Comparison of radiographic scoring systems for assessment of bone healing after tibial plateau leveling osteotomy in dogs.

Introduction: Accurate radiographic assessment of bone healing is vital in determining both clinical treatment and for assessing interventions aimed at the promotion of bone healing. Several scoring systems have been used to evaluate osteotomy changes following tibial plateau leveling osteotomy (TPLO). The goal of this study was to compare the ability of five radiographic scoring systems to identify changes in bone healing following TPLO over time (Aim I), and to evaluate the influence of limb positioning on TPLO osteotomy scoring (Aim II). Materials and methods: Phase I-A randomized, blinded, prospective study was conducted using similarly positioned postoperative TPLO radiographs from seven dogs taken immediately postoperatively, 6-weeks, and 8-weeks postoperatively. Ten reviewers assessed the radiographs, and five different scoring systems were tested for each set including three previously published ones, a Visual Analog Score (VAS), and a subjective 11-point scale. For each system, responses for 6-week postoperative were compared to 8-week postoperative. Scores were judged as correct (=showing an increase in score), incorrect (=decrease in score), or unchanged (=same score). Phase II-An international group of 39 reviewers was asked to score radiographs from three dogs, taken in different positions, using the VAS grading system. Scores were averaged and comparisons were made for each set. Results: Phase I-The VAS system identified the greatest number of sets correctly (76%), with the least unchanged scores (15%), and 9% incorrect scores. Phase II-All three patients had an increase in the average difference between VAS-scores for differently positioned radiographs compared to similarly positioned radiographs. The magnitude of change between different positions far exceeded the magnitude of comparison of the similarly positioned radiographs from the 6- and 8-week time point. Discussion/Conclusion: The VAS system appears to be the most appropriate of the tested systems to identify small changes in bone healing. In addition, the positioning of postoperative TPLO radiographs makes a substantial difference in the healing score that is assigned. Care must be undertaken when performing postoperative radiographs in both the clinical and research setting to ensure accurate assessment of bone healing.

Ultrasonographic and CT accuracy in localising surgical- or necropsy- confirmed solitary hepatic masses in dogs.

OBJECTIVES: To estimate the sensitivity and specificity of ultrasound and CT for localising solitary hepatic masses to particular liver divisions. MATERIALS AND METHODS: Dogs diagnosed with a solitary liver mass by ultrasound and/or CT, with surgical or necropsy confirmation within 1 month of imaging. Ultrasound reports were reviewed for mass location. CT scans were reviewed by two radiologists and mass location was determined by consensus agreement. Sensitivity and specificity were calculated for ultrasound and CT for each liver division. RESULTS: Fourteen of 71 dogs had CT only, 27 of 71 had ultrasound only and 30 of 71 had both. Location was correctly predicted in 42 of 57 dogs (74%) by ultrasound and in 37 of 44 dogs (84%) by CT. Both CT and ultrasound had high specificity for localising masses in all divisions. Sensitivity varied among divisions and was highest for left division masses. CLINICAL SIGNIFICANCE: The results suggest that either imaging modality is appropriate for presurgical planning. Prospective studies are recommended to help identify additional factors that may aid in determination of hepatic mass location.

Tissue classification in a canine model of Duchenne Muscular Dystrophy using quantitative MRI parameters.

Duchenne Muscular Dystrophy (DMD) is a genetic disorder caused by dystrophin protein deficiency. Muscle biopsy is the gold standard to determine the disease severity and progression. MRI has shown potential for monitoring disease progression or assessing the treatment effectiveness. In this study, multiple quantitative MRI parameters were used to classify the tissue components in a canine model of DMD disease using histoimmunochemistry analysis as a "ground truth". Results show that multiple MRI parameters may be used to reliably classify the muscular tissue and generate a high-resolution tissue type maps, which can be used as potential non-invasive imaging biomarkers for the DMD.

Putative Cerebral Microbleeds in Dogs Undergoing Magnetic Resonance Imaging of the Head: A Retrospective Study of Demographics, Clinical Associations, and Relationship to Case Outcome.

BACKGROUND: Cerebral microbleeds (CMBs) are focal intraparenchymal signal voids on gradient-echo magnetic resonance imaging (MRI), corresponding to regions of chronic hemorrhage. In humans, they are associated with systemic disease and shorter survival times. Although similar findings have been identified in dogs, their epidemiology and clinical correlations have not been investigated. OBJECTIVE: To determine epidemiological features, clinical associations, and associations with outcome for putative CMB-like foci (putative microbleeds [pMBs]) identified by T2*-weighted MRI in dogs. ANIMALS: Five hundred and eighty-two dogs undergoing 3T brain MRI between 2011 and 2016. METHODS: Retrospective case-control study. Demographic, diagnostic, and clinicopathological data were obtained from medical records and phone follow-up. Demographic variables were compared between dogs with and without evidence of pMBs. For dogs with such evidence, and a subset of matched controls, associations with clinical presentation, concurrent disease, and survival times were evaluated. RESULTS: Dogs with pMBs were older (P < .001) and smaller (P = .004) than unaffected dogs. Compared to matched controls, they presented more frequently for vestibular signs (P = .030). Cortical atrophy occurred concurrently with pMBs in 26% (14/54) of dogs. Diagnosed renal disease was not significantly associated with pMBs, but proteinuria was more common in dogs with pMBs than in matched controls (odds ratio = 3.01, P = .005). Dogs with pMBs had a shorter median survival time than did matched controls (P = .011). CONCLUSIONS AND CLINICAL IMPORTANCE: Putative microbleeds occurred in 54 of 582 (9.3%) of dogs undergoing brain MRI, but may not be a normal consequence of aging. They were associated with shorter survival time and proteinuria in the study population.

SOLiD SAGE sequencing shows differential gene expression in jejunal lymph node samples of resistant and susceptible red deer (Cervus elaphus) challenged with Mycobacterium avium subsp. paratuberculosis.

This study compared in vivo lymph node gene expression levels between six young red deer that were either relatively resistant (R) or susceptible (S) to paratuberculosis following experimental challenge with Mycobacterium avium subsp. paratuberculosis. Intestinal lymph nodes were biopsied at 4, 12 and 50 weeks post challenge (pc) and parallel changes in histopathology, immunology and bacterial load monitored. SOLiD SAGE (serial analysis of gene expression) next generation sequencing of biopsied lymph node samples generated a total of 373 million transcript tags 26-28bp in length after filtering. A total of 36,632 unique transcripts were identified and 14,325 of these were able to be annotated. The copy number of each transcript was counted, averaged and compared for R and S animals (R-S). P values and False Discovery Rates (FDR) were calculated for each transcript. Genes differentially upregulated ≥2 fold (FDR<0.5) totalled 9, 40 and 32 in R animals (+ values) and 23, 164 and 47 in S animals (- values) at weeks 4, 12, and 50pc, respectively. Transcripts displaying greatest differential expression between R and S animals at each time point were IFIT2 (189 fold) and S100A8 (-32.7 fold) at week 4, LRR1 (52.7 fold), SERPINF2 (-214.6 fold) at week 12 and CEACAM8 (84.6 fold), and STK31 (-129.5 fold) at week 50, respectively. All 9 genes significantly upregulated at week 4 in R animals relate specifically to host defence and all involve Type I interferon stimulated genes. By contrast genes upregulated in S animals at week 4, relate predominantly to inflammation, but also involve adaptive immune responses, mitochondrial function and apoptosis regulation. At week 12, the genes differentially upregulated in R animals are linked predominantly to regulation of adaptive immunity and mucosal immunity, while many of the genes in S animals are associated with pro-inflammatory interleukins involved with innate and adaptive immunity. These correlated with greater lesion severity and higher MAP numbers in lymph nodes of S animals. By week 50 the number of upregulated genes declined in both groups. A number of genes upregulated in R animals appear to be associated with host resistance and regulation of adaptive immunity, especially CEACAM8. Genes upregulated in S animals involve antigen presentation (ENDOD1) and gut associated immune pathology (HSH2D). In conclusion, gene expression in jejunal lymph nodes of resistant and susceptible deer infer that the resistant phenotype is associated with pathways of adaptive immunity, while susceptibility is linked with upregulated non-protective pro-inflammatory responses, following experimental MAP infection.

Localized MRI and histological image correlation in a canine model of duchenne muscular dystrophy.

Duchenne Muscular Dystrophy (DMD) is a fatal X-linked disorder. Therapeutic assessments currently require muscle biopsy to ascertain information about the status of disease progression. MRI shows potential to be used in place of muscle biopsy for therapeutic assessments. In this work, localized histological data and various MRI parameters were correlated in a canine model of DMD. The results indicate several MRI parameters may be useful as biomarkers of disease progression.

Quantitative magnetic resonance imaging in a naturally occurring canine model of spinal cord injury.

STUDY DESIGN: Retrospective cohort study. OBJECTIVES: To analyze magnetic resonance imaging (MRI) evaluator agreement in dogs with spinal cord injury (SCI) caused by intervertebral disk herniation (IVDH) using semiautomated and manual lesion segmentation and to analyze the associations between MRI and functional outcome. SETTING: United States of America. METHODS: T2-weighted MRIs from dogs with SCI resulting from thoracolumbar IVDH were identified from a database. Evaluators categorized MRIs on the basis of the presence or absence of a T2-hyperintense spinal cord lesion in axial and sagittal images. A semiautomated segmentation algorithm was developed and used to estimate the lesion volume. Agreement between evaluators and between semiautomated and manual segmentation was analyzed. The relationships of qualitative and quantitative MRIs with behavioral functional outcome were analyzed. RESULTS: Axial images more commonly depicted lesions compared with sagittal images. Lesions in axial images had more consistent associations with functional outcome compared with sagittal images. There was imperfect qualitative agreement, and lesion volume estimation was imprecise. However, there was improved precision using semiautomated segmentation compared with manual segmentation. CONCLUSION: Lesion volume estimation in dogs with naturally occurring SCI caused by IVDH is challenging, and axial images have important advantages compared with sagittal images. The semiautomated segmentation algorithm described herein shows promise but may require further refinement.

Epidemiology, diagnostics, and management of tuberculosis in domestic cattle and deer in New Zealand in the face of a wildlife reservoir.

The control of tuberculosis (TB) in cattle and farmed deer in New Zealand has been greatly influenced by the existence of a wildlife reservoir of Mycobacterium bovis infection, principally the Australian brushtail possum (Trichosurus vulpecula). The reduction in possum numbers in areas with endemic M. bovis infection through vigorous vector control operations has been a major contributor to the marked reduction in the number of infected cattle and farmed deer herds in the past two decades. Management of TB in cattle and farmed deer in New Zealand has involved a combination of vector control, regionalisation of diagnostic testing of cattle and deer herds, abattoir surveillance and movement control from vector risk areas. Accurate diagnosis of infected cattle and deer has been a crucial component in the control programme. As the control programme has evolved, test requirements have changed and new tests have been introduced or test interpretations modified. Subspecific strain typing of M. bovis isolates has proved to be a valuable component in the epidemiological investigation of herd breakdowns to identify whether the source of infection was domestic livestock or wildlife. New initiatives will include the use of improved models for analysing diagnostic test data and characterising disease outbreaks leading to faster elimination of infection from herds. The introduction of the National Animal Identification Tracing programme will allow better risk profiling of individual herds and more reliable tracing of animal movements. TB in cattle and farmed deer in New Zealand can only be controlled by eliminating the disease in both domestic livestock and the wildlife reservoir.

Lymphocytic ganglioneuritis secondary to intervertebral disc extrusion in a dog.

This study presents a case of lymphocytic ganglioneuritis in a dog secondary to intervertebral disc extrusion that mimicked a peripheral nerve sheath tumour on magnetic resonance imaging. A four-year-old spayed female dachshund with lumbar pain was imaged via magnetic resonance. A tubular, space-occupying, contrast-enhancing lesion was noted in the right intervertebral foramen at L6 to L7. This was presumed to represent focal enlargement of the right sixth lumbar spinal nerve. A right-sided haemilaminectomy was performed at L6 to L7 and material that grossly resembled extruded nucleus pulposus was removed. The right L6 dorsal root ganglion, dorsal nerve root and proximal spinal nerve were severely enlarged and a partial thickness biopsy was collected from the dorsal root ganglion. Results of histopathological examination of the submitted tissue samples were consistent with extruded disc material and lymphocytic ganglioneuritis. To the author's knowledge, this is the first published report of lymphocytic ganglioneuritis secondary to intervertebral disc disease in a dog.

Immunological and pathological responses of red deer resistant or susceptible genotypes, to experimental challenge with Mycobacterium avium subsp. paratuberculosis.

This study aimed to monitor the clinical, immunological and pathological changes in red deer for 49 weeks after experimental oral challenge with Mycobacterium avium subsp. paratuberculosis (MAP) and to assess the heritability of resistance in the offspring of two red stags. Eighteen young deer, which were bred from unselected hinds and sired by two stags resistant (R) or susceptible (S) to paratuberculosis, were challenged with MAP and monitored for 49 weeks. Biopsy samples of the jejunal lymph node were collected at Weeks 4 and 13 and at necropsy after euthanasia of clinically affected animals or when electively killed at Week 49. Three animals (two S and one R) developed clinical disease and were euthanised. The nine S offspring had significantly more severe lesions than the nine R offspring (Mantel-Haenszel Chi-square P=0.017). The average Lesion Severity Score (LSS) of R offspring was 5.9 (mild), and 7/9 had no or very mild lesions. In contrast, the LSS of S offspring averaged 11.7 (severe), and 7/9 had severe lesions. Most of the resistant, but not the susceptible, animals showed evidence of resolving lesions and a reduction in the number of MAP between 13 and 49 weeks after challenge. One R offspring appeared to completely cure itself, and progressed from mild culture-positive paratuberculosis lesions at Week 13 to having no signs of disease or infection 36 weeks later. This study showed significant heritable resistance/susceptibility to paratuberculosis and key differences in immunological responses in the first 3 months after challenge, indicating different paths to relative success or failure to control MAP. In general, R deer had higher IFN-γ levels, low antibody titres and fewer MAP, while S deer had lower IFN-γ levels, higher antibody and more MAP.

Immunoregulatory cytokines are associated with protection from immunopathology following Mycobacterium avium subspecies paratuberculosis infection in red deer.

Although the causative agent of Johne's disease, Mycobacterium avium subsp. paratuberculosis, is well known, the etiology of disease and the immune responses generated in response to infection are still poorly understood. Knowledge of definitive markers of protective immunity, infection, and the establishment of chronic granulomatous Johne's disease is necessary to advance vaccine and diagnostic development. We sought to profile the immune responses occurring within jejunal lymph nodes of experimentally challenged red deer (Cervus elaphus). Quantitative PCR was utilized to measure a range of cytokines, signaling molecules, and transcription factors involved in Th1, Th2, Treg, and Th17 immune responses. Significant differences in gene expression were observed between control, minimally diseased, and severely diseased animals, with severely diseased animals showing elevated proinflammatory transcripts and reduced anti-inflammatory transcripts. We identified a proinflammatory cytokine milieu of gamma interferon, interleukin-1α (IL-1α), and IL-17, which may contribute to the immunopathology observed during clinical Johne's disease and suggest that Th2 and Treg immune responses may play an important role in controlling the development of immunopathology in infected animals.

Johne's disease caused by Mycobacterium avium subsp. paratuberculosis infection in red deer (Cervus elaphus): an histopathological grading system, and comparison of paucibacillary and multibacillary disease.

AIM: To describe a grading system for evaluating lesions in the small intestine and mesenteric lymph nodes of red deer (Cervus elaphus) infected with Mycobacterium avium subsp. paratuberculosis (MAP), and report the distribution of granulomas and findings seen in paucibacillary and multibacillary forms of the disease. METHODS: Tissues were examined from red deer either experimentally (n=300) or naturally (n=131) infected with MAP. A disease severity score developed previously was expanded to help provide more sensitivity in assessing severity of disease. The distribution of granulomatous, paucibacillary and multibacillary lesions in sections of jejunum, ileocaecal valve and mesenteric lymph nodes was compared between sites and between animals with mild (severity score< or =7) and severe (severity score> or =8) forms of the disease. RESULTS: Based on the results of three published studies, the severity score related well with the clinical severity and gross lesions associated with the disease. Paucibacillary lesions tended to have smaller macrophages and increased numbers of Langhan's giant cells than multibacillary forms, but this was not a consistent finding. The multibacillary form of the disease had Langhan's giant cells, containing numerous acid-fast organisms (AFO), and in one form sheets of epithelioid-like macrophages with prominent vacuolated cytoplasm and few Langhan's giant cells. In deer experimentally infected with MAP, granulomatous lesions were more evident in mesenteric lymph nodes than in intestinal tissue, especially in the mild form of the disease. In mild cases, granulomas were significantly more evident in Peyer's patches than in the intestinal mucosa, but in severe cases, the difference was not significant. Paucibacillary forms of the disease were more evident in deer with the mild disease, and multibacillary forms were more evident in deer with the severe disease. CONCLUSIONS: The severity score provides an objective measure of the severity of Johne's disease, and is useful for comparing individuals and groups of deer in studies involving experimental or natural infection with MAP. In mild disease, lesions were more evident in mesenteric lymph nodes than in jejunum and ileocaecal tissue, and Langhan's giant cells were present in both paucibacillary and multibacillary forms of the disease. The posterior jejunum and ileocaecal-valve lymph nodes were the best sites for detecting mild lesions, while intestinal samples from the posterior jejunum and ileocaecal valve had a lesser but useful role.

Evidence of Mycobacterium avium subsp. paratuberculosis infection in Dutch farmed red deer.

Paratuberculosis is a chronic disease in ruminants caused by Mycobacterium avium subsp. paratuberculosis (MAP). Most economic losses due to MAP occur in the dairy industry. However, the infection is not restricted to cattle, but also occurs in other ruminants, such as sheep, goat, and deer. Although deer are of minimal economic importance in The Netherlands, they may constitute a source of infection for the dairy industry. This pilot study was conducted to estimate the prevalence of Johne's disease in farmed red deer in The Netherlands. Serum and faecal samples were collected from 140 animals, originating from 8 different farms. Four of the farms had animals that tested positive for Johne's disease. The within-herd MAP seroprevalence varied between 4.8% and 21.2%. In conclusion, this pilot study provides evidence of MAP infection in the Dutch farmed deer population, and thus there might be a risk of MAP transmission between farmed red deer and dairy cattle.

Age susceptibility of red deer (Cervus elaphus) to paratuberculosis.

The aim of this study was to measure the relative susceptibility of three age classes of red deer (Cervus elaphus) to the various manifestations of infection and disease states due to Mycobacterium avium subsp. paratuberculosis (MAP) after experimental oral challenge. Three groups of seronegative female deer (30 three-month-old weaners, 20 fifteen-month-old yearlings and 20 adults) received four oral doses of approximately 10(9) colony forming units (cfu) of a bovine strain of MAP. They were monitored for 50 weeks by weighing, blood sampling for immunological assays, skin testing and faecal culturing. Clinically affected animals were promptly euthanised and the remaining deer were killed at the end of the study. Necropsies were carried out and samples of intestine and associated lymph nodes were taken for culture and histopathology from all deer. Ten weaners developed clinical paratuberculosis and were euthanased 20-28 weeks post-challenge (pc). No clinical cases occurred in the yearlings or adults. All 10 clinically affected weaners had severe gross and histopathological lesions typical of paratuberculosis (Johne's disease). At slaughter, gross lesions were seen in the jejunal lymph nodes of 8/17 weaners, 2/19 yearlings, and 0/20 adults. MAP was cultured from samples of the intestine and/or lymph nodes from all 10 clinical cases and from 16/17 weaners, 19/19 yearlings and 18/20 adult hinds at slaughter. Lesion Severity Scores of deer slaughtered 50 weeks pc averaged 4.9, 3.5 and 1.1 for the weaner, yearling and adult groups, respectively. At some time over the course of the trial, 24/28 weaners were antibody positive and immediately prior to slaughter, 13/17 weaners, 15/19 yearlings and 3/20 hinds were antibody positive. There is a strong age-related resistance against clinical disease and subclinical disease, but not to infection with MAP, after heavy oral challenge.

Meningomyelitis in dogs: a retrospective review of 28 cases (1999 to 2007).

OBJECTIVES: To characterise dogs with meningomyelitis and to compare signalment, body temperature and vaccination status to a representative control group. METHODS: Dogs with meningomyelitis were identified retrospectively. Signalment, history, vaccination status, body temperature, severity of neurological dysfunction (modified Frankel score), diagnostic procedures, aetiology, survival to discharge and long-term survival were analysed. RESULTS: Affected dogs were younger (P<0.05) and more frequently hound or toy breeds (P<0.05) when compared with controls. Hound and toy breed dogs less than or equal to three years of age had a 13 times higher odds of meningomyelitis compared with other breeds (P<0.001). General proprioceptive ataxia, limb paresis and paraspinal hyperaesthesia were the most common clinical signs. Meningomyelitis of unknown aetiology and granulomatous meningomyelitis were the most common diagnoses. The median time to death or continued follow-up in dogs alive at discharge was 213 days. Meningomyelitis resulted in death or euthanasia in 14 of 28 dogs. Clinical signs improved or resolved in seven of 28 dogs. CLINICAL SIGNIFICANCE: Meningomyelitis is a differential diagnosis for dogs with clinical signs of myelopathy. Young dogs and toy or hound breeds seem to be predisposed. Clinical signs of meningomyelitis improve or resolve in some dogs.

Efficacy, immune responses and side-effects of vaccines against Johne's disease in young red deer (Cervus elaphus) experimentally challenged with Mycobacterium avium subsp paratuberculosis.

AIMS: To test the efficacy of a commercially available and an experimental vaccine against Johne's disease in young red deer (Cervus elaphus), using experimental challenge with live virulent Mycobacterium avium subsp paratuberculosis (M. ptb), measure injection-site reactions, and assess the effects of vaccination and challenge on results of subsequent skin tests and ancillary blood tests for bovine tuberculosis (Tb). METHODS: Ninety 6-8-week-old red deer fawns were randomly allocated to three equal groups of 30, and received either a 1-ml S/C injection of either a commercially available whole-cell killed vaccine with a mineral-oil adjuvant (COM), or a live attenuated M. ptb experimental vaccine with a lipid adjuvant (EXP), or were unvaccinated controls. Ten weeks later (Week 10), all 90 fawns received an oral challenge with approximately 10(8) cfu of a bovine strain of M. ptb daily for 4 days. The fawns were regularly weighed and monitored for clinical signs of Johne's disease, and regularly blood-sampled and tested for antibodies to M. ptb, using the Paralisa test, an IgG1 ELISA, and for antibodies to Mycobacterium bovis, using a similar test. A mid-cervical tuberculin skin test (MCT) was administered at Week 23, and comparative cervical skin tests (CCTs) were administered at Weeks 37 and 57. All animals were electively killed at Week 59, injection sites inspected, gastrointestinal tracts examined for gross lesions, and samples taken for culture and histopathology. RESULTS: There were no clinical cases of Johne's disease but, at slaughter, more gross lesions in intestinal lymph nodes were observed in Control (20%) than COM animals (0%; p<0.05). This latter group also had less severe histopathological lesions in samples of intestines and lymph nodes compared with the Control group (p<0.05), but not deer in the EXP group. Over 89% of deer in all three groups were shown by culture to be infected with M. ptb, while only 21-33% of faecal samples were culture-positive. Time to positive culture was longer for COM vs EXP and Control groups (p<0.01), reflecting fewer M. ptb organisms in samples from the ileocaecal valve (ICV) in that group. Almost all (>or=90%) deer reacted to the MCT at Week 23, and there were no significant differences between groups. One or two deer in each group were classified as Tb reactors to the CCT at Week 37, and none were classified as Tb reactors to the CCT at Week 57. At the time of challenge, over 50% of deer in the COM group were classified as positive (9/28) or suspicious (7/28) for M. ptb antibodies in the Paralisa test, one animal in the EXP group was classified as suspicious, and all the Controls were negative. From Week 23 to the end of the trial, 25/28 (89%) deer in the COM group were Paralisa-positive or -suspicious. The proportion of animals in the EXP and Control groups that were Paralisa-positive peaked at Week 39 (60% and 55%, respectively). The majority of deer in the COM group had significant levels of antibody to M. bovis 10 weeks after vaccination, while the proportion of M. bovis-antibody positive Control deer rose gradually throughout the trial, reaching 23/30 (77%) at slaughter. Injection-site lesions in COM deer ranged from 10-38 mm in diameter 4 weeks after vaccination, and then resolved. Minimal injection-site lesions were observed in EXP deer. At slaughter, 14 months after vaccination, 19/28 deer in the COM group had 5-15-mm nodules that were easily trimmed from the carcass. CONCLUSIONS: The experimental challenge with M. ptb produced subclinical Johne's disease in the majority of deer, but did not cause any clinical disease. The number and severity of gross and microscopic lesions was significantly reduced in the COM compared with Control and EXP groups; vaccination of the EXP group did not appear to give significant protection. Deer vaccinated with the commercial vaccine are likely to give a false-positive reaction to the MCT but should have an avian reaction to the CCT, if it is carried out >12 months after vaccination. Most of the deer vaccinated with the commercial vaccine produced significant levels of antibodies against both M. ptb and M. bovis, which interfered with ancillary Tb tests. If this vaccine or similar oil-based vaccines are used on deer farms in the future, it may be advisable to only vaccinate animals destined for slaughter, that would not need to be Tb-tested, but would be 'works-monitored' for evidence of Tb instead.

Experimental infections in young red deer (Cervus elaphus) with a bovine and an ovine strain of Mycobacterium avium subsp paratuberculosis.

AIMS: To compare the virulence of a 'bovine' and an 'ovine' strain of Mycobacterium avium subsp paratuberculosis (M. ptb) in red deer (Cervus elaphus) after experimental inoculation orally, and to examine the relationship between the dose of the bovine strain given and immunological, clinical and histopathological outcomes in young red deer. METHODS: Newly-weaned 4-month-old male red deer (n=81) were randomly assigned to one of five groups. Three groups (n=16) received high (10(9) colony forming units (cfu); HB), medium (10(7) cfu; MB) or low (10(3) cfu; LB) oral doses of a bovine strain of M. ptb, one group (n=16) received medium (10(7) cfu; MO) doses of an ovine strain of M. ptb, and a Control group (n=17) was not dosed. The HB and Control groups were grazed together, the MB and LB groups were grazed together, and the MO group was grazed alone, in separate small paddocks on a quarantined area of the farm for 45 weeks. Liveweight, clinical signs and immunoglobulin G1 (IgG1) antibody levels were monitored for up to 45 weeks. Deer affected with Johne's disease were euthanised when they showed obvious clinical signs. Unaffected deer were slaughtered at the end of the trial (Week 45), and all deer were necropsied. Faeces and tissue samples were cultured for M. ptb, and fixed tissues were examined for histopathology. RESULTS: Between 21 and 38 weeks post-challenge (pc), 5/16 animals in the HB group developed early signs of Johne's disease and were euthanised. The remaining deer in the five groups were all apparently healthy and reached good liveweights (approximately 100 kg average), and were euthanised and examined 45 weeks pc. Three deer (two HB and one MB) had small caseous lesions in their jejunal lymph nodes (JJLNs) and one HB animal had a small caseous lesion in a retropharyngeal lymph node. The remaining animals had no grossly-visible lesions. Mycobacterium avium subsp paratuberculosis was cultured from samples from 100% of the HB and MB animals, 50% of the LB group, 69% of the MO group and all Control animals. Thus all Control deer were infected by natural transmission from the HB group but none developed signs of clinical disease. Examination of histological sections of jejunum, ileocaecal valve (ICV) and associated lymph nodes showed a gradation of severity of lesions that was positively correlated (p<0.001) with dose of the bovine strain administered; mean lesion severity scores were 4.8, 2.9 and 0.9 for HB, MB and LB groups, and 2.2 and 0.9 for the Control and MO groups, respectively. IgG1 antibody levels at the time of euthanasia were also correlated with lesion severity scores at slaughter (p<0.001). CONCLUSIONS: The ovine strain of M. ptb used in this study was less virulent for red deer than the bovine strain. The correlation between dose of the bovine strain and the severity of lesions suggests that clinical Johne's disease in yearling red deer likely results from high oral challenge with a bovine strain whilst they are young. The minimum oral infective dose may be close to 10(3) cfu for this bovine strain.

Immunological and molecular characterization of susceptibility in relationship to bacterial strain differences in Mycobacterium avium subsp. paratuberculosis infection in the red deer (Cervus elaphus).

Johne's disease (JD) infection, caused by Mycobacterium avium subsp. paratuberculosis, represents a major disease problem in farmed ruminants. Although JD has been well characterized in cattle and sheep, little is known of the infection dynamics or immunological response in deer. In this study, typing of M. avium subsp. paratuberculosis isolates from intestinal lymphatic tissues from 74 JD-infected animals showed that clinical isolates of M. avium subsp. paratuberculosis from New Zealand farmed red deer were exclusively of the bovine strain genotype. The susceptibility of deer to M. avium subsp. paratuberculosis was further investigated by experimental oral-route infection studies using defined isolates of virulent bovine and ovine M. avium subsp. paratuberculosis strains. Oral inoculation with high (10(9) CFU/animal) or medium (10(7) CFU/animal) doses of the bovine strain of M. avium subsp. paratuberculosis established 100% infection rates, compared to 69% infection following inoculation with a medium dose of the ovine strain. The high susceptibility of deer to the bovine strain of M. avium subsp. paratuberculosis was confirmed by a 50% infection rate following experimental inoculation with a low dose of bacteria (10(3) CFU/animal). This study is the first to report experimental M. avium subsp. paratuberculosis infection in red deer, and it outlines the strong infectivity of bovine-strain M. avium subsp. paratuberculosis isolates for cervines.