Systemic Inflammatory Response in Equine Neonates

The systemic inflammatory response syndrome (SIRS) in equine neonates is a complex and dysregulated host reaction to infectious or non-infectious insults that can rapidly progress to sepsis and multi-organ dysfunction. Foals are particularly susceptible during the first days of life due to an immature immune system, compromised barrier function and the haemodynamic challenges associated with transition from intra- to extra-uterine life. Common initiating factors include bacteremia, perinatal asphyxia, failure of passive transfer and gastrointestinal translocation of endotoxin. The innate immune system mounts an immediate defence through activation of neutrophils, monocytes and the complement cascade, leading to the release of pro- and anti-inflammatory cytokines. When this response becomes excessive or uncontrolled, endothelial injury, capillary leak and coagulopathy ensue, resulting in hypoperfusion and organ dysfunction. Clinical signs in affected foals may include fever or hypothermia, tachycardia, tachypnoea, altered mentation and mucosal discolouration. Laboratory abnormalities often comprise leukocyte derangements, hypoglycaemia or hyperglycaemia, elevated acute-phase proteins and markers of tissue hypoxia. Early recognition relies on a combination of clinical criteria, laboratory markers and scoring systems, while management demands prompt antimicrobial therapy, judicious fluid resuscitation, haemodynamic support and metabolic correction. Despite advances in critical care, mortality rates remain high and long-term outcomes depend on the speed of intervention, the severity of inflammation and the foal’s underlying resilience. Research continues to refine prognostic models, identify reliable biomarkers and develop targeted immunomodulatory therapies that may improve survival and welfare in this vulnerable population.

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Studies in the past two decades have provided new insights into the management and prognosis of SIRS in foals. Research on blood glucose concentrations in critically ill neonatal foals has demonstrated that both hypoglycaemia and hyperglycaemia at admission correlate strongly with non-survival and with positive blood cultures or SIRS criteria, suggesting that tight glycaemic control may be beneficial in critical care. A more recent investigation into bacterial isolation and antimicrobial susceptibility changes in foals with sepsis revealed that isolates obtained after 48 hours of hospitalisation are less susceptible to first-line antimicrobials and shift towards more resistant Gram-negative and Enterococcus species, underlining the importance of repeated culture and tailored antimicrobial stewardship. Complementing these findings, the development and validation of a likelihood-of-survival scoring system for hospitalised equine neonates using boosted regression modelling has enabled clinicians to stratify risk on admission using six clinical and laboratory variables, thereby facilitating early decision-making and resource allocation.

Systemic Inflammatory Response in Equine Neonates publication trend

The graph below shows the total number of articles in systemic inflammatory response in equine neonates across all publications each year (not limited to Nature Index journals).

Technical terms

Systemic inflammatory response syndrome (SIRS): A clinical state defined by a dysregulated systemic reaction to infection or injury, characterised by specified alterations in temperature, heart rate, respiratory rate and white blood cell count.

Sepsis: Life-threatening organ dysfunction caused by a dysregulated host response to infection, which in foals often follows SIRS and carries high mortality.

Neutrophil: A type of white blood cell that provides first-line defence by phagocytosis, degranulation and generation of reactive oxygen species during acute inflammation.

Cytokine: Small signalling proteins released by immune cells that mediate and regulate inflammation, immune activation and cellular communication.

Biomarker: A measurable laboratory or clinical parameter that indicates the presence or severity of disease, predicts outcome or guides therapeutic intervention.

Foal: A horse of either sex less than six months of age; in this context, particularly those within the first few days of life when immune maturity is incomplete.

References

1. A Comparative Review of Equine SIRS, Sepsis, and Neutrophils. Frontiers in Veterinary Science (2019).
2. Blood Glucose Concentrations in Critically Ill Neonatal Foals. Journal of Veterinary Internal Medicine (2008).
3. Differences in isolation rate and antimicrobial susceptibility of bacteria isolated from foals with sepsis at admission and after ≥48 hours of hospitalization. Journal of Veterinary Internal Medicine (2020).
4. Development of a Likelihood of Survival Scoring System for Hospitalized Equine Neonates Using Generalized Boosted Regression Modeling. PLOS ONE (2014).