Neonatology

Question 1

The effect of neonatal dysphagia on subsequent racing performance in Standardbred horses

Answer 1

•Dysphagia, associated with environmental PAH exposure, does not negatively impact racing performance in foals that survive to training.
•No significant difference in age of first race, Speed Index, or Earnings Per Start Index between dysphagic and healthy foals. Started racing at same time (median 2 years).
•Racing outcomes for dysphagic foals align with general Standardbred statistics (66% of foals born between 2012-2017 raced).
• Treatment of neonatal dysphagia, though costly, is justified given the lack of long-term negative effects on athleticism.

Question 2

Comparison of the diagnostic predictability of serum amyloid A, white blood cell count and immunoglobulin G tests as indicators of early-onset, acute-phase morbidities in newborn foals

Answer 2

Serum amyloid A (SAA) is identified as a superior biomarker for detecting early-onset, acute-phase infections and inflammatory conditions in newborn foals compared to WBC count and IgG levels in foals <36hours old.
At a positivity threshold of 100 mg/L, SAA showed:
• Sensitivity: 41.7%
• Specificity: 94.7%
• Positive Predictive Value (PPV): 55.6%
• Negative Predictive Value (NPV): 91.1%
• SAA’s accuracy (87.4%) was higher than both WBC (73.1%) and IgG (81.7%).

SAA Testing:
• Detects inflammation rapidly due to its dynamic response.
• Elevated levels correlate with both infectious and non-infectious inflammatory conditions.
• Useful in identifying subclinical infections before clinical signs emerge.
• SAA testing combined with WBC count improved diagnostic accuracy and PPV to 66.7%.

• Limitations: False negatives: Some sick foals showed SAA levels below the positivity threshold (14 out of 24 nonhealthy foals). False positives: A few healthy foals had elevated SAA values, likely due to noninfectious inflammation or early-stage infection.

Question 3

Serum Amyloid A in Diagnosing Sepsis in Equine Neonates

Answer 3

Median SAA in septic foals: 114 µg/mL. Significantly greater than for other groups.
- For healthy vs septic: At diagnostic threshold of 100ug/ml, Sensitivity: 52.9%, specificity: 97.5%. High specificity but moderate sensitivity. PPV 75%, NPV 93.7%. AUC ROC curve 0.806
-could not distinguish healthy from SNS
-serial measurements may improve Se

Question 4

Diagnostic characteristics of refractometry cut-off points for estimating immunoglobulin G concentration in mare colostrum

Answer 4

•Both optical (OR) and digital refractometers (DR) were validated as effective tools for assessing colostrum quality by estimating immunoglobulin G (IgG) concentrations.
Optimal Cut-off Points: align closely with previous studies and indicate poor colostrum quality (<60 g/L IgG).
• DR: ≤23.75%
• OR: ≤23.90%

Digital Refractometer (DR): Sensitivity: 93.3% Specificity: 87.9% Positive Predictive Value (PPV): 63.6% Negative Predictive Value (NPV): 98.3%
Optical Refractometer (OR): Sensitivity: 93.3% Specificity: 81.8% PPV: 53.8% NPV: 98.2%
• Both refractometers demonstrated high accuracy, particularly in ruling out poor-quality colostrum due to high NPV values.
• Strong correlation observed between IgG concentrations measured by RID and refractometers for both Dr and OR
• High correlation between DR and OR readings ( =0.992), confirming interchangeability for colostrum assessment.
• Moderate correlation between serum and colostrum IgG concentrations (=0.542), supporting colostrum evaluation as an indirect predictor of neonatal immunity.

Use in combination with serum IgG measurement

Question 5

Comparative evaluation of clinical findings and prognostic outcome parameters in hospitalized, critically ill neonatal foals and crias

Answer 5

Foals: septic arthritis (11.8%), omphalitis (14.6%), and patent urachus (10.4%). Gastrointestinal diseases, including diarrhea (33.4%) and colic/constipation (13.2%), significantly more common.
Both species showed similar rates of lower respiratory disease (~32%).
Lower prevalence congential abnormalities (7.3%), with umbilical/inguinal hernias and skeletal deformities as most common defects. Only 23% of defects considered fatal.

SEPSISPED: Better predictor of mortality in both species compared to SEPSISNEO.
SEPSISNEO: Hyperlactatemia and hypoglycemia associated with foal mortality, not crias.

Shared Mortality Predictors:
Lower respiratory disease significantly increases mortality in both species (4.4–4.8-fold).
Oxygen therapy and glucose supplementation correlate with disease severity and poor outcomes.
Foal-Specific Predictors: Septic arthritis and omphalitis. Dysregulated glucose and lactate metabolism.

survival to discharge: foals 82.1%.

Question 6

Assessment of the immunocrit method to detect failure of passive immunity in newborn foals

Answer 6

• Demonstrated strong correlation (R = 0.871) with agarose gel electrophoresis (AGE), a gold standard for measuring serum immunoglobulin levels.
• Reliable cut-off established: Immunocrit: ≥9.5% AGE: ≥8 g/L
• Sensitivity: 94% Specificity: 82% NPV: 84.74% PPV: 92.76%

• Quick, quantitative, and inexpensive compared to traditional methods.
• Requires minimal equipment, making it accessible for on-farm diagnostics.
• Small sample volume (70 µL) and rapid processing time (6-7 minutes) enhance practicality. Does not differentiate types on immunoglobulin

Advantages of the Immunocrit Method
Area Under the Curve (AUC): 93.7% Indicates high diagnostic utility for detecting FPT.
Repeatability: Excellent agreement within triplicate measurements (Cohen’s Kappa = 0.92).
Accessibility: Ideal for field use in horse farms with limited access to sophisticated laboratory facilities.

Question 7

Normal regression of the internal umbilical remnant structures in Standardbred foals

Answer 7

• Rapid, linear regression of the umbilical vein, arteries, and urachus occurs over the first 5-6 weeks of life in Standardbred foals.
• The largest measurements were at 24 hours of age with a median umbilical vein diameter of 0.83 cm, median umbilical artery diameter of 0.61 cm and median urachal diameter of 1.07 cm.
• By 5-6 weeks, umbilical remnants, especially the arteries, become difficult to identify via ultrasonography.
•Median diameters of all structures significantly decrease: 16%-22% reduction within the first week of life. 66%-75% reduction by 6 weeks of age.
• Umbilical vein remained more identifiable compared to arteries as foals aged.
• Urachus often collapsed early, becoming a potential space rather than a fluid-filled lumen.

• Previously reported “normal” measurements did not consider foal age and might misguide clinical interpretations-> should use age adjusted ref values for more accurate identification of early pathology

Question 8

Transfusion with 2 litres of hyperimmune plasma is superior to transfusion of 1 litre for protecting foals against pneumonia attributed to Rhodococcus equi

Answer 8

• Retrospective cohort- propective study coming
• Transfusing 2 liters of hyperimmune plasma (REHIP) to foals significantly reduced the odds of pneumonia attributed to Rhodococcus equi (R. equi) compared to 1 liter.
• Odds of pneumonia were 2.4 times greater in foals receiving 1 liter (95% CI: 1.1–5.6; P = 0.0457).
• Findings align with prior studies indicating that antibody-mediated immunity offers protection against R. equi.
• Foals born in April and May had a 2.7-fold increased risk of developing pneumonia compared to those born earlier (January–March) (95% CI: 1.3–5.4; P = 0.0064).
• No adverse reactions to transfusions of 2 liters of plasma were observed
• variability in farm management practices, environment, or density as contributing factors.
• original study, used pony foals each of which weighed approximately 25 kg corresponding to a plasma dose of approximately 40 mL/kg. Since most horse foals weigh approximately 50-kg, 1 L of plasma represents a dose of REHIP of roughly 20 mL/kg of body weight.

Question 9

Nasal high flow oxygen therapy in hospitalised neonatal foals

Answer 9

• HFOT was successfully implemented using modified human systems, providing heated and humidified oxygen. Used in 14 foals, 10 survived to dischagre. Median duration 43 hours.

• Clinical improvements, including better respiratory patterns and reduced respiratory effort, were observed in most foals.
• Although improvements in oxygenation (PaO2) and carbon dioxide clearance (PaCO2) were noted, they were not statistically significant.
• No significant complications were associated with HFOT.

Indications for Use:
• HFOT is recommended for foals with worsening respiratory function despite TOT.
• Effective in cases where preventing atelectasis or providing additional respiratory support is necessary.

• HFOT avoids the complications and technical demands of mechanical ventilation.
• Compared to CPAP, HFOT is easier to implement and better tolerated, as it does not require a tight nasal seal.
• Unlike initial CPAP studies in foals, HFOT did not lead to hypercapnia.

Respiratory Support:
• Mechanisms of HFOT effectiveness include reduced airway resistance, enhanced dead space washout, and low positive airway pressure.
• Flow rates of 0.7 L/kg/min in foals align with effective rates used in humans for maintaining positive airway pressure.

A target starting respiratory gas flow rate of 40 L/min was used based on recommendations from human use. Specific FiO2 not targeted.The 40 L/min target could not be achieved when using 20 FR chest tubes and the maximum total flow rate was limited to between 25 and 35 L/min. the size of the nasal tubes was assessed to ensure that they did not obstruct more than 50% of the nasal diameter

Question 10

Red cell distribution width values and red cell distribution width-to-platelet ratio in Thoroughbred foals in the first 24 hours of life

Answer 10

• RPR was significantly higher in at-risk foals (0.073 ± 0.018) compared to healthy foals (0.068 ± 0.014, P = 0.01). Suggests RPR as a potential biomarker for identifying neonatal foals at risk of systemic disease.
• RDW values were not significantly different between healthy and at-risk foals. Negative correlation with gestational age (r = –0.156, P = 0.005), linking RDW to foal maturity.

• Elevated RPR reflects an imbalance in the proportion of RDW to platelet count, potentially linked to inflammatory responses and early systemic disorders.
• The correlation between RDW and gestational age suggests its utility in assessing neonatal maturity and potential vulnerabilities.

Requires validation for actually sick foals and on different farms
• Increased RDW may result from inflammatory mediators (e.g., tumor necrosis factor, interleukin-6) suppressing erythropoiesis and reducing red blood cell (RBC) maturation. Acute hypoxic events and systemic inflammation can increase RDW variability.

Question 11

Differences in isolation rate and antimicrobial susceptibility of bacteria isolated from foals with sepsis at admission and after ≥48 hours of hospitalization

Answer 11

Hospital-acquired pathogens (Acinetobacter spp., Enterococcus spp., Klebsiella spp., Pseudomonas spp., Serratia spp.) showed significantly higher odds of being isolated:
• Acinetobacter spp.: Odds ratio (OR) 7.63 (95% CI: 1.28–45.45).
• Enterococcus spp.: OR 5.37 (95% CI: 2.64–10.90).
• Klebsiella spp.: OR 2.27 (95% CI: 1.05–4.89).
• Pseudomonas spp.: OR 3.49 (95% CI: 3.49–240.50).
• Serratia spp.: OR 20.23 (95% CI: 2.20–186.14).

Decreased Isolation:
• Bacteria susceptible to initial antimicrobial treatment, such as Actinobacillus spp. (OR 0.15, 95% CI: 0.00–0.91) and Streptococcus spp. (OR 0.35, 95% CI: 0.13–0.91), were less frequently isolated after 48 hours.

•Escherichia coli remained the most frequently isolated bacterium at both time points, although its susceptibility to antimicrobials decreased over time.

Resistance Trends:
• Bacteria isolated after ≥48 hours were significantly less susceptible to all tested antimicrobials except for imipenem:
• Amikacin: Susceptibility dropped from 68.6% at admission to 42.4% after 48 hours.
• Ceftiofur: Susceptibility dropped from 90.9% to 49.4%.
• Gentamicin: Susceptibility dropped from 68.6% to 30.6%.
• Imipenem maintained relatively high efficacy (94.1% vs. 77.6%, OR 0.49, 95% CI: 0.18–1.33).
• Resistance patterns were unpredictable, complicating empirical treatment decisions.
• Even within E. coli, susceptibility decreased significantly for most drugs, suggesting selection of resistant strains and development of acquired resistance during hospitalization.

Of 82 isolates collected after ≥48 hours:
• 85.4% (n = 70) were not isolated at admission, suggesting potential hospital-acquired infections (HAIs).
• 6.1% (n = 5) were isolated at both time points and remained susceptible to the initial treatment, indicating treatment failure.
• 4.9% (n = 4) were initially susceptible but became resistant, suggesting acquired resistance during hospitalization.
• 3.7% (n = 3) were resistant at both time points.

• HAIs are likely a significant source of sepsis in hospitalized foals. Bacteria commonly associated with HAIs in human and veterinary medicine (Enterococcus spp., Klebsiella spp., Pseudomonas spp., Acinetobacter spp.) were frequently isolated after 48 hours.
• Controlling HAIs is critical to reducing morbidity and mortality in neonatal intensive care units (NICUs).
• Initial empirical regimens are appropriate at admission but become less effective over time due to resistance development.
• Empirical treatment should be adjusted promptly based on susceptibility testing of new isolates collected during hospitalization.
• Imipenem and other critically important antimicrobials should be reserved for cases with no other effective options, following World Health Organization (WHO) guidelines.
•The unpredictable resistance patterns observed in this study highlight the limitations of relying solely on admission culture results to guide therapy for ongoing infections

Considering that results of culture and antimicrobial susceptibility testing typically are not available for at least 48 hours after sample collection, it would be rational to repeat bacteriological culture and susceptibility testing at 48 hours intervals on foals hospitalized in
neonatal intensive care units, in order to detect on-going infections or HAIs at an early stage and select effective antimicrobials for treatment.

Question 12

Plasma iron concentrations and systemic inflammatory response syndrome in neonatal foals

Answer 12

• Plasma iron concentrations showed large variability among healthy neonatal foals, with a wider range (58.8–305 µg/dL) than previously reported in adult horses (105–277 µg/dL).
• This variability was particularly evident in the first 3 days of life, reflecting rapid changes in iron metabolism during early neonatal adaptation.
• No significant difference in plasma iron concentration was observed between foals with systemic inflammatory response syndrome (SIRS) and non-SIRS foals. Or outcome
• Plasma iron concentration negatively correlated with age in sick foals (r = –0.598) and healthy hospitalized foals (r = –0.387). Concentrations were higher in younger foals and declined with age during the first two weeks of life.

• Healthy foals from the hospital had significantly lower plasma iron concentrations (126.1 µg/dL) than those from the stud farm (181.8 µg/dL). This difference may reflect varying maternal conditions, colostrum/milk intake, or environmental factors, compounded by the age differences between these groups.

• Iron concentrations in healthy foals rise rapidly after birth due to colostrum absorption and subsequently decrease, mirroring patterns seen in human neonates. The initial rise in plasma iron supports erythropoiesis, while subsequent declines may be driven by hemoglobin catabolism and shifts in oxygen demand post-birth.
• Mechanisms such as hepcidin-mediated iron sequestration, which play a role in adult inflammation, might not function identically in neonatal foals.
• Interpretation of plasma iron values in foals requires age-specific reference ranges due to significant age-related changes in concentration during the neonatal period.

Question 13

Oxidative state in equine neonates: Anti- and pro-oxidants

Answer 13

• TBARS (a lipid peroxidation marker) levels were highest at 5 minutes post-birth and decreased significantly at 72 and 168 hours postpartum. Indicates high reactive oxygen species (ROS) production at birth, related to neonatal adaptation processes like pulmonary expansion and oxygen exposure.

Antioxidant Systems:
• Unconjugated Bilirubin (UB): Levels increased at 12 hours postpartum and decreased by 72 hours, stabilizing by 168 hours. Negative correlation between UB and TBARS suggests UB’s protective role against lipid peroxidation.
• Glutathione Peroxidase (GPx): Activity increased at 12 and 72 hours compared to immediately after birth, complementing UB’s role in ROS neutralization. GPx showed a negative correlation with TBARS and positive correlations with UB and TB, indicating a coordinated antioxidative mechanism.
• Superoxide Dismutase (SOD): Activity remained constant throughout the first week of life, suggesting SOD was not the primary mechanism for managing oxidative stress during this period.

•High lipid peroxidation shortly after birth reflects the stress of transitioning from fetal to neonatal life. Antioxidant systems, particularly UB and GPx, are crucial in maintaining oxidative homeostasis and protecting against ROS damage.

Question 14

Hanoverian F/W-line contributes to segregation of Warmblood fragile foal syndrome type 1 variant

Answer 14

• The PLOD1:c.2032G>A mutation was confirmed as the causative variant for Warmblood Fragile Foal Syndrome Type 1 (WFFST1).
• The mutant allele was identified at a frequency of 14% in Hanoverian horses, higher than previously reported in other Warmblood populations (5.5% in Brazil).

•Affected foals exhibited severe connective tissue abnormalities, including fragile skin, subcutaneous emphysema, and joint hyperextension.
• Histopathology revealed: Loosely arranged, thinned collagen fibers in the dermis.
• Electron microscopy showed irregularly shaped, swollen collagen fibrils and fibrillar plaques interspersed in an amorphous matrix.

Association with Performance Traits:
• Significant correlations were observed between WFFST1 carrier status and positive breeding values (EBVs) for traits like gait quality, elasticity, and dressage performance.
• No significant associations were found with embryonic loss or stallion fertility, suggesting that losses in homozygous foals occur during late gestation or at birth, not during early embryonic development.

Pedigree and Origin Analysis:
• Pedigree tracing identified Stallion A (1861 Hanoverian F/W line) as the most recent common ancestor (MRCA) for all 81 tested genetic carriers.
• The WFFST1 mutation likely originated in Thoroughbreds, which contributed 34.8% of the Hanoverian genetic pool (1980-2000).

Biological Implications
• The PLOD1 mutation disrupts lysyl hydroxylase activity, critical for collagen cross-linking and stability.
• Variations in collagen expression between tissues may explain phenotypic differences among affected foals and carrier horses.
•The mutation’s widespread prevalence in Warmblood horses reflects both historical gene flow and the selective use of carriers in dressage-focused breeding programs.
• Positive selection for gait and conformation traits likely facilitated the mutation’s propagation.

Question 15

Retrospective evaluation of the association between hyponatremia and neurological dysfunction in hospitalized foals: 109 cases

Question 16

Factors associated with the risk of positive blood culture in neonatal foals presented to a referral centre

Answer 16

Positive Blood Culture Risk Factors:
• Umbilical Abnormalities: OR 11.01
• Hypoglycemia:OR: 13.51.
• Low HCT: In isolation, not significant, but its interaction with umbilical abnormalities increased the risk dramatically (adjusted OR: >999.99).
• Prematurity: Not significant in multivariable modeling but initially noted as a risk factor in univariate analysis (OR: 1.89).
• Factors such as diarrhea, FPT, and maternal health issues were not significant in this study.

Microbial Patterns:
• Both Gram-positive (51%) and Gram-negative (49%) organisms were identified.
• E. coli was the most common Gram-negative isolate (17% of total isolates).
• Staphylococcus spp. and Streptococcus spp. were the most prevalent Gram-positive organisms (17% and 13%, respectively).
• Polymicrobial Infections: Found in 22% of positive cases

Variable Susceptibilities:
• Amikacin (80%) and gentamicin (73%) were moderately effective against Gram-negative organisms.
• Ceftiofur had relatively low efficacy (66% overall), raising concerns about its frequent use as a first-line treatment.
• Tetracyclines (72% susceptible) and trimethoprim-sulfonamide combinations (55%) had variable efficacy.
• The modified Foal Sepsis Score (mSS) demonstrated moderate sensitivity (54%) and specificity (66%) in predicting bacteremia.

• Clinicians should carefully consider the use of ceftiofur due to increasing resistance and its limited efficacy. (Oaklahoma)
• Empirical therapies must account for local resistance patterns and balance broad-spectrum coverage with antimicrobial stewardship principles.

Question 17

Faecal microbiota and antimicrobial resistance gene profiles of healthy foals

Answer 17

• Firmicutes and Bacteroidetes were dominant bacterial phyla in the faecal microbiota of healthy foals, consistent with findings in other mammalian species.
• Age significantly influenced microbiota richness and composition:
-Foals aged 1–2 weeks had significantly lower microbiota richness compared to foals >3 weeks old.
-Treponema spp. (associated with fiber digestion) and Christensenellaceae were more abundant in foals >3 weeks, reflecting dietary shifts towards forage consumption.
• The progressive colonization of the foal gastrointestinal tract with bacterial taxa reflects environmental exposure and dietary changes.
• Increase in fiber-digesting bacteria and diversity with age indicates adaptation to forage-based diets, crucial for post-weaning development.

Antimicrobial Resistance Genes (ARGs):
• Tetracycline resistance genes (tetQ, tetO, and tetW) were the most abundant ARGs detected, likely due to the dominance of Bacteroides and other host genera.
• ARG abundance and diversity varied by age: Younger foals (1–2 weeks) had significantly higher abundances of specific ARGs (aphA3, sat4, tetM, and tetX) compared to older foals.
• ARGs of high clinical concern (e.g., extended-spectrum beta-lactamase genes blaSHV and blaCTX-M, fluoroquinolone resistance gene qnrB) were rare.
• Co-Occurrence of ARGs: ARGs co-occurred in clusters, often associated with mobile genetic elements (e.g., class I integrons).
• Examples of linked ARGs: Sulfonamide and streptomycin resistance genes (sul2, strB) on plasmids. Aminoglycoside resistance genes (aphA3, sat4, aadE) linked on transposons.

• ARGs in foal microbiota are shaped by intrinsic bacterial communities rather than direct antimicrobial exposure.
• The presence of tetracycline resistance genes highlights their widespread dissemination via mobile genetic elements in normal bacterial flora.
• Co-occurrence of ARGs and integrons suggests the potential for horizontal gene transfer among bacteria, even in the absence of antimicrobial pressure.

Question 18

Symmetric dimethylarginine concentrations in healthy neonatal foals and mares

Answer 18

• SDMA levels were significantly higher in neonatal foals compared to adult reference values throughout the first month of life.
• Median SDMA levels decreased from 70 µg/dL at birth to 18 µg/dL by 20–30 days postpartum.
The upper reference limit decreased over time:
•100 µg/dL at birth.
•85 µg/dL for 1–4 days old.
•36 µg/dL for 5–10 days old.
•24 µg/dL for 20–30 days old.
Serum Creatinine (sCr) Dynamics:
• Elevated sCr concentrations were observed in foals at birth but normalized within 72 hours.
• This pattern aligns with previously described spurious hypercreatininemia due to placental insufficiency or delayed urination.
Lack of Correlation with Mare Values:
• SDMA and sCr levels in foals showed no significant correlation with their corresponding mare levels, indicating no placental or colostral transfer of SDMA.

The higher SDMA levels in neonates may reflect:
• Immature renal function or incomplete nephrogenesis.
• Increased arginine methylation and metabolic activity during growth.
• Despite higher SDMA, foal renal function (glomerular filtration rate [GFR]) is comparable to that of adult horses, suggesting other mechanisms behind elevated SDMA levels.

Question 19

Blood thiamine (vitamin B1), ascorbic acid (vitamin C), and cortisol concentrations in healthy and ill neonatal foals

Answer 19

Thiamine (Vitamin B1) and Illness in Foals:
• Thiamine concentrations were significantly lower in septic foals at 72 and 120 hours compared to healthy foals.
• Hypovitaminosis B1 was more common in septic foals (57%) than in sick-nonseptic (SNS) foals (15%).
• Thiamine deficiency in septic foals likely results from increased metabolic demand during systemic inflammation and decreased intake.

Ascorbic Acid (Vitamin C) and Illness in Foals:
• Plasma ascorbic acid levels were significantly lower in both septic and SNS foals at 72 and 120 hours compared to healthy foals.
• Deficiency is attributed to:
-Increased demand due to reactive oxygen species (ROS) production during sepsis and inflammation.
-Reduced dietary intake or synthesis in sick foals.Horses can synthesize ascorbic acid endogenously, but illness-related factors can reduce production.

Cortisol Concentrations:
• Cortisol levels were significantly higher in septic foals at admission compared to SNS and healthy foals.
• This reflects an activated hypothalamic-pituitary-adrenal (HPA) axis, common in septic and critically ill neonates.
• No significant association was found between cortisol levels and survival outcomes.

Survival and Vitamin Levels:
• Nonsurviving foals showed trends toward lower thiamine and ascorbic acid levels and higher cortisol levels compared to survivors, though these differences were not statistically significant.

Biological Implications
• Thiamine Deficiency: may exacerbate organ dysfunction, neurodegeneration, or energy deficits, as observed in critically ill humans.
•Ascorbic Acid Role: deficiencies could contribute to oxidative stress, endothelial dysfunction, and systemic inflammation.
•Cortisol Elevations: Elevated levels are indicative of adrenal activation but do not always correlate with better outcomes due to the complex interplay of immune-modulating and metabolic effects.

Clinical Implications
• Routine assessment of thiamine and ascorbic acid levels may be warranted in septic or critically ill foals.
• Supplementation with thiamine and ascorbic acid could support metabolic and antioxidant needs, though efficacy and dosing require further study.
• Elevated cortisol levels should be interpreted as part of a broader assessment of illness severity.

Question 20

Evaluation of a continuous glucose monitoring system in neonatal foals

Answer 20

n=4, extremes not measured.

• CGMS (Dexcom G6) demonstrated strong correlation with the laboratory chemistry analyzer (CHEM), considered the gold standard: r=0.81 (CGMS vs. CHEM). Mean bias: 3.97 mg/dL, within acceptable clinical limits. 85% of CGMS measurements were within 15% of CHEM readings, comparable to performance observed in humans using the same device.
•POC glucometer showed higher correlation with CHEM (r=0.92) but exhibited a larger mean bias (22.18 mg/dL). Only 49.5% of POC glucometer readings fell within 15% of CHEM, indicating lower accuracy than CGMS.

• CGMS eliminated the need for repeated venipunctures, reducing stress, phlebitis, and thrombosis risks.
• Sensors remained effective for 6-10 days without causing skin irritation or inflammation. Placed on lateral HQ- measurements every 5 minutes.
• User-configurable alarms notify clinicians of glucose levels outside preset ranges, enabling timely interventions.
• Hypoglycemia (≤ 75mg/dL) was not observed in the study population, limiting evaluation of CGMS performance in low glucose ranges.
• Lag Effect: CGMS measures interstitial glucose, which lags behind blood glucose by 5-10 minutes. This delay should be considered during rapid glucose fluctuations, such as stress-induced hyperglycemia or after dextrose boluses.
• Improved Accuracy Over Time: CGMS accuracy improved after the first 30 hours of placement, consistent with trends reported in human use of the Dexcom G6.

Question 21

The fecal bacterial microbiota of healthy and sick newborn foals

Answer 21

• Gram-positive bacteria (Streptococcus spp., Enterococcus spp., Staphylococcus spp.) and Gram-negative bacteria (Escherichia coli, Aerococcus spp., Psychrobacter spp.) were isolated from blood cultures of septic foals.
• High relative abundance of these bacteria in the gastrointestinal tract (GIT) suggests the gut could be a significant source of systemic infections in foals.

• Septic foals had higher alpha-diversity (richness, evenness) compared to healthy foals, contrary to expectations based on other species, where lower diversity is associated with disease.
• Differences in bacterial membership (presence/absence of taxa) were noted between sick (septic and sick-nonseptic) and healthy foals.
• Beta-diversity (community structure and shared taxa abundances) was similar between groups, with minor clustering differences observed.

Dominant Taxa and Enrichment:
• Common genera in all groups included Enterobacteriaceae, Enterococcus, and Streptococcus.
Enriched taxa in sick foals included:
• Septic foals: Lactobacillus, Facklamia, and unclassified Pasteurellaceae.
• Sick-nonseptic foals (SNS): Akkermansia, Porphyromonas, and Phascolarctobacterium.

Biological Implications
• GIT as a Source of Sepsis: The presence of bacteremia-causing organisms in the fecal microbiota supports the hypothesis that bacterial translocation from the gut plays a role in neonatal sepsis. Factors increasing gut permeability (e.g., immature intestinal barrier, hypoxia, gastrointestinal inflammation) can facilitate this translocation, particularly in foals with failure of passive immunity transfer (low serum IgG).
• Unstable Colonic Microbiota in Sick Foals: Higher diversity in septic and SNS foals could reflect:
-Delayed colonic colonization and stabilization due to reduced colostrum intake.
-Increased exposure to environmental microorganisms due to hospitalization or disease conditions.
•Role of Colostrum: Lower serum IgG levels in sick foals suggest inadequate colostrum intake, potentially delaying microbiota establishment and increasing susceptibility to dysbiosis and translocation.

Question 22

Dynamics of androgens in healthy and hospitalized newborn foals

Answer 22

• Healthy neonatal foals exhibited a steady decline in serum androgen levels (DHEA, androstenedione, testosterone, DHT) over time, consistent with normal postnatal clearance of fetal steroids.
• In critically ill or nonsurviving foals, androgen concentrations remained elevated, suggesting impaired clearance due to disease severity.
• Higher serum androgen levels were significantly correlated with nonsurvival, with critically ill foals showing reduced androgen clearance compared to survivors.
• Elevated androgen levels (DHEA, testosterone, DHT) at specific time points (e.g., 24–72 hours) increased the odds of mortality by up to 7-fold.

ACTH and Androgen Interactions:
• ACTH concentrations were elevated in septic and NMS foals at admission but decreased over time, while androgen levels in these groups remained high.
• The lack of a consistent relationship between ACTH and androgens across groups suggests that impaired clearance, rather than increased production, is the primary mechanism for elevated androgen levels in sick foals.

Neurosteroid Role in Neonatal Disorders:
• Elevated androgens in NMS foals support a potential role in the pathogenesis of neonatal maladjustment syndrome, likely through interactions with neuronal receptors such as GABA-A and NMDA.
• Androgens’ immunosuppressive effects (e.g., modulation of cytokines like IL-10 and TGF-β) could exacerbate sepsis-related outcomes.

Biological Implications
• Impaired clearance of androgens in critically ill foals is likely due to hepatic dysfunction or altered protein binding, both common in septic neonates.
• The lipophilic nature of steroids means most circulate bound to proteins like SHBG, which may be reduced in illness, affecting bioavailability and metabolism.

Nonsurvival
• high testosterone (>3x), hgih DHES (>3.6) high DHT at 72 hours (>3.6). No association with androstenedione
• steroid Δ <0 DHEA, androstenedione, DHT (>4)

Question 23

Antibiograms of field and hospital acquired equine neonatal bacterial fluid cultures in the Midwestern United States: 149 samples (2007-2018)

Answer 23

• Gram-positive organisms dominated neonatal bacterial fluid cultures, comprising 56% of isolates.
• Common isolates included Escherichia coli (16%), Actinobacillus spp. (14%), Staphylococcus spp. (13%), and Streptococcus spp. (12%).
• Anaerobes represented 13% of isolates, exceeding previous reports (1.2%-6.3%).

Greater than 70% of aerobic isolates were susceptible to:
• Ampicillin, ceftiofur, chloramphenicol, trimethoprim-sulfamethoxazole, and combination protocols.
• Chloramphenicol exhibited the highest efficacy, with 92% of isolates susceptible.
• 34% of isolates were classified as multidrug-resistant (MDR), with higher MDR prevalence among gram-positive isolates.
• Routine anaerobic culture efforts at the reporting institution contributed to the higher detection of anaerobes.

Antimicrobial Efficacy:
• Ceftiofur demonstrated strong efficacy (85% susceptibility) and practicality for field and hospital use, but its classification as a critically important antimicrobial warrants cautious use.
• Ampicillin was more effective than penicillin against specific organisms (e.g., Actinobacillus spp.), supporting its use in combination protocols.

• Overall survival was 77%, with foals showing negative fluid cultures having higher survival rates (85%) than those with positive cultures (68%).
• Survival was not significantly associated with polymicrobial infections or the appropriateness of initial empirical antimicrobial therapy.

• Routine inclusion of anaerobic cultures is recommended for all neonatal fluid samples to improve pathogen detection and treatment outcomes.
• Frequent reevaluation of bacterial isolates during hospitalization (e.g., every 48 hours) helps detect emerging infections and resistance patterns.
• Ceftiofur’s pharmacokinetic profile supports its utility for both hospital and field cases, but extra-label dosing may enhance its clinical efficacy.

Question 24

Assessment of the hypothalamic-pituitary-adrenocortical axis function using a vasopressin stimulation test in neonatal foals

Answer 24

• Administration of arginine vasopressin (AVP) reliably stimulated the hypothalamic-pituitary-adrenocortical axis (HPAA) in neonatal foals: (healthy/ mildly ill)
• Significant increases in ACTH and cortisol were observed within 15 and 30 minutes, respectively.
• The 5 IU dose was found to be the optimal balance for effective stimulation with minimal adverse effects. Higher doses (7.5 IU) induced greater ACTH peaks without significantly enhancing cortisol response.

• Cortisol responses demonstrated a 7-fold increase at the highest dose of AVP, indicating a robust adrenal response.
• ACTH and cortisol time-to-peak values were dose-dependent, with higher doses prolonging cortisol peak times.
• No changes in endogenous corticotropin-releasing hormone (CRH) were detected following AVP administration, supporting AVP’s direct effect on ACTH release without hypothalamic feedback involvement.

• Minor transient side effects, such as a slight drop in heart rate and paler mucous membranes, were observed across all doses. No delayed adverse effects were noted during or after the study.
• AVP acts at multiple levels, including direct adrenal stimulation via V1a receptors.

• AVP elicited a more consistent cortisol response compared to traditional ACTH stimulation tests, suggesting its potential superiority as a diagnostic tool for HPAA function in foals.
• AVP stimulation may help identify relative adrenal insufficiency (RAI) in septic foals, facilitating early interventions.

Question 25

The hypothalamic-pituitary-adrenal axis response to ovine corticotropin-releasing hormone stimulation tests in healthy and hospitalised foals

Answer 25

• Administration of ovine corticotropin-releasing hormone (oCRH) resulted in dose-dependent increases in cortisol, ACTH, and endogenous CRH (eCRH) in healthy and hospitalized neonatal foals.
• The highest dose of oCRH (1 µg/kg) elicited the most pronounced and sustained hormonal responses compared to 0.1 and 0.3 µg/kg doses.
• ACTH and cortisol increases occurred within 15-30 minutes of administration and returned to baseline after 90 minutes.

• Neonatal foals exhibited lower peak cortisol concentrations compared to adult horses stimulated with the same oCRH dose.
• AVP Response: Arginine vasopressin (AVP) concentrations remained unchanged across all oCRH doses, suggesting that AVP secretion is not directly stimulated by oCRH in foals. may be more responsive to pathophysiological stimuli such as sepsis or cytokine activity.
• eCRH concentrations increased following oCRH administration, contrary to expected feedback inhibition by cortisol. Possible explanations include:
-A feed-forward mechanism where exogenous oCRH stimulates hypothalamic eCRH secretion.
-Cross-reactivity between oCRH and eCRH assays.
• The 1 µg/kg dose of oCRH is proposed as the optimal dosage for assessing HPA axis function in neonatal foals due to its robust and reproducible hormonal responses.

Question 26

Effect of plasma transfusion on serum amyloid A concentration in healthy neonatal foals and foals with FTPI

Answer 26

• Plasma transfusion did not significantly alter SAA concentrations in neonatal foals, regardless of whether the foals had Failure of Transfer of Passive Immunity (FTPI) or were healthy.
• The SAA concentration increased over time in all foal groups (HNT, RP, and FTPI) from baseline (t0h) to 24 hours (t24h), but there was no direct correlation with plasma transfusion.
• Healthy nontransfused (HNT) foals exhibited an increase from baseline (1 µg/mL) to 24 hours (45 µg/mL), while FTPI foals increased from 0 µg/mL to 29 µg/mL, and Rhodococcus equi prophylaxis foals (RP) showed a similar increase.
• The model also found that the baseline SAA concentration at t0h was the strongest predictor for SAA levels at t24h, irrespective of plasma transfusion.

• The increase in SAA from t0h to t24h, regardless of plasma transfusion, suggests that this rise is likely due to the normal physiological response of the foal’s body to the ingestion of colostrum. The SAA increase could be due to inflammatory mediators, such as cytokines (IL-1β, IL-6, TNF), absorbed from colostrum, which stimulate hepatic production of SAA.
• Cortisol, which increases after foaling, could contribute to the rise in SAA, as it stimulates the liver to produce acute-phase proteins like SAA.
• SAA concentrations can be a helpful indicator of systemic inflammation or infection in foals but should be interpreted cautiously.

Question 27

Enterococcus durans infection and diarrhea in Thoroughbred foals

Answer 27

• Farm based investiagation of outbreak of diarrhoea.
• A significant association was observed between E. durans infection and diarrhea in Thoroughbred foals:
• E. durans was detected in 71% of foals with diarrhea compared to none of the foals without diarrhea (P < .01).
• Detection in broodmares was also associated with foal infections, suggesting potential vertical or environmental transmission.

• The first case of diarrhea in the study tested negative for E. durans, but the broodmare tested positive, indicating either false-negative results or environmental contamination as a source. 3/5 of the dxa in the same barn then tested positive
• Lateral transmission was likely responsible for additional cases within the same barn over a 12-day period.

Other Pathogens:
•the frequency of C. perfringens (culture), C. perfringens (enterotoxin), or C. difficile (toxin A) was not different (P ≥ .6) in foals with or without dxa. C diff toxin B was lower in foals with diarrhoea!

Role of E. durans in Foal Diarrhea:
• E. durans has been implicated in diarrhea in other species (calves, piglets, dogs) and is known to adhere to the intestinal epithelium, causing inflammation and disruption of gut barrier integrity.
• In foals, E. durans infection is a newly recognized contributor to neonatal diarrhea, potentially via direct enteropathogenic effects or by influencing microbiota composition.
• The co-detection of E. durans with other pathogens like C. perfringens and C. difficile raises questions about synergistic interactions that may exacerbate clinical signs.
• E. durans is a commensal of the gastrointestinal tract and can persist in environmental reservoirs (e.g., soil, water), highlighting the importance of environmental management in controlling outbreaks.

• Routine inclusion of E. durans in fecal pathogen panels is recommended for foals presenting with diarrhea, especially in outbreaks.
• Regular monitoring of broodmares for E. durans and addressing environmental contamination could further reduce transmission risks.
• Therapeutic protocols should consider the potential pathogenic role of E. durans, alongside addressing co-infections with other enteropathogens.
• Antibiotic stewardship is crucial, as Enterococcus species are known for multidrug resistance.

Question 28

Association of the neutrophil-lymphocyte ratio with outcome in sick hospitalized neonatal foals

Answer 28

•The Neutrophil-Lymphocyte Ratio (NLR) was significantly lower in sick hospitalized foals compared to healthy controls.
Among hospitalized foals:
•Septic foals had the lowest NLR (median = 2.00), followed by sick-nonseptic (SNS) foals (median = 3.55).
•Healthy foals had the highest NLR (median = 6.61).
•Nonsurviving foals had a significantly lower NLR compared to survivors: Median NLR for nonsurvivors = 1.97. Median NLR for survivors = 4.10.
• In septic foals, nonsurvivors exhibited the lowest NLR (median = 1.47).

ROC analysis demonstrated the diagnostic utility of NLR:
• NLR < 3.06 had an odds ratio of 3.21 for nonsurvival.
• NLR < 1.6 increased the odds ratio to 4.03 for nonsurvival.
• A lower NLR was strongly associated with higher sepsis scores, reflecting greater systemic inflammation.

NLR and Immune Dysregulation:
•The low NLR in septic foals was primarily driven by neutropenia rather than lymphopenia, distinguishing it from patterns observed in humans and other species. This suggests a more severe immune and inflammatory response in critically ill foals.
• The dynamic relationship between neutrophils and lymphocytes highlights NLR’s role in reflecting the intensity of the immune-inflammatory response to sepsis and critical illness.

• Neutrophil Counts Drive Prognostic Value: Neutrophil counts alone had comparable sensitivity and specificity to NLR for predicting nonsurvival. . in septic foals NLR had a sensitivity of 86% and a specificity of 86% (AUC = 0.92) (but, neutrophil count <5.6 in septic foals had a sensitivity of 91% and specificity of 87% (AUC = 0.95)

Question 29

Single and double vaccination against Lawsonia intracellularis in foals: Investigation of the humoral immune response

Answer 29

• Vaccinated foals (single or double vaccination) showed significantly higher seroconversion rates (43.2%) compared to non-vaccinated controls (4.2%).
• There was no significant difference in seroconversion rates between foals receiving a single vaccination (45.7%) versus two vaccinations (40.6%).
• The time from first vaccination to seroconversion was similar across vaccination protocols (median 31 days for single and 29 days for double vaccination).
•Vaccinated foals exhibited a gradual increase in antibody titres over time, which was not observed in non-vaccinated controls.
• A larger proportion of vaccinated foals had detectable antibody titres at later timepoints
• No foals developed clinical or subclinical equine proliferative enteropathy (EPE) during the study period, although six foals (two vaccinated, four unvaccinated) were diagnosed with EPE 3–10 weeks post-study.
• Only one of the EPE-diagnosed foals had seroconverted during the study, suggesting serological response alone may not predict clinical protection.
• Seroconversion rates were lower than those observed in earlier studies with different vaccine formulations or dosages, suggesting variability in vaccine performance.

• Vaccination stimulated a detectable humoral response in foals, but seroconversion was inconsistent and did not correlate directly with clinical protection.
• Immune responses likely involve additional mechanisms beyond the systemic humoral response, such as cell-mediated immunity or localized mucosal responses.
-Cellular immune responses, including IFN-γ production, may play a critical role in protecting against L. intracellularis. Previous studies in pigs and foals have shown that IFN-γ is associated with effective immunity.

Question 30

Red blood cell distribution width to platelet ratio in neonatal foals with sepsis

Answer 30

• Red cell distribution width to platelet ratio (RPR) was significantly higher in septic foals (median = 0.099) compared to sick-nonseptic (SNS, median = 0.085) and healthy foals (median = 0.081).
• RPR showed strong diagnostic utility with an Area Under the Curve (AUC) of 82.1%, supporting its use as a marker for sepsis in foals.
• An RPR cutoff of 0.0928 achieved a sensitivity of 62.7% and specificity of 66.2%.
• Nonsurviving foals exhibited higher RPR values than survivors, highlighting its association with poor outcomes.
• Kaplan-Meier analysis indicated reduced survival rates in foals with RPR values ≥0.0928, though log-rank tests did not reach statistical significance (P = 0.1).
• Elevated RPR reflects systemic inflammation and may indicate a disparity between RDW and platelet counts during sepsis.

Pathogenesis of RPR Elevation: Sepsis-induced inflammation affects erythropoiesis and platelet production:
• Increased RDW reflects altered red blood cell production and maturation.
• Reduced platelet counts in septic foals may stem from consumption in coagulation pathways.

Question 31

Cervical articular process joint osteochondrosis in Warmblood foals

Answer 31

Articular process joint OC in Warmblood foals is common and is not more prevalent at CVM predilection sites, suggesting that abnormalities of enchondral ossification may not be major contributors to CVM.
• OC was found in 20.6% of facets.
• Prevalence decreased with age up to 1 year, but not up to 5 months.
• severity increased with age
• Highest prevalence was in the cranial facets of the cervical and cervico-thoracic joints and the caudal facet of the thoracic joint.
•No specific predilection site was identified.
• The study did not find evidence linking OC to CVM predilection sites.
• The majority of lesions were mild to moderate.

Question 32

α-Casozepine supplementation shows no effect on foals’ growth and cortisol levels before and after weaning

Answer 32

No significant differences in cortisol levels, weight gain, or height gain were observed between groups. Numerical trends suggested less decline in growth metrics in the treatment group, but these were not statistically significant.

Question 33

Osteochondral necrosis of the femoral condyles in Thoroughbred foals: eight cases (2008–2018)

Answer 33

All foals had femoral condyle necrosis, predominantly affecting the medial condyle. Lesions often showed septic characteristics, with bacterial colonization in 7 foals. Imaging revealed crescent-shaped osteochondral flaps and subchondral bone lysis, with detachment of cartilage from the underlying bone. Histopathology confirmed osteochondral necrosis, inflammation, and degenerative changes.

The findings suggest osteochondral necrosis is more likely related to bacterial septicemia rather than osteochondrosis. Histopathology showed a predominantly inflammatory process with evidence of septic arthritis or osteomyelitis in most cases.