A framework for longitudinal latent factor modelling of treatment response in clinical trials with applications to Psoriatic Arthritis and Rheumatoid Arthritis

OBJECTIVE

Clinical trials involve the collection of a wealth of data, comprising multiple diverse measurements performed at baseline and follow-up visits over the course of a trial. The most common primary analysis is restricted to a single, potentially composite endpoint at one time point. While such an analytical focus promotes simple and replicable conclusions, it does not necessarily fully capture the multi-faceted effects of a drug in a complex disease setting. Therefore, to complement existing approaches, we set out here to design a longitudinal multivariate analytical framework that accepts as input an entire clinical trial database, comprising all measurements, patients, and time points across multiple trials.

METHODS

Our framework composes probabilistic principal component analysis with a longitudinal linear mixed effects model, thereby enabling clinical interpretation of multivariate results, while handling data missing at random, and incorporating covariates and covariance structure in a computationally efficient and principled way.

RESULTS

We illustrate our approach by applying it to four phase III clinical trials of secukinumab in Psoriatic Arthritis (PsA) and Rheumatoid Arthritis (RA). We identify three clinically plausible latent factors that collectively explain 74.5% of empirical variation in the longitudinal patient database. We estimate longitudinal trajectories of these factors, thereby enabling joint characterisation of disease progression and drug effect. We perform benchmarking experiments demonstrating our method's competitive performance at estimating average treatment effects compared to existing statistical and machine learning methods, and showing that our modular approach leads to relatively computationally efficient model fitting.

CONCLUSION

Our multivariate longitudinal framework has the potential to illuminate the properties of existing composite endpoint methods, and to enable the development of novel clinical endpoints that provide enhanced and complementary perspectives on treatment response.

Large scale genome-wide association analyses identify novel genetic loci and mechanisms in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is an important cause of morbidity and mortality with both monogenic and polygenic components. We here report results from the largest HCM genome-wide association study (GWAS) and multi-trait analysis (MTAG) including 5,900 HCM cases, 68,359 controls, and 36,083 UK Biobank (UKB) participants with cardiac magnetic resonance (CMR) imaging. We identified a total of 70 loci (50 novel) associated with HCM, and 62 loci (32 novel) associated with relevant left ventricular (LV) structural or functional traits. Amongst the common variant HCM loci, we identify a novel HCM disease gene, SVIL, which encodes the actin-binding protein supervillin, showing that rare truncating SVIL variants cause HCM. Mendelian randomization analyses support a causal role of increased LV contractility in both obstructive and non-obstructive forms of HCM, suggesting common disease mechanisms and anticipating shared response to therapy. Taken together, the findings significantly increase our understanding of the genetic basis and molecular mechanisms of HCM, with potential implications for disease management.

Advancing data science in drug development through an innovative computational framework for data sharing and statistical analysis

Background

Novartis and the University of Oxford’s Big Data Institute (BDI) have established a research alliance with the aim to improve health care and drug development by making it more efficient and targeted. Using a combination of the latest statistical machine learning technology with an innovative IT platform developed to manage large volumes of anonymised data from numerous data sources and types we plan to identify novel patterns with clinical relevance which cannot be detected by humans alone to identify phenotypes and early predictors of patient disease activity and progression.

Method

The collaboration focuses on highly complex autoimmune diseases and develops a computational framework to assemble a research-ready dataset across numerous modalities. For the Multiple Sclerosis (MS) project, the collaboration has anonymised and integrated phase II to phase IV clinical and imaging trial data from ≈35,000 patients across all clinical phenotypes and collected in more than 2200 centres worldwide. For the “IL-17” project, the collaboration has anonymised and integrated clinical and imaging data from over 30 phase II and III Cosentyx clinical trials including more than 15,000 patients, suffering from four autoimmune disorders (Psoriasis, Axial Spondyloarthritis, Psoriatic arthritis (PsA) and Rheumatoid arthritis (RA)).

Results

A fundamental component of successful data analysis and the collaborative development of novel machine learning methods on these rich data sets has been the construction of a research informatics framework that can capture the data at regular intervals where images could be anonymised and integrated with the de-identified clinical data, quality controlled and compiled into a research-ready relational database which would then be available to multi-disciplinary analysts. The collaborative development from a group of software developers, data wranglers, statisticians, clinicians, and domain scientists across both organisations has been key. This framework is innovative, as it facilitates collaborative data management and makes a complicated clinical trial data set from a pharmaceutical company available to academic researchers who become associated with the project.

Conclusions

An informatics framework has been developed to capture clinical trial data into a pipeline of anonymisation, quality control, data exploration, and subsequent integration into a database. Establishing this framework has been integral to the development of analytical tools.

Study on the use of toltrazuril to eliminate Neospora caninum in congenitally infected lambs born from experimentally infected ewes

To determine if toltrazuril was effective in eliminating Neospora caninum infection from congenitally infected lambs. Twenty-eight ewes were allocated to 3 groups where animals in Groups A and B were inoculated with 1 × 10(7)N. caninum tachyzoites on Day 120 of gestation and Group C was maintained as a negative control group. Lambs born from ewes in Group A were treated with toltrazuril (20mg/kg) on Days 0, 7, 14 and 21 after birth. Lambs in Groups B and C were untreated. All lambs in Groups A and B were seropositive at 12 weeks of age. At 12 weeks of age, no differences between lambs in Group A and Group B were observed in serological results (ELISA and western blot), presence of N. caninum-related brain histopathological lesions or the number of organisms detected by qPCR. Group C remained negative for serology, detection of N. caninum DNA as well as histopathology throughout the study. Results indicate that N. caninum congenitally-infected lambs had a continuing infection with N. caninum despite being treated with toltrazuril.

Vertical transmission in experimentally infected sheep despite previous inoculation with Neospora caninum NcNZ1 isolate

Recent reports indicate N. caninum has a possible role in causing abortions in sheep in New Zealand. Knowledge about the mode of transmission of neosporosis in sheep in New Zealand is limited. This study aimed to determine the rate of vertical transmission that would occur in lambs born from experimentally inoculated ewes and to determine if previous inoculation would protect the lambs from N. caninum infection. A group of 50 ewes was divided into 2 groups with one group being inoculated with 5×10(6) N. caninum tachyzoites prior to pregnancy in Year 1. In Year 2, each of these groups was subdivided into 2 groups with one from each original group being inoculated with 1×10(7) N. caninum tachyzoites on Day 120 of gestation. Inoculation of N. caninum tachyzoites into ewes prior to mating resulted in no congenital transmission in lambs born in Year 1 but without further inoculation, 7 out of 11 lambs in Year 2 were positive for N. caninum infection. Ewes that were inoculated in both years resulted in all 12 lambs born in Year 2 being positive for N. caninum infection. This indicates that previous inoculation in Year 1 did not result in any vertical transmission in that year but did not provide any protection against vertical transmission in Year 2. These results suggest that vertical transmission occurs readily once the ewe is infected.

Epidemiology of vaginal prolapse in mixed-age ewes in New Zealand

AIMS

Identify environmental, animal, and management factors associated with risk of vaginal prolapse in ewes, to enable farmers and advisors to make pragmatic decisions based on empirical observations for control of the condition.

METHODS

Two longitudinal studies conducted over 2 years to identify factors associated with incidence of prolapse in (i) cohorts of 200 individually identified mixed-age (MA) ewes, and (ii) all MA ewes, on voluntarily participating sheep-breeding farms in Hawkes Bay (HB) and Southland regions of New Zealand.

RESULTS

The overall annual incidences of prolapse on 113 farms in 2000 and 88 in 2001 were 1.21 and 0.82 per 100 MA ewes, respectively, and 1.05 for both years combined. A total of 406 prolapses were recorded among 36,695 individually identified cohort ewes. Individual farm incidences for both years varied from 0-5.9 (mean=1.56, median=1.39) on Southland and 0-3.9 (mean=0.75, median=0.54) per 100 ewes on HB farms. The crude relative risk of a prolapse occurring in a MA ewe was 5.31 times higher for ewes carrying twins and 11.3 times higher for ewes carrying triplets, than single lambs. Flocks made up of predominantly pure or crossbred Perendale ewes appeared to be at lower risk than flocks with other breeds. Shearing in the 3 months leading up to mating appeared to be protective, as was shearing in the second half of pregnancy. The risk was higher on farms with moderate to steep terrain than on farms with flat terrain. The identified risk factors in the individually identified cohorts were: access to salt and feeding of swedes in the latter part of pregnancy, moderate to steep lambing paddocks, multiple lambs detected at scanning, and weight gain between start of mating and scanning. The condition recurred in 2001 in six (35%) of 17 study ewes that had prolapsed during 2000. Culling policies for female offspring of affected ewes did not influence incidence at the farm level; nor did feeding hay or grain in late pregnancy. Furthermore, there was no association between incidence and body condition scores measured prior to and after mating, at scanning, or at time of set stocking.

CLINICAL SIGNIFICANCE

Vaginal prolapse is an inevitable consequence of sheep reproduction and its incidence is expected to increase as reproductive rates increase. This study provides some firm leads as to the relative importance of risk factors and gives guidance for risk reduction, e.g. by identification and separate management of ewes carrying twins or triplets, using flat paddocks for lambing, and guarding against gain in weight between the start of mating and scanning.

Liver biopsy histopathology for diagnosis of Johne's disease in sheep

Sheep with Johne's disease develop epithelioid macrophage microgranulomas, specific to Mycobacterium avium subsp. paratuberculosis (Map) infection, in the terminal ileum, mesenteric lymph nodes, and organs distant to the alimentary tract such as the liver. The objectives of this study were to determine whether liver pathology was present in ewes affected by Map and whether liver cores provide adequate tissue for this potential diagnostic marker. One hundred and twenty-six adult, low body condition ewes were euthanized, necropsied, and underwent simulated liver biopsy. Ileal lesions typical of Map were found in 60 ewes. Hepatic epithelioid microgranulomas were observed in all ewes with Type 3b (n = 40) and 82% (n = 11) with Type 3c ileal lesions. None were found in ewes unaffected by Map or with Type 1, 2, or 3a ileal lesions. Liver biopsy core samples provided adequate tissue for histopathology with a sensitivity and specificity of 96% (95% confidence interval [CI], 0.87-0.99) and 100% (95% CI, 0.95-1), respectively for detection of types 3b and 3c ileal lesions.

Adaptation of a commercial ELISA to determine the IgG avidity in sheep experimentally and naturally infected with Neospora caninum

Recent reports indicate Neospora caninum has a possible role in causing abortions in sheep in New Zealand. Knowledge about the epidemiology of neosporosis in sheep is limited. This study aimed to adapt and validate a commercially available ELISA assay as an IgG avidity assay to discriminate between acute (primary and re-inoculated) and chronic N. caninum infections in sheep. In addition, it was used to compare the antibody avidity values between lambs from ewes inoculated with N. caninum either during the pregnancy or in the previous year. The avidity assay was undertaken by using 6M urea for the first wash after incubation with the primary antibody in the commercial ELISA (Chekit* Neospora antibody test kit, IDEXX Laboratories, Australia). Sequential serum samples were obtained from naïve ewes (n=16) experimentally inoculated with live N. caninum tachyzoites. All ewes were seropositive by two weeks post-inoculation and remained seropositive for 20 weeks post-inoculation. There was a linear relationship between time after inoculation and avidity values (p<0.05) over the first 24 weeks. In Week 4, all animals had avidity values <35% and by Week 8, 8/16 animals had avidity values of >35%. These results suggest that an avidity value of <35% indicates a recent primary infection while a value of >35% is indicative of a chronic infection. The assay was then validated using samples from other groups of experimentally inoculated sheep as well as samples from naturally infected ewes. When comparing sample to positive ratio (S/P) and avidity values from lambs born from recently inoculated ewes with those from ewes inoculated the previous year and re-inoculated in the current year, it was possible to differentiate the lambs at 2 weeks of age. Lambs from recently inoculated ewes had low S/P and avidity values at 2 weeks of age which increased by 12 weeks of age. In comparison, lambs from re-inoculated ewes had high S/P and avidity values at 2 weeks of age, due to maternal antibody influence but values were similar to those from lambs that were born from recently inoculated ewes at 12 weeks of age. Avidity values for four naturally infected ewes were all >60% indicating chronic infection. These results suggest that the assay is able to discriminate between recent and chronic infection in sheep as well as able to differentiate lambs with maternal immunity compared to their own de novo immunity. As such it can be utilized to understand the kinetics of N. caninum infection in sheep.

Seroconversion and semen shedding in rams experimentally infected with Brucella ovis

AIM

To determine the time taken for rams to develop antibodies to Brucella ovis in serum, shed B. ovis in semen and develop lesions of epididymitis following infection with B. ovis.

METHODS

Fifteen 19-month-old rams were artificially infected with B. ovis by inoculation of infected semen onto the nasal and rectal mucus membranes (Day 0). Serum was collected from each ram at 2 to 8-day intervals and tested at commercial laboratories using a complement fixation test (CFT) and an ELISA. Cut-off values for the CFT were 0-4/4 negative; 1/8-3/8 suspicious and 4/8-4/128 positive, and for the ELISA were <10% negative; ≥10 to <50% suspicious and ≥50% positive. Selected serum samples were also tested using a gel diffusion test (GDT). At 7 to 8-day intervals semen was collected for bacterial culture and the scrotal contents were palpated to identify lesions of epididymitis. The study was terminated after 56 days.

RESULTS

On Day 28 B. ovis was isolated from the semen of one ram and by Day 49 it was isolated from the semen of 10 rams. All 10 rams had suspicious or positive ELISA or CFT titres by Day 36 and 56, respectively. The GDT results were all negative on Day 36 and in general did not become positive in individual rams until 7-28 days after semen shedding commenced. Epididymitis was detected in one ram on Day 36; by Day 56 eight rams had epididymitis detectable by scrotal palpation.

CONCLUSIONS

The B. ovis ELISA test identified infected rams at an earlier stage than the CFT; this was at 19-36 days after exposure. Rams can begin shedding B. ovis in semen as early as 28 days after exposure and lesions of epididymitis develop as early as 36 days after exposure.

CLINICAL RELEVANCE

During a test and slaughter campaign for the control of B. ovis, the most appropriate serological re-testing interval is likely to be around 28 days (4 weeks) using the ELISA with or without the CFT, although caution is required in interpretation of "suspicious" ELISA results. Following a B. ovis breakdown, two negative CFT or ELISA tests 60 days apart are recommended to confirm freedom from infection, supporting current guidelines.

The impact of highly concentrated Mo and Cu dietary supplements, fed as a bolus, on the efficacy of chelated versus inorganic Cu in cattle on a low-Cu diet

AIM

To compare the efficacy of chelated versus inorganic forms of dietary Cu supplements, fed as a bolus, when challenged by a daily bolus of dietary Mo in cattle on a low-Cu diet.

METHODS

Forty non-lactating, Friesian dairy cows of adequate Cu status were assigned to four groups and fed a basal diet of baled silage containing 5.3 mg Cu and 0.4 mg Mo/kg DM. The experimental design was a factorial of two chemical forms of supplemental Cu and two levels of Mo intake, provided as pelleted grain supplements made from crushed barley/molasses plus Cu and Mo. The supplements contained 140 mg Cu/kg as Cu sulphate pentahydrate (CS), 140 mg Cu/kg as Cu glycinate (CG), CS plus 38 mg Mo/kg as sodium molybdate (CS+Mo), or CG plus 38 mg Mo/kg (CG+Mo). Commencing on Day 0, supplements were fed once daily (offered 1-1.2 kg/cow) and were completely consumed within 5-10 minutes, which constitutes a bolus type of administration. Liver samples were collected by biopsy at Days -24, 13, 41 or 47, and 69 for Cu determinations.

RESULTS

The diets fed to the Cu+Mo groups were roughly equivalent to 25 mg Cu and 5.7 mg Mo/kg DM. Mean initial concentration of Cu in liver for all groups was 516 (SE 54) μmol Cu/kg fresh tissue. In cows supplemented with CS and CG, the final (Day 69) concentrations increased (p<0.01) to 939 (SE 166) and 853 (SE 163) μmol Cu/kg, respectively. These values were not different (p=0.72). For groups CS+Mo and CG+Mo, the final concentrations of 535 (SE 122) and 453 (SE 102) μmol Cu/kg were not different from initial values or from each other (p>0.25). The rate of accumulation of Cu in liver following bolus Cu and Mo intake was highly variable but was not affected by initial concentration of Cu in liver (p>0.9) or by the form of Cu (p>0.6). Mean rates of accumulation of Cu in liver were 4.0 (SD 3.8) and 0.65 (SD 2.0) μmol Cu/kg fresh tissue/day for the Cu-only treatments and the Cu+Mo treatments, respectively.

CONCLUSIONS

When fed together as a bolus, high Mo intake negated the effect of supplemental Cu but it did not reduce liver Cu stores. There was no difference in the reaction of dietary Mo with chelated Cu (as glycinate) versus inorganic Cu (as sulphate) dietary supplements.

Pulsed-field gel electrophoresis typing of Campylobacter fetus subsp. fetus from sheep abortions in the Hawke's Bay region of New Zealand

AIM

To type Campylobacter isolates from sheep abortions from the Hawke's Bay region of New Zealand.

METHODS

Campylobacter isolates were collected from aborted sheep fetuses from commercial farms in the Hawke's Bay region. Information on the Campylobacter vaccination status of flocks in the study was collected. Isolates were identified to species level using standard phenotypic tests, then typed using pulsed-field gel electrophoresis (PFGE).

RESULTS

Eighty-one C. fetus subsp. fetus isolates were cultured from aborted sheep fetuses from 25 farms and four C. jejuni isolates were cultured from fetuses from three farms. The C. fetus subsp. fetus isolates were classified into six PFGE groups. A single pulsed-field type predominated amongst isolates from 19 of the 25 farms. The C. jejuni isolates comprised two types.

CONCLUSIONS

A range of C. fetus subsp. fetus PFGE types was identified, and one type, B1, was found most frequently. Campylobacter fetus subsp. fetus was only isolated from samples from sheep that had not been vaccinated with C. fetus subsp. fetus vaccine that season.

The prevalence of disseminated Mycobacterium avium subsp. paratuberculosis infection in tissues of healthy ewes from a New Zealand farm with Johne's disease present

AIM

To determine the prevalence of disseminated Mycobacterium avium subsp. paratuberculosis (Map) infection in healthy ewes in a flock with a history of clinical Johne's disease.

METHODS

Twenty-four healthy ewes, from a large sheep and cattle farm with a history of clinical Johne's disease in the ewe flock, were randomly selected, euthanased, blood sampled, and examined at necropsy. BACTEC™ radiometric culture for Map was performed on samples of faeces, ileum, mesenteric lymph node, biceps femoris muscle and mononuclear cells in peripheral blood. Serum antibody ELISA tests were performed. Histological sections and Ziehl Neelsen (ZN) stains of impression smears of ileum and mesenteric lymph node were examined for pathological lesions characteristic of Johne's disease and acid fast organisms (AFO). Indirect quantification of Map was performed, using BACTEC radiometric growth indices measuring the time taken for the production of (14)CO(2.)

RESULTS

No histological evidence of Johne's disease or AFO was found in the ileum and mesenteric lymph nodes. Twelve of the 24 ewes (50%) had Map cultured from the ileum (n=6) and/or mesenteric lymph nodes (n=8) while none had Map cultured from the faeces, biceps femoris muscle or blood mononuclear cells. One of the 12 Map culture positive ewes was serum ELISA positive. The culture growth rates in liquid medium suggest low numbers of Map were present in the tissues of the culture positive ewes.

CONCLUSION

Fifty per cent of clinically healthy ewes exposed to Map within a Johne's infected flock were Map culture positive in the ileum and/or mesenteric lymph node(s), while the ELISA was positive in 8% of those animals (n=1). There was no faecal shedding of Map and no Map was cultured from skeletal muscle or from blood mononuclear cells suggesting that systemic Map infection, defined as positive culture of Map from skeletal muscle and/or blood, may be uncommon in healthy mixed age ewes without clinical Johne's disease.

CLINICAL RELEVANCE

ELISA serology detected 1 of 12 ewes infected with Map whilst none were detected from faecal BACTEC radiometric culture, suggesting biosecurity measures used to control the spread of Map may be of limited use. Map was not cultured from blood mononuclear cells or skeletal muscle, indicating that meat from healthy ewes, from farms where Johne's disease is present, is an unlikely source of Map exposure for humans. Further research is warranted to establish the prevalence and dissemination of Map in tissues outside the alimentary tract of healthy ewes from farms throughout New Zealand where Map is present.

The role of liver Cu kinetics in the depletion of reserves of Cu in dairy cows fed a Cu-deficient diet

AIM

To determine how the concentration of Cu in liver affects the rate of depletion of that Cu when cows are fed a Cu-deficient diet under experimental conditions, and to mathematically model the rate of depletion of Cu over time.

METHODS

In June 2010, 25 non-lactating Friesian cows were assigned to three groups such that initial mean concentrations of Cu in liver were 265, 534 and 1,486 μmol Cu/kg fresh tissue (Day 0). All cows were managed as a single group and fed a Cu-deficient diet of primarily baled silage. No mineral Cu supplements were given. Liver biopsies were collected from cows on Days 0, 53, 98 and 161 to determine concentrations of Cu. At about the same time, samples of silage and pasture herbage were collected to determine Cu, Mo and S concentrations.

RESULTS

Median concentration of Cu in silage was 6.5 (min 6, max 9) mg/kg DM. Concentration of Cu in liver decreased in all groups (p<0.001), over the duration of the study. The amount of Cu depleted from liver was greater in groups that started the study with higher initial concentrations of Cu in liver. The rate of decline followed exponential first-order kinetics with an elimination rate constant k of 0.0057 (CI 95%=0.0039-0.0074), meaning that about 0.57% of liver Cu reserves were depleted each day. For individual cows this loss amounted to 0.1-14 μmol Cu/kg liver/day.

CONCLUSIONS AND CLINICAL RELEVANCE

Depletion of Cu from liver was dependent on initial concentration of Cu. These results can be used to predict how long an unsupplemented herd will remain in adequate Cu status, which adds confidence to decisions about when Cu supplementation should be withdrawn or reinstated. Cows with high concentrations of Cu in liver can maintain adequate Cu status for months without supplements. Intake of less Cu and more Mo would increase the rate of depletion, and seasonal factors would also have some influence.

Pathology of Brucella ovis infection in red deer stags (Cervus elaphus)

AIM

To describe the pathology of the reproductive tract of red deer stags with active Brucella ovis infection and in stags in which B. ovis infection had resolved.

METHODS

Twenty-three red deer stags of varying history were slaughtered and their epididymides and accessory sex glands examined grossly and by histopathology. At the time of slaughter five of the stags had an active B. ovis infection of 24-55 days duration following exposure to infected rams, 10 stags had been experimentally infected with B. ovis by intravenous inoculation 649 days previously and had developed an active infection but the bacterial infection had resolved at least 308 days prior to slaughter, and eight stags had not been exposed to B. ovis at any time.

RESULTS

Of the five stags with an active infection, one had gross enlargement of the epididymides that could be detected by scrotal palpation. Histological lesions in all five stags included mild to severe, predominantly non-suppurative epididymitis, vesiculitis, prostatitis and ampullitis, with neutrophil exudation in associated glandular ducts. Additional lesions in the epididymides were spermatic granulomas and epithelial hyperplasia with intra-epithelial cyst formation. Of the 10 stags in which the bacterial infection had resolved, two had gross enlargement of the epididymides. The histological lesions were similar to those in stags with active infection but were generally milder, with increased periductal scar tissue in the epididymides. The lesions seen in stags resembled those seen in rams with B. ovis infection but they were usually less florid and had fewer plasma cells. No gross abnormalities or histopathological lesions were detected in the non-infected stags.

CONCLUSIONS

Only a small percentage of red deer stags infected with B. ovis develop lesions of epididymitis that can be detected by scrotal palpation. Gross and histological lesions of the genital tract of stags associated with B. ovis infection are similar to the lesions seen in rams. Lesions in stags persist for >300 days after the bacterial infection has resolved.

CLINICAL RELEVANCE

Brucella ovis infection should be considered when there are gross lesions of epididymitis or histological evidence of inflammation in the epididymides or accessory sex glands of red deer stags. Retrospective diagnosis of B. ovis in stags could be achieved by histological examination of the reproductive organs.

Ram and buck management

Careful management is necessary to ensure the reproductive success in any small ruminant farm and to maximise the productive longevity of rams and bucks. Rams and bucks are frequently overlooked outside of the breeding period, but year-round attention to nutrition, parasite control and general disease control is important in keeping them healthy and sound for breeding. Pre-mating soundness examinations are an inexpensive and relatively easy way to assess the potential ability of a ram or buck to perform during the breeding period and should be incorporated annually into the management of any flock. During the breeding period, careful thought should be given to the appropriate use of males, and the effectiveness of mating should be monitored.

Detection of Mycobacterium avium subsp. paratuberculosis in skeletal muscle and blood of ewes from a sheep farm in New Zealand

AIM

To determine whether viable Mycobacterium avium subsp. paratuberculosis (Map) is present in skeletal muscle and blood in ewes with and without Johne's disease confirmed histologically.

METHODS

A total of 51 mixed-aged ewes in poor body condition from a farm with a history of clinical Johne's disease were culled and examined at necropsy. BACTEC radiometric culture was performed on samples of skeletal muscle from the biceps femoris, mononuclear cells in peripheral blood (hereafter referred to as blood), and ileum. Histological sections and Ziehl-Neelsen (ZN)-stained impression smears of terminal ileum and mesenteric lymph nodes were examined. Ewes were defined as having confirmed Johne's disease if there was histopathological evidence typical of the disease within the ileum and adjacent lymph nodes.

RESULTS

Eighteen of 21 (86%) ewes with confirmed clinical Johne's disease were culture-positive for Map from sites peripheral to the alimentary tract, comprising 15 from skeletal muscle and 13 from blood. Five of 30 (17%) ewes that did not have Johne's disease were culture-positive, with four from skeletal muscle and one from blood. The likelihood that ewes with confirmed Johne's disease had systemic Map infection compared with ewes without was determined as OR=30 (95% CI=6.3-142.0; p<0.001).

CONCLUSION

The prevalence of Map infection of skeletal muscle and blood in ewes with confirmed Johne's disease was 71% and 62% respectively, and in unaffected ewes was 13% for muscle and 3% for blood.

CLINICAL RELEVANCE

Skeletal muscle and blood are potential sources of exposure of humans to Map, and the risk appears higher from sheep with Johne's disease.

Prevalence of anthelmintic resistance on 62 beef cattle farms in the North Island of New Zealand

AIM

To establish the prevalence of anthelmintic resistance in parasitic nematodes on a random sample of beef cattle herds in the North Island of New Zealand.

METHODS

A cross-sectional prevalence study was conducted using a standardised faecal nematode egg count (FEC) reduction (FECR) test (FECRT) for ivermectin, levamisole and albendazole on 60 calves on each of 62 farms in the North Island chosen at random from farms that conformed with the selection criteria. Resistance to an anthelmintic was inferred when there was <95% reduction in FEC 7-10 days after treatment. Larval cultures were performed for all control groups and for treated groups for which resistance was evident.

RESULTS

Of the farms that completed the FECRT, 4/61 (7%) showed > or =95% reduction in FEC for all anthelmintics tested. Resistance to ivermectin was evident on 56/61 (92%) farms, to albendazole on 47/62 (76%) farms, and to both ivermectin and albendazole on 45/61 (74%) farms. Resistance to levamisole was evident on only 4/62 (6%) farms. The parasites most prevalent in resistant populations cultured were Cooperia spp. On 45/61 (74%) farms where Cooperia spp were present in sufficient numbers, resistance to both ivermectin and albendazole was evident. No cases of levamisole-resistant Cooperia spp were detected. Resistance of Ostertagia spp to ivermectin was evident on 4/45 (9%) farms, to albendazole on 15/46 (35%) farms, and to levamisole on 4/46 (9%) farms.

CONCLUSION

Anthelmintic resistance in parasitic nematodes of cattle is common in the North Island of New Zealand. Beef farmers need to be aware of the risks posed by anthelmintic resistance, and routine FECR testing is recommended to ensure optimal productivity and to guide decision-making when purchasing anthelmintics to be used on-farm.

An inherited cataract in New Zealand Romney sheep

A bilateral cataract was noted to occur in sheep on a New Zealand Romney stud. Extensive breeding trials showed that this defect was inherited as an autosomal dominant. As such this form of cataract is of minimal importance to the sheep industry as control is merely by culling affected individuals.

A strain ofHaemonchus contortusresistant to thiophanate

The occurrence of a field strain of Haemonchus contortus resistant to thiophanate is reported for the first time in New Zealand. In a controlled anthelmintic trial with experimentally infected animals, thiophanate at 50-100 mg/kg had no appreciable effect on the Haemonchus burden. Albendazole reduced faecal strongylate egg counts by 95% in animals with naturally acquired 59 infections.

Ovine dermatophilosis in young sheep associated with the grazing ofBrassicaspp. crops

The occurrence of dermatophilosis in five month old lambs associated with the grazing of Brassica spp. crops is reported on four farms. The prevalence of the disease varied from 3% to 45% within affected flocks. An additional finding was the occurrence of nervous signs in a small number of more severely affected lambs, characterised by a sudden lowering of the hindquarters. The association between dermatophilosis and the grazing of Brassica spp. crops is discussed.

Nematode worm egg output by ewes

The results from routine monitoring of parasite burdens in ewe flocks from 1980 to 1991 by the Massey University Veterinary Clinic were analysed. Faecal strongylate nematode egg counts from 401 flock samples were analysed according to ewe age (two-tooth, 16-23 month-old vs mixed-age, greater than 2-year-old ewes) and month of the year. Each flock sample contained faeces from ten ewes and nematode egg counts were carried out on each faecal sample. ln the mixed-age ewes, the overall mean faecal egg count per gram of faeces (epg) was lowest during January (82 epg) and rose to a peak during October (539 epg). The overall mean faecal egg count in two-tooth ewes remained constant from January (240 epg) to June (294 epg) and dropped during July (156 epg). Overall, 8% of the mixed-age ewes and 12% of the two-tooth ewe submissions had a mean egg count equal to or greater than 500 epg. It is possible that these data over-estimate the pasture contamination by ewes as farmers are more likely to submit faecal samples and to seek veterinary assistance when parasitism is thought to be a problem. The role of ewes as a source of pasture contamination should be considered when developing parasite control regimes on farms.

Effects ofBrucella ovisinfection on semen characteristics of 16-month-old red deer stags

AIM

To determine the effects of Brucella ovis infection on semen characteristics of 16-month-old red deer stags (Cervus elaphus).

METHODS

At monthly intervals during March, April and May, semen was collected using electro-ejaculation from 9 yearling red deer stags that had been artificially infected with B. ovis 3 months previously. In March, semen was also collected from 6 non-infected stags from the same peer group for comparison. Semen was evaluated for gross appearance, percentage of sperm showing forward motility, sperm morphology and sperm density/ml of semen, and the presence of white blood cells was determined. In addition, at the time of semen collection, the epididymes of each stag were palpated and lesions recorded.

RESULTS

Grossly visible purulent material was present in semen from 6/9 infected stags and the percentage of sperm showing forward motility did not exceed 20% in any of these samples. Increased numbers of white blood cells and cellular debris were evident in semen from 8/9 infected stags. Compared with non-infected stags, sperm motility in semen from infected stags was significantly reduced (p<0.05). There were no differences in percentage of morphologically normal sperm between groups, but infected stags had more detached sperm heads present in semen than non-infected stags (p<0.05). Only 2 of the infected stags had lesions of epididymitis evident on scrotal palpation.

CONCLUSIONS

B. ovis infection is likely to have a detrimental effect on stag semen quality. While there was variation between individual animals, overall sperm motility was decreased and semen from infected stags had increased numbers of white blood cells and detached sperm heads.

CLINICAL RELEVANCE

The fertility of breeding stags may be reduced if they are infected with B. ovis and this possibility should be considered when investigating reproductive problems of deer.

Farm management practices associated with macrocyclic lactone resistance on sheep farms in New Zealand

AIM

To identify farm practices associated with the presence of resistance to a macrocyclic lactone (ML) anthelmintic on sheep farms in New Zealand.

METHODS

A cross-sectional study was conducted to test for associations between the presence of resistance to an ML anthelmintic (ivermectin) and management practices on sheep farms in New Zealand. Selection of farms was both random (n=80) and purposive (n=32; being farms with a history of suspected ML resistance). Resistance was inferred from faecal nematode egg count (FEC) reduction (FECR) tests (FECRTs) when there was <95% reduction in FEC 7-10 days after treatment with a half dose of ivermectin (0.1 mg/kg). A logistic regression model was built to identify farm-level factors that were associated with the presence or absence of ML resistance.

RESULTS

Of the 112 flock managers that were approached for interview, 103 (92%) returned useable questionnaires. The odds of ML resistance were increased: on farms that had used long-acting ML products in ewes as a pre-lambing treatment for > or =3 of the previous 5 years (odds ratio (OR) = 7.2; 95% confidence interval (CI) = 1.7-30.3); on farms where <70% of the total stock units mid-winter were from sheep (OR=6.5; 95% CI=1.6-25.6); on farms which over the year purchased >10% of the number of sheep present mid-winter (OR=7.1; 95% CI=1.5-34.7); and on farms where the average wool diameter of the main flock was <37 (OR=4.1; 95% CI=1.1-14.7) microns. The model provided a good fit to the data (pseudo R2=0.64; Hosmer-Lemeshow statistic = 0.38).

CONCLUSIONS

Explanatory factors identified as associated with the presence of ML (ivermectin) resistance on farms included the use of long-acting anthelmintic formulations in ewes pre-lambing, sources of refugia of unselected parasites on the farm, breed of sheep and their requirements for anthelmintic treatments, and the importing of resistant parasites with purchased stock. The study provides support for controls that aim to provide refugia of susceptible worms and that minimise the risk of introduction of resistance through effective quarantine drenching.

Anthelmintic resistance and management of nematode parasites on beef cattle-rearing farms in the North Island of New Zealand

AIM

To provide information on current farmers' opinions and farming practices thought to be related to anthelmintic resistance, and to test for associations between the presence of anthelmintic resistance and management practices on beef-cattle rearing farms in the North Island of New Zealand.

METHODS

A study using an interview-based questionnaire about management of internal parasites was conducted on 62 beef cattle-rearing farms in the North Island of New Zealand, using case-control analyses to test for associations between management practices and the presence or absence of resistance to ivermectin or albendazole. Resistance was inferred from faecal nematode egg count (FEC) reduction (FECR) tests (FECRTs) when there was <90% reduction in FEC 7-10 days after treatment of calves <12 months of age.

RESULTS

Of the 59 farmers who completed the questionnaire, most (n=40) ranked parasites highly, and at about the same level as quality and quantity of feed, as important production-limiting factors for their enterprises. In contrast, anthelmintic resistance was not perceived to be a problem on 13 farms, and its importance was rated low on 24, moderate on 15, and high on only six farms. Despite all farms having planned parasite control programmes, there was heavy reliance on clinical signs of parasitism to determine frequency of treatments. About one in three farmers with beef breeder cows routinely treated their calves at marking, one in five treated mixed-age cows, and almost half treated rising 2-year-old cows before calving. One in four farmers used anthelmintics on calves on 8-12 occasions in their first year of life. Co-grazing with other species was rare, but follow-on grazing within 3 months after older cattle or sheep was common. On most farms, grazing cattle was restricted to part of the farm, a finding with implications for parasite control and persistence of larvae in refugia. Macrocyclic lactone (ML) anthelmintics or their combinations with other action families were currently, and for the past 5 years, used more frequently than benzimidazoles and levamisole, and benzimidazole-levamisole combinations. The prevalence of resistance to ivermectin was high (82%) and no plausible model of associations could be constructed from the data. The prevalence of resistance to albendazole was 60%, and the risk of resistance increased as the number of rising 1-year-old cattle present mid-winter increased, and decreased as the number of breeding cows >2 years old present mid-winter increased.

CONCLUSION

It is clear that in practice anthelmintic resistance is a secondary consideration to obtaining productivity advantages from the use of anthelmintics in beef cattle. Farmers' opinions were divided on many issues and the overall impression was of confused and diverse thinking regarding the principles of the use of anthelmintics. The overall outlook regarding anthelmintic resistance in cattle is bleak unless the need for integrated and long-term research activities is acted upon soon.

Prevalence of anthelmintic resistance on sheep farms in New Zealand

AIM

To establish the prevalence of anthelmintic resistance in parasitic nematodes on sheep farms in New Zealand.

METHODS

A cross-sectional prevalence study was conducted, using a standardised faecal nematode egg count (FEC) reduction (FECR) test (FECRT) for ivermectin, at a full (0.2 mg/kg) and half (0.1 mg/kg) dose rate, and albendazole, levamisole and albendazole-levamisole in combination, on 60 lambs (n=10 per group) on farms selected from throughout New Zealand. Farms that conformed with selection criteria were chosen at random (n=80) or with a history of suspected resistance to macrocyclic lactone (ML) anthelmintics (n=32). Resistance to an anthelmintic was inferred when there was <95% reduction in FEC 7-10 days after treatment. Larval cultures were performed for all control groups and for treated groups for which resistance was evident.

RESULTS

Of the farms randomly selected, 36% showed > or =95% FECR for all anthelmintics tested; resistance to ivermectin at 0.1 and 0.2 mg/kg liveweight was evident on 36% and 25% of these farms, respectively. Resistance to both ivermectin (0.2 mg/kg) and levamisole was evident on 8/80 (10%) farms, to ivermectin and albendazole on 10/80 (13%) farms, and to ivermectin, levamisole and albendazole on 6/80 (8%) farms. The prevalence of resistance to a half dose of ivermectin tended to be more prevalent on farms with a history of suspected ML resistance (p=0.06). Resistance to albendazole was seen across all the main parasite genera, and to levamisole in Nematodirus, Ostertagia (= Teladorsagia) and Trichostrongylus species. Resistance to ivermectin was dominated by Ostertagia spp, although Cooperia, Nematodirus and Trichostrongylus species were also implicated.

CONCLUSION

Anthelmintic resistance in parasitic nematodes of sheep is common in New Zealand. Not only was resistance to albendazole and levamisole common, but resistance to the ML, ivermectin, was at a higher prevalence than expected. Sheep farmers and advisors in New Zealand need to re-evaluate the way they manage parasites, and more research is urgently needed if the steady decline in anthelmintic susceptibility is to be halted.

Inherited chondrodysplasia in Texel sheep

CASE HISTORY

A skeletal disease characterised by dwarfism, limb deformity and sometimes sudden death occurred over a period of 5 years in lambs born on a commercial sheep farm in Southland. The disease showed variable expression and occurred in crossbred sheep. A genetic aetiology was supported by the birth of affected lambs over two seasons in a flock of putative carrier and affected sheep transported to Massey University.

CLINICAL FINDINGS

Affected lambs appeared normal at birth but showed evidence of dwarfism, wide-based stance and exercise intolerance as early as 1 week of age. Most died within the first 3 months of life, often after developing bilateral varus deformity of the forelimbs. Some severely-affected lambs died suddenly of respiratory embarrassment, probably due to tracheal collapse. Mildly-affected individuals had a short, blocky stature and some survived to breeding age.

PATHOLOGICAL FINDINGS

Gross and microscopic lesions of variable severity were present in the tracheal, articular, epiphyseal and physeal cartilages. In severe cases, articular cartilage in major joints was eroded from weight-bearing surfaces. The trachea was flaccid, abnormally kinked, and had thickened cartilaginous rings and a narrow lumen. Affected sheep that survived to breeding age eventually developed severe degenerative joint disease. Histologically, chondrocytes were disorganised, surrounded by concentric rings of abnormal fibrillar material, and the matrix often contained focal to coalescing areas of chondrolysis.

DIAGNOSIS

Inherited chondrodysplasia of Texel sheep. CLINICAL RELEVANCE AND CONCLUSIONS: This chondrodysplasia differs from those previously described in sheep and is considered to be a newly-recognised, recessively-inherited genetic disease of the Texel breed. A defect in the synthesis of glycosaminoglycans in cartilage matrix is suspected. This disease of sheep may provide a suitable model for studying various forms of therapy for human chondrodysplasias.

The effect of the maturity and prior breeding activity of rams and body condition score of ewe hoggets on the reproductive performance of ewe hoggets

AIM

To determine the effect of age and prior use of mature rams at a given ram-to-ewe ratio, and the effect of body condition on breeding performance and pregnancy rate of ewe hoggets.

METHODS

Ewe hoggets (n=733) aged 7-8 months were weighed and their body condition scored, then randomly assigned to one of three treatment groups (Day 0) and joined with either four two-tooth rams (20 months of age) not used previously (n=244; Two-tooth), four mixed-aged mature rams that had not been used earlier in the season (n=244; Mature-fresh), or four mixed-aged mature rams that had been used with mature ewes immediately prior to joining with hoggets (n=245; Mature-used). The breeding period was 34 days. Ewe hoggets were identified as having been marked during the first 17 days only, during both 17-day periods, during the second 17 days only, or not marked. Hoggets were re-weighed on Day 34, and pregnancy status determined using ultrasound on Day 92. The breeding soundness of the rams was assessed on Days -34 and -1.

RESULTS

Semen samples obtained from the rams did not differ significantly in any of the parameters measured (p>0.05). Ewe hoggets joined with Mature-fresh rams were less likely (p<0.05) to be marked in the second 17 days of breeding only than those joined with either Two-tooth or Mature-used rams. No other breeding parameters were affected by breeding group (p>0.05). Hoggets marked in the first 17 days only were heavier (p<0.05) at Day 0 than those marked in the second 17 days only or not marked. Hoggets diagnosed as twin-bearing were heavier (p<0.05) than non-pregnant or single-bearing hoggets. Those hoggets marked in the first 17 days only had a greater (p<0.05) body condition score (BCS) than those marked in the second 17 days only or not marked at all. These differences were no longer apparent after correction for liveweight (LW).Correction for LW at Day 0 or change in LW during the breeding period did not affect the results for breeding performance.

CONCLUSIONS

Under the conditions of this study, two-tooth rams and mature rams that had been used previously were just as suitable as mature rams that had not been used previously for breeding with ewe hoggets. Further studies are warranted to verify this result. The re-use of rams without reducing breeding performance would reduce breeding costs and may make breeding hoggets a more viable option for farmers. The BCS of ewe hoggets affected breeding performance, and can thus be used to identify those animals most suitable for breeding.

Prevalence of pathogenic Leptospira spp. in sheep in a sheep-only abattoir in New Zealand

AIM

To determine the prevalence of the two most commonly diagnosed pathogenic Leptospira spp. serovars, Hardjobovis and Pomona, in sheep in a sheep-only abattoir in New Zealand, and to determine the prevalence of kidneys which were leptospire culture-positive collected from sheep seropositive or seronegative to the microscopic agglutination test (MAT).

METHODS

A repeated cross-sectional observational study was conducted of serological and kidney culture prevalences of Leptospira borgpetersenii serovar Hardjobovis and Leptospira interrogans serovar Pomona. Lines of sheep and individual sheep were systematically randomly selected at a sheep-only abattoir during 18 May 2004 to November 2004 and 06 December 2004 to 14 June 2005. Additionally, a cross-sectional study examined prevalences in a purposively selected line of sheep from a flock with clinical evidence of an outbreak of leptospirosis.

RESULTS

In the study population of 15,855 sheep of which 2,758 were sampled, 5.7 (95% CI=4.9-6.7)% were seropositive to one or both serovars; 44.2 (95% CI=34.6-54.2)% of 95 lines of sheep and 44.9 (95% CI=35.0-55.3)% of 89 farms showed serological evidence of infection. The serological prevalence of serovar Hardjobovis was significantly higher than that of serovar Pomona both at line (33% and 4%, respectively) and individual (5% and 1%, respectively) levels. A low but persistent seroprevalence of Hardjobovis throughout both years suggested low-level endemicity to this serovar, whereas Pomona infections appeared to be sporadic. Leptospires were isolated from kidneys of 8/37 (22%) Hardjobovis- and 1/6 (17%) Pomona-seropositive, and 5/499 (1%) seronegative animals. Of the animals purposively sampled from a farm with a clinical outbreak of leptospirosis, all kidneys from the 13 seropositive animals were culture-positive, indicating a high risk of exposure of meat workers in outbreak situations. Kidneys of MAT-seropositive sheep were 21.7 (95% CI=7.6-61.9) times more likely to test culture-positive than kidneys from animals with negative MAT titres. In general, the results indicated that 13/1,000 sheep slaughtered were potentially shedding leptospires.

CONCLUSIONS

The study demonstrated the presence of a definite risk of occupational exposure of meat workers in a sheep-only slaughterhouse to the two most commonly diagnosed pathogenic Leptospira spp. serovars in New Zealand.

Health information Websites: characteristics of US users by race and ethnicity

We conducted a national public opinion survey of adults aged 18 years or older in the continental US to determine their use of health Websites. Of the 928 individuals contacted, 868 (94%) reported their race/ethnicity. More non-Hispanic Whites reported using the Internet (34%) than African Americans (31%) and Hispanics (20%). We used logistic regression to estimate adjusted odds ratios describing the relationship between Website usage and covariates across the racial/ethnic subgroups. Whereas better perceived health was associated with greater Website use among Hispanics and Whites, stronger health literacy was associated with greater use among Hispanics. No African American or Hispanic respondent aged 65 years or older reported going online. The relationship between education and use was more than twice as strong for African Americans and Hispanics than other groups. That some minority groups are less likely to use the World Wide Web for health information may further compound existing disparities. One place where this problem may be addressed is in the nation's schools.

Effect of the age of rams on reproductive performance of ewe hoggets

AIM

To determine the effect of the age of rams, used at a standardised ram-to-ewe ratio, on the breeding performance and pregnancy rate of ewe hoggets.

METHODS

Ewe hoggets ((1/2) Romney x (1/4) Texel x (1/4) Finnish Landrace; n=582) aged 7-8 months were exposed to nine two-tooth, harnessed, vasectomised teaser rams for a period of 17 days (Days 1-17). The ewe hoggets were then weighed and randomly assigned to one of three treatment groups (on Day 18) and joined with either four ram hoggets not used previously (n=194), four two-tooth rams not used previously (n=196), or four mixed-age mature rams (n=192) that had been used previously to mate mature ewes immediately before breeding with the ewe hoggets. The breeding period was 34 days. Ewe hoggets were identified as having been mated during the first 17 days only, during both 17-day periods, during the second 17 days only, or not mated. All ewe hoggets were scanned for pregnancy using ultrasound, 54 days after the end of the breeding period.

RESULTS

Liveweights of ewe hoggets did not differ between treatment groups. More ewe hoggets were mated by the mature rams in the first 17 days than by either ram hoggets or two-tooth rams (p<0.05). However, more of the ewe hoggets mated by mature rams returned to service (failed to conceive), and the percentage of ewe hoggets bred in the first 17 days only or pregnant from a service in the first 17 days did not differ significantly between groups. Fewer of the ewe hoggets joined with ram hoggets were diagnosed as pregnant after 34 days of breeding compared with those joined with either two-tooth or mature rams (p<0.05), as more ewe hoggets failed to be mated at all by ram hoggets compared with those joined with mature rams (p<0.05). There was also a tendency for more ewe hoggets joined with ram hoggets not to be mated at all compared with those joined with two-tooth rams (p=0.07).

CONCLUSIONS

Two-tooth rams previously unused and mature rams previously used for mating were a better option than unused ram hoggets to maximise the pregnancy rate of ewe hoggets to a 34-day breeding period. However, further work is required as it was unclear why lower conception rates were observed in ewe hoggets joined with mature rams which had been used previously. As a result, the advantage of using mature rams may have been underestimated.

Rapid detection of Escherichia coli virulence factor genes using multiplex real-time TaqMan® PCR assays

Three multiplex real-time TaqMan PCR assays were developed for the detection of Escherichia coli virulence factor genes in veterinary samples. Target virulence factors chosen were the fimbriae K88 (F4), K99 (F5), F41, F17, F18 and 987p (F6) and the toxins LT, STa and CDT IV. Detection of genes coding GAD were included in each assay as an internal control. These assays allow rapid identification of virulence factor genes using identical cycling conditions on an Mx3000Ptrade mark real-time PCR machine with the capacity to test up to 20 strains for 9 virulence genes in 1h.

Dose response effects of long-acting injectable vitamin B12 plus selenium (Se) on the vitamin B12 and Se status of ewes and their lambs

AIM

To determine the effect of increasing doses of long-acting injectable vitamin B12 plus selenium (Se) given pre-mating on the vitamin B12 and Se status of ewes and their lambs from birth to weaning.

METHODS

Four groups of 24 Poll Dorset ewes each were injected 4 weeks pre-mating with different doses of a long-acting vitamin B12 + Se product, containing 3 mg vitamin B12 and 12 mg Se per ml. The treatment groups received 5 ml (15 mg vitamin B12 + 60 mg Se), 4 ml (12 mg vitamin B12 + 48 mg Se), 3 ml (9 mg vitamin B12 + 36 mg Se), or no vitamin B12 or Se (control). Twelve of the twin-bearing ewes per group were selected for the study. Efficacy of the product was evaluated from changes in the concentrations of vitamin B12 in serum and liver, and of Se in blood, liver and milk in the ewes during gestation and lactation, and in their lambs from birth to weaning. Pasture samples in paddocks grazed by the ewes and lambs were collected at about 2-monthly intervals from 200-m transects.

RESULTS

The flock was Se-deficient, as the mean initial concentration of Se in the blood of ewes was 182 (SE 20.3) nmol/L. Compared with untreated controls, all doses significantly (p < 0.01) increased concentrations of Se in the blood of ewes for at least 300 days. Selenium concentrations in milk were likewise increased throughout lactation, as were those in the blood and liver of lambs. The mean concentration of vitamin B12 in the serum of ewes was initially > 1,000 pmol/L, but this decreased within 28 days to < 460 pmol/L. Treatment with the 5-ml and 4-ml doses raised serum vitamin B12 concentrations of ewes for at least 176 days (p < 0.01), while their lambs had significantly greater concentrations of vitamin B12 in serum and liver for less than 37 days after birth. Tissue concentrations and duration of elevation of both vitamin B12 and Se were proportional to the dose administered. The mean concentrations of Se and cobalt (Co) in the pastures were 32 and 74 microg/kg dry matter (DM), respectively.

CONCLUSIONS

Injecting ewes from a Se-deficient flock 4 weeks prior to mating with 48 or 60 mg Se and 12 or 15 mg vitamin B12 increased and maintained the Se status of ewes for at least 300 days, and of their lambs from birth to weaning. The vitamin B12 status of ewes was increased for at least 176 days and that of their lambs for less than 37 days. Due to the proportional nature of the response to increasing dosage, the dose rate of the formulation tested can be adjusted according to the severity of Se and Co deficiency in a flock.

CLINICAL SIGNIFICANCE

A single subcutaneous injection of vitamin B12 + Se administered pre-mating to Se-deficient flocks is likely to prevent Se deficiency in ewes and their lambs until weaning, as well as increase the vitamin B12 status of ewes and their lambs until 5 weeks after lambing.

Pulsed-field gel electrophoresis of Campylobacter jejuni sheep abortion isolates

Campylobacter species are a significant cause of sheep abortion in most sheep-raising countries. In New Zealand, Campylobacter fetus subsp. fetus is the leading cause of diagnosed sheep abortion and the species C. jejuni and C. coli have also been implicated. To date, strain typing information of C. jejuni sheep abortion isolates is limited. The objective of the present study was to genotype C. jejuni isolates cultured from sheep abortions submitted to diagnostic laboratories in New Zealand during the 2000 breeding season, using pulsed-field gel electrophoresis (PFGE). In this study, C. jejuni isolates were cultured from approximately 10% of farms from which Campylobacter species were isolated from sheep abortions in the year 2000. This equated to 25 C. jejuni isolates from 21 farms. These isolates were obtained from the veterinary diagnostic laboratories and strain typed using the molecular typing technique PFGE. Ten distinct PFGE types were identified amongst the isolates. No particular PFGE type was found most frequently amongst these C. jejuni sheep abortion isolates. However, indistinguishable or similar C. jejuni PFGE types were identified from different aborted foetuses from the same flock, consistent with the role of C. jejuni as an infectious cause of abortion in sheep. These strain types were similar or indistinguishable from C. jejuni sheep abortion isolates obtained in 1999 in a smaller study (Mannering, S.A., Marchant, R.M., Middelberg, A., Perkins, N.R., West, D.M., Fenwick, S.G., 2003. Pulsed-field gel electrophoresis typing of C. fetus subsp. fetus from sheep abortions in the Hawke's Bay region of New Zealand. NZ Vet. J. 51, 33-37).

The effect of length of use of teaser rams prior to mating and individual liveweight on the reproductive performance of ewe hoggets

AIM

To determine the effects of liveweight (LW) and duration of teasing with vasectomised rams prior to breeding on both the mating performance and pregnancy rate of ewe hoggets.

METHODS

Five hundred and forty-six (1/2) Romney x (1/4) Texel x (1/4) Finnish Landrace ewe hoggets were weighed and randomly assigned to one of three treatment groups: either exposed to five harnessed vasectomised (teaser) rams for 17 days prior to the breeding period (T17; n =181); exposed to five harnessed teaser rams for 8 days prior to the breeding period (T8; n = 184); or not exposed to teasers (unteased; n = 181). Harnessed entire rams of the same breed were then introduced for the duration of two oestrous cycles. Using crayon marks, hoggets were identified as having been mated in the first 5 days, Days 6-10, Days 11-17, during the first 17 days only, during both 17-day periods, during the second 17 days only, or not mated. All hoggets that were mated were scanned for pregnancy, using ultrasound, 48 days after the end of the breeding period, and identified as being either non-pregnant, or as singleton- or twin-bearing.

RESULTS

Hoggets mated in the second 17-day period only were significantly lighter than those mated in either the first 17-day period only (p < 0.001), or in both the first and second 17-day periods (p < 0.02). At Day 1, twin-bearing hoggets were heavier than singleton-bearing hoggets (p < 0.001) and tended to be heavier (p = 0.06) than non-pregnant hoggets. At Day 18, twin-bearing hoggets were heavier than non-pregnant (p = 0.01) and singleton-bearing (p < 0.01) hoggets. A lesser proportion (p < 0.001) of unteased hoggets was mated in the first 17-day period only, compared to T17 hoggets. Conversely, a greater proportion of unteased hoggets was mated in the second 17-day period only, compared to either T8 (p < 0.01) or T17 (p < 0.001) hoggets. A lesser proportion of unteased hoggets was mated in the first 17 days of breeding, regardless of whether they returned to oestrus or not, in comparison to either T8 (p = 0.001) or T17 (p < 0.001) hoggets. Of those mated in the first 17 days of the breeding period, T8 hoggets were less likely (p < 0.05) to be mated in the first 5 days of that period but more likely to be mated in the last 7 days, compared to unteased and T17 hoggets. T17 hoggets had higher pregnancy rates to the first 17 days of breeding compared with either unteased (p = 0.01) or T8 hoggets (p = 0.06), and were more likely (p < 0.05) to be twin-bearing. In addition, the scanning percentage of T17 hoggets was higher than either unteased or T8 hoggets (p < 0.05).

CONCLUSIONS

Heavier hoggets at breeding are more likely to be mated during the first 17 days of breeding and to be twin-bearing. While teasing for just 8 days increased the numbers mated in the first 17 days of breeding it did not increase the numbers of hoggets pregnant to that period. In contrast, teasing for 17 days did increase the numbers pregnant to the first 17 days of breeding and also increased the overall scanning percentage. It is recommended that farmers use a 17-day period of teasing before the breeding of ewe hoggets.

Persistence, serodiagnosis and effects on semen characteristics of artificialBrucella ovisinfection in red deer stags

AIMS

To investigate the persistence of infection and serum antibody titres after infection of red deer (Cervus elaphus) stags with Brucella ovis, and compare these with those of rams. To assess the effects of recent and chronic infection on semen characteristics of stags.

METHODS

Fourteen stags and eight rams were artificially infected with B. ovis by intravenous inoculation. Semen and blood samples were collected at approximately monthly intervals for 649 days. Semen samples were subjected to bacterial culture, and sera were tested for B. ovis antibodies using a complement fixation test (CFT) and an enzyme-linked immunosorbent assay (ELISA). At the end of the study, animals were slaughtered and reproductive organs subjected to bacterial culture. During the first and second breeding seasons, three and five semen samples, respectively, were evaluated from each stag for sperm motility and morphology.

RESULTS

Twelve of 14 (86%) stags and 6/8 (75%) rams developed a patent B. ovis infection and shed the organism in semen. All six infected rams continued to shed B. ovis in semen throughout the 649-day study period, and at slaughter B. ovis was isolated from the reproductive tract and urinary bladder. In contrast, 10/12 (83%) infected stags stopped shedding B. ovis in semen 103-342 days after inoculation, and the organism could not be isolated from their reproductive tracts at slaughter. The remaining two infected stags shed B. ovis in semen throughout the study period and the organism was isolated from their reproductive tracts at slaughter. All inoculated animals initially developed serum antibody titres detectable using the B. ovis CFT and ELISA. For infected stags, the diagnostic sensitivity of these tests was 100% for the first 166 days, but decreased to 50-90% after this. The diagnostic sensitivity for the infected rams was 100% throughout the study period. Infection in stags resulted in variable effects on semen characteristics. Eight of 12 (67%) infected stags had a mean sperm motility of < 50%, and < 60% mean normal sperm in the first year of infection. Seven of these stags had resolved the infection by the following breeding season, and there was a significant improvement in sperm motility and morphology.

CONCLUSIONS

Stags are as susceptible as rams to experimental B. ovis infection. However, the majority of infected stags resolved the infection within a year, whereas rams remained infected for at least 649 days (22 months). Serology, using CFT and ELISA, was effective at detecting infection during the first 166 days in both species, but after this time was less effective at detecting infection in stags than in rams. Infection with B. ovis had variable but generally deleterious effects on the semen characteristics of stags, which resolved following resolution of the infection. Differences in the characteristics of the disease in stags compared with rams mean that different control methods are warranted for the two species.

CLINICAL RELEVANCE

Most stags infected with B. ovis are likely to resolve the infection within a year, and semen characteristics return to levels acceptable for breeding. Serology is useful for detection of infection in the early stages of the disease, but once disease has been present in the herd for some time false-negative reactions are likely to occur in individual stags.

Observations on an outbreak of foot abscess in sheep

An outbreak of ovine interdigital dermatitis and foot abscess in which approximately a third of 300 Perendale ram hoggets had acute lameness was investigated. Both foot infections occurred simultaneously in the flock, and ovine interdigital dermatitis preceded the occurrence of foot abscess in seven instances. It was suggested that the behaviour pattern and sexual activity of the young rams predisposed them to ovine interdigital dermatitis and foot abscess. Although no controlled trials were conducted, the lame sheep responded well following the combined therapeutic measures of dry surroundings, formalin footbathing and selected antibiotic therapy.

The effects of iodine deficiency on ewe fertility and perinatal lamb mortality

AIMS

To substantiate a previous report of improved fertility and perinatal lamb mortality rate following iodine supplementation in a Manawatu Romney ewe flock. To contribute data which might be used to predict a response to iodine supplementation.

METHODS

A controlled iodine supplementation trial was performed over 2 successive years. The possible confounding factor of different lambing paddocks on perinatal lamb mortality was removed by the reversal of the paddocks used by the supplemented and control ewes during the second year.

RESULTS

During 2 successive years, iodine supplementation resulted in improved reproductive performance in a Manawatu Romney flock with 21% and 14% more lambs born to supplemented than to control mixed-age ewes in 1996 and 1997 respectively. Supplementation also resulted in improved perinatal lamb survival, although this effect was greater during the wetter 1996 Lambing season. Despite the production response during both years, a difference in lamb thyroid:bodyweight ratio was only noted following the drier 1997 winter. Ewe thyroid hormone concentrations before mating and during mid-pregnancy were poor indices of deficiency.

CONCLUSIONS

Iodine deficiency should be included in the list of differential diagnoses for poor reproductive performance in ewes and in the investigation of high perinatal lamb mortality rates.

CLINICAL SIGNIFICANCE

The annual cost associated with iodine deficiency in this Manawatu Romney flock is conservatively estimated at dollar 6.00 per ewe. This economic loss is considerably greater than the annual cost of iodine supplementation using iodised oil.

The efficacy of a subcutaneous injection of soluble Vitamin B12 in lambs

AIMS

To assess the efficacy of a soluble Vitamin B12 injection in lambs by measuring changes in the serum and liver Vitamin B12 concentrations.

METHODS

Thirty-six lambs were injected subcutaneously with 2 mg of soluble Vitamin B12 while another group of 36 served as untreated controls. Blood and liver biopsy samples for Vitamin B12 determinations were collected just before the injection and at days 1, 2, 5, 8, 16, 24, 30 and 45.

RESULTS

The serum Vitamin B12 concentrations of the Vitamin B12 treated lambs increased rapidly compared to the untreated lambs. Concentrations peaked at day 2, decreased rapidly to day 8, and then decreased more slowly until day 24 when there were no longer differences between the groups. Liver Vitamin B12 concentrations of the Vitamin B12 treated lambs were significantly greater over days 8-24.

CONCLUSION

A subcutaneous injection of 2 mg of soluble Vitamin B12 was effective in increasing and maintaining the Vitamin B12 status of lambs for about 24 days.

CLINICAL SIGNIFICANCE

This Vitamin B12 product is only effective for preventing cobalt deficiency in lambs for about 4 weeks.

The effect of progesterone supplementation post mating and shearing of ewes in early pregnancy on the reproductive performance of ewes and birthweight of lambs

AIM

To determine whether short-term progesterone supplementation post mating or shearing of ewes in early pregnancy affected either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs.

METHODS

Romney ewes (n=457) were synchronised in oestrus using controlled internal drug-releasing (CIDR) devices containing progesterone, and mated to Romney rams over a 5-day period. The mid-point of mating (Day 0) occurred 2 days after the withdrawal of CIDR devices. Ewes mated (n=397) were randomly allocated to one of four treatment groups: shearing at Day 5, shearing at Day 30, no shearing, and no shearing plus progesterone supplementation using a CIDR device inserted on Day 3 for 6 days. During the period from Day 5 to Day 27, six harnessed Suffolk rams were placed with the ewes and matings recorded. At Day 48, all ewes that did not return to the Suffolk rams were scanned for pregnancy using ultrasound. At Day 140, single- and multiple-bearing ewes were set-stocked at 15.1 and 12.2 ewes/ha, respectively, and equivalent numbers of ewes from each treatment group were placed in each paddock. Blood samples from 10 unshorn and 10 progesterone-supplemented ewes were collected on Days 3, 6 and 9, and analysed for plasma progesterone concentrations. Lambs were identified to their dam and weighed within 12 h of birth, and again at 27 and 93 days after the mid-point of lambing. The ewes were weighed at regular intervals throughout the trial.

RESULTS

Plasma progesterone concentrations of supplemented ewes were higher than those of unsupplemented ewes (3.28 vs 1.75 ng/ml) on Day 6 (p=0.02) but not on Day 9 (4.58 vs 4.63 ng/ml). Treatment of ewes had no effect on either the proportion of ewes which lambed to the synchronised mating period or that had multiple lambs. Lambs born to ewes shorn at Day 30 tended (p=0.09) to be heavier at birth (by 0.28 kg) than those born to unshorn ewes but this effect was not evident when data were corrected for length of gestation. Neither shearing at Day 5 nor progesterone supplementation had any effect on the birthweight of lambs, and the treatment of ewes had no effect on the survival rate of lambs to weaning.

CONCLUSIONS

Progesterone supplementation for 6 days beginning 3 days post mating did not increase either the proportion of ewes that lambed or that had multiple lambs, or the birthweight of lambs. Shearing 5 days after mating had no significant effect on the reproductive performance of ewes and need not be avoided, but is unlikely to result in an increase in lamb birthweight. Shearing ewes at Day 30 may result in an increase in the birthweight of lambs but, ideally, ewes should be further advanced in pregnancy before shearing is undertaken.

The effect of individual liveweight and use of teaser rams prior to mating on the reproductive performance of ewe hoggets

AIM

To determine the effects of liveweight (LW) and use of teaser rams prior to mating on both the mating performance and pregnancy rate of ewe hoggets.

METHODS

Romney hoggets (n=841) were weighed and randomly assigned to one of two treatment groups; either exposed to seven harnessed, vasectomised (teaser) rams for 17 days prior to the breeding period (n=283); or not exposed to teaser rams (unteased, n=558). Harnessed Perendale rams were then introduced for two oestrous cycles. Using crayon marks, hoggets were identified as having been mated during the first 17 days only, during the second 17 days only, during both periods, or not mated. All mated hoggets were then scanned for pregnancy using ultrasound, 48 days after the end of the breeding period, and identified as being either non-pregnant, or as single-, twin or triplet-bearing.

RESULTS

Hoggets mated in either the first 17 days only or in both the first and second 17-day periods were heavier than those mated in the second period only (p<0.001). Those mated in the first or second 17-day period only, and those mated in both periods were all heavier prior to mating than those not mated at all (p<0.001). Twin-bearing hoggets were heavier than both their single-bearing and non-pregnant counterparts (p<0.001). A greater proportion of the teased hoggets were mated in the first 17 days only compared with unteased hoggets (62.6 vs 32.1%; p<0.001). In contrast, more of the unteased hoggets were marked in the second 17-day period only (p<0.001). A greater proportion of mated, unteased hoggets were found to be non-pregnant in comparison to their teased counterparts (17.8 vs 11.2%; p=0.02).

CONCLUSIONS

Heavier hoggets at breeding were more likely to be mated in the first 17 days of the breeding period and more likely to be twin-bearing. Use of teaser rams for 17 days prior to the breeding period increased the proportion of hoggets mated in the first 17 days, increased conception rates, and thus increased the proportion of pregnant hoggets. These results indicate that farmers should utilise teasers for 17 days prior to commencement of the breeding period and avoid mating hoggets that weigh below 36 kg.

Transmission of Brucella ovis from rams to red deer stags

AIM

To determine whether B. ovis will transmit from infected rams to non-infected red deer stags (Cervus elaphus) grazing together in the same paddock.

METHODS

Six rams artificially infected with B. ovis were grazed with six non-infected 14-month-old red deer stags for a four and a half month period from March 4 to July 20, 1999. Stags were blood sampled at one- to six-weekly intervals to test for B. ovis antibodies using a complement fixation test. Stags that seroconverted were semen sampled to test for B. ovis infection by bacteriological culture.

RESULTS

Between day 92 and day 124 of grazing together (June 4 and July 6), sera from five of the six stags became positive in the B. ovis complement fixation test. B. ovis was cultured from semen samples from four of the seropositive stags.

CONCLUSIONS

Brucella ovis can be transmitted from infected rams to non-infected stags grazing in the same paddock, suggesting that B. ovis infection in farmed deer in New Zealand initially came from infected rams. Whether transmission occurs from direct contact between rams or stags, or indirectly by environmental contamination needs to be established.