The pathology and pathogenesis of paratuberculosis in ruminants and other species

Non-tuberculous mycobacterial infections of veterinary relevance

Mycobacteria play an important role in human and animal health fields. We here examine the place of non tuberculous mycobacteria (NTM) infections in the veterinary context. Relevant aspects of a reference laboratory experience and a literature review are presented in this article. Importance is given both to productivity and to economic losses due to misdiagnosis with bovine tuberculosis and paratuberculosis. The impact NTM may have is relative to geographical location, ecology, husbandry, extent of surveillance programs and bovine tuberculosis and paratuberculosis prevalence. The role of the most relevant NTM in animal disease is summarized with a special focus on Mycobacterium avium subsp. paratuberculosis, given its role as causative agent of paratuberculosis, a disease with huge economic consequences for ruminant livestock.

Dose-dependent interferon-gamma release in dairy calves experimentally infected with Mycobacterium avium subspecies paratuberculosis

The interferon-gamma (IFN-γ) release assay is considered useful for diagnosis of subclinical paratuberculosis. However, interpretation can be subjective and complex; therefore, additional information regarding the course of the cellular immune response and effects of age and dose at infection would be helpful. Thirty-three calves were randomly allocated to 10 challenge groups and a negative control group. Calves were inoculated orally at 2 weeks or at 3, 6, 9, or 12 months of age. Within each age group, calves received either a high or low dose of Mycobacterium avium subspecies paratuberculosis (MAP). Monthly blood samples were collected, stimulated with Purified Protein Derivative (PPD) Johnin in vitro, and the subsequent release of IFN-γ measured. Calves inoculated with a high dose had earlier and stronger IFN-γ responses than low-dose calves. Furthermore, calves inoculated at 2 weeks of age produced less IFN-γ compared to those inoculated later in life. The IFN-γ response peaked (on average) 4 months after exposure; therefore, this would be an optimal interval to test cattle for MAP-infection (although the timing of field-based infections is unknown and clearance of infection a possibility). To conclude, the IFN-γ release assay could be a valuable diagnostic test on herd-level to indicate exposure to MAP.

The Mycobacterium avium ssp. paratuberculosis specific mptD gene is required for maintenance of the metabolic homeostasis necessary for full virulence in mouse infections

Mycobacterium avium subspecies paratuberculosis (MAP) causes Johne's disease, a chronic granulomatous enteritis in ruminants. Furthermore, infections of humans with MAP have been reported and a possible association with Crohn's disease and diabetes type I is currently discussed. MAP owns large sequence polymorphisms (LSPs) that were exclusively found in this mycobacteria species. The relevance of these LSPs in the pathobiology of MAP is still unclear. The mptD gene (MAP3733c) of MAP belongs to a small group of functionally uncharacterized genes, which are not present in any other sequenced mycobacteria species. mptD is part of a predicted operon (mptABCDEF), encoding a putative ATP binding cassette-transporter, located on the MAP-specific LSP14. In the present study, we generated an mptD knockout strain (MAPΔmptD) by specialized transduction. In order to investigate the potential role of mptD in the host, we performed infection experiments with macrophages. By this, we observed a significantly reduced cell number of MAPΔmptD early after infection, indicating that the mutant was hampered with respect to adaptation to the early macrophage environment. This important role of mptD was supported in mouse infection experiments where MAPΔmptD was significantly attenuated after peritoneal challenge. Metabolic profiling was performed to determine the cause for the reduced virulence and identified profound metabolic disorders especially in the lipid metabolism of MAPΔmptD. Overall our data revealed the mptD gene to be an important factor for the metabolic adaptation of MAP required for persistence in the host.

Facts, myths and hypotheses on the zoonotic nature of Mycobacterium avium subspecies paratuberculosis

Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of paratuberculosis (Johne's disease [JD]), a chronic granulomatous enteritis in ruminants. JD is one of the most widespread bacterial diseases of domestic animals with significant economic impact. The histopathological picture of JD resembles that of Crohn's disease (CD), a human chronic inflammatory bowel disease of still unresolved aetiology. An aetiological relevance of MAP for CD has been proposed. This and the ambiguity of other published epidemiological findings raise the question whether MAP represents a zoonotic agent. In this review, we will discuss evidence that MAP has zoonotic capacity.

Mycobacterium avium Subspecies paratuberculosis: Human Exposure through Environmental and Domestic Aerosols

Mycobacterium avium subspecies paratuberculosis (Map) causes Johne's disease in animals and is significantly associated with Crohn's disease (CD) in humans. Our previous studies have shown Map to be present in U.K. rivers due to land deposition from chronic livestock infection and runoff driven by rainfall. The epidemiology of CD in Cardiff showed a significant association with the River Taff, in which Map can be detected on a regular basis. We have previously hypothesized that aerosols from the river might influence the epidemiology of CD. In this preliminary study, we detected Map by quantitative PCR in one of five aerosol samples collected above the River Taff. In addition, we examined domestic showers from different regions in the U.K. and detected Map in three out of 30 independent samples. In detecting Map in river aerosols and those from domestic showers, this is the first study to provide evidence that aerosols are an exposure route for Map to humans and may play a role in the epidemiology of CD.

Sequential development of lesions 3, 6, 9, and 12 months after experimental infection of goat kids with Mycobacterium avium subsp paratuberculosis

The development of lesions after infection with Mycobacterium avium subsp paratuberculosis (MAP) was examined in an experimental infection model. Goat kids were orally inoculated 10 times with 10 mg bacterial wet mass of MAP (total dose 2.6 × 10(8) colony-forming units). Six to 7 inoculated goats and 3 controls were autopsied 3, 6, 9, and 12 months postinoculation (mpi), lesions were documented, and samples were collected for histology, immunohistochemistry (IHC), and bacterial culture. Twenty-five of the 26 inoculated goats did not develop clinical signs. Macroscopic lesions were detected in 3 of the 7 inoculated goats as soon as 3 mpi. Jejunal Peyer's patches (JPPs) were thickened and had ulcerated surfaces and circumscribed serositis. Characteristic granulomatous infiltrates were seen in all goats in gut-associated lymphoid tissues (GALTs), especially JPPs and lymphoid tissue at the ileocecal valve and in intestinal lymph nodes. Granulomatous intestinal infiltrates not associated with GALT were seen beginning at 6 mpi and with increasing frequency thereafter. Interindividual differences in lesions were most pronounced at 12 mpi, varying from mild focal paucibacillary to severe diffuse multibacillary patterns. Bacterial culture of MAP confirmed the IHC findings but was more sensitive and revealed widespread dissemination at 3 and 12 mpi. Granulomatous arteritis was found in intestinal submucosa of several goats. This may contribute to the spreading of MAP to the intestinal wall and possibly systemically. The different lesions observed during the clinically inapparent period of paratuberculosis are most likely indicators for the later progression of infection and development of clinical disease.

Evaluation of immunodominant proteins of Mycobacterium avium paratuberculosis cell wall by Western blot analysis

Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) is a slow growing mycobactin, whose dependence on mycobacterial species is known to be the causative agent of Johne's disease (paratuberculosis) in all species of domestic ruminants worldwide. The organism is transmitted via close contact, ingestion, or transplacentally from mother to fetus and occurs commonly in grazing domestic animals. Johne's disease (JD) is characterized by gradual weight loss, decreased milk production, and diarrhea due to the chronic, progressive, granulomatous enteritis and lymphadenitis. The disease can cause serious economic damage to the dairy industry due to the loss of milk production and early culling of infected animals. In recent years, researchers have focused on the identification of a specific antigen of M. paratuberculosis to use in diagnosis test and preparation of effective vaccine. The goal of this study is evaluation of the immunodominant proteins of M. paratuberculosis cell wall. The amount of protein was determined with a Lowry assay (22.68 μg/100 μL). For production of polyclonal antibody against proteins of M. paratuberculosis cell wall, a New Zealand white rabbit was immunized with antigen and Freund's adjuvant. After immunization, the rabbit was bled to produce enriched serum. Antibodies were purified from serum with ion exchange chromatography. In the Ouchterlony test, the reactions between antigen and antibodies were seen in dilutions of one quarter for serum, one quarter for Ig, and one half for IgG by clear precipitation lines due to the well immunization of the rabbit. Electrophoresis and Western blot analysis were used and subsequently a sharp band appeared in nitrocellulose paper; these bands were about 25, 37, 50, 75, and 150 kDa molecular weight, which indicated immunodominant proteins.

Immunoreactivity of protein tyrosine phosphatase A (PtpA) in sera from sheep infected with Mycobacterium avium subspecies paratuberculosis

Evasion of host defense mechanisms and survival inside infected host macrophages are features of pathogenic mycobacteria including Mycobacterium avium subspecies paratuberculosis, the causative agent of Johne's disease in ruminants. Protein tyrosine phosphatase A (PtpA) has been identified as a secreted protein critical for survival of mycobacteria within infected macrophages. The host may mount an immune response to such secreted proteins. In this study, the humoral immune response to purified recombinant M. avium subsp. paratuberculosis PtpA was investigated using sera from a cohort of sheep infected with M. avium subsp. paratuberculosis and compared with uninfected healthy controls. A significantly higher level of reactivity to PtpA was observed in sera collected from M. avium subspecies paratuberculosis infected sheep when compared to those from uninfected healthy controls. PtpA could be a potential candidate antigen for detection of humoral immune responses in sheep infected with M. avium subspecies paratuberculosis.

Lymphoproliferative and gamma interferon responses to stress-regulated Mycobacterium avium subsp. paratuberculosis recombinant proteins

Johne's disease in ruminants is a chronic infection of the intestines caused by Mycobacterium avium subsp. paratuberculosis. An important strategy to control disease is early detection, and a potentially efficient method for early detection is measurement of cell-mediated immune responses developed by the host in response to exposure or infection. One method is to measure lymphoproliferation and cytokine release from the host cells when exposed to the organism or parts of the organism. In this study, 10 recombinant M. avium subsp. paratuberculosis proteins known to be upregulated under in vitro stress conditions were evaluated by examining their ability to evoke memory as a result of exposure by vaccination or oral challenge with live Mycobacterium avium subsp. paratuberculosis. Out of 10 proteins, MAP2698c was found to induce higher cell-mediated immune responses in vaccinated and challenged sheep in comparison to healthy controls. The findings suggest that not all stress-regulated proteins have the diagnostic potential to detect cell-mediated immune responses in ovine paratuberculosis.

Mycobacterium avium Subsp. avium infection in four veal calves: differentiation from intestinal tuberculosis

Mycobacterium avium subsp. avium (Maa) is an intracellular pathogen belonging to the Mycobacterium avium-intracellulare complex (MAC). Reservoirs of MAC are the natural environment, wildlife and domestic animals. In adult bovine, MAC infections are typically caused by Mycobacterium avium subsp. paratuberculosis (Map). Maa infections in bovine are rarely reported but may cause clinical disease and pathological lesions similar to those observed in paratuberculosis or those induced by members of the Mycobacterium tuberculosis complex (MTBC). Therefore, differentiation of MAC from MTBC infection should be attempted, especially if unusual mycobacterial lesions are encountered. Four veal calves from a fattening farm dying with clinical signs of otitis media, fever, and weight loss were submitted for necropsy. Samples from affected organs were taken for histologic investigation, bacteriologic culture, and bacterial specification using PCR. Macroscopic thickening of the intestinal mucosa was induced by granulomatous enteritis and colitis. Intracytoplasmic acid-fast bacteria were detected by Ziehl-Neelsen stains and PCR revealed positive results for Mycobacterium avium subsp. avium. Clinical and pathological changes of Maa infection in veal calves had features of Mycobacterium avium subsp. paratuberculosis and the MTBC. Therefore, Mycobacterium tuberculosis complex infection should be considered in cases of granulomatous enteritis in calves.

Evaluation of novel oral vaccine candidates and validation of a caprine model of Johne's disease

Johne's disease (JD) caused by Mycobacterium avium subspecies paratuberculosis (MAP) is a major threat to the dairy industry and possibly some cases of Crohn's disease in humans. A MAP vaccine that reduced of clinical disease and/or reduced fecal shedding would aid in the control of JD. The objectives of this study were (1) to evaluate the efficacy of 5 attenuated strains of MAP as vaccine candidates compared to a commercial control vaccine using the protocol proposed by the Johne's Disease Integrated Program (JDIP) Animal Model Standardization Committee (AMSC), and (2) to validate the AMSC Johne's disease goat challenge model. Eighty goat kids were vaccinated orally twice at 8 and 10 weeks of age with an experimental vaccine or once subcutaneously at 8 weeks with Silirum® (Zoetis), or a sham control oral vaccine at 8 and 10 weeks. Kids were challenged orally with a total of approximately 1.44 × 10⁹ CFU divided in two consecutive daily doses using MAP ATCC-700535 (K10-like bovine isolate). All kids were necropsied at 13 months post-challenge. Results indicated that the AMSC goat challenge model is a highly efficient and valid model for JD challenge studies. None of the experimental or control vaccines evaluated prevented MAP infection or eliminated fecal shedding, although the 329 vaccine lowered the incidence of infection, fecal shedding, tissue colonization and reduced lesion scores, but less than the control vaccine. Based on our results the relative performance ranking of the experimental live-attenuated vaccines evaluated, the 329 vaccine was the best performer, followed by the 318 vaccine, then 316 vaccine, 315 vaccine and finally the 319 vaccine was the worst performer. The subcutaneously injected control vaccine outperformed the orally-delivered mutant vaccine candidates. Two vaccines (329 and 318) do reduce presence of JD gross and microscopic lesions, slow progression of disease, and one vaccine (329) reduced fecal shedding and tissue colonization.

Genome-wide association analysis and genomic prediction of Mycobacterium avium subspecies paratuberculosis infection in US Jersey cattle

Paratuberculosis (Johne’s disease), an enteric disorder in ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP), causes economic losses in excess of $200 million annually to the US dairy industry. To identify genomic regions underlying susceptibility to MAP infection in Jersey cattle, a case-control genome-wide association study (GWAS) was performed. Blood and fecal samples were collected from ∼5,000 mature cows in 30 commercial Jersey herds from across the US. Discovery data consisted of 450 cases and 439 controls genotyped with the Illumina BovineSNP50 BeadChip. Cases were animals with positive ELISA and fecal culture (FC) results. Controls were animals negative to both ELISA and FC tests that matched cases on birth date and herd. Validation data consisted of 180 animals including 90 cases (positive to FC) and 90 controls (negative to ELISA and FC), selected from discovery herds and genotyped by Illumina BovineLD BeadChip (∼7K SNPs). Two analytical approaches were used: single-marker GWAS using the GRAMMAR-GC method and Bayesian variable selection (Bayes C) using GenSel software. GRAMMAR-GC identified one SNP on BTA7 at 68 megabases (Mb) surpassing a significance threshold of 5×10⁻⁵. ARS-BFGL-NGS-11887 on BTA23 (27.7 Mb) accounted for the highest percentage of genetic variance (3.3%) in the Bayes C analysis. SNPs identified in common by GRAMMAR-GC and Bayes C in both discovery and combined data were mapped to BTA23 (27, 29 and 44 Mb), 3 (100, 101, 106 and 107 Mb) and 17 (57 Mb). Correspondence between results of GRAMMAR-GC and Bayes C was high (70–80% of most significant SNPs in common). These SNPs could potentially be associated with causal variants underlying susceptibility to MAP infection in Jersey cattle. Predictive performance of the model developed by Bayes C for prediction of infection status of animals in validation set was low (55% probability of correct ranking of paired case and control samples).

Experimental infection of lambs with C and S-type strains of Mycobacterium avium subspecies paratuberculosis: immunological and pathological findings

The two main genotypes of recognized isolates of Mycobacterium avium subsp. paratuberculosis (Map) are cattle (C) and sheep (S) strains. An experimental infection was conducted to establish the effect of Map strain on the pathogenesis of ovine paratuberculosis. Twenty-four out of thirty 1.5-month-old Assaf lambs were divided into 4 groups of 6 and infected orally with three low passage field isolates, two of S- (22G and the pigmented Ovicap49) and one of C– (764) type, and the reference K-10 strain (C type). The remaining six animals were unchallenged controls. Animals were euthanized at 150 and 390 days post-infection (dpi). Throughout the experiment, the peripheral immune response was assessed and histological and molecular (PCR) studies were conducted on samples of intestine and related lymphoid tissue. Specific antibody and IFN-γ production was significantly higher in animals infected with the C strains, while no consistent IFN- γ responses were observed in the S-type strain infected groups. A positive intradermal skin test response was detected in all infected groups. Lambs infected with S-type strains had granulomatous lesions restricted to the lymphoid tissue with no differences in the lesion intensity over time. In both C–type strain groups, lesions were more severe at 150 dpi while at 390 dpi lesions, characterized by well-demarcated granulomas with fibrosis, decreased in severity. Only infected lambs were positive to PCR. These results suggest that the strain of Map has a strong influence over the immune and pathological responses developed by the host. Lesions induced by C–type strains in lambs show a regressive character and tend to decrease as the infection progresses.

Detection of Antibodies and Confirmation of Mycobacterium avium Subspecies paratuberculosis Using Nested PCR in Bulk Milk Samples from Nakasongola and Sembabule Districts, Uganda

Mycobacterium avium subspecies paratuberculosis (MAP) is an emerging pathogen in many livestock and wildlife populations around the world. Concerns range from the serious economic impacts on livestock productivity to its suspected role in the human inflammatory bowel disease syndrome. Milk and faeces of infected animals are the main vehicles through which the organism spreads from infected to susceptible hosts. In this study, a survey was done in Nakasongola and Sembabule districts of Uganda involving a total of seven dairy collection centres to determine the prevalence of antibodies to MAP in bulk milk samples. The milk was tested with a commercial ELISA kit for MAP testing in milk. Positive and suspicious milk samples were further tested using nested PCR. Of the 257 milk samples tested, 11 (4.3%) were positive and five (1.9%) were suspicious. All the ELISA positive and suspicious milk samples were positive using nested PCR. The results show that MAP infection occurs in cattle from the two districts and highlight the need for a paratuberculosis control program in these and other districts where MAP infection has been reported.

Early weight development of goats experimentally infected with Mycobacterium avium subsp. paratuberculosis

Johne's disease is an infectious chronic inflammatory bowel disease in ruminants. The key factor for the management of this disease is an early positive diagnosis. Unfortunately, most diagnostics detect animals with Johne's disease in the clinical stage with positive serology and/or positive fecal cultures. However, for effective management of the disease within herds, it is important to detect infected animals as early as possible. This might only be possible with the help of parameters not specific for Johne's disease but that give an early indication for chronic infections such as weight development. Here we report our findings on the development of total body weight and weight gain during the first six months of goats experimentally infected to induce Johne's disease. Twenty dairy goat kids age 2 to 5 days were included in this study. Goats were divided into two groups: a negative control group and a positive infected group. The weight was obtained weekly throughout the study. Goats of the positive group were infected at the age of seven weeks. We detected significant changes in weight gain and total body weight as early as one week after infection. Differences are significant throughout the six month time period. Weight as a non-specific parameter should be used to monitor infection especially in studies on Johne's disease using the goat model. Our study suggests that goats with Johne's disease have a reduced weight gain and reduced weight when compared with healthy goats of the same age.

Antemortem and postmortem examinations of the cattle calf naturally infected with Mycobacterium avium subsp. paratuberculosis

A male cattle calf was detected as subclinically and naturally infected with Mycobacterium avium subspecies paratuberculosis (MAP) by a series of antemortem and postmortem tests. The MAP infection was identified by strong antibody and cell-mediated immune (CMI) response by a commercial ELISA kit and an intradermal Johnin test, respectively, in the initial antemortem examination. The antemortem status of the calf was further confirmed by MAP-specific interferon gamma (IFN-γ) response. For detection of IFN-γ response, MAP-specific IFN-γ release assays (IGRAs): (a) immuno capture ELISA (IC-ELISA) and (b) ELISPOT was employed. In addition, the presence of intracellular cytokine IFN-γ was detected by flow cytometry. For all cytokine assays, MAP-specific recombinant antigens HSP65 and 35 kDa were employed to overcome the poor sensitivity and specificity resulting from the use of Johnin, the crude protein purified derivative of MAP. Postmortem examination of the MAP-infected/suspected cattle calf did not reveal any pathognomonic gross lesions in the gastro-intestinal tract. Histopathological examination of multiple organs showed the presence of epithelioid cells/macrophages and edematous lesions in the mesenteric lymph nodes suggestive of MAP; however, no granulomas were observed in the intestinal tract. The necropsy samples of rectum and mesenteric lymph nodes were positive for isolation of MAP by culture in the BACTEC™ MGIT™ 960 system, and acid fast bacilli were demonstrated by fluorescence microscopy confirming the infection. Due to differential and complex expression patterns of MAP antigens reported in literature, a combination of assays such as those based on IGRAs and antibody detection is essential. Therefore, the current experimental evidence confirms the efficacy of the approach adopted. However, further studies will be needed to understand the optimal combination MAP-specific antigens for use in IGRAs or antibody assays that can be used for detecting MAP infection in every stage of the disease.

Host-Mycobacterium avium subsp. paratuberculosis interactome reveals a novel iron assimilation mechanism linked to nitric oxide stress during early infection

BACKGROUND

The initial interaction between host cell and pathogen sets the stage for the ensuing infection and ultimately determine the course of disease. However, there is limited knowledge of the transcripts utilized by host and pathogen and how they may impact one another during this critical step. The purpose of this study was to create a host-Mycobacterium avium subsp. paratuberculosis (MAP) interactome for early infection in an epithelium-macrophage co-culture system using RNA-seq.

RESULTS

Establishment of the host-MAP interactome revealed a novel iron assimilation system for carboxymycobactin. Iron assimilation is linked to nitric oxide synthase-2 production by the host and subsequent nitric oxide buildup. Iron limitation as well as nitric oxide is a prompt for MAP to enter into an iron sequestration program. This new iron sequestration program provides an explanation for mycobactin independence in some MAP strains grown in vitro as well as during infection within the host cell. Utilization of such a pathway is likely to aid MAP establishment and long-term survival within the host.

CONCLUSIONS

The host-MAP interactome identified a number of metabolic, DNA repair and virulence genes worthy for consideration as novel drug targets as well as future pathogenesis studies. Reported interactome data may also be utilized to conduct focused, hypothesis-driven research. Co-culture of uninfected bovine epithelial cells (MAC-T) and primary bovine macrophages creates a tolerant genotype as demonstrated by downregulation of inflammatory pathways. This co-culture system may serve as a model to investigate other bovine enteric pathogens.

Evaluation of age-dependent susceptibility in calves infected with two doses of Mycobacterium avium subspecies paratuberculosis using pathology and tissue culture

The longstanding assumption that calves of more than 6 months of age are more resistant to Mycobacterium avium subspecies paratuberculosis (MAP) infection has recently been challenged. In order to elucidate this, a challenge experiment was performed to evaluate age- and dose-dependent susceptibility to MAP infection in dairy calves. Fifty-six calves from MAP-negative dams were randomly allocated to 10 MAP challenge groups (5 animals per group) and a negative control group (6 calves). Calves were inoculated orally on 2 consecutive days at 5 ages: 2 weeks and 3, 6, 9 or 12 months. Within each age group 5 calves received either a high - or low - dose of 5 × 10⁹ CFU or 5 × 10⁷ CFU, respectively. All calves were euthanized at 17 months of age. Macroscopic and histological lesions were assessed and bacterial culture was done on numerous tissue samples. Within all 5 age groups, calves were successfully infected with either dose of MAP. Calves inoculated at < 6 months usually had more culture-positive tissue locations and higher histological lesion scores. Furthermore, those infected with a high dose had more severe scores for histologic and macroscopic lesions as well as more culture-positive tissue locations compared to calves infected with a low dose. In conclusion, calves to 1 year of age were susceptible to MAP infection and a high infection dose produced more severe lesions than a low dose.

Paratuberculosis in different breeds of sheep: A retrospective study of cases

Spontaneous ovine paratuberculosis in an organized farm was diagnosed based on histopathological lesions, demonstration of acid-fast bacilli in different visceral organs, and detection of antibody levels against Mycobacterium paratuberculosis by agar gel immunodiffusion test (AGID). Out of 190 morbid specimens examined histopathologically, 77% of specimens had pathological lesions, which included predominant epithelioid cell formation, infiltration of lymphocytes, monocytes and macrophages. In acid-fast staining of tissue sections, 74% of intestinal specimens and 53% of mesenteric lymph nodes were positive for the presence of acid-fast bacilli. Hematologically, the animals were showing leucopenia, macrocytic and normochromic anemia. Out of 49 animals tested, 28.5% of animals were positive for antibodies against M. paratuberculosis. Local breeds, namely Nilagiri and Sandyno sheep, were found to be more susceptible than exotic breeds, namely Dorset. Females were more susceptible than males. Mortality was noticed in the age group of 4months to 10years.

Evaluation of a Salmonella vectored vaccine expressing Mycobacterium avium subsp. paratuberculosis antigens against challenge in a goat model

Johnes disease (JD), caused by Mycobacterium avium subsp paratuberculosis (MAP), occurs worldwide as chronic granulomatous enteritis of domestic and wild ruminants. To develop a cost effective vaccine, in a previous study we constructed an attenuated Salmonella strain that expressed a fusion product made up of partial fragments of MAP antigens (Ag85A, Ag85B and SOD) that imparted protection against challenge in a mouse model. In the current study we evaluated the differential immune response and protective efficacy of the Sal-Ag vaccine against challenge in a goat model as compared to the live attenuated vaccine MAP316F. PBMCs from goats vaccinated with Sal-Ag and challenged with MAP generated significantly lower levels of IFN-γ, following in vitro stimulation with either Antigen-mix or PPD jhonin, than PBMC from MAP316F vaccinated animals. Flow cytometric analysis showed the increase in IFN-γ correlated with a significantly higher level of proliferation of CD4, CD8 and γδT cells and an increased expression of CD25 and CD45R0 in MAP316F vaccinated animals as compared to control animals. Evaluation of a range of cytokines involved in Th1, Th2, Treg, and Th17 immune responses by quantitative PCR showed low levels of expression of Th1 (IFN-γ, IL-2, IL-12) and proinflammatory cytokines (IL-6, IL-8, IL-18, TNF-α) in the Sal-Ag immunized group. Significant levels of Th2 and anti-inflammatory cytokines transcripts (IL-4, IL-10, IL-13, TGF-β) were expressed but their level was low and with a pattern similar to the control group. Over all, Sal-Ag vaccine imparted partial protection that limited colonization in tissues of some animals upon challenge with wild type MAP but not to the level achieved with MAP316F. In conclusion, the data indicates that Sal-Ag vaccine induced only a low level of protective immunity that failed to limit the colonization of MAP in infected animals. Hence the Sal-Ag vaccine needs further refinement to increase its efficacy.

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

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

Mycobacterium avium subspecies paratuberculosis is widely distributed in British soils and waters: implications for animal and human health

In the first comprehensive geographical survey of distribution in Great Britain, Mycobacterium avium ssp. paratuberculosis (MAP) was detected in 115 of 1092 (10.5%) soil cores, in the range of 5 × 10(2) to 3 × 10(6) MAP cell equivalents (CE) g(-1) wet weight soil with the majority of the positive PCR reactions (n = 75; 65%) occurring around the limit of detection (500-5000 CE g(-1) wet weight soil). The distribution of MAP significantly increased from North to South and was significantly correlated with increasing cattle numbers over the same longitudinal axis. Similarly MAP occurrence significantly increased towards easterly latitudes although none of the parameters measured were associated. Comparisons of land use indicated that MAP was widely distributed in both farming and non-farming areas. Soil core samples taken from the rivers Wyre and Douglas catchments (Lancashire, UK) and river Tywi (South Wales) were negative for MAP. However, river monitoring showed a consistent presence of MAPs throughout those catchments over a 6-month period. We concluded that MAP is widely distributed within and outside the confines of the farming environment; its geographical distribution is wider than originally anticipated and; monitoring rivers describes the MAP status of catchment better than individual soil samples.

Evaluation of a Mycobacterium avium subsp. paratuberculosis leuD mutant as a vaccine candidate against challenge in a caprine model

Johne's disease (JD) is prevalent worldwide and has a significant impact on the global agricultural economy. In the present study, we evaluated the protective efficacy of a leuD (Δleud) mutant and gained insight into differential immune responses after challenge with virulent M. avium subsp. paratuberculosis in a caprine colonization model. The immune response and protective efficacy were compared with those of the killed vaccine Mycopar. In vitro stimulation of peripheral blood mononuclear cells with johnin purified protein derivative showed that Mycopar and ΔleuD generated similar levels of gamma interferon (IFN-γ) but significantly higher levels than unvaccinated and challenged phosphate-buffered saline controls. However, only with ΔleuD was the IFN-γ response maintained. Flow cytometric analysis showed that the increase in IFN-γ correlated with proliferation and activation (increased expression of CD25) of CD4, CD8, and γδT cells, but this response was significantly higher in ΔleuD-vaccinated animals at some time points after challenge. Both Mycopar and ΔleuD vaccines upregulated Th1/proinflammatory and Th17 cytokines and downregulated Th2/anti-inflammatory and regulatory cytokines at similar levels at almost all time points. However, significantly higher levels of IFN-γ (at weeks 26 and 30), interleukin-2 (IL-2; week 18), IL-1b (weeks 14 and 22), IL-17 (weeks 18 and 22), and IL-23 (week 18) and a significantly lower level of IL-10 (weeks 14 and 18) and transforming growth factor β (week 18) were detected in the ΔleuD-vaccinated group. Most importantly, ΔleuD elicited an immune response that significantly limited colonization of tissues compared to Mycopar upon challenge with wild-type M. avium subsp. paratuberculosis. In conclusion, the ΔleuD mutant is a promising vaccine candidate for development of a live attenuated vaccine for JD in ruminants.

Comparison of a quantitative real-time polymerase chain reaction (qPCR) with conventional PCR, bacterial culture and ELISA for detection of Mycobacterium avium subsp. paratuberculosis infection in sheep showing pathology of Johne's disease

A quantitative real-time PCR (qPCR) assay employing IS900 gene specific primers of Mycobacterium avium subsp. parartuberculosis (MAP) was compared with conventional PCR, bacterial culture and enzyme-linked immunosorbent assay in 38 sheep showing granulomatous enteritis and lymphadenitis with and without demonstration of acid-fast bacilli (AFB). The lesions were classified as multibacillary (MB) (n = 23), which had diffuse granulomatous lesions with abundant AFB, and paucibacillary (PB) (n = 15), which had focal or multifocal granulomatous lesions with few or no AFB. In the multibacillary group (MB), IS900 PCR detected 19 (82.6%), and qPCR detected all 23 (100%) sheep positive for MAP in the intestine and lymph node tissues. In the paucibacillary group (PB), IS900 PCR detected 2 (13.3%), and qPCR detected all 15 (100%) sheep positive for MAP in tissues. When results of both groups were taken together, IS900 PCR detected 21(55.2%), and qPCR detected all 38 (100%) animals positive for MAP genome either in the intestine or lymph node tissues. On Herrold egg yolk medium, tissues of 14 (60.9%) MB and 5 (33.3%) PB sheep were found to be positive for MAP. Out of 27 sheep (PB = 8, MB = 19) tested by an ELISA, 21 (77.7%) were found to be positive for MAP antibody, of which 25% (2/8) and 100% (19/19) sheep were from PB and MB sheep, respectively. Based on the results of the present study, it was concluded that qPCR was a highly sensitive test in comparison to conventional PCR, ELISA and bacterial culture for the diagnosis of paratuberculosis on infected tissues especially from paucibacillary sheep.

Purification of native HBHA from Mycobacterium avium subsp. paratuberculosis

Background

Paratuberculosis remains today a major global problem in animal health, especially for dairy cattle. However, the diagnosis of its etiologic agent, Mycobacterium avium subsp. paratuberculosis (Map), still lacks sensitivity because of the lack of available antigens. Little is known about the virulence factors for this pathogen. In this study we have developed a method to produce and purify the heparin-binding hemagglutinin (HBHA), a major adhesin of Mycobacteria, from a culture of Map.

Findings

For this extremely slow-growing Mycobacterium, a culture was established in a 3-liter bioreactor. Using the bioreactor the amount of the Map biomass was increased 5-fold compared to a classical culture in flasks. The map-HBHA was purified from a Map lysate by heparin-Sepharose chromatography on HiTrap columns. Binding of map-HBHA onto heparin-Sepharose can be reduced in the presence of salt. Consequently, all steps of sample preparation and column equilibration were carried out in 20 mM Tris–HCl (pH 7.2). The map-HBHA was eluted by a linear NaCl gradient. High resolution mass spectrometry analyses revealed that the native form of map-HBHA has posttranslational modifications, including the removal of the initiation methionine, acetylation of the alanine residue at the N-terminal extremity and the presence of methylated lysines in the C-terminal domain of the protein.

Conclusions

An optimized culture of Map in a bioreactor was established to purify the native map-HBHA from a Map lysate by heparin-Sepharose chromatography. The availability of this antigen offers the possibility to study the structure of the protein and to examine its role in pathogenicity, in particular to better understand the specific interactions of Map with the intestinal tissue. The map-HBHA obtained in its native immunogenic form may also be useful to improve the diagnostic test, especially for the development of a new T-cell-based interferon gamma release assays.

Paratuberculose em ruminantes no Brasil

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

Host responses to persistent Mycobacterium avium subspecies paratuberculosis infection in surgically isolated bovine ileal segments

A lack of appropriate disease models has limited our understanding of the pathogenesis of persistent enteric infections with Mycobacterium avium subsp. paratuberculosis. A model was developed for the controlled delivery of a defined dose of M. avium subsp. paratuberculosis to surgically isolated ileal segments in newborn calves. The stable intestinal segments enabled the characterization of host responses to persistent M. avium subsp. paratuberculosis infections after a 9-month period, including an analysis of local mucosal immune responses relative to an adjacent uninfected intestinal compartment. M. avium subsp. paratuberculosis remained localized at the initial site of intestinal infection and was not detected by PCR in the mesenteric lymph node. M. avium subsp. paratuberculosis-specific T cell proliferative responses included both CD4 and γδ T cell receptor (γδTcR) T cell responses in the draining mesenteric lymph node. The levels of CD8(+) and γδTcR(+) T cells increased significantly (P < 0.05) in the lamina propria, and M. avium subsp. paratuberculosis-specific tumor necrosis factor alpha (TNF-α) and gamma interferon secretion by lamina propria leukocytes was also significantly (P < 0.05) increased. There was a significant (P < 0.05) accumulation of macrophages and dendritic cells (DCs) in the lamina propria, but the expression of mucosal toll-like receptors 1 through 10 was not significantly changed by M. avium subsp. paratuberculosis infection. In conclusion, surgically isolated ileal segments provided a model system for the establishment of a persistent and localized enteric M. avium subsp. paratuberculosis infection in cattle and facilitated the analysis of M. avium subsp. paratuberculosis-specific changes in mucosal leukocyte phenotype and function. The accumulation of DC subpopulations in the lamina propria suggests that further investigation of mucosal DCs may provide insight into host responses to M. avium subsp. paratuberculosis infection and improve vaccine strategies to prevent M. avium subsp. paratuberculosis infection.

Free-ranging Rocky Mountain bighorn sheep and an outbreak of inflammatory bowel disease along the Clark Fork River in Plains, Montana

Nine individuals with ulcerative colitis or Crohn disease grew up or lived in Plains, Montana, a 1,200-person community adjacent to the Clark Fork River near herds of free ranging Rocky Mountain bighorn sheep. This inflammatory bowel disease outbreak is similar to others that have occurred along rivers contaminated by animal feces.

Alteration of GI symptoms in a cow with Johne disease by the dietary organosulfur, 2-mercaptoethanol

Sub-phenotypes of inflammatory bowel disease (IBD)-Crohn disease, ulcerative colitis and some cases of irritable bowel syndrome-are generally considered a consequence of gastrointestinal inflammation of unknown etiology. Conventional therapy and more recently biologic agents, all with varying degrees of drawbacks, have resulted in improved control of these diseases. However, as the incidence and prevalence continue to rise, needs for prevention, permanent remission and cures remain unmet, plus there still remain needs for improved control of symptoms, such as pain and diarrhea. The case report herein describes a serendipitous, novel means for curtailing these symptoms associated with a bovine gastrointestinal disease that may have applicability for patients with diseases characterized by abdominal-visceral pain and diarrhea.

Immune response and protective efficacy of live attenuated Salmonella vaccine expressing antigens of Mycobacterium avium subsp. paratuberculosis against challenge in mice

Mycobacterium avium subsp. paratuberculosis (MAP) causes chronic granulomatous enteritis in ruminants that leads to diarrhea and eventually death. Existing vaccines have proven useful in limiting disease progression but have not been effective in preventing infection. To address this problem we constructed an attenuated Salmonella (ΔyejE; ΔssaV) strain harboring a plasmid that expressed a fusion protein comprised of the Salmonella Type III secretion system (T3SS) effector SopE and MAP antigens (85A, 85B, SOD, 74F) and evaluated its potential as vaccine candidate against MAP infection in mice. Of various SopE-MAP fusion proteins analyzed, only SopE104-Ag85A C-terminal(202-347)-SOD N-terminal(1-72)-Ag85B C-terminal(173-330) and SopE104-74F(1-148+669-786)were successfully expressed and secreted into culture media as revealed by western blot analysis. Mice immunized with attenuated Salmonella (ΔyejE; ΔssaV) harboring the SopE104-Ag85A C-terminal(202-347)-SOD N-terminal(1-72)-Ag85B C-terminal(173-330) and SopE104-74F(1-148+669-786)plasmid generated a potent and long lasting Th1 response characterized by production of IFN-γ. The cytokine profile varied at various time points after immunization and challenge, which showed down regulation of Th2 cytokines (IL-4, IL-10) and up-regulation of proinflammatory cytokines (IL-12 and IL-17). Further, the immune response correlated with protection as revealed by reduced bacterial load and improved histopathology of spleen and liver, which showed fewer granulomas and lower numbers of acid-fast bacilli as compared to PBS controls. Interestingly, vaccination with antigens mixed with Ribi adjuvant (Agmix+Ribi) imparted better protection than the attenuated salmonella vectored vaccine. Thus, priming with a live recombinant Salmonella strain that secretes MAP antigens represents a promising approach that could lead to development of an efficacious and cost effective vaccine for Johne's disease.

Paratuberculose em pequenos ruminantes domésticos

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

Expression of sheep interleukin 23 (IL23A, alpha subunit p19) in two distinct gastrointestinal diseases

This paper reports the sequence of sheep interleukin 23A (p19), and shows that it shares 98% identity with bovine IL23A, 85% with human and 76% with mouse IL23A. It also reports the existence of two allelic variants that differ largely within the region encoding the amino terminal polypeptide signal sequence. An optimized RT-qPCR assay was used to quantify IL23A transcripts in sheep infected with two common gastrointestinal pathogens, the intracellular bacterium Mycobacterium avium subspecies paratuberculosis and the parasitic nematode Teladorsagia circumcincta. No differential expression of IL23A was detected in the mesenteric lymph node of sheep with the different pathogenic forms of paratuberculosis, however significantly high levels of IL23A were detected in the ileal mucosa of the paucibacillary form in comparison with the asymptomatic or multibacillary forms. Similarly, significantly high levels were present in the gastric lymph node draining T. circumcincta-infected abomasum in susceptible sheep. High levels of IL23A seem to be associated with lymphocytic infiltration and inflammation in both diseases but not with the macrophage infiltrate of multibacillary paratuberculosis.

Frequência de anticorpos para paratuberculose em bovinos no semiarido paraíbano

A paratuberculose é uma doença importante em bovinos na Paraíba, tendo sido diagnosticados, pelo Hospital Veterinário da Universidade Federal de Campina Grande, cinco focos da doença nos últimos quatro anos. Neste trabalho objetivou-se realizar um estudo sorológico em rebanhos com e sem histórico da doença para estimar a frequência da infecção por Mycobacterium avium subsp. paratuberculosis (Map) em diferentes regiões do semiárido Paraibano. Utilizando o teste de ELISA pesquisou-se a frequência de animais soropositivos contra Map em duas fazendas onde tinha sido diagnosticada a doença, encontrando-se 72,22% (13/18) e 68,75% (11/16), respectivamente de bovinos sorologicamente positivos. Amostras de soro de 486 bovinos de 36 fazendas sem histórico da doença de diferentes regiões da Paraíba (sertão, cariri e agreste), também foram examinados por ELISA. A frequência de animais soropositivos foi de 10,08±1,07% (49/486). Foram encontrados animais positivos em 21 (58.33%) das 36 fazendas estudadas. Os resultados sugerem que o agente da paratuberculose está disseminado em bovinos na Paraíba e que são necessárias medidas de controle para diminuir a frequência de casos clínicos e subclínicos da doença.

Immune responses associated with progression and control of infection in calves experimentally challenged with Mycobacterium avium subsp. paratuberculosis

This study examined the immune responses related to the infection, progression and control of Mycobacterium avium subsp. paratuberculosis (MAP) infection in calves. Twenty calves were challenged orally with MAP and 11 non-challenged calves served as controls. Approximately half the calves from each group were sacrificed at either 7 or 15 months post-challenge (PC). The majority of the challenged calves (19/20) shed MAP in feces 2-4 months PC, but thereafter fecal shedding reduced markedly. The severity of infection was reduced at 15 months PC compared to that at 7 months PC as seen from a significantly lower isolation of MAP from tissues and lower lesion scores (P<0.05). In addition, there was a reduction in the upregulation of gene expression of gamma interferon, interleukin-10 (IL-10) and inducible nitric oxide synthase from the antigen-stimulated mesenteric lymph node (MLN) cultures of the challenged calves. No evidence of infection was detected in the control calves. The severity of the infection in individual calves at 15 months PC as indicated from the number of tissue culture positive sites, was negatively related to IL-10 released from antigen-stimulated peripheral blood mononuclear cells (P<0.05). Collectively the data indicated that the severity of the MAP infection was reduced in the calves at 15 months PC and in a specific time period during infection, IL-10 may play a role in reducing the severity of this disease.

Transmission of Mycobacterium avium subsp. paratuberculosis: dose-response and age-based susceptibility in a sheep model

Factors which influence the transmission of Mycobacterium avium subsp. paratuberculosis (MAP) between susceptible hosts are poorly defined, despite this organism causing economically significant disease in ruminants worldwide. A randomised longitudinal field trial was conducted using natural pasture-based exposure of 840 Merino sheep in a factorial design to test infection and disease outcomes in relation to age at first exposure and the level of exposure to MAP. Pasture contamination was initiated by MAP infected "donor" sheep which were present for 14.5 weeks of the 2.5 year study period. Sheep exposed to higher doses had 3.5 times greater odds to shed MAP in their faeces (assessed by faecal culture) compared to animals exposed to lower doses of infection. Similarly, sheep exposed to MAP as lambs had 7 times higher odds to shed MAP compared to sheep that were exposed for the first time as adults. However, animals of all ages and exposed at all doses were equally likely to be colonised by MAP (measured by culture of intestinal tissues) suggesting that some animals are inherently susceptible to infection. Age at first exposure was a significant determinant of histopathological lesion development, as lambs had about three times higher odds of developing severe lesions than adults after equivalent time (P=0.026). Mortalities due to paratuberculosis were strongly determined by the level of exposure; sheep exposed to high doses had 18 fold higher odds of death (P=0.007). Sheep exposed as lambs had 5 fold higher odds of dying due to paratuberculosis than adults (P=0.046). The results of this study provide sound experimental evidence for management recommendations in extensively grazed livestock to reduce the transmission of MAP by limiting exposure of young animals and reducing the levels of MAP pasture contamination.

Isolation of Mycobacterium avium subspecies paratuberculosis from Ugandan cattle and strain differentiation using optimised DNA typing techniques

Background

The occurrence of paratuberculosis in Ugandan cattle has recently been reported but there is no information on the strains of Mycobacterium avium subspecies paratuberculosis (MAP) responsible for the disease. The aim of this study was to isolate and characterise MAP from seropositive cattle and paratuberculosis lesions in tissues obtained from slaughtered cattle in Uganda.

Results

Twenty one isolates of MAP were differentiated into 11 genotype profiles using seven genotyping loci consisting of Insertion Sequence 1311(IS1311), Mycobacterial interspersed repeat units (MIRU) (loci 2, 3), Variable number tandem repeats (VNTR) locus 32 and Short sequence repeats (SSR) (loci 1, 2 and 8). Three different IS1311 types and three MIRU 2 profiles (7, 9, 15 repeats) were observed. Two allelic variants were found based on MIRU 3 (1, 5 repeats), while VNTR 32 showed no polymorphism in any of the isolates from which it was successfully amplified. SSR Locus 1 revealed 6 and 7 G1 repeats among the isolates whereas SSR locus 2 revealed 10, 11 and 12 G2 repeats. SSR locus 8 was the most polymorphic locus. Phylogenetic analysis of SSR locus 8 sequences based on their single nucleotide polymorphisms separated the isolates into 8 genotypes. We found that the use of Ethylene glycol as a PCR additive improved the efficiency of the PCR reactions for MIRUs (2, 3), VNTR 32 and SSR (loci 1 and 2).

Conclusions

There is a high strain diversity of MAP in Uganda since 21 isolates could be classified into 11 genotypes. The combination of the seven loci used in this study results into a very precise discrimination of isolates. However analysis of SNPs on locus alone 8 is very close to this combination. Most of the genotypes in this study are novel since they differed in one or more loci from other isolates of cattle origin in different studies. The large number of MAP strains within a relatively small area of the country implies that the epidemiology of paratuberculosis in Uganda may be complicated and needs further investigation. Finally, the use of Ethylene glycol as a PCR additive increases the efficiency of PCR amplification of difficult templates.

Genome-wide analysis of the emerging infection with Mycobacterium avium subspecies paratuberculosis in the Arabian camels (Camelus dromedarius)

Mycobacterium avium subspecies paratuberculosis (M. ap) is the causative agent of paratuberculosis or Johne's disease (JD) in herbivores with potential involvement in cases of Crohn's disease in humans. JD is spread worldwide and is economically important for both beef and dairy industries. Generally, pathogenic ovine strains (M. ap-S) are mainly found in sheep while bovine strains (M. ap-C) infect other ruminants (e.g. cattle, goat, deer), as well as sheep. In an effort to characterize this emerging infection in dromedary/Arabian camels, we successfully cultured M. ap from several samples collected from infected camels suffering from chronic, intermittent diarrhea suggestive of JD. Gene-based typing of isolates indicated that all isolates belong to sheep lineage of strains of M. ap (M. ap-S), suggesting a putative transmission from infected sheep herds. Screening sheep and goat herds associated with camels identified the circulation of this type in sheep but not goats. The current genome-wide analysis recognizes these camel isolates as a sub-lineage of the sheep strain with a significant number of single nucleotide polymorphisms (SNPs) between sheep and camel isolates (∼1000 SNPs). Such polymorphism could represent geographical differences among isolates or host adaptation of M. ap during camel infection. To our knowledge, this is the first attempt to examine the genomic basis of this emerging infection in camels with implications on the evolution of this important pathogen. The sequenced genomes of M. ap isolates from camels will further assist our efforts to understand JD pathogenesis and the dynamic of disease transmission across animal species.