Background: Prognostic indicators for equine multinodular pulmonary fibrosis (EMPF), an interstitial fibrosing lung disease, are poorly described. Hypothesis/Objectives: Describe diagnostic findings and outcome predictors for EMPF. Animals: Forty-six adult horses with EMPF. Methods: Retrospective multicenter case series from 2009 to 2019. Radiographic (n = 27) and ultrasonographic studies (n = 19) from EMPF horses and bronchoalveolar lavage fluid (BALF) cytology from 6 EMPF and 13 asthma cases were independently reviewed and blinded to diagnosis and outcome. Associations between predictor variables and survival were assessed by predictor screening followed by Fisher's exact and Wilcoxon rank sum tests. Results: Primary clinical findings were weight loss (36/46, 78%), increased respiratory effort (33/46, 72%), tachypnea (32/46, 70%), and fever (18/46, 39%). Macrophage atypia was seen in more EMPF than asthmatic horse BALF (67% vs. 8%; P = .02). Equine herpesvirus 5 (EHV-5) was detected in 24 of 30 (80%) and hyperfibrinogenemia in 25 of 28 (89%) cases. Twenty-seven of 46 horses (59%) and 11 of 45 (24%) survived to discharge and to 3 months, respectively. Three-month survival was associated with lower median (range) respiratory rates (30 [24-36] vs. 41 [30-60] breaths per minute; P = .04), and higher BALF lymphocyte:neutrophil ratios (4.7 [1.4-22] vs. 0.47 [0.11-1.9]; P = .01) and blood lymphocyte counts (1.25 [0.93-2.55] vs. 0.90 [0.70-1.24] × 109/L; P = .03). Imaging findings, EHV-5 detection, and corticosteroid treatment were not associated with survival. Conclusions and Clinical Importance: Fever is not a sensitive clinical sign of EMPF. Diagnostic testing should be pursued for horses with increased respiratory rate and effort and weight loss. The prognosis for EMPF horses is poor. Corticosteroid treatment does not improve 3-month survival.

Equine asthma is considered a non-infectious respiratory disease characterized by inflammation and hypersensitivity. Given the importance of antimicrobial stewardship, an international survey was designed to investigate the use of antimicrobials in asthmatic horses and the factors influencing prescription behavior. An online survey was distributed in six languages by international mailing lists and social media from December 2020 to January 2022. Of the 434 responses recorded, 249 veterinarians working in 25 countries finished the survey. These included 79 ECEIM/ACVIM diplomats. A total of 204 respondents confirmed national regulations concerning antimicrobial use in their country. Knowledge of the asthma definitions as presented in the revised ACVIM consensus statement was greater in veterinarians treating over 95% of equine patients compared to veterinarians treating more species, based on 10 questions (answers consistent with the consensus statement in 7 (IQR 5–9) and 4 (IQR 3–6) questions, respectively, (p < 0.001)). A total of 131 respondents stated to use antimicrobials (at least ‘sometimes’) in at least one of the three presented cases consistent with equine asthma. Trimethoprim-Sulfa combinations, penicillin(s), and tetracyclines were prescribed most (by 105, 53 and 38 veterinarians, respectively). Aminoglycosides, cephalosporins and fluoroquinolones were also selected (22, 15, 9 veterinarians respectively). Tetracyclines and cephalosporins are prescribed more often by veterinarians working without national regulations (p 0.019 and p 0.035, respectively). The most selected factors influencing prescription behavior were: ‘tracheal wash culture’ (62% of 131 veterinarians using antimicrobials in these cases), ‘whether other horses in the barn have similar complaints’ (60%), and ‘response to other forms of therapy’ (53%). In conclusion, insight into prescription behavior is the first step towards minimizing and optimizing antimicrobial use.

In hospitalized foals, limited data are available on the utility of sequential measurement of SAA concentrations and the value of these data in a clinical setting. To determine serum amyloid A (SAA) concentrations in ill neonatal foals at multiple timepoints during hospitalization, and to evaluate a potential association with systemic inflammatory response syndrome (SIRS) status, blood culture (BC) result, and survival. Hospitalized ill foals (n = 90, ≤ 14 days). In this retrospective study, foals were classified based on SIRS criteria: “SIRS” or “NonSIRS,” BC results, and survival. Serum amyloid A concentrations on admission (ADM), day 1 (D1) and day 2 (D2) were compared within and between groups, using nonparametric tests. Results are presented as median (IQR) (effect size; 95% CI). Serum amyloid A concentrations were higher in SIRS than in NonSIRS foals both on ADM (401 mg/L (99; 855) vs 67 mg/L (23; 685), [ES 129, 95% CI, 15-385]), and on D1 (836 mg/L (616; 1240) vs 212 mg/L (69; 890), [ES 501, 95% CI, 121-724]). On D2, but not on ADM, foals with a positive BC had higher SAA (1244 mg/L (757; 2004)) than BC negative foals (153 mg/L (57; 695), [ES 1002; 95% CI, 282-1418]). On D1, but not on ADM, SAA was higher in non-survivors (729 mg/L (469; 1347) than in survivors (323 mg/L (75; 889), [ES 373; 95% CI, 28-651]). Serum amyloid A measurements on D1 and D2 of hospitalization likely reflect both the severity of disease and response to initial treatment. Repeated SAA measurements during hospitalization can aid clinicians in determining severity of disease and can be useful as a prognosticator in ill neonatal foals.

Background: Thrombophlebitis is a possible complication of the use of indwelling catheters in hospitalized neonatal foals. Limited data are available concerning associated risk factors, and long-term prognosis regarding vein patency is currently unknown. Hypothesis/Objectives: Identify risk factors for catheter-associated thrombophlebitis in neonatal foals and assess long-term prognosis in a small subset. Animals: Two hundred twenty-three foals < 31 days of age, hospitalized in Utrecht University Equine Hospital between 2019 and 2024. Methods: Retrospective review of medical records. Foals that received an indwelling intravenous catheter and lived for at least two subsequent days were included. Odds ratios were determined, using logistic regression, for factors potentially associated with thrombophlebitis. Owners of affected horses were contacted, and horses available for follow-up were visited for clinical evaluation. Results: Twenty-one foals (9.4%) developed catheter-associated thrombophlebitis. In a multivariable model, hospitalization in the neonatal intensive care unit (NICU, OR 5.2, 95%CI 1.5-19.7), diarrhea (OR 4.6, 95%CI 1.4-17.3), Friesian breed (OR 4.1, 95%CI 1.1-13.9) and dwell time over four days (OR 3.9, 95%CI 1.3-14.8) were significantly associated with thrombophlebitis development. Seventeen affected foals survived to discharge. Eight horses, aged five months to five years, were available for follow-up by clinical evaluation and demonstrated appropriate blood flow. Conclusions and clinical importance: Risk factors for developing catheter-associated thrombophlebitis in hospitalized neonatal foals were identified. This knowledge can aid in implementation of preventive measures.

Information on safe and effective gentamicin dosing in foals is limited. This study aimed to provide guidance regarding optimal dosing regimens by means of a population pharmacokinetic (popPK) model. Gentamicin plasma concentration of 290 samples from 72 hospitalized foals (≤ 14 days old), treated with intravenous (IV) gentamicin, was measured using a validated LC–MS/MS method. A 2‐compartment popPK model was developed with age as a significant covariate on clearance. The final popPK model was used to simulate the commonly used clinical dosing regimens. Mean simulated f AUC _0‐24H (10th–90th percentile) in respectively 1‐day‐old and 14‐day‐old foals following IV administration of 6.6 mg/kg q24h was 66.3 mg/L*h (44.7–91.2) and 41.9 mg/L*h (26.0–61.0) and following 12 mg/kg q36h 120.5 mg/L*h (81.3–165.8) and 76.2 mg/L*h (47.3–110.9). Trough concentrations were < 2 mg/L for both dosing regimens, irrespective of age. Based on a pharmacodynamic target of f AUC _0‐24H /MIC > 80, the 12 mg/kg q36h regimen has a higher probability of target attainment (PTA) than 6.6 mg/kg q24h. A simulated hypothetical dose of 15 mg/kg q36h demonstrated promising PTA with mean trough values ≤ 2 mg/L. Despite substantial interindividual variability, the model provides a rational basis for selecting a dosing regimen in hospitalized neonatal foals.