New Zealand veterinary journal最新文献

Case history: In a 520-cow, spring-calving, pasture-based Waikato dairy farm, the bulk milk somatic cell count (SCC) increased by approximately 20% from 203,000 cells/mL in the 2020/21 season to 245,000 cells/mL in the 2021/22 season. Analysis of herd test SCC data found that the incidence of intramammary infection increased more than 10-fold from 1.8 to 19.2 cows/30 days at the March 2021 and March 2022 herd tests, respectively.

Laboratory findings: Milk sampling of all quarters of 43 cows with a SCC > 200,000 cells/mL following herd testing in March 2022, identified 12 quarters from 10 cows infected with Staphylococcus aureus. Antimicrobial sensitivity testing by disc diffusion testing found nine of these isolates (from seven cows) were methicillin resistant.

Diagnosis: Whole genome sequencing demonstrated the presence of mecA, a gene encoding an alternative penicillin-binding protein (PBP2a) associated with methicillin-resistant Staph. aureus (MRSA). These isolates were sequence type 5, spa type t002, and all were carrying one or more of the immune human immune evasion cluster genes, scn, chp, sak and sea.

Conclusions: Due to concerns for public safety, the Ministry for Primary Industries, the milk processor and the farm's staff were notified. A comprehensive management plan was implemented which focused on reducing the risk of human exposure by wearing gloves, discouraging consumption of raw milk, and smoking or eating in the milking parlour, alongside measures designed to minimise cow-to-cow transmission such as improving teat spray application, milking machine maintenance, additional sampling, and segregation of likely infected (that is, high SCC and confirmed presence of Staph. aureus) cows. Implementation of the plan resulted in a significantly lower bulk milk SCC and reduced incidence rate of new infections in the subsequent two lactations. However, MRSA was isolated from cows for at least a further 13 months, with some cows remaining infected this entire period despite having been treated with cloxacillin-based antimicrobials at the end of lactation. One staff member had a history of being hospitalised during 2021/22 for significant soft tissue infections.

Clinical relevance: Given the sequence type, spa type, and presence of the immune evasion cluster genes, it is probable that the MRSA was introduced into the herd from a human. Veterinarians need to be aware of the possibility of MRSA within dairy herds and the possible human origin for these infections.

Abbreviations: BMSCC: Bulk milk somatic cell count; MRSA: Methicillin-resistant Staphylococcus aureus; NAS: Non-aureus staphylococci; PBP: Penicillin-binding protein; SCC: Somatic cell count; spa: Staphylococcal protein A; ST: Sequence type.

Aims: To assess the accuracy of the morphological identification of Lucilia cuprina and Lucilia sericata by using molecular analysis as a reference standard test, and to describe the seasonality of these species.

Methods: A convenience sample of L. cuprina and L. sericata flies was caught on eight farms from across New Zealand and stored at room temperature in 70% alcohol. They were first morphologically identified using published keys and then molecularly identified using primers to amplify the 28S rRNA region of the nuclear genome. The accuracy of the morphological identification was then estimated for each species using the molecular identification as a reference standard test. The correctness of the published keys was also tested by re-examining a sample of misidentified flies using enhanced magnification and photography.

Results: The accuracy of the morphological identification for L. cuprina was 0.66 (95% CI = 0.58-0.73) and for L. sericata was 0.7 (95% CI = 0.62-0.77). There was no evidence for a difference in accuracy between species (p = 0.56), and re-examination of the misidentified flies found no faults in the published keys. The study confirmed that L. cuprina has a longer season of activity than L. sericata.

Conclusions: These results emphasise the need to use molecular methods to confirm the identification of these species, especially when dealing with large, stored collections, rather than to rely on morphological identification alone.

Clinical relevance: Without accurate fly identification and knowledge of insecticide resistance status, effective control and prevention of flystrike in New Zealand could be handicapped.

Aims: To evaluate the efficacy of hydrogen peroxide gas plasma (HPGP) in sterilising biologically contaminated nerve-stimulating needles for reuse, which could contribute to sustainability and reduce medical waste.

Methods: Nine sterile, 21-gauge x 4-inch Stimuplex nerve-stimulating needles were inoculated by passing Geobacillus stearothermophilus spore suspension through the lumen and tubing, as an indicator for the efficacy of sterilisation. One additional nerve-stimulating needle was not inoculated as a negative control. All 10 needles were packaged in individual sterilisation pouches with an HPGP-specific biological and chemical indicator. Eight samples were sterilised with HPGP. The remaining inoculated sample was not sterilised as a positive control. Tryptic soy broth (TSB) was aspirated through all 10 needles into individual TSB tubes that were then incubated at 60°C for 48 hours and inspected for a colour change indicating bacterial growth. An aliquot from each TSB tube was plated on agar plates and incubated at 60°C for 24 hours. All colonies grown were speciated by matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) mass spectrometry.

Results: All chemical and biological indicators confirmed a successful sterilisation cycle. However, in contrast to the indicators, the TSB cultures from all eight inoculated needles post-sterilisation and the untreated positive control, underwent a colour change indicating bacterial growth, and bacterial colonies, confirmed as G. stearothermophilus, were observed on nutrient agar plates from these nine cultures. No bacterial growth was observed on the negative control plate.

Conclusions: HPGP autoclaving, though appropriate for temperature-sensitive equipment, is ineffective for nerve localiser needles.

Clinical relevance: While reducing medical waste is important, it must not compromise patient safety. Not all medical materials can be reliably sterilised. Stimuplex nerve-stimulating needles should remain single-use only and are not suitable for re-sterilisation with HPGP.

Abbreviations: FDA: Food and Drug Administration; HPGP: Hydrogen peroxide gas plasma; MALDI-TOF: Matrix-assisted laser desorption/ionisation time-of-flight; TSB: Tryptic soy broth.

Aims: To report short- and long-term outcomes of dogs with medial coronoid process disease (MCPD) treated by needle arthroscopy-assisted fragment removal (NA-FR) and to identify potential tomodensitometric and arthroscopic criteria associated with functional prognosis.

Methods: Medical records of dogs diagnosed with MCPD by CT and presented to a single veterinary teaching hospital, between 2021 and 2023 and treated with NA-FR were retrospectively reviewed. Data collected and analysed included: subjective lameness scores (0-5 scale) evaluated by surgeons before, and 15 days and 1 month after surgery; modified International Elbow Working Group (mIEWG; 0-12 scale) score determined by CT, modified Outerbridge score (MOS, 0-5 scale) assessed during surgery; and Canine Orthopaedic Index (COI; 16-80 scale) scores collected from owners at the time of presentation, 1 month after surgery and at long-term follow-up (≥ 12 months).

Results: Data from 41 clinically affected elbows (30 dogs) diagnosed with MCPD by CT were included. A decrease in lameness scores compared to before surgery was observed at 15 days (2 (IQR 2-3) vs. 0 (IQR 0-1); p = 0.05) and 30 days post-operatively (2 (IQR 2-3) vs. 0 (IQR 0-2); p = 0.0002). Dogs that were still lame 30 days post-operatively had a higher ulnar MOS than those that were no longer lame (3 (IQR 3-4) vs. 2 (IQR 2-3); p = 0.02). At long-term follow-up (median 24 (IQR 16-32) months after surgery; available for 18/30 dogs), there was a reduction in COI scores (median 21 (IQR 19-24)) compared to the pre-operative period (median 48 (IQR 45-56); p = 0.002). Furthermore, COI scores were higher in dogs having an ulnar or humeral MOS > 2 or mIEWG > 6 compared to those having an ulnar or humeral MOS ≤ 2 or mIEWG ≤ 6 (28 (IQR 25-44) vs. 19 (IQR 18-21), p = 0.004 and 26 (IQR 25-28) vs. 19 (IQR 19-23), p = 0.02).

Conclusions and clinical relevance: MCPD treated by NA-FR showed satisfactory short- and long-term post-operative outcomes. Increased humeral or ulnar MOS scores as well as modified IEWG scores were associated in our study with a poorer long-term outcome. Further assessments are needed to validate this strategy and to establish the criteria for identifying dogs that will best benefit from NA-FR.

Aims: To determine the importance of 11 climate variables on pasture spore count of Pseudopithomyces chartarum, a risk indicator of facial eczema (FE), and to forecast spore counts in New Zealand until 2100, using longitudinal P. chartarum pasture spore count data.

Methods: Between 2010 and 2017, spore counts (n = 6,975) were collected from 862 paddocks spread over 102 farms in the North Island of New Zealand. Historical and projected climate data were obtained from the National Institute of Water and Atmospheric Research. The spore count dataset was merged with climate data from corresponding locations, incorporating time lags of 1-53 weeks. Linear regression models were fitted for describing crude associations, while random forest models were fitted for determining variable importance and predicting future spore counts.

Results: Mixed-effect linear regression models explained up to 11% of the variance of log-transformed spore counts by a single lagged climate covariate. The best-fit random forest model had a testing accuracy of 80% in classifying low or high FE risk (> 20,000 spores) with an R² value of 43%. The random forest models suggested time-dependent importance of soil temperature at 10 cm depth, solar radiation, potential evapotranspiration, vapour pressure, soil moisture and minimum temperature, while no or weak evidence of variable importance was found for maximum temperature, rainfall, mean sea level atmospheric pressure, relative humidity and wind speed. Over the next 80 years, our model predicted an increase in the seasonal mean spore counts in the study farms by a mean of 17% (min 6, max 30%) under the high-end greenhouse gas emission scenario (representative concentration pathways (RCP) 8.5). Every decade was associated with an increase in the probability of high-risk spore counts (> 20,000) by 14-22% for the moderate to high emission scenarios (RCP 4.5-8.5). The model indicated increased peak spore counts across most regions over the next 80 years. Specifically, the entire North Island and three districts in the South Island were projected to have high mean peak spore counts by 2100.

Conclusions and clinical relevance: These findings could be used to target high-risk areas to implement mitigation or adaptation measures for FE. In addition, the study highlights the value of ecological data for forecasting environmental disease risks to enhance preparedness for climate change.

Aims: To quantify the production effects of outbreaks of clinical salmonellosis in seasonal calving, pasture-based dairy herds in New Zealand, from which non-Brandenburg Salmonella enterica subsp. enterica were isolated, and to use these results to undertake a financial analysis of their consequences.

Methods: In this retrospective cohort study, we collated routinely available data for cow demographics, disease treatment, and accumulated whole of lactation milk solids (MS) yield from five spring-calving, pasture-based dairy herds that experienced naturally occurring clinical salmonellosis outbreaks in milking cows over the study period from 1 June 2021 until 31 May 2022. We used multivariable generalised linear models to estimate the effects of cow-level risk factors for clinical salmonellosis and the effects of disease on accumulated whole of lactation MS yield and risk of removal by culling or death. The financial consequences of salmonellosis were estimated with a partial budget model using the study results and publicly available information.

Results: The median herd incidence risk of clinical salmonellosis over the study period was 2.6% (min 0.5, max 7.0%). The adjusted marginal mean incidence risk for disease for cows of age 2, 3-4, 5-6 and ≥ 7 years of age were 0.93% (95% CI = 0.39-2.18%), 0.98% (95% CI = 0.49-1.93%), 3.5% (95% CI = 2.15-5.63%) and 4.8% (95% CI = 3.06-7.40%), respectively. In three of the four herds with milk production records, there was no measurable effect of disease on MS yield and in a single herd, the adjusted marginal mean effect was a reduction in affected cows of 150 (95% CI = 98-202) kg (p < 0.001) accumulated MS yield per cow (36%). In a study of median-sized hypothetical herds, under six different scenarios differing in the level of impact of salmonellosis on MS yield and with differing incidence risks of disease, we estimated a total herd-level increase in expenditure and decrease in income for the season in which the outbreak occurred of NZ$1,873-NZ$13,444.

Conclusions: This preliminary study suggests that the financial consequences of clinical salmonellosis in New Zealand dairy herds are highly variable and are driven mainly by the incidence risk of disease and its effect on milk production.

Clinical relevance: Our results provide a preliminary guide to the range of biological and financial impacts of salmonellosis outbreaks in New Zealand dairy herds, which can aid in the planning of future research and inform farmer decision-making on control measures.

Aims: To assess the association between the sample/positive (S/P) ratios from a milk IgG ELISA, specific for Staphylococcus aureus and the somatic cell count (SCC) in cow composite milk samples taken at routine herd testing, and the association between the S/P ratio and milk solids (MS; kg fat + protein/cow/day) in cows in a pasture-based, seasonal-calving, New Zealand dairy herd.

Methods: Data from cow-composite milk samples were retrospectively analysed to determine the associations between the S/P ratios from a milk IgG ELISA specific for S. aureus, SCC (transformed to linear scores (LS) for analysis), and MS from cow-composite milk samples collected on four occasions across two lactations. A generalised linear mixed model was used to assess the effect of age, breed, month in lactation, and their interactions on the S/P ratio. To assess agreement between cows defined as infected based on S/P and on SCC, cows were classified as uninfected or infected using test positive cutpoints ≥ 0.38 for the S/P ratio and ≥ 150,000 cells/mL for SCC, and the agreement between these categories was compared by Gwet's agreement coefficient (AC). A generalised linear mixed model was used to assess associations between S/P and MS production with age, breed, and herd test date, with their interactions as explanatory variables, and cow as a random effect.

Results: The S/P varied by month of lactation, and there was an interaction between age and breed. There was a moderate agreement between the dichotomised S/P ratios and the dichotomised SCC (Gwet's AC = 0.59 (SE = 0.02); p < 0.001). When the MS production of cows defined as S/P test negative, suspicious or positive was analysed, there was an age by S/P interaction whereby there was no association between S/P category and MS amongst 2-year-olds, while in older cows, test-positive cows had lower MS than test-negative cows.

Conclusions: This observational study demonstrated moderate agreement between S/P ratio and SCC. Additionally, there were negative associations between the S/P ratio and MS amongst older cows and in late lactation. Thus, the S/P ratio of an S. aureus-specific IgG ELISA is correlated with a well-defined marker of mastitis (SCC) and with milk yield depression. Further assessment of these associations using microbiology, and investigation of associations between the antibody results and long-term survival in the herd would further strengthen the validity and utility of the test.

Qualitative research is increasingly recognised as an essential component of veterinary inquiry, especially when exploring the complex human, ethical, and contextual factors that influence animal health and welfare. This primer offers a practical and straightforward guide to the most commonly used qualitative methods in veterinary settings, including interviews, focus groups, and open-ended surveys as methods of data collection, and reflexive thematic analysis as one approach to data analysis. Aimed at veterinary practitioners and researchers with limited prior experience in qualitative approaches, it explains the reasons for using these methods and how to conduct them rigorously, and highlights common pitfalls to avoid. Drawing on published examples from veterinary science, the article clarifies the process of qualitative data collection and analysis, emphasising reflexivity and ethical responsibility. Although qualitative research does not produce statistically generalisable results, it offers valuable insights into how veterinary professionals and clients experience and understand their world. By providing readers with the foundational tools to design, evaluate, and conduct high-quality qualitative research, this guide helps build a more comprehensive evidence base for informed veterinary decision-making.

Aims: To describe a novel knotless subcuticular suture technique using traditional smooth suture material, and to demonstrate its safety by comparing the post-operative complications with traditional interrupted cruciate skin sutures.

Methods: Forty-four dogs undergoing ovariohysterectomy were randomised into two groups, whereby the skin was closed using either a knotless subcuticular suture (NKSS; n = 22) pattern or traditional cruciate skin sutures (CSS; n = 22). The surgical wounds were assessed using a semiquantitative scoring system 10-14 days post-operatively. Data was analysed for variables associated with any wound reaction first using univariable comparisons. Then, to address small event counts and complete separation, multivariable analysis was conducted using Firth's penalised logistic regression.

Results: Wound reactions occurred in 0/22 dogs with NKSS vs. 5/22 (22.7%) with CSS (p = 0.048). The univariable odds of reaction calculated using Haldane's correction were lower with NKSS (OR = 0.071 (95% CI = 0.0037-1.37); Fisher's exact p = 0.0796). Only suture type was retained in the logistic regression, with findings for the protective effect of NKSS consistent in direction but with greater precision (OR  = 0.071 (95% CI = 0.000-0.693); p = 0.0190).

Conclusions: In this prospective cohort, the absolute risk of any wound reaction was 0% with NKSS and 22.7% with CSS. Findings are compatible with reduced odds of wound reactions for NKSS, but precision is limited by the small sample size and few events. Larger, blinded studies are required before firm conclusions about comparative safety can be drawn.

Clinical relevance: The novel knotless subcuticular suture technique was safe and effective for the skin closure of ovariohysterectomy incisions in dogs, and it may result in lower superficial wound reactions.