Antimicrobial Resistance in Equines: A Growing Threat to Horse Health and Beyond-A Comprehensive Review.

The equine industry holds substantial economic importance not only in the USA but worldwide. The occurrence of various infectious bacterial diseases in horses can lead to severe health issues, economic losses, and restrictions on horse movement and trade. Effective management and control of these diseases are therefore crucial for the growth and sustainability of the equine industry.

Antimicrobial Residue Accumulation Contributes to Higher Levels of Carrying Resistance Genes in the Environment of Horse-Breeding Farms.

Antimicrobial residues excreted in the environment following antimicrobial treatment enhance resistant microbial communities in the environment and have long-term effects on the selection and maintenance of antimicrobial resistance genes (AMRGs). In this study, we focused on understanding the impact of antimicrobial use on antimicrobial residue pollution and antimicrobial resistance (AMR) in the environment of horse-breeding farms. is an ideal microbe to study these associations because it lives naturally in the soil, exchanges AMRGs with other bacteria in the environment, and can cause disease in animals and humans.

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

Background: The neutrophil-lymphocyte ratio (NLR) in human medicine is an objective biomarker that reflects prognosis. The NLR as an independent biomarker to help predict nonsurvival in hospitalized neonatal foals has not been thoroughly interrogated.

Objectives/hypothesis: Retrospectively evaluate if the NLR at admission is associated with nonsurvival in sick hospitalized foals <4 days old.

Neonates and Periparturient Mares: Tips and Tricks for Diagnosis and Management.

Colic is a common presenting complaint in foals. Unfortunately, evaluation of foals with colic can be difficult due to the common clinical presentation of acute abdominal pain attributable to a wide variety of disorders and a broad range of etiologies. Similar to foals, colic is one of the most common diseases of pregnant and periparturient mares.

Enterococcus durans infection and diarrhea in Thoroughbred foals.

Background: Diarrhea remains an important cause of morbidity and mortality in neonatal foals, and correct identification of etiologic agents is essential for effective disease management.

Objective: To examine the association between diarrhea and detection of Enterococcus durans or other enteropathogens in neonatal foals on 1 breeding farm in Kentucky, USA.

Animals: Fifty-nine Thoroughbred foals and their broodmares.

Symmetric dimethylarginine concentrations in healthy neonatal foals and mares.

Background: Symmetric dimethylarginine (SDMA) is a renal biomarker correlated with glomerular filtration rate (GFR).

Objectives: Describe changes in SDMA in clinically healthy foals and their mares during the first month postfoaling.

Animals: Convenience sampling of healthy periparturient Thoroughbred mares and their full-term foals from a population of client-owned horses.

Identification of a Ruminant Origin Group B Rotavirus Associated with Diarrhea Outbreaks in Foals.

Equine rotavirus group A (ERVA) is one of the most common causes of foal diarrhea. Starting in February 2021, there was an increase in the frequency of severe watery to hemorrhagic diarrhea cases in neonatal foals in Central Kentucky. Diagnostic investigation of fecal samples failed to detect evidence of diarrhea-causing pathogens including ERVA.

Circovirus in Blood of a Febrile Horse with Hepatitis.

Circoviruses infect vertebrates where they can result in a wide range of disease signs or in asymptomatic infections. Using viral metagenomics we analyzed a pool of five sera from four healthy and one sick horse. Sequences from parvovirus-H, equus anellovirus, and distantly related to mammalian circoviruses were recognized.

Association between antimicrobial treatment of subclinical pneumonia in foals and selection of macrolide- and rifampicin-resistant strains at horse-breeding farms in central Kentucky.

Objective: To compare soil concentrations of macrolide- and rifampicin-resistant strains (MRRE) on horse-breeding farms that used thoracic ultrasonographic screening (TUS) to identify foals with subclinical pneumonia combined with subsequent administration of macrolides and rifampin to affected foals (TUS farms) versus soil concentrations on farms that did not (non-TUS farms), determine whether the combined use of TUS and antimicrobial treatment of subclinically affected foals was associated with soil concentration of MRRE, and assess whether there were temporal effects on soil concentrations of MRRE during the foaling season.

Samples: 720 soil samples and 20 completed questionnaires from 20 horse-breeding farms (10 TUS farms and 10 non-TUS farms) in central Kentucky.

Procedures: A questionnaire was used to gather information from participating farms about their 2019 foaling season.

Clostridioides (Clostridium) difficile in neonatal foals and mares at a referral hospital.

Background: Understanding the epidemiology of Clostridium difficile is important for the development and assessment of infection prevention and control practices, as well as surveillance methods and interpretation of diagnostic testing results.

Objective: Our objective was to longitudinally evaluate C. difficile shedding in neonatal foals and mares admitted to a referral hospital neonatal intensive care unit.

Spread of Multidrug-Resistant Rhodococcus equi, United States.

Multidrug resistance has been detected in the animal and zoonotic human pathogen Rhodococcus equi after mass macrolide/rifampin antibioprophylaxis in endemically affected equine farms in the United States. Multidrug-resistant (MDR) R. equi emerged upon acquisition of pRERm46, a conjugative plasmid conferring resistance to macrolides, lincosamides, streptogramins, and, as we describe, tetracycline.

A nonsense variant in Rap Guanine Nucleotide Exchange Factor 5 (RAPGEF5) is associated with equine familial isolated hypoparathyroidism in Thoroughbred foals.

Idiopathic hypocalcemia in Thoroughbred (TB) foals causes tetany and seizures and is invariably fatal. Based upon the similarity of this disease with human familial hypoparathyroidism and occurrence only in the TB breed, we conducted a genetic investigation on two affected TB foals. Familial hypoparathyroidism was identified, and pedigree analysis suggested an autosomal recessive (AR) mode of inheritance.

The novel and transferable erm(51) gene confers macrolides, lincosamides and streptogramins B (MLS ) resistance to clonal Rhodococcus equi in the environment.

The use of mass antimicrobial treatment has been linked to the emergence of antimicrobial resistance in human and animal pathogens. Using whole-genome single-molecule real-time (SMRT) sequencing, we characterized genomic variability of multidrug-resistant Rhodococcus equi isolated from soil samples from 100 farms endemic for R. equi infections in Kentucky.

Point-of-Care Diagnostics in Equine Practice.

Point-of-care testing (POCT) refers to benchtop diagnostic modalities that have been translated into portable and easy-to-use formats suitable for patient-side use. Recent advances in diagnostic technology have allowed the development of a growing collection of POCT assays available to equine practitioners. Advantages include rapid results that reduce initial guesswork and promote diagnosis-targeted patient care, which may ultimately provide better clinical outcomes.

A Common Practice of Widespread Antimicrobial Use in Horse Production Promotes Multi-Drug Resistance.

The practice of prophylactic administration of a macrolide antimicrobial with rifampin (MaR) to apparently healthy foals with pulmonary lesions identified by thoracic ultrasonography (i.e., subclinically pneumonic foals) is common in the United States.

Retrospective evaluation of the association between hyponatremia and neurological dysfunction in hospitalized foals (2012-2016): 109 cases.

Objective: Hyponatremia and rapid correction of hyponatremia can lead to neurological abnormalities. The objective of the study was to determine whether plasma sodium concentrations (Na ) and speed of correction of hyponatremia are significantly associated with neurological abnormalities in foals.

Design: Retrospective cohort study 2012 to 2016.

Identification of macrolide- and rifampicin-resistant Rhodococcus equi in environmental samples from equine breeding farms in central Kentucky during 2018.

Rhodococcus equi causes severe pneumonia in foals and is most often recognized in people as an opportunistic pathogen. Longitudinal studies examining antimicrobial-resistant R. equi from environmental samples are lacking.

Evaluation of updated sepsis scoring systems and systemic inflammatory response syndrome criteria and their association with sepsis in equine neonates.

Background: The original equine sepsis score provided a method of identifying foals with sepsis. New variables associated with sepsis have been evaluated, but the sepsis score has not been updated.

Objectives: To evaluate the sensitivity and specificity of 2 updated sepsis scores and the systemic inflammatory response syndrome (SIRS) criteria in regard to detecting sepsis in foals.

Factors associated with equine shedding of multi-drug-resistant Salmonella enterica and its impact on health outcomes.

Background: Salmonella enterica is an important cause of healthcare-associated infections in veterinary hospitals - with outbreaks of multi-drug resistant (MDR) Salmonella among equine cases resulting in high case fatality rates and substantial financial cost.

Objectives: Study objectives were to 1) investigate factors associated with shedding of MDR-Salmonella enterica and 2) evaluate the effect shedding may have on health outcomes of previously hospitalised horses and their stablemates.

Study Design: Retrospective case-control study with prospective cohort study.

Sales performance and athletic outcome in young Thoroughbreds with pericarditis.

Background: Pericarditis is a sporadic, but important cause of critical illness in horses of all ages. There is limited information on whether Thoroughbred horses that survive pericarditis are able to reach athletic potential.

Objectives: To determine how pericarditis affected horses that had the disease as young animals with regard to selling price in public sales and the ability to race successfully.

Factors Associated with Survival in 97 Horses with Septic Pleuropneumonia.

Background: Septic pleuropneumonia is a common cause of morbidity and mortality in horses, but there is limited data available regarding factors associated with survival.

Hypothesis/objectives: To identify factors predictive of survival in horses with septic pleuropneumonia.

Animals: A total of 97 horses with septic pleuropneumonia at 2 referral institutions.