has been essential for their adaptation, evolution, and colonization of a wide range of environments. Of the many stressors affecting bacteria, we can highlight heavy metals, and amongst these, copper stands out for its great antibacterial capacity. Using Mycobacterium tuberculosis (Mtb) as a model, the action of proteins involved in copper homeostasis has been put forward as an explanation for the tolerance or adaptive response of this mycobacteria to the toxic action of copper. Therefore, the aim of this study was to confirm the presence and evaluate the expression of genes involved in copper homeostasis at the transcriptional level after challenging Mycobacterium avium subsp. paratuberculoisis (MAP) with copper ions. Methodology: Buffer inoculated with MAP was treated with two stressors, the presence of copper homeostasis genes was confirmed by bioinformatics and genomic analysis, and the response of these genes to the stressors was evaluated by gene expression analysis, using qPCR and the comparative ΔΔCt method. Results: Through bioinformatics and genomic analysis, we found that copper homeostasis genes were present in the MAP genome and were overexpressed when treated with copper ions, which was not the case with H2O2 treatment. Conclusion: These results suggest that genes in MAP that code for proteins involved in copper homeostasis trigger an adaptive response to copper ions.

Sarcoidosis, Mycobacterium paratuberculosis and Noncaseating Granulomas: Who Moved My Cheese

Clinical and histological similarities between sarcoidosis and tuberculosis have driven repeated investigations looking for a mycobacterial cause of sarcoidosis. Over 50 years ago, "anonymous mycobacteria" were suggested to have a role in the etiology of sarcoidosis. Both tuberculosis and sarcoidosis have a predilection for lung involvement, though each can be found in any area of the body. A key histopathologic feature of both sarcoidosis and tuberculosis is the granuloma-while the tuberculous caseating granuloma has an area of caseous necrosis with a cheesy consistency; the non-caseating granuloma of sarcoidosis does not have this feature. This article reviews and reiterates the complicity of the infectious agent, Mycobacterium avium subsp. paratuberculosis (MAP) as a cause of sarcoidosis. MAP is involved in a parallel story as the putative cause of Crohn's disease, another disease featuring noncaseating granulomas. MAP is a zoonotic agent infecting ruminant animals and is found in dairy products and in environmental contamination of water and air. Despite increasing evidence tying MAP to several human diseases, there is a continued resistance to embracing its pleiotropic roles. "Who Moved My Cheese" is a simple yet powerful book that explores the ways in which individuals react to change. Extending the metaphor, the "non-cheesy" granuloma of sarcoidosis actually contains the difficult-to-detect "cheese", MAP; MAP did not move, it was there all along.

Mycobacterium avium Subspecies paratuberculosis in Asymptomatic Zoo Herbivores in Poland

Mycobacterial infections are significant issues in zoo animals, influencing animal welfare, conservation efforts, and the zoonotic potential of pathogens. Although tuberculosis is recognised to be highly dangerous, paratuberculosis can also lead to animal losses and is potentially dangerous for humans. The aim of the current study was to confirm whether Mycobacterium avium spp. paratuberculosis (MAP) infections are currently present in zoos in Poland. Faeces samples (n = 131) were collected from different animal species from eight zoos in Poland. The faeces were decontaminated and inoculated into Herrold’s Egg Yolk Media. The species was determined using commercial DNA testing. The IS900 was checked using RT-PCR. The culture was positive in seven samples: five with M. avium, one with Mycobacterium fortiatum, and one without any identified Mycobacterium species. RT-PCR confirmed MAP genetic material in nine animals. Our findings represent the first confirmation of MAP in bongo (Tragelaphus eurycerus), indicating that it is present in Polish zoological gardens. Fortunately, the disease can be monitored more easily due to recent legislation (the Animal Health Law).

Exploration of Solanum xanthocarpum Schrad. & Wendl. against Mycobacterium avium Subspecies paratuberculosis and Assessment of Its Immunomodulatory and Anti-Inflammatory Potential

Mycobacterium avium subspecies paratuberculosis (MAP), being a dairy-borne pathogen, resistant of pasteurization and other sterilization techniques, is a major cause for development of inflammatory bowel disorders such as Johne's disease (JD) in dairy animals and Crohn's Disease (CD) in humans, for which no therapy is available to date. In the absence of effective therapy or a vaccine, management of CD has been accomplished by removal of the affected intestines. However, usually, even after removal of 2/3 of the intestine, CD reoccurs. Hence, there exists a need to develop an alternative therapy for such infection. The potential of herbals remains unexplored against MAP and related infections. Therefore, the conducted study is a novel initiative for the evaluation of anti-mycobacterial activity of bioactive extracts of Solanum xanthocarpum Schrad. & Wendl. against MAP infection. The said plant was authenticated according to the Ayurvedic Pharmacopoeia of India. Qualitative and quantitative evaluation of the extracts were done using chromatographic and spectroscopic techniques. Preliminary in vitro pharmacological assessments revealed the immunomodulatory and anti-inflammatory potential of the extracts. REMA assay was conducted to determine their anti-MAP activity along with determination of the best active extract. The hydro-alcoholic extract showed the best inhibition of MAP, providing a potential ray of hope against this emerging major pathogen of animals, and associated with Crohn's disease and other autoimmune disorders in human beings.

Sheep vaccinated against paratuberculosis have increased levels of B cells infiltrating the intestinal tissue

Systemic immunisation delivered subcutaneously is currently used to control paratuberculosis, a chronic enteritis of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). These vaccines do not provide complete protection and a small cohort of animals still succumb to clinical disease. The aim of this study was to assess mycobacterial infection site-specific variations in immune cells in vaccinated sheep that did or did not develop the disease following controlled exposure to MAP. Immunohistochemical staining of terminal ileum demonstrated that vaccination increased infiltration of CD4 + T cells and B cells. Infiltration of large numbers of CD4 + T and B cells was also seen in sheep that successfully cleared infection. Vaccination promoted the polarisation of macrophages to an M1 activation state. The presence of certain cells at the site of infection, especially CD4 + T cells, is likely to contribute to vaccine success by increasing the speed and potency of the local immune response. Systemic immunisation against MAP can alter the composition of innate and adaptive immune cell populations at the predilection site for MAP infection in the ileum one year after vaccination. This informs understanding of the impact of vaccination at the site of infection and also the duration of vaccine-elicited changes. This information may assist vaccine development and allow targeting of protective immune responses in the gut of ruminants.

Genome-wide association studies for the identification of cattle susceptible and resilient to paratuberculosis

Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne's disease or paratuberculosis (PTB), with important animal health and economic implications. There are no therapeutic strategies to control this disease, and vaccination with inactivated vaccines is limited in many countries because it can interfere with the intradermal test used for bovine tuberculosis detection. Thus, infected animals either get culled after a positive ELISA or fecal PCR result or die due to clinical disease. In this study, we review recent studies aimed to discover genetic markers which could help to identify and select cattle less susceptible and more resilient to PTB. In recent years, the genotyping and subsequent imputation to whole-genome sequence (WGS) has allowed the identification of single-nucleotide polymorphisms (SNPs), quantitative trait loci (QTL), and candidate genes in the Bos taurus genome associated with susceptibility to MAP infection. In most of these genome-wide association studies (GWAS), phenotypes were based on ante-mortem test results including serum ELISA, milk ELISA, and detection of MAP by fecal PCR and bacteriological culture. Cattle infected with MAP display lesions with distinct severity but the associations between host genetics and PTB-associated pathology had not been explored until very recently. On the contrary, the understanding of the mechanisms and genetic loci influencing pathogen resistance, and disease tolerance in asymptomatic individuals is currently very limited. The identification of long-time asymptomatic cattle that is able to resist the infection and/or tolerate the disease without having their health and milk production compromised is important for disease control and breeding purposes.

Effect of heat-inactivated Mycobacterium avium subspecies paratuberculosis (MAP) vaccine on the lesions and immunopathology developed in target tissues of naturally MAP-infected goats

Paratuberculosis (PTB) is a disease caused by Mycobacterium avium subspecies paratuberculosis (MAP), which affects a broad range of hosts, including domestic and wild animals. PTB is a chronic granulomatous enteritis and lymphadenitis that compromises animal welfare and causes economic losses. The objective of this study was to evaluate the effect of a commercial heat-inactivated MAP vaccine on lesions and immunopathology developed in the target tissues of goats naturally infected with MAP. Lesions compatible with PTB in the intestine and regional lymph nodes (LNs), as well as local immune response to MAP, were evaluated and compared in Gudair®-vaccinated (n = 14) and unvaccinated (n = 11) goats from a MAP-infected farm. The percentage of animals with multifocal granulomatous lesions in the jejunal (p = 0.05) and ileocecal (p = 0.02) LNs was higher in unvaccinated animals, while a lesion score reduction of 50% was found in the LNs of vaccinated animals. Unvaccinated animals showed increased numbers and wider distribution of macrophages (MΦs, CD68 +) in histiocytic infiltrate (p = 0.0003), associated with increased numbers of mycobacteria. Increased inducible nitric oxide synthase (iNOS) expression was also reported in these animals, while M2 MΦs (CD163 +) were scarce in both groups. Vaccinated animals showed an increase in CD3 + lymphocytes, although differences in interferon gamma (IFNγ) were negligible. These results support the hypothesis that heat-inactivated MAP vaccination could reduce the severity of PTB lesions and mycobacterial load in target tissues in vaccinated adult goats.

Bayesian estimation of sensitivity and specificity of fecal culture, fecal PCR and serum ELISA for diagnosis of Mycobacterium avium subsp. paratuberculosis infections in sheep

The objective of the present study was to evaluate the diagnostic accuracy of the individual fecal culture (IFC), fecal PCR (FPCR), and serum ELISA for the detection of Mycobacterium avium subsp. paratuberculosis (MAP) infections in sheep from four governorates in Egypt, using a latent class model (LCM) fitted within a Bayesian framework. Furthermore, the within-governorate prevalence of MAP infection in sheep was estimated as a secondary objective. Fecal and blood samples were collected from 370 sheep in four Egyptian governorates. Fecal samples were analyzed by IFC and RT-PCR based on ISMav2 gene, while ELISA was performed on serum samples. The sensitivity (Se) and specificity (Sp) of the three diagnostic tests were estimated using a three-tests-four-populations Bayesian LCM to obtain posterior estimates [medians and 95% Bayesian credible intervals (95% BCI)] for each parameter. The median Se estimates (95% BCI) for IFC, FPCR, and serum ELISA were 31.8% (22.8-41.4), 49.7% (31.8-79.9), and 61.2% (39.8-81.4), respectively. The median Sp estimates (95% BCI) for IFC, FPCR, and serum ELISA were 97.7% (96.1-98.9), 97.7% (95.6-99.5), and 98.4% (96.9-99.3), respectively. The median within-governorate paratuberculosis prevalence (95% BCI) was 5.2% (1.1-13.6), 8.4% (2.9-17.7), 9.4% (3.0-20.7), and 18.2% (10.5-29.5) for the Gharbia, Menoufia, Qalyubia, and Kafr El-Sheikh governorates, respectively. In conclusion, at a ratio of the optical density (OD) sample/OD positive control threshold of > 45%, ELISA showed the highest Se among the three tests and comparable Sp to IFC and FPCR. The test ELISA evaluated in this study is an interesting alternative for detecting MAP in sheep due to its higher Se, lower cost, and shorter turnaround laboratory time compared to IFC and FPCR.

Multiplex qPCR for differentiation of Mycobacterium avium subspecies paratuberculosis in active and passive infection of goats

Mycobacterium avium paratuberculosis (MAP) is causative agent of Johne's disease (JD) in domestic animals and has broad host range. JD infected animals shed viable MAP in their milk, feces, blood, and tissues which get transmitted to human beings directly or indirectly by consumption of animal products, through contact, animal handling and through contaminated environment, aerosols. In this current study, we developed hydrolysis probe based TaqMan® real-time PCR assay where samples were investigated by targeting IS900 mRNA and ModD gene to differentiate live MAP shedders from inactive/dead MAP bacilli shedding animals. The IS900 mRNA and ModD gene primers were designed using discontiguous unique conserved sequences of IS900 more towards the 3' end and fibronectin attachment protein (FAP) genes, respectively. Two different reporter dyes Cy5 and TexasRed, with compatible quenchers BHQ-1 and BHQ-2, respectively, were used for probe designing of IS900 and ModD genes. Triplex PCR assay was developed by using serially diluted positive MAP culture in log₁₀ dilution and probe and template titration. TaqMan® probe real-time PCR targeting IS900 mRNA and ModD gene detects the MAP infection at early stage with high sensitivity and specificity. The specificity of developed TaqMan probe real-time PCR was found to be high while validated by using Escherichia coli and Staphylococcus aureus in addition to the MAP culture as there is no non-specific signal from other microbes. The sensitivity of developed TaqMan® probe real-time PCR was computed based on copy numbers ranged from 4.14 × 10¹¹ to 4.14 × 10⁴ for IS900 (FAM), 1.27 × 10¹¹ to 1.27 × 10⁴ for IS900 mRNA (Cy5), and 3.68 × 10¹⁰ to 3.68 × 10⁴ for ModD (TexasRed), and lowest limit to detect MAP was 4.14 × 10⁴, 1.27 × 10⁴, and 3.68 × 10⁴ copies for respective genes. This assay would be of great aid to contain the MAP infection in the large herd, where silent shedders spread active infection can be differentiated from passive shedding by non-infected animals. This test would also be equivalent to culture test in terms of specificity and hence can be able to be undertaken in molecular epidemiological studies to represent the actual disease prevalence in the future. KEY POINTS: • Multiplex mRNA-based qPCR was developed to identify the actively infective MAP bacilli from passive ones. • ModD and IS900 used as targets to assess active MAP bacilli in fecal samples of suspected animals. • The LOD was computed using copy numbers with 4.14 × 10⁴ and 3.68 × 10⁴ copies for IS900 and ModD, respectively.

Quantitative Risk Assessment of Exposure to Mycobacterium avium subsp. paratuberculosis (MAP) via Different Types of Milk for the Slovenian Consumer

This study aimed to assess the risk of exposure to Mycobacterium avium subsp. paratuberculosis (MAP) via milk for the Slovenian consumer. MAP is suspected to be associated with several diseases in humans, therefore the risk of exposure should be better understood. The primary source of MAP for humans is thought to be cattle, in which MAP causes paratuberculosis or Johne’s disease. We developed a stochastic quantitative risk assessment model using Monte Carlo simulations. Considering the assumptions and uncertainties, we estimated the overall risk of exposure to MAP via milk to be low. For people consuming raw milk from MAP positive farms, the risk was high. On-farm pasteurisation reduced the risk considerably, but not completely. The risk of exposure via pasteurised retail milk was most likely insignificant. However, with a higher paratuberculosis prevalence the risk would also increase. Given the popularity of raw milk vending machines and homemade dairy products, this risk should not be ignored. To reduce the risk, consumers should heat raw milk before consumption. To prevent a potential public health scare and safeguard farmers’ livelihoods, a reduction in paratuberculosis prevalence should be sought. Our results show that culling clinically infected cows was insufficient to reduce milk contamination with MAP.

Use of uncoated magnetic beads to capture Mycobacterium smegmatis and Mycobacterium avium paratuberculosis prior detection by mycobacteriophage D29 and real-time-PCR

Uncoated tosyl-activated magnetic beads were evaluated to capture Mycobacterium smegmatis and Mycobacterium avium subspecies paratuberculosis (MAP) from spiked feces, milk, and urine. Centrifugation and uncoated magnetic beads recovered more than 99% and 93%, respectively, of 1.68 × 10⁷ CFU/mL, 1.68 × 10⁶ CFU/mL and 1.68 × 10⁵ CFU/mL M. smegmatis cells resuspended in phosphate buffer saline. The use of magnetic beads was more efficient to concentrate cells from 1.68 × 10⁴ CFU/mL of M. smegmatis than centrifugation. Likewise, the F57-qPCR detection of MAP cells was different whether they were recovered by beads or centrifugation; cycle threshold (Ct) was lower (p < 0.05) for the detection of MAP cells recovered by beads than centrifugation, indicative of greater recovery. Magnetic separation of MAP cells from milk, urine, and feces specimens was demonstrated by detection of F57 and IS900 sequences. Beads captured no less than 10⁹ CFU/mL from feces and no less than 10⁴ CFU/mL from milk and urine suspensions. In another detection strategy, M. smegmatis coupled to magnetic beads were infected by mycobacteriophage D29. Plaque forming units were observed after 24 h of incubation from urine samples containing 2 × 10⁵ and 2 × 10³ CFU/mL M. smegmatis. The results of this study provide a promising tool for diagnosis of tuberculosis and Johne's disease.

Mycobacterium avium subsp. paratuberculosis and microbiome profile of patients in a referral gastrointestinal diseases centre in the Sudan

Mycobacterium avium subsp. paratuberculosis (MAP) causes Johne’s disease in animals with zoonotic potential; it has been linked to many chronic diseases in humans, especially gastrointestinal diseases (GID). MAP has been extensively studied in Europe and America, but little reports were published from Africa. Sudan is a unique country with close contact between humans and livestock. Despite such interaction, the one health concept is neglected in dealing with cases of humans with GID. In this study, patients admitted to the reference GID hospital in the Sudan over a period of 8 months were screened for presence of MAP in their faeces or colonic biopsies. A total of 86 patients were recruited for this study, but only 67 were screened for MAP, as 19 did not provide the necessary samples for analysis. Both real-time PCR and culture were used to detect MAP in the collected samples and the microbial diversity in patients´ faecal samples was investigated using 16S rDNA nanopore sequencing. In total, 27 (40.3%) patients were MAP positive: they were 15 males and 12 females, of ages between 21 and 80 years. Logistic regression analysis revealed no statistical significance for all tested variables in MAP positive patients (occupation, gender, contact with animal, milk consumption, chronic disease, etc.). A unique microbiome profile of MAP-positive patients in comparison to MAP-negative was found. These findings suggest that a considerable proportion of the population could be MAP infected or carriers. Therefore, increase awareness at community level is urgently needed to decrease the risk of MAP at human/animal interface. This study represents the first report of MAP in humans in the Sudan; nevertheless, a better view of the situation of MAP in humans in the country requires a larger study including patients with other conditions.

Genome-wide association analysis for susceptibility to infection by Mycobacterium avium ssp. paratuberculosis in US Holsteins

Paratuberculosis, or Johne's disease, is a chronic, granulomatous, gastrointestinal tract disease of cattle and other ruminants caused by the bacterium Mycobacterium avium subspecies paratuberculosis (MAP). Control of Johne's disease is based on programs of testing and culling animals positive for infection with MAP and concurrently modifying management to reduce the likelihood of infection. The current study was motivated by the hypothesis that genetic variation in host susceptibility to MAP infection can be dissected and quantifiable associations with genetic markers identified. Two separate GWAS analyses were conducted, the first using 897 genotyped Holstein artificial insemination sires with phenotypes derived from incidence of MAP infection among daughters based on milk ELISA testing records. The second GWAS analysis was a case-control design using US Holstein cows phenotyped for MAP infection by serum ELISA or fecal culture tests. Cases included cows positive for either serum ELISA, fecal culture, or both. Controls consisted of animals negative for all tests conducted. A total of 376 samples (70 cases and 306 controls) from a University of Minnesota Johne's management demonstration project and 184 samples (76 cases and 108 controls) from a Michigan State University study were used. Medium-density (sires) and high-density (cows) genotype data were imputed to full genome sequence for the analyses. Marker-trait associations were analyzed using the single-step (ss)GWAS procedure implemented in the BLUPF90 suite of programs. Evidence of significant genomic contributions for susceptibility to MAP infection were observed on multiple chromosomes. Results were combined across studies in a meta-analysis, and increased support for genomic regions on BTA7 and BTA21 were observed. Gene set enrichment analysis suggested pathways for antigen processing and presentation, antimicrobial peptides and natural killer cell-mediated cytotoxicity are relevant to variation in host susceptibility to MAP infection, among others. Genomic prediction was evaluated using a 5-fold cross-validation, and moderate correlations were observed between genomic breeding value predictions and daughter averages (∼0.43 to 0.53) for MAP infection in testing data sets. These results suggest that genomic selection against susceptibility to MAP infection is feasible in Holstein cattle.

More Insights about the Efficacy of Copper Ion Treatment on Mycobacterium avium subsp. paratuberculosis (MAP): A Clue for the Observed Tolerance

Background: Scientific evidence is scarce for the antimicrobial effect of copper on bacteria characterized as more resistant. Using Mycobacterium avium subsp. paratuberculosis (MAP), a highly resistant microorganism, as a pathogen model, copper ion treatment has shown a significant bactericidal effect; however, the sustainability of MAP against copper toxicity was also reported in several studies. Accordingly, the present study aimed to evaluate the impacts of copper on MAP. Methodology: This study considered physicochemical properties and copper concentration in a buffer since it could modulate MAP response during the application of copper treatment. Results: Despite the efficacy of copper ions in significantly reducing the MAP load in Phosphate Buffered Saline, some MAP cells were able to survive. The copper concentration generated by the copper ion treatment device increased significantly with increasing exposure times. MAP bacterial load decreased significantly when treated with copper ions as the exposure times increased. An increase in pH decreased oxygen consumption, and an increase in conductivity was reported after treatment application. Conclusions: Even with higher concentrations of copper, the efficacy of MAP control was not complete. The concentration of copper must be a key element in achieving control of highly resistant microorganisms.

Development and Validation of a Novel ELISA for the Specific Detection of Antibodies against Mycobacterium avium Subspecies paratuberculosis Based on a Chimeric Polyprotein

Bovine paratuberculosis (PTB) is caused by Mycobacterium avium subsp. paratuberculosis (MAP). The optimization of detection tests specific for MAP is crucial to improve PTB control. In this work, we aimed to develop and validate a diagnostic tool based on an ELISA to specifically detect anti-MAP antibodies from bovine serum samples. For that purpose, we designed a recombinant polyprotein containing four specific antigens from MAP and optimized the ELISA. The validation consisted of the assessment of 10 sera from PTB-infected and healthy bovines with different OD values. The diagnostic performance of the polyprotein-ELISA was evaluated by testing 130 bovine serum samples (47 healthy, 48 MAP-infected, and 35 M. bovis-infected bovines). The ELISA using the polyprotein yielded an area under the ROC curve (AUC) of 0.9912 (95% CI, 0.9758–1.007; P < 0.0001). Moreover, for this ELISA, the cut-off selected from the ROC curve based on the point with a sensitivity of 95.56% (95% CI, 0.8485–0.9946) and specificity of 97.92 (95% CI, 0.8893–0.9995) was 0.3328. Similar results were obtained with an ELISA using the commercial Paratuberculosis Protoplasmatic Antigen (PPA). However, the ELISA with the polyprotein antigen showed a better performance against sera from animals infected with Mycobacterium bovis compared to the ELISA with PPA: lower cross-reactivity (2.85% versus 25.71%). These results demonstrate a very low cross-reactivity of the polyprotein with antibodies present in serum samples from animals infected with M. bovis. The designed polyprotein and the validated ELISA could be very useful for the specific identification of MAP-infected animals in herds.

Antibodies from healthy or paratuberculosis infected cows have different effects on Mycobacterium avium subspecies paratuberculosis invasion in a calf ileal loop model

In this work, we used a calf ileal loop model to evaluate whether the preincubation of Mycobacterium avium subspecies paratuberculosis (MAP) with antibodies from healthy, MAP-positive or Lipoarabinomannan (LAM) immunized cows could affect the results of infection after 3.5 h. Bacterial load in tissue was assessed by Ziehl-Neelsen and by culture for each loop. MAP was detectable in all infected loops after 3.5 h.p.i.; although the presence of antibodies from MAP-positive cows significantly reduced bacterial load in loops as compared with antibodies from healthy donors (by Ziehl-Neelsen and culture, p-value < 0.003 and 0.0203, respectively). A possible direct effect of antibodies on MAP viability was shown to be not significant. Severity of histopathologic changes induced by MAP infection also varied according to the pretreatment: MAP induced less changes when inoculated in the presence of antibodies from MAP-positive cows as compared with antibodies from healthy donors. Overall, our results show that the presence of antibodies from MAP-positive cows reduced MAP invasion and consequent early histological changes in this ileal short-term loop model. These results may suggest a protective role of antibodies in the response against MAP at the portal of entry in cattle.

A rapid phage assay for detection of viable Mycobacterium avium subsp. paratuberculosis in milk

Paratuberculosis is an incurable gastroenteritis among ruminants that is promoted by Mycobacterium avium subsp. paratuberculosis (MAP), an acid-fast mycobacterium. To accelerate the detection of viable pathogen, a conventional (peptide mediated magnetic separation: PMS) and novel (phage-bead qPCR: PBQ) phage based assay was optimized. A superior limit of detection (LOD) of 10 MAP per 10 mL milk was suggested for PBQ compared to 100 cells/10 mL for PMS-phage assay. Via PBQ, viable MAP was found in 48.78% out 41 unpasteurized sheep and goat milk samples. Sheep milk samples (n = 29) that were tested by PMS-phage assay contained no viable MAP. The absence of viable MAP in milk collected from 21 of the recent sheep animals was also confirmed by PBQ after a 2-week gap. Although, the two phage assays comparably detected no viable MAP in the milk samples, MAP DNA and antibodies against MAP were recognized in milk and sera of some of these animals within two instances of sampling representing that some sheep animals were MAP shedders. In conclusion, PBQ and PMS-phage could be promising methods for the assessment of MAP viability in milk samples. However, PBQ was privileged over the PMS-phage assay due to the lower LOD, rapidity, higher sensitivity, lack of need to M. smegmatis and consequent virucidal treatment that are essential in PMS-phage assay for making lawn and inactivation of exogenous mycobacteriophages respectively.

The epidemiology of inflammatory bowel disease: Clues to pathogenesis?

Historically, inflammatory bowel disease (IBD) was most common in North America and Europe and more common with a north-south gradient. Over the past century, there has been a marked increase in IBD in general and in childhood IBD in particular and over the past 50 years IBD has spread into the developing world. The greatest risk factor of developing IBD is an affected family member. Concordance rates between dizygotic twins is ∼4% and ∼50% in monozygotic twins, and more than half of pairs are diagnosed within 2 years of each other. Nevertheless, most patients with IBD do not have an affected family member. More than 200 genes are associated with an increased risk for IBD, but most associations are weak with odds ratios between 1.2 and 2.0 suggesting the environment plays a role. IBD is more common in urban than rural regions and is associated with "good standards" of domestic hygiene during childhood. People who migrate from areas with a low incidence to areas with a high incidence of IBD have an increased risk of developing IBD and the younger they are when they migrate, the greater their risk of developing IBD. Moreover, people who migrate from regions with a high incidence to areas with a low incidence of IBD have a decreased risk of developing IBD. Together, these findings strongly suggest particular environmental exposures occurring early in life may trigger inflammatory bowel disease in genetically susceptible individuals. The key is figuring out what those exposures might be.

Bayesian estimation of prevalence of Johne's disease in dairy herds in Southern Italy

Johne's disease (JD) is a chronic granulomatous disease caused by Mycobacterium avium subsp. paratuberculosis (MAP) causing important losses on dairy farms. In Italy, voluntary programs to control MAP infection in dairy cattle are implemented in the Northern part of the country, where several studies have been carried out. Conversely, the disease status has not been fully investigated in the Southern regions. The aims of this study were to (i) determine the herd-level true prevalence (HTP) and (ii) the conditional within herd animal-level prevalence (CWHP) of JD in selected dairy cattle herds in Southern Italy. Serum samples were taken from 27 farms and analysed using a commercial ELISA test. A Bayesian model was fitted to the data. The estimated posterior mean of HPT was 0.46 (89 % CI 0.25-0.67), while the mean CWHP was 0.03 (89 % CI: 0.012-0.045). The results presented in this study call for designing and implementing an effective JD control program at national level.

MicroRNA profiling in bovine serum according to the stage of Mycobacterium avium subsp. paratuberculosis infection

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease (JD), and it causes diarrhea and weakness in cattle. During a long subclinical stage, infected animals without clinical signs shed pathogens through feces. For this reason, the diagnosis of JD during the subclinical stage is very important. Circulating miRNAs are attracting attention as useful biomarkers in various veterinary diseases because of their expression changes depending on the state of the disease. Based on current knowledge, circulating miRNAs extracted from bovine serum were used to develop a diagnostic tool for JD. In this study, the animals were divided into 4 groups according to fecal shedding, the presence of antibodies, and clinical signs. Gene expression was analyzed by performing miRNA sequencing for each group, and it was identified that the miRNA expression changed more as the MAP infection progressed. The eight miRNAs that were differentially expressed in all infected groups were selected as biomarker candidates based on their significant differences compared to the control group. These biomarker candidates were validated by qRT-PCR. Considering the sequencing data, two upregulated miRNAs and two downregulated miRNAs showed the same trend in the validation results. Network analysis was also conducted and the results showed that mRNAs (IL-10, TGF-β1) associated with regulatory T cells were predicted to be activated in the subclinical stage. Taken together, our data suggest that two miRNAs (bta-miR-374b, bta-miR-2887) may play major roles in the immune response to MAP infection during the subclinical stage.

Comparison of Cattle Serum Antibody Responses to Five Different Mycobacterial Antigens in an ELISA System

The presence of common zoonosis diseases caused by Mycobacterium tuberculosis complex (MTBC) and nontuberculous mycobacteria (NTM), such as Johne's and Crohn's diseases, poses a public health threat and economic losses to Iranian livestock. Therefore, the early detection of mycobacteria is of paramount importance. In this regard, enzyme-linked immunosorbent assay (ELISA) is a new, simple to use, rapid, and useful diagnostic tool. This study was performed to evaluate different crude antigens obtained from Mycobacterium species using an indirect ELISA test to identify the mycobacterial infection in infected livestock. Five different strains of Mycobacteria including M. tuberculosis, M. phlei, M. bovis, M. aviumsubspecies paratuberculosis, and M. bovis AN5 were cultured. The crude antigens in the samples were precipitated with trichloroacetic acid 4%. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis of crude antigens isolated from different Mycobacterium species was reported. The total level of protein was determined by the Lowry protein assay. After the crude antigen preparation, the ELISA test was performed and the results were compared with the purified protein derivative skin test. Data analysis was performed using SPSS software version 25. All five strains were detected in more than 92% of healthy animals. The highest sensitivity of ELISA tests was in M. bovis AN5 antigen which was greater than 83%. The highest diagnostic specificity and efficiency of assays were in M. avium subspecies paratuberculosis which was 95.83% and over 83%, respectively. Regarding the results, M. avium subspecies paratuberculosis and M. bovis AN5 antigens were promising candidates for the design of diagnostic ELISA due to their sensitivity, specificity, and efficiency.

Mycobacterium avium subsp. paratuberculosis (MAP) molecular diversity in cattle, sheep, and goats from Latin America and the Caribbean: a systematic review

This study aimed to systematically collect and appraise the scientific evidence to answer the research question: What MAP genotypes have been isolated from cattle, sheep, and goats in Latin America and the Caribbean? An electronic search was conducted on three platforms (i.e., OVID®, Web of Science®, SciELO) as well as on the proceedings of the International Colloquium on Paratuberculosis. Inclusion and exclusion criteria were defined a priori and conserved through the systematic process and only articles published in peer-reviewed journals were considered. A total of 26 articles met the definitive inclusion criteria. All were published in English, in 15 different journals, and between 1989 and 2020. The relevant articles reported the use of six different genotyping techniques (i.e., polymerase chain reaction-restriction endonuclease analysis, restriction fragment length polymorphism, type-specific-PCR, mycobacterial interspersed repetitive units-variable number of tandem repeats, multi-locus short sequence repeat, single nucleotide polymorphism) in isolates from seven countries. Genotypes found so far in the region using typing techniques were mainly C type. MIRU-VNTR mostly reported INMV 1, INMV 2, and INMV 11 subtypes, among others. MLSSR reported genotypes from four different countries, reporting nine different subtypes of which 7g–10g–4ggt was the most common for loci 1, 2, and 8, respectively. Regardless the high diversity of techniques used so far to genotype Latin American and Caribbean MAP isolates, the original question of this systematic review has been answered. In addition, a relative genetic similarity between MAP strains recovered from cattle, goats, and sheep unrelatedly of the matrix and geographic origin was identified.

HERV-W and Mycobacteriumavium subspecies paratuberculosis Are at Play in Pediatric Patients at Onset of Type 1 Diabetes

The etiology of T1D remains unknown, although a variety of etiological agents have been proposed as potential candidates to trigger autoimmunity in susceptible individuals. Emerging evidence has indicated that endogenous human retrovirus (HERV) may play a role in the disease etiopathogenesis; although several epigenetic mechanisms keep most HERVs silenced, environmental stimuli such as infections may contribute to the transcriptional reactivation of HERV-Wand thus promote pathological conditions. Previous studies have indicated that also Mycobacterium avium subspecies paratuberculosis (MAP) could be a potential risk factor for T1D, particularly in the Sardinian population. In the present study, the humoral response against HERV-W envelope and MAP-derived peptides was analyzed to investigate their potential role in T1D etiopathogenesis, in a Sardinian population at T1D onset (n = 26), T1D (45) and an age-matched healthy population (n = 45). For the first time, a high serum-prevalence of anti-Map and anti-HERV-W Abs was observed in pediatric patients at onset of T1D compared to T1D patients and healthy controls. Our results support the hypothesis that external infections and internal reactivations are involved in the etiology of T1D, and that HERV-W activation may be induced by infectious agents such as MAP.

Attempted Control of Paratuberculosis in Dairy Calves by Only Changing the Quality of Milk Fed to Calves

One of the important routes of Mycobacterium avium subsp. paratuberculosis (MAP) transmission in dairy calves is milk. The aim of the present study was to assess the efficacy of milk treatments to prevent MAP infection transmission to calves. A one-year longitudinal study was carried out. Newborn calves were assigned to one of four experimental groups: 5 calves received naturally MAP-contaminated milk, 5 calves received copper treated milk, 4 calves were fed calf milk replacer, and 3 were fed UHT pasteurized milk. MAP load in milk was estimated. Infection progression was monitored monthly. After one year, calves were euthanized, and tissue samples were cultured and visually examined. MAP was undetectable in milk replacer and UHT milk. Copper ion treatment significantly reduced the number of viable MAP in naturally contaminated milk. Fecal shedding of MAP was observed in all study groups but began earlier in calves fed naturally contaminated milk. Paratuberculosis control programs must place multiple hurdles between the infection source, MAP-infected adult cows, and the most susceptible animals on the farm, young calves. As our study shows, strict dependence on a single intervention to block infection transmission, no matter how important, fails to control this insidious infection on dairy farms.

Using Omics Approaches in the Discovery of Biomarkers for Early Diagnosis of Johne's Disease in Sheep and Goats

Simple Summary

Johne’s disease (JD) is caused by Mycobacterium avium subsp. paratuberculosis (MAP) and is an important and emerging problem in livestock. Most JD research has been carried out on cattle, but interest in the pathogenesis and diagnosis of this disease in sheep and goats is greatest in developing countries. Sheep and goats are also a relevant part of livestock production in Europe and Australia, and these species provide an excellent resource to study and better understand the mechanism of survival of MAP and gain insights into possible approaches to control this disease. This review gives an overview of the literature on paratuberculosis in sheep and goats, highlighting the immunological aspects and the potential for “omics” approaches to identify effective biomarkers for the early detection of infection.

Abstract

Johne’s disease (JD) is caused by Mycobacterium avium subsp. paratuberculosis (MAP) and is an important and emerging problem in livestock; therefore, its control and prevention is a priority to reduce economic losses and health risks. Most JD research has been carried out on cattle, but interest in the pathogenesis and diagnosis of this disease in sheep and goats is greatest in developing countries. Sheep and goats are also a relevant part of livestock production in Europe and Australia, and these species provide an excellent resource to study and better understand the mechanism of survival of MAP and gain insights into possible approaches to control this disease. This review gives an overview of the literature on paratuberculosis in sheep and goats, highlighting the immunological aspects and the potential for “omics” approaches to identify effective biomarkers for the early detection of infection. As JD has a long incubation period before the disease becomes evident, early diagnosis is important to control the spread of the disease.

Early Detection of Mycobacterium avium subsp. paratuberculosis Infected Cattle: Use of Experimental Johnins and Innovative Interferon-Gamma Test Interpretative Criteria

Paratuberculosis (PTB), also known as Johne's disease, is a chronic proliferative enteritis of ruminants caused by Mycobacterium avium subsp.paratuberculosis (MAP). To date, PTB diagnosis, based on serology, fecal culture, and real-time polymerase chain reaction, has identified animals in advanced stages of infection. To detect MAP infection in animals earlier, the interferon-gamma (IFN-γ) test may be applied. This assay detects cytokines produced by T-lymphocytes of infected subjects after stimulation with purified protein derivatives (PPDs), extracted from Mycobacterium bovis (MB) and from M. avium (MA). The study involved three bovine herds: one PTB-infected herd, one PTB-free herd, and one with an outbreak of bovine tuberculosis. The IFN-γ test was performed on 235 animals, using bovine PPD (PPDB), avian PPD (PPDA), and three experimental PPD Johnins (PPDJs) extracted from a synthetic liquid medium culture of MAP (PPDJ A, B, and C), to assess early MAP detection and avoid false reactions to MB. Furthermore, IFN-γ results were evaluated using 12 interpretative criteria (ICs), based on the differences and ratio between PPD optical density (OD) and IFN-γ basal OD values after lymphocytic stimulation. IC accuracy was expressed as area under the receiver operating characteristic curve. Through a longitudinal study, PPDJs proved to be specific and sensitive in the detection of MAP-infected animals. Among the evaluated ICs, six showed the best performance in terms of accuracy (p < 0.0001), highlighting PTB subclinical infections. In particular, the two best criteria reached sensitivity values of 100% [confidence interval (CI) 95%, 94.1–100%] with a specificity of 91.8% (CI 95%, 81.9–97.3%) and sensitivity levels of 80.6% (CI 95%, 69.1–89.2%) with a specificity of 100% (CI 95%, 94.1–100%). Thus, the IFN-γ assay proved to be a useful diagnostic tool to identify early subclinical MAP-infected animals, in order to manage infected cattle or those exposed to MAP and to monitor younger calves within a herd. Furthermore, the IFN-γ test can be considered an additional test to avoid the introduction of MAP-infected animals, especially in herds where disease has already been eradicated and preservation of the health status is required to maintain the PTB certification level.

Functional Variants Surrounding Endothelin 2 Are Associated With Mycobacterium avium Subspecies paratuberculosis Infection

Bovine paratuberculosis, caused by Mycobacterium avium subspecies paratuberculosis (MAP), continues to impact the dairy industry through increased morbidity, mortality, and lost production. Although genome-wide association analyses (GWAAs) have identified loci associated with susceptibility to MAP, limited progress has been made in identifying mutations that cause disease susceptibility. A 235-kb region on Bos taurus chromosome 3 (BTA3), containing a 70-kb haplotype block surrounding endothelin 2 (EDN2), has previously been associated with the risk of MAP infection. EDN2 is highly expressed in the gut and is involved in intracellular calcium signaling and a wide array of biological processes. The objective of this study was to identify putative causal mutations for disease susceptibility in the region surrounding EDN2 in Holstein and Jersey cattle. Using sequence data from 10 Holstein and 10 Jersey cattle, common variants within the 70-kb region containing EDN2 were identified. A custom SNP genotyping array fine-mapped the region using 221 Holstein and 51 Jersey cattle and identified 17 putative causal variants (P < 0.01) located in the 5′ region of EDN2 and a SNP in the 3′ UTR (P = 0.00009) associated with MAP infection. MicroRNA interference assays, mRNA stability assays, and electrophoretic mobility shift assays were performed to determine if allelic changes at each SNP resulted in differences in EDN2 stability or expression. Two SNPs [rs109651404 (G/A) and rs110287192 (G/T)] located within the promoter region of EDN2 displayed differential binding affinity for transcription factors in binding sequences harboring the alternate SNP alleles. The luciferase reporter assay revealed that the transcriptional activity of the EDN2 promoter was increased (P < 0.05) with the A allele for rs109651404 and the G allele for rs110287192. These results suggest that the variants rs109651404 and rs110287192 are mutations that alter transcription and thus may alter susceptibility to MAP infection in Holstein and Jersey cattle.