Prevalence, survival analysis and multimorbidity of chronic diseases in the general veterinarian-attended horse population of the UK

A transmandibular lateral transsphenoidal navigated surgical approach to access a pituitary macroadenoma in a warmblood mare

A 16-year-old warmblood mare was referred with a progressive history of behavioral changes and left-sided blindness. Following neuroanatomical localization to the forebrain, magnetic resonance imaging of the head revealed a well-delineated, 4.5 cm in diameter, round pituitary mass causing marked compression of the midbrain and optic chiasm. Euthanasia was recommended but declined by the owners. Veterinary specialists and a human neurosurgeon collaboratively prepared for surgical case management. A novel navigated transmandibular lateral transsphenoidal approach was developed to access the region of the sella turcica and practiced on cadaver specimens. The horse was anesthetized and placed in sternal recumbency with the head above the heart line. Using a cone beam computed tomography (CBCT)-coupled navigation system, a navigated pin traversing the vertical ramus of the mandible and the lateral pterygoid muscle was placed in a direct trajectory to the predetermined osteotomy site of the basisphenoid bone. A safe corridor to the osteotomy site was established using sequential tubular dilators bypassing the guttural pouch, internal and external carotid arteries. Despite the use of microsurgical techniques, visualization of critical structures was limited by the long and narrow working channel. Whilst partial resection of the mass was achieved, iatrogenic trauma to the normal brain parenchyma was identified by intraoperative imaging. With consent of the owner the mare was euthanized under the same general anesthesia. Post-mortem magnetic resonance imaging and gross anatomical examination confirmed partial removal of a pituitary adenoma, but also iatrogenic damage to the surrounding brain parenchyma, including the thalamus.

The role of an equine nutritionist in equine health, performance and wellbeing: Ideas stemming from an equine science society symposium workshop

In the United States, there is little clarity on the qualifications and availability of equine nutritionists. Currently, no regulatory body exists for formal credentialing outside of veterinary medicine. Most equine nutritionists are not veterinarians but do have advanced scientific degrees (Master of Science and/or Doctor of Philosophy) in the field of Animal Science. However, not all reporting to be equine nutritionists have formal education in the field of equine nutrition. To discuss this, a workshop was held at the 2023 Equine Science Society (ESS) meeting. The purpose of this discussion was to share ideas among equine nutrition professionals about how best to provide support for the inclusion of the specialty as part of a horse's health team, alongside the veterinarian, farrier and other equine health specialists. In human, small animal and livestock practices, the importance of nutrition as part of an overall health, production (livestock) and well-being plan has been documented. However, surveys of veterinarians, the top source of information for horse owners, reveal a lack of confidence in the area of nutrition after graduating from veterinary school and a lack of available continuing education opportunities to learn more. Further, it appears that many horse owners may unknowingly be obtaining nutrition information from unverified sources (such as the internet). The discussion included formal and informal education of equine nutritionists, as well as avenues to open lines of communication with the veterinary community to provide nutrition resources for horse owners, managers and veterinarians.

BEVA primary care clinical guidelines: Diagnosis and management of equine pituitary pars intermedia dysfunction

BACKGROUND

Pituitary pars intermedia dysfunction (PPID) is a prevalent, age-related chronic disorder in equids. Diagnosis of PPID can be challenging because of its broad spectrum of clinical presentations and disparate published diagnostic criteria, and there are limited available treatment options.

OBJECTIVES

To develop evidence-based primary care guidelines for the diagnosis and treatment of equine PPID based on the available literature.

STUDY DESIGN

Evidence-based clinical guideline using the Grading of Recommendations, Assessment, Development and Evaluation (GRADE) framework.

METHODS

Research questions were proposed by a panel of veterinarians and developed into PICO or another structured format. VetSRev and Veterinary Evidence were searched for evidence summaries, and systematic searches of the NCBI PubMed and CAB Direct databases were conducted using keyword searches in July 2022 and updated in January 2023. The evidence was evaluated using the GRADE framework.

RESULTS AND RECOMMENDATIONS

The research questions were categorised into four areas: (A) Case selection for diagnostic testing, pre-test probability and diagnostic test accuracy, (B) interpretation of test results, (C) pharmacological treatments and other treatment/management options and (D) monitoring treated cases. Relevant veterinary publications were identified and assessed using the GRADE criteria. The results were developed into recommendations: (A) Case selection for diagnostic testing and diagnostic test accuracy: (i) The prevalence of PPID in equids aged ≥15 years is between 21% and 27%; (ii) hypertrichosis or delayed/incomplete hair coat shedding provides a high index of clinical suspicion for PPID; (iii) the combination of clinical signs and age informs the index of clinical suspicion prior to diagnostic testing; (iv) estimated pre-test probability of PPID should be considered in interpretation of diagnostic test results; (v) pre-test probability of PPID is low in equids aged <10 years; (vi) both pre-test probability of disease and season of testing have strong influence on the ability to diagnose PPID using basal adrenocorticotropic hormone (ACTH) or ACTH after thyrotropin-releasing hormone (TRH) stimulation. The overall diagnostic accuracy of basal ACTH concentrations for diagnosing PPID ranged between 88% and 92% in the autumn and 70% and 86% in the non-autumn, depending on the pre-test probability. Based on a single study, the overall diagnostic accuracy of ACTH concentrations in response to TRH after 30 minutes for diagnosing PPID ranged between 92% and 98% in the autumn and 90% and 94% in the non-autumn, depending on the pre-test probability. Thus, it should be remembered that the risk of a false positive result increases in situations where there is a low pre-test probability, which could mean that treatment is initiated for PPID without checking for a more likely alternative diagnosis. This could compromise horse welfare due to the commencement of lifelong therapy and/or failing to identify and treat an alternative potentially life-threatening condition. (B) Interpretation of diagnostic tests: (i) There is a significant effect of breed on plasma ACTH concentration, particularly in the autumn with markedly higher ACTH concentrations in some but not all 'thrifty' breeds; (ii) basal and/or post-TRH ACTH concentrations may also be affected by latitude/location, diet/feeding, coat colour, critical illness and trailer transport; (iii) mild pain is unlikely to have a large effect on basal ACTH, but caution may be required for more severe pain; (iv) determining diagnostic thresholds that allow for all possible contributory factors is not practical; therefore, the use of equivocal ranges is supported; (v) dynamic insulin testing and TRH stimulation testing may be combined, but TRH stimulation testing should not immediately follow an oral sugar test; (vi) equids with PPID and hyperinsulinaemia appear to be at higher risk of laminitis, but ACTH is not an independent predictor of laminitis risk. (C) Pharmacologic treatments and other treatment/management options: (i) Pergolide improves most clinical signs associated with PPID in the majority of affected animals; (ii) Pergolide treatment lowers basal ACTH concentrations and improves the ACTH response to TRH in many animals, but measures of insulin dysregulation (ID) are not altered in most cases; (iii) chasteberry has no effect on ACTH concentrations and there is no benefit to adding chasteberry to pergolide therapy; (iv) combination of cyproheptadine with pergolide is not superior to pergolide alone; (v) there is no evidence that pergolide has adverse cardiac effects in horses; (vi) Pergolide does not affect insulin sensitivity. (D) Monitoring pergolide-treated cases: (i) Hormone assays provide a crude indication of pituitary control in response to pergolide therapy, however it is unknown whether monitoring of ACTH concentrations and titrating of pergolide doses accordingly is associated with improved endocrinological or clinical outcome; (ii) it is unknown whether monitoring the ACTH response to TRH or clinical signs is associated with an improved outcome; (iii) there is very weak evidence to suggest that increasing pergolide dose in autumn months may be beneficial; (iv) there is little advantage in waiting for more than a month to perform follow-up endocrine testing following initiation of pergolide therapy; there may be merit in performing repeat tests sooner; (v) timing of sampling in relation to pergolide dosing does not confound measurement of ACTH concentration; (vi) there is no evidence that making changes after interpretation of ACTH concentrations measured at certain times of the year is associated with improved outcomes; (vii) evidence is very limited, however, compliance with PPID treatment appears to be poor and it is unclear whether this influences clinical outcome; (viii) evidence is very limited, but horses with clinical signs of PPID are likely to shed more nematode eggs than horses without clinical signs of PPID; it is unclear whether this results in an increased risk of parasitic disease or whether there is a need for more frequent assessment of faecal worm egg counts.

MAIN LIMITATIONS

Limited relevant publications in the veterinary scientific literature.

CONCLUSIONS

These findings should be used to inform decision-making in equine primary care practice.

Evaluation of seasonal influences on adrenocorticotropic hormone response to the thyrotropin-releasing hormone stimulation test and its accuracy for diagnosis of pituitary pars intermedia dysfunction

Pituitary pars intermedia dysfunction (PPID) is an age-related neurodegenerative disorder, affecting >20 % of older horses. There is a need for improved endocrine tests for early disease detection, and the thyrotropin-releasing hormone (TRH) stimulation test has been recommended for diagnosis of early or mild cases. However, it is currently not recommended for year-round use due to marked seasonal variability. The aims of this cohort study were to evaluate effects of month and season on adrenocorticotropic hormone (ACTH) responses to TRH stimulation and to derive monthly cut-offs for PPID diagnosis. Sixty-three horses were assigned to control (n = 17), subclinical PPID (n = 21) and clinical PPID (n = 25) groups, based on a composite reference standard that combined clinical history and examination findings with endocrine test results. TRH stimulation tests were performed monthly for a 12-month period. Circannual changes were evaluated with one- and two-way repeated-measures analysis of variance and receiver operating characteristic curve analysis was used to derive cut-off values for basal and TRH-stimulated ACTH. TRH-stimulated ACTH concentrations were lowest in February-May and highest in August-October. Specificity of both basal and 30 min post-TRH ACTH was generally higher than sensitivity, and TRH stimulation had improved diagnostic accuracy compared to basal ACTH, although its sensitivity was not significantly greater year-round. TRH stimulation tests yielded considerably more positive results than basal ACTH in the subclinical group, but few additional positive results in clinical PPID cases. There were large differences between cut-offs that maximised sensitivity or specificity for TRH-stimulated ACTH, highlighting the importance of considering clinical presentation alongside test results in diagnostic decision-making.

Diagnosis of equine pituitary pars intermedia dysfunction

Equine pituitary pars intermedia dysfunction (PPID) is common in aged horses. The majority of horses respond well to treatment, but treatment is lifelong, meaning accurate diagnosis of PPID is important. Similar to any condition, there is no perfect laboratory test to diagnose PPID and accuracy is affected by the characteristics of the population in which the test is being evaluated. This review details the importance of consideration of clinical factors and diagnostic test accuracy. Basal adrenocorticotrophic hormone (ACTH) concentration is used most frequently in practice and has very good diagnostic accuracy when used in combination with clinical judgement and the correct application of diagnostic thresholds. The thyrotropin-releasing hormone stimulation test can be used in horses with equivocal test results following basal ACTH testing, or to evaluate subtle cases due to its improved accuracy.

Epidemiology of Colic: Current Knowledge and Future Directions

Epidemiologic studies are essential for the generation of evidence-based, preventive health care strategies. This includes ways to minimize colic risk and assist informed decision making concerning diagnosis, treatment, and likely outcomes. It is important to consider that colic is not a simple "disease" but is a syndrome of abdominal pain that encompasses multiple different disease processes, and which is multifactorial in nature. This review focuses on prevention and diagnosis of colic, including specific forms of colic, communications with owners/carers concerning colic risk and management, and areas of future research.

Equine Endocrine Disease: Challenges With Case Definition for Research

Equine endocrine disease is an important area for equine research, requiring an appropriate case definition for inclusion and criteria for exclusion from disease. Defining a case for research may be different from criteria for clinical diagnosis. Further, clinical diagnosis recommendations have been changing regularly, making this area challenging for equine scientists. This review discusses the diagnosis of major equine endocrine diseases, pituitary pars intermedia dysfunction, equine metabolic syndrome and insulin dysregulation, focusing on the most appropriate diagnostic methods for research case definitions. Different diagnostic methods, including use of reference intervals and clinical decision limits, will be discussed with their relative merits for use in case definition for research.

Survey of the knowledge and perceptions of horse owners in Ireland of common clinical conditions and their impact

BACKGROUND

As the primary decision-maker for their horse's health and welfare, owners' knowledge of clinical conditions may impact their horse's health. Anecdotal evidence suggests that the emotional impact of equine illness on the owner can be severe but research is lacking.

OBJECTIVES

To evaluate horse owners' self-declared knowledge of eight common equine health conditions and perceptions of the quality of information available; to ascertain respondents' perceptions of the severity of impact on their horse of the conditions and potential emotional impact on themselves and to establish the factors of greatest concern to owners when their horse has a health condition and influential factors on end-of-life decisions.

STUDY DESIGN

Online survey of horse owners.

METHODS

An online survey comprising three sections was created: respondent demographics; vignettes of clinical conditions; concerns and decision-making regarding illness and euthanasia. Vignettes focused on arthritis; Pars Pituitary Intermedia Dysfunction; Equine Metabolic Syndrome (EMS); gastric ulcers; high intestinal worm burden; dermatophilosis ('mud rash'); quidding and head tossing; and equine asthma. Respondents were self-selecting. The survey was circulated for completion by horse owners residing in Ireland and Northern Ireland obtaining 491 valid responses.

RESULTS

Respondents declared that they had the highest knowledge of mud rash, with 84.1% rating their knowledge as very good compared to 42% of respondents for EMS. There was positive correlation between the perceived impact on their horse and emotional impact on the owner for all conditions ranging from weak (arthritis 0.36, P < 0.001) to strong (EMS 0.62, P < 0.001). Pain, discomfort, and quality of life were reported as the most common concerns when their horse has a medical condition or when considering euthanasia.

MAIN LIMITATIONS

Potential bias among respondents towards computer literate owners, with good literacy and interest in equine health conditions.

CONCLUSIONS

Knowledge of equine health conditions, perceived impact of conditions on the horse and emotional impact on their owners varied significantly between conditions.

Cars dent, horse riders break: Analysis of police-recorded injury incidents involving ridden horses on public roads in Great Britain

INTRODUCTION

Police-recorded road injury data are frequently used to approximate injury risk for different road user groups but a detailed analysis of incidents involving ridden horses has not previously been conducted. This study aims to describe human injuries resulting from interactions between ridden horses and other road users on public roads in Great Britain and identify factors associated with severe to fatal injuries.

METHOD

Police-recorded road incident data involving ridden horses (2010-2019) were extracted from the Department for Transport (DfT) database and described. Multivariable mixed-effects logistic regression modeling was used to identify factors associated with severe/fatal injury outcomes.

RESULTS

A total of 1,031 injury incidents involving ridden horses were reported by police forces, involving 2,243 road users. Out of 1,187 road users injured, 81.4% were female, 84.1% were horse riders, and 25.2% (n = 293/1,161) were in the 0-20 year age category. Horse riders represented 238/267 serious injuries and 17/18 fatalities. Vehicle types involved in incidents where horse riders were seriously/fatally injured were mostly cars (53.4%, n = 141/264) and vans/light goods vehicles (9.8%, n = 26). Horse riders, cyclists, and motorcyclists had higher odds of severe/fatal injury compared to car occupants (p < 0.001). Severe/fatal injuries were more likely on roads with 60-70 mph speed limits versus 20-30 mph roads, while odds of severe/fatal injury increased with increasing road user age (p < 0.001).

CONCLUSIONS

Improved equestrian road safety will largely impact females and young people as well as reducing risk of severe/fatal injuries in older road users and those using modes of transport such as pedal-cycles and motorcycles. Our findings support existing evidence that reductions in speed limits on rural roads would help reduce the risk of serious/fatal injuries.

PRACTICAL APPLICATIONS

More robust equestrian incident data would better inform evidence-based initiatives to improve road safety for all road users. We suggest how this can be done.

Pituitary pars intermedia dysfunction in horses associated to pituitary adenoma

ABSTRACT: The clinical syndrome of the pituitary pars intermedia dysfunction (PPID) is the most common endocrinopathy of older horses. This syndrome is characterized by several clinical and pathological changes, which are usually associated with adenomas of the pars intermedia (PI) of the pituitary gland. The aim of this work is to describe five cases of pituitary adenoma of the PI associated with PPID in horses, addressing its clinical and pathological aspects. The horses had a mean of 22 years of age. The main clinical signs were hirsutism and paresis of hind limbs, and at post mortem examination all horses had hirsutism, and a nodule in the pituitary gland, which was histologically characterized as an adenoma of PI (5/5). Furthermore, two horses had gross lesions suggestive of chronic laminitis. Moreover, there was intense parasitism of Sarcocystis neurona (2/5), Strongylus vulgaris (1/5), Parascaris equorum (1/5), Draschia megastoma (1/5), and Klossiella equi (1/5).

The usual suspects: Co-occurrence of integument injuries in turkey flocks

The present study investigated the prevalence and co-occurrence of integument injuries in Canadian turkeys. Participating farmers scored 30 birds in their flock for integument injuries to the head/neck (HN), back/tail (BT), and footpad (FP) using a simplified scoring system (0: no sign of injury, 1: mild injury, 2: severe injury). Information from 62 flocks was used to calculate the prevalence of any (score ≥1) and severe (score 2) injuries on a flock- and individual-level. Chi-square analyses were performed to determine the likelihood of integument injury co-occurrence. The prevalence of each type of injury varied between flocks. While the majority of flocks reported injuries, the within-flock prevalence was relatively low and largely comprised of mild cases (score 1). Given their higher prevalence, the data indicate that FP injuries are overall more widespread and more severe among Canadian turkey flocks than HN and BT injuries. Co-occurrence of different integument injuries was observed in 7% of birds and 58.1% of flocks reported at least one bird with co-occurring injury types. Despite the low prevalence of multiple injury types, birds with one type of injury were more likely to present with other injury types. Indeed, birds with HN injuries were 4 times more likely to have BT injuries, and birds with FP injuries were 1.5 times more likely to have BT injuries compared to birds that do not have these respective injuries. The data increase our understanding of the co-occurrence of these common integument injuries which can help inform a holistic management approach to rear turkeys with healthy skin and feather cover.

Retrospective Analysis of Cause-of-Death at an Equine Retirement Center in the Netherlands Over an Eight-Year Period

Geriatric horses (>15 years) represent a substantial proportion of the equine population. The objective of this study was to (1) report on the cause of death in geriatric horses on a single retirement centre, (2) to evaluate the relationship between PPID status, and mortality rate. Data of 194 horses was collected over an eight-year period. This providing data for 80 geriatric cases of mortality. The average age of horses that died was 26.2 years (±4.8 years). The majority (95%) of mortalities were euthanised, most frequently due to colic (20%), old age (19%), and lameness (15%). Overall mortality rate was 16.3 per 100 horse years at risk (95% C.I. 15.2-17.5) for the total geriatric (>15 years) population. PPID had a prevalence of 48.8% (61 out of 125 horses). The results of this study demonstrate increasing mortality rates with increasing age in geriatric horses. The most common reasons for euthanasia were lameness, old age, and colic. The treatment of PPID does not result in an older age of death. The effect of treatment on the welfare status was not studied. Management, of both veterinarians and care taker, has an important role in maintaining health and welfare in geriatric horses. Findings of this study could be relevant to veterinary surgeons and stable managers providing care for geriatric horses.

Factors Associated with Owner-Reported Euthanasia in Equids in France

There is limited evidence regarding the proportion of dead equids in France that were euthanized and the factors influencing the decision-making of euthanasia. The better understanding of which could facilitate research on improvement of welfare, especially on end of life issues. The aim of this study was to estimate the proportion of euthanasia and identify associated factors in equids in France. A web-based survey was created and distributed by the French horse and riding institute to owners who reported an equine death between April 2017 and April 2018 (n = 5 158). Factors associated with euthanasia were identified using a multivariable logistic regression model. The percentage of responses was 10.6% (n = 548/5 158; 95% CI 9.8% to 11.5%). The proportion of euthanasia was 71.0% (n = 389/548; 95% CI 67.2% to 74.8%). The factors "age category", "cause of natural death or reason for euthanasia" and "the length of time during which the animal was reported to be ill by the owner" were significantly associated with euthanasia (P <0.001). The results highlighted that a large majority of owners faced euthanasia decisions and our findings could support veterinarians and owners to better prepare for such an eventuality.

Assessment of the impact of age and of blood-derived inflammatory markers in horses with colitis

OBJECTIVES

To determine the impact of age on survival in horses with colitis and to elucidate whether a lower type-1/type-2 cytokine ratio or an exaggerated inflammatory state contribute to reduced survival in aged horses.

DESIGN

Part 1: Retrospective cohort analysis. Part 2: Analytic observational study.

ANIMALS

Part 1: One hundred twenty-four adult horses with colitis. Part 2: Twenty-nine adult horses with new diarrhea onset while hospitalized.

MEASUREMENTS AND MAIN RESULTS

Part 1: Patient signalment, select clinicopathological data, diagnoses, treatment, hospitalization length, and invoice were compared between survivors (n = 101) and nonsurvivors (n = 23). Only age and plasma transfusion retained statistical significance in the final multivariate outcome model, with 8.5 times lower odds of survival in transfused horses (95% confidence interval [CI], 2.6-27.2%). Additionally, the likelihood of nonsurvival increased by 11.8% (95% CI, 4-20.2%) for every year the horse aged (P = 0.002). Similarly, geriatric horses (≥20 years) were 15.2 times more likely to die than young-adults (2-12 years, P = 0.03), independent of financial investment, documented comorbidities, and duration of hospitalization. Part 2: Select cytokine analyses were performed on serum collected from hospitalized horses within 1 hour of diarrhea onset (T0) and 6 hours later. At T0, all recorded clinicopathological variables were comparable between geriatric and young-adult horses, suggesting a similar degree of systemic illness. The median concentration of type-2 cytokines interleukin-4 and interleukin-10, and type-1 cytokine interferon-γ did not differ between age groups. Inflammatory cytokines interleukin-6 and tumor necrosis factor-α were significantly higher in geriatric compared to young-adult horses at both sampling time points.

CONCLUSIONS

Outcome of colitis was less favorable in aging horses and patients receiving a plasma transfusion. Although an exaggerated inflammatory state, based on increased interleukin-6 and tumor necrosis factor-α concentrations, in geriatric horses may contribute to reduced survival, a lower type-1/type-2 cytokines ratio was not identified in our geriatric population.

An equine veterinary surveillance network for the UK horse population

April Lawson and Gina Pinchbeck of the University of Liverpool introduce a new initiative that will use electronic health records to create an evidence base for equine research and surveillance.

Evaluation of the sensitivity and specificity of basal plasma adrenocorticotrophic hormone concentration for diagnosing pituitary pars intermedia dysfunction in horses: A systematic review

Measurement of basal adrenocorticotrophic hormone (ACTH) is currently used to diagnose pituitary pars intermedia dysfunction (PPID) in horses, yet a systematic review of the evidence for its use has not been undertaken. This study aimed to systematically review evidence regarding the sensitivity and specificity of the basal ACTH diagnostic test. Electronic databases were systematically searched in January 2019, September 2020 and January 2021, for English language publications published prior to these dates. Screening, data extraction and quality assessment of publications was undertaken by the authors using predefined criteria. Study design, methodology and information reported in included studies were assessed using Standards for Reporting of Diagnostic Accuracy (STARD) checklists. Risk of bias and applicability were appraised using the Quality Assessment tool for Diagnostic Accuracy Studies (QUADAS-2) quality assessment tool. Due to identified biases and marked between-study variations, meta-analysis was not undertaken. After removal of duplicates, 415 publications were identified, of which 25 were evaluated in full, with 11 of these meeting inclusion criteria. In most studies, basal ACTH was reported to have good sensitivity (overall median 75.5%; interquartile range [IQR], 64.0-86.5%; range, 36.0-100%) and excellent specificity (overall median, 95.2%; IQR, 84.2-98.9%; range, 63.3-100%). However, QUADAS-2 and STARD assessment highlighted that studies did not utilise optimal study design and/or study populations for the evaluation of a diagnostic test and the majority were subject to bias, or provided insufficient information to fully assess possible biases. Based on this review, basal ACTH performed better at ruling out PPID than detecting it.

Caring for the Older Horse: A Conceptual Model of Owner Decision Making

The number of aged horses in the UK has been growing over recent years, with many horses remaining active and being cared for into old age. However, increasing age is paralleled with a heightened risk of morbidity and mortality; therefore, owners of older horses must manage changes in their horse, making decisions about management and health care provision. In this paper, we discuss data collected from an open-access online discussion forum, where forum users sought advice arising from concerns about their older horse. Qualitative data analysis was performed using grounded theory methods. A conceptual model was developed to demonstrate the multifaceted ways in which ageing affects the human-horse relationship and impacts upon outcomes for the horse. The model reflects the dynamic nature of caring for an older horse to accommodate change over time-outcomes for the horse shift as the context of day-to-day life changes. The model provides novel insight into how decisions around older horse care are made.

Translating research into practice: Adoption of endocrine diagnostic testing in cases of equine laminitis

Research demonstrating insulin's causal role in endocrinopathic laminitis has greatly advanced understanding of equine laminitis. However, the degree to which this knowledge has been translated into clinical practice has not been assessed. This two-part study aimed to investigate veterinary surgeons' current diagnostic approach to laminitis, whether this had changed over time, and the impact of diagnosing an endocrinopathy on laminitis case management and outcome. Two cross-sectional online surveys of equine veterinary surgeons working within the UK were undertaken. The first study population comprised 141 veterinary surgeons, who had graduated a median of 8 years previously. Overall, 83.6% of respondents (n = 117/140) had changed their diagnostic approach to laminitis since graduating, primarily through increasing use of endocrine testing (88.7%; n = 86/97). Ninety-nine percent (n = 140/141) performed endocrine diagnostic test(s) for some or all laminitis cases at initial and/or subsequent examinations. The second study had 120 participating veterinary surgeons, ≥76% of whom considered diagnosing underlying endocrine diseases greatly influenced their laminitis case management. Where an endocrinopathy was identified, 75.0% (n = 90/120) considered that client communication regarding laminitis was facilitated, and ≥67% considered that treating the endocrinopathy was effective in reducing laminitis recurrence. This study demonstrates successful translation of research knowledge into equine practice, with the vast majority of veterinary surgeons adopting endocrine diagnostic testing within their routine approach to laminitis cases. Respondents perceived that this change in diagnostic approach has resulted in improvements in several non-clinical and clinical healthcare outcomes, including client communication and reduction in recurrent laminitis episodes.

PD-L1 expression in equine malignant melanoma and functional effects of PD-L1 blockade

Programmed death-1 (PD-1) is an immunoinhibitory receptor expressed on lymphocytes. Interaction of PD-1 with its ligand PD-ligand 1 (PD-L1) delivers inhibitory signals and impairs proliferation, cytokine production, and cytotoxicity of T cells. In our previous studies, we have developed anti-bovine PD-L1 monoclonal antibodies (mAbs) and reported that the PD-1/PD-L1 pathway was closely associated with T-cell exhaustion and disease progression in bovine chronic infections and canine tumors. Furthermore, we found that blocking antibodies that target PD-1 and PD-L1 restore T-cell functions and could be used in immunotherapy in cattle and dogs. However, the immunological role of the PD-1/PD-L1 pathway for chronic equine diseases, including tumors, remains unclear. In this study, we identified cDNA sequences of equine PD-1 (EqPD-1) and PD-L1 (EqPD-L1) and investigated the role of anti-bovine PD-L1 mAbs against EqPD-L1 using in vitro assays. In addition, we evaluated the expression of PD-L1 in tumor tissues of equine malignant melanoma (EMM). The amino acid sequences of EqPD-1 and EqPD-L1 share a considerable identity and similarity with homologs from non-primate species. Two clones of the anti-bovine PD-L1 mAbs recognized EqPD-L1 in flow cytometry, and one of these cross-reactive mAbs blocked the binding of equine PD-1/PD-L1. Of note, immunohistochemistry confirmed the PD-L1 expression in EMM tumor tissues. A cultivation assay revealed that PD-L1 blockade enhanced the production of Th1 cytokines in equine immune cells. These findings showed that our anti-PD-L1 mAbs would be useful for analyzing the equine PD-1/PD-L1 pathway. Further research is warranted to discover the immunological role of PD-1/PD-L1 in chronic equine diseases and elucidate a future application in immunotherapy for horses.

Equine Dental Floating (Crown Osontoplasty)

Odontoplasty (floating and occlusal equilibration) is the most commonly performed procedure in equine dentistry. From an anatomic perspective, an irregular occlusal surface, prominent cingula, transverse ridges, and enamel points all contribute to the function, form, and longevity of the equine cheek tooth. With limited reserve crown available and an average functional life range between 18 and 25 years, removal of tooth structure should be conservative. The authors consider a quality oral examination to be the most important dental procedure performed in the horse. Individual tooth evaluation should lead to a specific diagnosis and treatment plan. Tooth odontoplasty should be site-specific.

Efficacy of pergolide for the management of equine pituitary pars intermedia dysfunction: A systematic review

Pergolide, a dopamine agonist, is commonly administered to manage pituitary pars intermedia dysfunction (PPID), a progressive neurodegenerative disease prevalent in aged horses. However, available evidence regarding pergolide's efficacy in improving clinical and endocrine parameters is limited. The aim of this systematic review was to assess published literature and evaluate evidence regarding whether pergolide treatment results in improvement of clinical signs and/or adrenocorticotrophic hormone (ACTH) concentration compared to no treatment or other unlicensed treatments. Systematic searches of electronic databases were undertaken in April 2019, repeated in August and October 2019, and updated in July 2020. English language publications published prior to these dates were included. Screening, data extraction and quality assessment of publications was undertaken individually by the authors using predefined criteria and subsequently cross-checked. Modified critically appraised topic data collection forms were used to extract data. Due to marked between-study variations, meta-analysis was not undertaken. After removal of duplicate records; 612 publications were identified, of which 129 abstracts were screened for eligibility and 28 publications met criteria for inclusion in the review. Most studies were descriptive case series, cohort studies or non-randomised, uncontrolled field trials. Despite marked variation in study populations, case selection, diagnostic protocols, pergolide dose, follow-up period and outcome measures, in the vast majority of the included studies, pergolide was reported to provide overall clinical improvement in >75% of cases. However, reported improvements in individual clinical signs varied widely. A reduction in plasma ACTH concentrations was reported in 44-74% of cases, while normalisation to within reported reference intervals occurred in 28-74% of cases.

A short life on the farm: aging and longevity in agricultural, large-bodied mammals

As average human lifespans increase across the globe, companion animals, specifically dogs and cats, are also living longer with more age-related morbidities. However, a similar trend is not seen in mammalian livestock species. Cows, pigs, goats, and sheep, as well as more niche mammalian species raised across the world, have been primarily raised for their economic benefit to humans and are culled from the population once their production declines. To this end, we lack clear knowledge about the age-related morbidities and causes of death that afflict livestock animals due to natural aging, as well as detailed age-specific survival rates. Here, we review the current state of the field of agricultural mammal aging, as well as provide specific questions and directions that may provide novel resources for veterinarians and aging biologists. By raising awareness of the overall quality of life and ongoing health of individual livestock animals, we can potentially increase production into older life stages, leading to decreased costs to farmers and improved welfare for the animals themselves.

Aging Equines: Understanding the Experience of Caring for a Geriatric Horse with a Chronic Condition

This study evaluated the experience of 1,448 people in the United States who currently care for or had previously cared for a geriatric horse and how that experience was qualified by the presence or absence of a chronic condition in the horse. An anonymous, online questionnaire was distributed to a cross-country sample to investigate the burden of caregivers from the perspective of owners of geriatric horses. Traumatic events and veterinary care decisions were also explored. Findings from the study supported the hypothesis that owners of geriatric horses with a chronic condition experienced higher levels of physical and emotional care burden, regardless of the age of the geriatric horse. Attachment levels reported by participants were high, regardless of the health status of the horse. This exploratory study provides the equine practitioner a greater understanding of the care burden experienced by owners of geriatric horses, particularly of owners of geriatric horses with a chronic condition, who rely on their veterinarian to guide their management and health care decisions. Veterinarians can help prepare and support clients as they navigate the complexities of caring for an older horse with a chronic condition.

Factors associated with euthanasia in horses and ponies enrolled in a laminitis cohort study in Great Britain

Euthanasia is a complex topic, with animal owners using multiple factors to shape their decision-making process. Previous epidemiological studies have described causes of equine mortality in specific populations, but there is limited evidence regarding factors contributing specifically to equine euthanasia in Great Britain (GB). This observational study used a prospective cohort design: the objectives were to describe owner-reported reasons for euthanasia, estimate the rate of euthanasia and identify associated factors in horses/ponies enrolled in a web-based epidemiological study of laminitis in GB. Self-selected horse/pony owners submitted regular management and health data over 29 months and reported dates and reasons for euthanasia during this period. The overall incidence of euthanasia was estimated and associated factors were identified using multivariable Cox regression modelling, adjusted for age, with variables retained in the final model if P ≤ 0.05. Data were available for 1070 horses/ponies contributing 1093 horse-years at risk (HYAR), with 80 owner-reported euthanasias. The incidence of euthanasia was 7.3 euthanasias per 100 HYAR (95 % confidence interval [CI] 5.9, 9.1). The most frequently reported health reasons contributing to euthanasia were laminitis-related consequences (25.0 % ; CI 16.8, 35.5 %), colic (21.3 % ; CI 13.7, 31.4 %), non-laminitic lameness (20.0 % ; CI 12.7, 30.1 %) and age-related deterioration, including owner-perceived compromised quality of life (20.0 % ; CI 12.7, 30.1 %). Health-related factors associated with significantly higher rates of euthanasia were colic (hazard ratio [HR] 26.4; CI 12.5, 55.8), pituitary pars intermedia dysfunction (HR 3.0; CI 1.7, 5.4) and lameness due to navicular syndrome (HR 5.9; CI 1.8, 20.0), soft tissue injury (HR 6.5; CI 2.7, 15.6) or laminitis (HR 2.7; CI 1.3, 5.7). Further factors included being pure bred (HR 1.7; CI 1.0, 2.8), female (HR 1.7; CI 1.0, 2.9), having poor owner-perceived hoof quality (HR 2.4; CI 1.1, 5.2), being entirely stabled (HR 5.0; HR 2.1, 12.0), being on loan or under temporary care of the study participant (HR 2.3; CI 1.2, 4.4) and participating in affiliated or professional competitions (HR 5.9; CI 2.4, 14.8). Euthanasia rates were significantly higher in the first two study years compared to the third (P < 0.001). Animals whose owners used the study's custom-designed weight tracker tool had significantly lower rates of euthanasia (HR 0.6; CI 0.3, 0.95). This study has identified a number of, arguably preventable, health-related factors associated with higher rates of euthanasia. Data on owners' decision-making process regarding euthanasia, including emotive and financial impacts, were not recorded but are important contributors to euthanasia that require better understanding.

Immunoreactive insulin stability in horses at risk of insulin dysregulation

Background

Diseases associated with insulin dysregulation (ID), such as equine metabolic syndrome and pituitary pars intermedia dysfunction, are of interest to practitioners because of their association with laminitis. Accurate insulin concentration assessment is critical in diagnosing and managing these diseases.

Hypothesis/Objectives

To determine the effect of time, temperature, and collection tube type on insulin concentrations in horses at risk of ID.

Animals

Eight adult horses with body condition score >6/9.

Methods

In this prospective study, subjects underwent an infeed oral glucose test 2 hours before blood collection. Blood samples were divided into ethylenediaminetetraacetic acid, heparinized, or serum tubes and stored at 4 or 20°C. Tubes were centrifuged and analyzed for insulin by a chemiluminescent assay over 8 days. Changes in insulin concentrations were compared with a linear mixed effects model.

Results

An overall effect of time, tube type and temperature was identified (P = .01, P = 0.001, and P = 0.001, respectively). Serum and heparinized samples had similar concentrations for 3 days at 20°C and 8 days at 4°C; however, after 3 days at 20°C, heparinized samples had significantly higher insulin concentrations (P = .004, P = .03, and P = .03 on consecutive days). Ethylenediaminetetraacetic acid samples had significantly lower insulin concentrations regardless of time and temperature (P = .001 for all comparisons).

Conclusions and Clinical Importance

These results suggest an ideal protocol to determine insulin concentrations involves using serum or heparinized samples with analysis occurring within 3 days at 20°C or 8 days at 4°C.

Incidence and clinical signs of owner-reported equine laminitis in a cohort of horses and ponies in Great Britain

BACKGROUND

Previous robust epidemiological studies of equine laminitis have utilised only veterinary-diagnosed episodes of disease, potentially underestimating true disease frequency.

OBJECTIVES

To estimate the incidence of, and describe clinical signs associated with, owner-reported active laminitis in horses/ponies, using both veterinary-diagnosed and nonveterinary-diagnosed episodes.

STUDY DESIGN

Prospective cohort.

METHODS

Data were collected from horse/pony owners in Great Britain between August 2014 and December 2016 using a web-based application. The incidence of owner-reported laminitis was estimated using both first incident and repeat episodes reported during the study period via a previously validated laminitis reporting form. Owner-reported clinical signs present in these episodes were recorded.

RESULTS

A total of 1070 horses/ponies contributed 1068 horse-years at risk (HYAR) and 123 active laminitis episodes were reported in 97 animals. Sixty-two of these episodes (50.4%, 95% confidence interval [CI] 41.6, 59.2%) were veterinary-diagnosed and 75.3% (CI 66.7, 83.8%; n = 73) of horses/ponies reported to have laminitis during the study had a previous laminitis history. Overall owner-reported first episode incidence was 9.6 episodes (CI 7.8, 11.7)/100 HYAR, whereas incidence including repeat episodes was 11.5 episodes (CI 9.7, 13.7)/100 HYAR. Laminitis occurred throughout the year with no significant differences between seasonal incidence estimates. Incidence was highest in Connemara and New Forest and lowest in Draught and Cob breed categories. The most prevalent owner-reported clinical signs (≥70%) were difficulty turning and a short/stilted or lame walk. Laminitis was reported in all limbs, however; both forelimbs were most commonly affected (62.9%, CI 54.1, 71.7%; n = 73/116).

MAIN LIMITATIONS

Self-selection enrolment of participants may limit generalisability of the findings.

CONCLUSIONS

Laminitis remains a considerable year-round welfare issue of horses and ponies, with frequency estimates utilising owner-reported data more representative of the true impact of the disease. The clinical signs reported by horse/pony owners were reflective of those previously described by veterinary surgeons.

Proportion of nonsteroidal anti-inflammatory drug prescription in equine practice

BACKGROUND

There is little knowledge of the prescription of nonsteroidal anti-inflammatory drugs (NSAIDs) and whether their prescription varies between countries.

OBJECTIVE

To describe prescription practices of NSAIDs in equids in the United Kingdom (UK), United States of America (USA) and Canada.

STUDY DESIGN

Descriptive observational study.

METHODS

Free-text electronic medical records from 141,543 equids from 10 equine practices in the UK, 255,777 equids from 7 equine practices with 20 branches from the USA and 2 practices with 7 branches from Canada were evaluated. A validated text-mining technique was used to describe the proportion of equids prescribed NSAIDs at least once in these countries. The choice of NSAIDs in orthopaedic and colic cases was evaluated.

RESULTS

The prescription of NSAIDs is more common in the USA (42.4%) and Canada (34.2%) than in the UK (28.6%). Phenylbutazone and flunixin meglumine were the drugs mostly prescribed in all countries. While flunixin meglumine was most prescribed with colic cases in all countries, a proportion received phenylbutazone despite this drug being licensed for use only with musculoskeletal disease. Phenylbutazone was the most commonly prescribed drug in cases with orthopaedic disease followed by flunixin meglumine in all countries. Only a small proportion of cases received meloxicam, ketoprofen or firocoxib.

MAIN LIMITATIONS

The retrospective design might have resulted in an unknown number of incomplete records, particularly in the reporting of colic and orthopaedic disease. Although the data set is large, the relatively small number of practices recruited from each country may introduce bias.

CONCLUSIONS

Clinical practice can differ between countries although the influence of individual practitioners and practice-specific policy on apparent intercountry differences requires further research. Despite several other NSAIDs being available and a substantial effort being made to evaluate their efficacy, the prescription of NSAIDs other than phenylbutazone and flunixin meglumine remains rather limited.

Prevalence of owner-reported ocular problems and veterinary ocular findings in a population of horses aged ≥15 years

BACKGROUND

Previous studies suggest that ocular disease is common among aged horses but owners may fail to identify or underestimate their clinical relevance.

OBJECTIVES

To document the prevalence of owner-reported ocular disease in horses aged ≥15 years. In a subset of these horses, to document ophthalmic findings from veterinary examination and compare with owner-reported ocular disease, and to determine risk factors for veterinary ophthalmic findings.

STUDY DESIGN

Cross-sectional study.

METHODS

Owners of aged horses completed a survey on management, clinical signs and medical history. Risk factors for the presence of ocular disease as reported by the owner were determined. A subset of these horses underwent an ophthalmological examination. Risk factors for the presence of ocular disease detected during this examination were determined. Agreement between owner-reported data and veterinary ophthalmic findings was assessed.

RESULTS

Abnormal ocular findings were detected in 287/327 horses aged ≥15 years that underwent a complete ophthalmic examination, whereas the presence of ocular disease as reported by the horse-owners was only 3.3%. Agreement between owner-reported ocular disease and results of the veterinary examination was low for all categories analysed. An owner-reported history of ocular discharge was associated with increased odds of veterinary-reported diminished vision. Increasing age was associated with increased odds of the presence of an eye abnormality (any) and cataracts. Appaloosa horses had increased odds of cataract compared with other breeds. Horses in work were less likely to have an eye abnormality.

MAIN LIMITATIONS

Volunteer bias may have influenced our results with owners of sick horses or those more concerned about their horses more likely to volunteer at the initial recruitment phase.

CONCLUSIONS

This study showed a high prevalence of ocular lesions in aged horses which was not reflected in owner-reported disease. This has highlighted problems in obtaining information on ocular conditions from horse-owners.

Epidemiology of pituitary pars intermedia dysfunction: A systematic literature review of clinical presentation, disease prevalence and risk factors

Pituitary pars intermedia dysfunction (PPID) is caused by an age-related degenerative disease of dopaminergic neurones. Despite its importance in equine practice, available information regarding its epidemiology is limited. This systematic review aimed to assess published literature to evaluate available evidence regarding the clinical presentation, prevalence and risk factors for PPID in horses and ponies. Electronic database searches were undertaken using a range of terms, and English language publications published prior to August 2016 were included. Both authors independently reviewed screened papers for inclusion, extracted data, and assessed the quality of reporting using predefined criteria. Data were extracted using modified critically appraised topic data collection forms. Meta-analysis was not undertaken due to marked between-study variations. Following removal of duplicate records, of 358 published papers yielded by the search, 97 abstracts were screened for eligibility and 29 publications meeting inclusion criteria were included in the review. Most studies reviewed were case series or cross-sectional studies, with considerable variation in study populations and PPID case definition. Hypertrichosis and/or other hair coat abnormalities, laminitis and epaxial muscle wastage or muscle atrophy are the most frequently reported clinical signs, with prevalence of these signs increasing with increasing horse age. The most robust prevalence estimates for PPID were 21.2% in horses and ponies aged ≥15 years and 2.9% amongst the general equine population. Findings regarding breed and sex predispositions were equivocal and only increasing age has been identified as a significant risk factor for PPID.