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. Based on Illumina-based metagenomic sequencing, we identified a novel equine rotavirus group B (ERVB) in fecal specimens from the affected foals in the absence of any other known enteric pathogens. Interestingly, the protein sequence of all 11 segments had greater than 96% identity with group B rotaviruses previously found in ruminants. Furthermore, phylogenetic analysis demonstrated clustering of the ERVB with group B rotaviruses of caprine and bovine strains from the USA. Subsequent analysis of 33 foal diarrheic samples by RT-qPCR identified 23 rotavirus B-positive cases (69.69%). These observations suggest that the ERVB originated from ruminants and was associated with outbreaks of neonatal foal diarrhea in the 2021 foaling season in Kentucky. Emergence of the ruminant-like group B rotavirus in foals clearly warrants further investigation due to the significant impact of the disease in neonatal foals and its economic impact on the equine industry

Gallium Maltolate as an Alternative to Macrolides for Treatment of Presumed Rhodococcus equi Pneumonia in Foals

Background: Macrolide-resistant isolates of Rhodococcus equi are emerging, prompting the search for clinically effective alternative antimicrobials. Hypothesis: The proportion of foals with ultrasonographic evidence of pneumonia presumed to be caused by R. equi that had a successful outcome when administered gallium maltolate (GaM) PO would not be more than 10% inferior (ie, lower) than that of foals receiving standard treatment. Animals: Fifty-four foals with subclinical pulmonary abscesses among 509 foals at 6 breeding farms in Kentucky. Methods: Controlled, randomized, prospective noninferiority study. Foals with ultrasonographic lesions >1 cm in diameter (n = 54) were randomly allocated to receive per os either clarithromycin combined with rifampin (CLR+R) or GaM, and followed up for 28 days by daily physical inspections and weekly (n = 1 farm) or biweekly (n = 4 farms) thoracic ultrasound examinations by individuals unaware of treatment-group assignments. Treatment success was defined as resolution of ultrasonographically identified pulmonary abscesses within 28 days of initiating treatment. Noninferiority was defined as a 90% confidence interval for the observed difference in CLR+R minus GaM that was ≤10%. Results: The proportion of GaM-treated foals that resolved (70%; 14/20) was similar to that of foals treated with CLR+R (74%; 25/34), but we failed to demonstrate noninferiority for GaM relative to CLR+R; however, GaM was noninferior to CLR+R treatment when results from a noncompliant farm were excluded. Conclusions and Clinical Importance: Gallium maltolate is not inferior to macrolides for treating foals with subclinical pneumonia. Use of GaM might reduce pressure for macrolide-resistance in R. equi

Antimicrobial Residue Accumulation Contributes to Higher Levels of <i>Rhodococcus equi</i> 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. Rhodococcus equi 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. The environment is the main source of R. equi infections in foals; therefore, higher levels of multidrug-resistant (MDR) R. equi in the environment contribute to clinical infections with MDR R. equi. We found that macrolide residues in the environment of horse-breeding farms and the use of thoracic ultrasonographic screening (TUS) for early detection of subclinically affected foals with R. equi infections were strongly associated with the presence of R. equi carrying AMRGs in the soil. Our findings indicate that the use of TUS contributed to historically higher antimicrobial use in foals, leading to the accumulation of antimicrobial residues in the environment and enhancing MDR R. equi

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. METHODS: Serum and EDTA whole blood samples were collected from mares in their last month of pregnancy and then from mares and foals at approximately &lt;12 hours, 48 hours, 7 days, and 30 days postbirth. Samples were processed at a commercial reference laboratory for CBC and serum biochemistry, including SDMA concentrations. RESULTS: A total of 125 foals and 104 mares were included. Upper limits for SDMA concentrations in foals were above the adult horse reference interval for the first 20 or more days of life. Median SDMA concentrations decreased from 70 μg/dL (range, 7-100 μg/dL) to 18 μg/dL (range, 6-27 μg/dL) during the first 3 to 4 weeks of life. At birth, the SDMA concentration reference range was established as 0 to 100 μg/dL (upper limit of the assay); 0 to 85 μg/dL for 1 to 4 days old, 0 to 36 μg/dL for 5 to 10 days old, and 0 to 24 μg/dL for 20 to 30 days old. The upper reference limits for SDMA concentrations in mares did not differ from the general reference interval for adult horses. No correlation was identified between mare and foal SDMA concentrations (ρ&nbsp;=&nbsp;.06, P&nbsp;=&nbsp;.58). CONCLUSIONS AND CLINICAL IMPORTANCE: Foal SDMA concentrations remained higher than the upper limit of the adult reference range and foals require a different reference range dependent on age

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

Abstract 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. We hypothesized that a lower NLR will be associated with nonsurvival. Animals One thousand one hundred ninety‐six client‐owned foals <4 days old of any breed and sex: 993 hospitalized foals and 203 healthy foals. Methods Retrospective multicenter study. Medical records of foals presenting to 3 equine referral hospitals were reviewed. Foals were included if they had complete CBCs, sepsis scores, and outcome data. The NLR was calculated by dividing the absolute neutrophil count by the absolute lymphocyte count. Data were analyzed by nonparametric methods and univariate analysis. Results Of the 993 sick hospitalized foals, 686 were sick nonseptic and 307 were septic. The median NLR was lower in sick hospitalized foals (median [95% confidence interval], 3.55 [0.5‐13.9]) compared with healthy foals (6.61 [3.06‐18.1]). Septic foals had the lowest NLR (2.00 [0.20‐9.71]). The NLR was lower in nonsurviving (1.97 [1.67‐2.45]) compared with surviving foals (4.10 [3.76‐4.33]). Nonsurviving septic foals had the lowest NLR (1.47 [1.70‐3.01]). Foals with a NLR of <3.06 or <1.6 at admission had odds ratio of 3.21 (2.24‐4.29) and 4.03 (2.86‐5.67) for nonsurvival, respectively. Conclusions and Clinical Importance A NLR < 3.06 at admission in sick hospitalized foals is readily available and clinically useful variable to provide prognostic information

Macrolide- and Rifampin-Resistant Rhodococcus equi on a Horse Breeding Farm, Kentucky, USA

Macrolide and rifampin resistance developed on a horse breeding farm after widespread use was instituted for treatment of subclinical pulmonary lesions in foals. Resistance occurred in 6 (24%) of 25 pretreatment and 8 (62%) of 13 (62%) posttreatment isolates from affected foals. Drug-resistant isolates formed 2 distinct genotypic clusters

Vitamin D Metabolites and Their Association with Calcium, Phosphorus, and PTH Concentrations, Severity of Illness, and Mortality in Hospitalized Equine Neonates

<div><p>Background</p><p>Hypocalcemia is a frequent abnormality that has been associated with disease severity and outcome in hospitalized foals. However, the pathogenesis of equine neonatal hypocalcemia is poorly understood. Hypovitaminosis D in critically ill people has been linked to hypocalcemia and mortality; however, information on vitamin D metabolites and their association with clinical findings and outcome in critically ill foals is lacking. The goal of this study was to determine the prevalence of vitamin D deficiency (hypovitaminosis D) and its association with serum calcium, phosphorus, and parathyroid hormone (PTH) concentrations, disease severity, and mortality in hospitalized newborn foals.</p><p>Methods and Results</p><p>One hundred newborn foals ≤72 hours old divided into hospitalized (n = 83; 59 septic, 24 sick non-septic [SNS]) and healthy (n = 17) groups were included. Blood samples were collected on admission to measure serum 25-hydroxyvitamin D₃ [25(OH)D₃], 1,25-dihydroxyvitamin D₃ [1,25(OH) ₂D₃], and PTH concentrations. Data were analyzed by nonparametric methods and univariate logistic regression. The prevalence of hypovitaminosis D [defined as 25(OH)D₃ <9.51 ng/mL] was 63% for hospitalized, 64% for septic, and 63% for SNS foals. Serum 25(OH)D₃ and 1,25(OH) ₂D₃ concentrations were significantly lower in septic and SNS compared to healthy foals (P<0.0001; P = 0.037). Septic foals had significantly lower calcium and higher phosphorus and PTH concentrations than healthy and SNS foals (P<0.05). In hospitalized and septic foals, low 1,25(OH)₂D₃ concentrations were associated with increased PTH but not with calcium or phosphorus concentrations. Septic foals with 25(OH)D₃ <9.51 ng/mL and 1,25(OH) ₂D₃ <7.09 pmol/L were more likely to die (OR=3.62; 95% CI = 1.1-12.40; OR = 5.41; 95% CI = 1.19-24.52, respectively).</p><p>Conclusions</p><p>Low 25(OH)D₃ and 1,25(OH)₂D₃ concentrations are associated with disease severity and mortality in hospitalized foals. Vitamin D deficiency may contribute to a pro-inflammatory state in equine perinatal diseases. Hypocalcemia and hyperphosphatemia together with decreased 1,25(OH)₂D₃ but increased PTH concentrations in septic foals indicates that PTH resistance may be associated with the development of these abnormalities.</p></div

Effects of Location for Collection of Air Samples on a Farm and Time of Day of Sample Collection on Airborne Concentrations of Virulent \u3cem\u3eRhodococcus equi\u3c/em\u3e at Two Horse Breeding Farms

Objective: To determine whether airborne concentrations of virulent R equi varied by housing location, time of day, and month (February through July) at 2 horse breeding farms. Sample Population: 2 farms with recurrent R equi foal pneumonia in central Kentucky. Procedures: From February through July 2008, air samples were collected hourly for a 24-hour period each month from stalls and paddocks used to house mares with foals. Virulent concentrations of airborne R equi were determined using a colony immunoblot technique and differences were compared using zero-inflated negative binomial methods to determine effects of location, time, and month. Results: The presence of mares and foals at the sampling site significantly (P = 0.017) modified the effect of location (stall versus paddock) by increasing airborne concentrations of virulent R equi. Relative to the period from midnight through 5:59 AM, airborne concentrations of virulent R equi were significantly (P = 0.016) higher between 6:00 PM through 11:59 PM midnight. There were no significant differences in airborne concentrations between farms or among months. Conclusions: Airborne concentrations of virulent R. equi were significantly increased by sampling when horses were predominately housed in the sampling site area (ie, higher in stalls when horses were predominately stalled, and higher in paddocks when horses were predominately in paddocks). For ecological and epidemiological studies, there appears to be no difference in airborne concentrations of virulent R. equi among air samples collected between the hours of 6:00 AM and midnight

Serum 25(OH)D₃ and 1,25(OH)₂D₃ concentrations in healthy, SNS, and septic foals.

<p>Values are expressed as median and 95% CI. (A) Septic and SNS foals had significantly lower serum 25(OH)D_<b>3</b> concentrations compared to healthy foals (P < 0.0001). (B) Septic and SNS foals had significantly lower serum 1,25(OH)_<b>2</b>D_<b>3</b> concentrations compared to healthy foals (P = 0.037). * indicates a statistically significant difference from healthy foals.</p