David Byrne

Background
Sand enteropathy is a common disease in horses worldwide. The presence of sand does not always cause disease. The amount of sand required to cause clinical disease is not well established.

Objectives
To establish a weight-indexed cut-off for the diagnosis of clinically relevant sand enteropathy based on radiographic area.

Study design
Cross-sectional.

Methods
Abdominal radiographs were acquired from clinically normal horses and compared with horses with clinical sand enteropathy. Sand area and sand area per kilogram of body weight were calculated. A receiver operating characteristic (ROC) curve was used to differentiate groups.

Results
Seventy clinically normal horses and 57 sand enteropathy cases were included. Median sand area in control horses was 1 cm2 per 100 kg (interquartile range 0–6 cm2 per 100 kg), and in sand enteropathy horses was 118 cm2 per 100 kg (interquartile range 83–180 cm2 per 100 kg). Receiver operator characteristic (ROC) analysis revealed that using a cut-off of 21 cm2 per 100 kg had a sensitivity of 98.25% (CI 90.71%–99.1%) and a specificity of 92.54% (CI 83.69%–96.77%) for a diagnosis of clinical sand enteropathy.

Conclusions
A weight-based cut-off of >21 cm2 per 100 kg for the diagnosis of sand enteropathy was determined with excellent sensitivity and good specificity. This may aid in determining if the amount of sand accumulation in a horse is of clinical consequence.

Introduction: A multicenter description and comparison of antimicrobial treatment approaches for acute diarrhea in horses is missing. This study aimed to describe and compare the treatment approaches for diarrheic horses used in different regions of the world.

Study Design: Multicenter retrospective study.

Methods: Information from diarrheic horses presented to participating institutions between 2016 and 2020, including clinicopathological data, pathogens detected, and antimicrobial drug use, was collected.

Results: This study included 1438 horses and 26 referral institutions across 5 continents (North and South America, Europe, Australia, and Asia). The fatality rate was 24%, with no differences between regions. A pathogen was identified in 16% of the horses. 55% (792/1419) of the horses were administered one or a combination of antimicrobial drugs within the first 24 hours of admission. Penicillin and gentamicin were the most used combination (25%, 198/792). The proportion of horses treated with antimicrobial drugs differed among institutions, varying from 17% to 94%. The proportion of horses treated with antimicrobial drugs was lower in Europe and Australia than in the other geographic areas (P < .05). In total, 540/1139 (47%) horses had leukopenia, and 70% (380/540) of those horses were administered antimicrobial drugs, while 49% (293/599) of the horses without leukopenia received antimicrobial drugs. 66% (794/1105) of the horses met SIRS criteria, and 28% (311/1105) did not. Of those, 68% (542/794) and 44% (136/311) of the horses that did and did not me SIRS criteria, respectively, were administered antimicrobial drugs.

Discussion: Treatments varied between regions and hospitals. Prospective clinical trials are required to evaluate the effects of antimicrobial treatment on survival.

Clinical relevance: The high prevalence of antimicrobial use in diarrheic horses, even without evidence of systemic compromise, indicates that factors other than disease severity influence clinicians' decisions to administer antimicrobial drugs to diarrheic horses.

Objective: Data from two-plane electrical impedance tomography (EIT) can be reconstructed into various slices of functional lung images, allowing for more complete visualisation and assessment of lung physiology in health and disease. The aim of this study was to confirm the ability of 3d EIT to visualise normal lung anatomy and physiology at rest and during increased ventilation (represented by rebreathing).

Approach: Two-plane EIT data, using two electrode planes 20cm apart, were collected in 20 standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were reconstructed into 3d EIT whereby tidal impedance variation (TIV), ventilated area, and right-left and ventral-dorsal centres of ventilation (CoVRL and CoVVD, respectively) were calculated in cranial, middle and caudal slices of lung, from data collected using the two planes of electrodes.

Main results: There was a significant interaction of time and slice for TIV (p < 0.0001) with TIV increasing during rebreathing in both caudal and middle slices. The ratio of right to left ventilated area was higher in the cranial slice, in comparison to the caudal slice (p = 0.0002). There were significant effects of time and slice on CoVVD whereby the cranial slice was more ventrally distributed than the caudal slice (p < 0.0009 for the interaction).

Significance: The distribution of ventilation in the three slices corresponds with topographical anatomy of the equine lung. This study confirms that 3d EIT can accurately represent lung anatomy and changes in ventilation distribution during rebreathing in standing sedate horses.

Background
Equine Coronavirus (ECoV) can cause gastrointestinal disease and was first described in 2000 in the USA followed by several international outbreak case reports. Disease manifestation is characterised by vague clinical signs, including mild pyrexia, lethargy and anorexia. Morbidity ranges greatly from 10% to 83%. Although uncommon, ECoV may result in death secondary to disruption to the gastrointestinal barrier causing endotoxaemia and hyperammonaemic encephalopathy. Unfortunately to date, there is no vaccine available to prevent ECoV.

Case reports
Three faecal quantitative polymerase chain reaction (qPCR)-positive ECoV cases are described that presented with mild to severe colic signs: a 2-year-old Miniature Pony gelding from South Australia, an 8-year-old Arabian Riding Pony gelding, and a 6-year-old Warmblood mare, both from Western Australia. The diagnosis was based on a positive faecal qPCR, which is currently the gold standard diagnostic tool. All horses in this case series survived after medical management. The Miniature Pony presented with anorexia and mild colic signs. On day 5, the pony revealed severe colic signs unresponsive to analgesia along with severe abdominal distension secondary to caecal distension requiring surgical intervention.

Conclusion
To the authors' knowledge, this case series is the first published report of ECoV cases in Australia, and it adds both to the clinical description of the disease in horses and to the differential diagnosis list of colic signs.

Background
This study aimed to describe and compare therapeutic approaches for horses with acute diarrhea in different geographic regions worldwide.

Methods
Clinical information was retrospectively collected from diarrheic horses presented to participating institutions between 2016 and 2020, including fluid therapy on admission, antimicrobial drugs, probiotics, anti-endotoxic medications, anti-inflammatory drugs, gastroprotectants, digital cryotherapy, and toxin-binding agents. Seasonal and geographic differences were investigated.

Results
1438 horses from 26 participating hospitals from 5 continents were included. On admission, 65% (926/1419) of horses were administered a fluid bolus. Antimicrobial drugs were administered to 55% (792/1419) within the first 24 hours of admission, with penicillin and gentamicin being the most used combination (25%, 198/792). Horses with leukopenia (OR: 2.264, 95%CI: 1.754 to 2.921; P<0.001) or meeting systemic inflammatory response syndrome criteria (OR: 2.542, 95%CI: 1.919 to 3.368; P<0.001) had higher odds of being administered antimicrobial drugs. Other treatments administered included probiotics (15%, 215/1438), polymyxin B (13%; 187/1438), pentoxifylline (8%; 118/1438), gastroprotectants (44%; 626/1419), digital cryotherapy (34%; 489/1435), plasma transfusion (13%; 182/1410) and toxin-binding agents (36%; 515/1438).

Limitations
Due to the retrospective nature of the study, the rationale for treatment decisions was unavailable, and associations with survival could not be evaluated.

Conclusions
Treatments varied between hospitals from different geographic regions. Prospective clinical trials are required to evaluate the effects of various treatments on survival.

Clostridioides difficile poses an ongoing threat as a cause of gastrointestinal disease in humans and animals. Traditionally considered a human healthcare-related disease, increases in community-associated C. difficile infection (CDI) and growing evidence of inter-species transmission suggest a wider perspective is required for CDI control. In horses, C. difficile is a major cause of diarrhoea and life-threatening colitis. This study aimed to better understand the epidemiology of CDI in Australian horses and provide insights into the relationships between horse, human and environmental strains. A total of 752 faecal samples from 387 Western Australian horses were collected. C. difficile was isolated from 104 (30.9%) horses without gastrointestinal signs and 19 (37.8%) with gastrointestinal signs. Of these, 68 (55.3%) harboured one or more toxigenic strains, including C. difficile PCR ribotypes (RTs) 012 (n = 14), 014/020 (n = 10) and 087 (n = 7), all prominent in human infection. Whole-genome analysis of 45 strains identified a phylogenetic cluster of 10 closely related C. difficile RT 012 strains of equine, human and environmental origin (0–62 SNP differences; average 23), indicating recent shared ancestry. Evidence of possible clonal inter-species transmission or common-source exposure was identified for a subgroup of three horse and one human isolates, highlighting the need for a One Health approach to C. difficile surveillance.

Electrical impedance tomography (EIT) is a non-invasive diagnostic tool for evaluating lung function. The objective of this study was to compare respiratory flow variables calculated from thoracic EIT measurements with corresponding spirometry variables. Ten healthy research horses were sedated and instrumented with spirometry via facemask and a single-plane EIT electrode belt around the thorax. Horses were exposed to sequentially increasing volumes of apparatus dead space between 1,000 and 8,500 mL, in 5–7 steps, to induce carbon dioxide rebreathing, until clinical hyperpnea or a tidal volume of 150% baseline was reached. A 2-min stabilization period followed by 2 minutes of data collection occurred at each timepoint. Peak inspiratory and expiratory flow, inspiratory and expiratory time, and expiratory nadir flow, defined as the lowest expiratory flow between the deceleration of flow of the first passive phase of expiration and the acceleration of flow of the second active phase of expiration were evaluated with EIT and spirometry. Breathing pattern was assessed based on the total impedance curve. Bland-Altman analysis was used to evaluate the agreement where perfect agreement was indicated by a ratio of EIT:spirometry of 1.0. The mean ratio (bias; expressed as a percentage difference from perfect agreement) and the 95% confidence interval of the bias are reported. There was good agreement between EIT-derived and spirometry-derived peak inspiratory [−15% (−46–32)] and expiratory [10% (−32–20)] flows and inspiratory [−6% (−25–18)] and expiratory [5% (−9–20)] times. Agreement for nadir flows was poor [−22% (−87–369)]. Sedated horses intermittently exhibited Cheyne-Stokes variant respiration, and a breath pattern with incomplete expiration in between breaths ( crown-like breaths). Electrical impedance tomography can quantify airflow changes over increasing tidal volumes and changing breathing pattern when compared with spirometry in standing sedated horses.

Background
The natural progression of equine glandular gastric disease (EGGD) in the absence of treatment has not yet been described in the literature, nor has the prevalence in a teaching herd population been reported.

Objectives
The aims of this study were to determine the prevalence of disease in a teaching population over the study period (2019–2021) and to observe the changes over time in disease severity of naturally occurring diseases (not experimentally induced) without medical intervention.

Methods
Twenty-one horses underwent an initial gastroscopy and a repeat gastroscopy between 14 and 731 days later. Gastroscopy data were graded quantitatively and described qualitatively. Prevalence and 95% confidence intervals (CI) were calculated. The changes over time were determined by comparing initial and repeat gastroscopies.

Results
The prevalence from initial, repeat and total number of gastroscopies was 62% (95% CI: 40.8–79.3), 71% (95% CI: 50.0–86.2) and 67% (95% CI: 51.6–79), respectively. The changes over time included worsening of disease in 29% of horses (95% CI: 13.8–50.0), improvement of disease to a lower grade in 24% (95% CI: 10.6–45.1), no change in grade in 38% (95% CI: 20.8–59.1), and complete resolution of disease to grade 0 in 10% (95% CI: 2.7–28.9).

Main limitations
Limitations included a maximum of two gastroscopies per horse given COVID-19 restrictions on data collection, and highly varied interval times between initial and repeat gastroscopies.

Conclusion
In conclusion, there is a high prevalence of disease in this teaching herd. The changes over time in naturally occurring diseases without medical intervention might include worsening, improvement, no change or resolution of disease.
Main limitations

Limitations included a maximum of two gastroscopies per horse given COVID-19 restrictions on data collection, and highly varied interval times between initial and repeat gastroscopies.

Conclusion
In conclusion, there is a high prevalence of disease in this teaching herd. The changes over time in naturally occurring diseases without medical intervention might include worsening, improvement, no change or resolution of disease.

Background

Right dorsal colitis (RDC) is a nonsteroidal anti-inflammatory drug (NSAID) induced, protein losing enteropathy in horses associated with a high case fatality rate.

Objectives

To describe signalment, NSAID usage, clinical presentations, clinical pathology, ultrasonographic findings, treatments, outcomes, and factors associated with survival in horses diagnosed with RDC.

Animals

Thirty-five horses from 7 Australian equine hospitals diagnosed with RDC.

Methods

Retrospective case series. Clinical records of cases were accepted if definitively or presumptively diagnosed by an internist with RDC and had ≥3 of: hypoproteinemia or hypoalbuminemia; diarrhea with negative test results for infectious diseases; colic for which other diseases were excluded or right dorsal colon thickening on ultrasound. Descriptive data analysis was performed for categorical and continuous variables. Univariate binominal logistic regressions were used to assess factors associated with survival.

Results

An overdose of NSAIDs occurred in 84% (21/25) cases where dose was known. Common clinical presentations included diarrhea (69%; 22/32), colic (61%; 20/33), and tachycardia (53%, 17/32). Common clinicopathological findings included hypoalbuminemia (83%; 26/31), hypocalcaemia (79%, 23/29), and hyperlactatemia (77%, 14/18). The right dorsal colon wall appeared subjectively thickened in 77% (24/31) cases using ultrasonography. Case fatality rate was 43% (15/35). Odds of survival significantly decreased with increasing heart rate (odds 0.84, 95% CI = 0.71-0.92, P = .01), packed cell volume (odds 0.91, 95% CI 0.82-0.98, P = .05) and abnormal appearance of mucous membranes (odds 0.05, 95% CI 0.005-0.28, P = .001) on hospital presentation.

Conclusions and Clinical Importance

An overdose of NSAIDs is common in horses diagnosed with RDC. Serum albumin concentrations should be monitored in horses receiving a prolonged course of NSAIDs. Overall prognosis for RDC remains fair.

Background
Clinicopathological findings and their association with the outcome and development of laminitis in horses with acute diarrhoea has not been investigated in a multicentre study across different geographic regions.

Objectives
Describe and compare clinicopathologic findings of diarrhoeic horses between different geographic regions, survival rates and factors associated with non-survival and laminitis.

Study design
Multicentre retrospective case series.

Methods
Information from horses with acute diarrhoea presenting to participating institutions between 2016 and 2020 was collected, and clinicopathological data were compared between surviving and non-surviving horses and horses that did and did not develop laminitis. Survival rates and seasonal and geographic differences were also investigated.

Results
One thousand four hundred thirty-eight horses from 26 participating institutions from 4 continents were included; 76% survived to discharge with no differences identified between geographic regions. The survival proportion of horses with SIRS and creatinine concentrations > 159 μmol/L was 55% (154/279) compared with 81% (358/437) for those with SIRS and creatinine concentrations < 159 μmol/L (p < 0.001). The survival proportion of horses with SIRS that had an L-lactate concentration > 2.8 mmol/L was 59% (175/298) compared with 81% (240/296) in horses with SIRS and L-lactate concentration < 2.8 mmol/L (p < 0.001). The proportion of horses that developed laminitis was lower in Europe (4%, 19/479) compared with North America (8%, 52/619), Australia (8%, 12/138) and Latin America (11%, 16/146) (p < 0.05). More horses developed laminitis in the summer (46%, 39/85) compared with winter (18%, 15/85), spring (18%, 15/85) and fall (19%, 16/85) (p < 0.01). Horses with laminitis had greater odds of non-survival than those without laminitis (OR: 3.73, 95% CI: 2.47–5.65).

Main limitations
Not all variables were available for all horses due to the retrospective nature.

Conclusions
Clinicopathological findings in horses with acute diarrhoea and their association with survival are similar across geographic regions. However, developing laminitis secondary to diarrhoea is less common in Europe. In addition, factors associated with non-survival were indicative of disease severity and subsequent cardiovascular compromise.