Corinne R. Sweeney

Rhodococcus equi pneumonia in 48 foals: Response to antimicrobial therapy

Case records of 48 foals with pneumonia due to Rhodococcus equi were reviewed. Twenty of the 48 foals survived and 28 died or were euthanized. There was no significant difference between the survivors and non-survivors in the age of onset of illness, duration of illness prior to admission, the mean white blood cell (WBC) count, or the mean plasma fibrinogen content. All foals had R. equi isolated from a tracheobronchial aspirate or lung specimens obtained at necropsy. All organisms were susceptible in vitro (Kirby-Bauer) to erythromycin and gentamicin. Susceptibilities to other drugs were: trimethoprim-sulfamethoxazole (88%), tetracycline (87%), chloramphenicol (83%); 97% were resistant to cephalothin and 83% to penicillin. Thirteen of the 20 surviving foals were treated with erythromycin and/or rifampin. A decline in mortality rate was observed with the introduction of the combination of erythromycin and rifampin. None of the 17 foals treated with penicillin and gentamicin survived. Chronic, active, non-septic synovitis was confirmed in 17 foals. These foals had joint distension with mild or no apparent lameness.

Exercise Induced Pulmonary Hemorrhage in Horses: American College of Veterinary Internal Medicine Consensus Statement

Background Published studies of exercise‐induced pulmonary hemorrhage (EIPH), when assessed individually, often provide equivocal or conflicting results. Systematic reviews aggregate evidence from individual studies to provide a global assessment of the quality of evidence and to inform recommendations. Objectives Evaluate evidence to determine: if EIPH adversely affects the health, welfare or both of horses; if EIPH affects the athletic capacity of horses; the efficacy of prophylactic interventions for EIPH; and if furosemide affects the athletic capacity of horses. Animals None. Materials and Methods Systematic review. A panel of 7 experts was formed to assess evidence in the peer reviewed literature addressing each of the 4 objectives. Methodology followed that of the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE). Publications were assessed for quality of evidence by working groups of the panel, and a summary of findings was presented in tables. Recommendations were based on quality of evidence and were determined by a vote of the panel. Results Much of the evidence was of low to very low quality. Experimental studies frequently lacked adequate statistical power. There was moderate to high quality evidence that EIPH is progressive, is associated with lung lesions, that it adversely affects racing performance, that severe EIPH (Grade 4) is associated with a shorter career duration, that furosemide is efficacious in decreasing the incidence and severity of EIPH, and that administration of furosemide is associated with superior race performance. Conclusions and clinical significance Strong recommendation that EIPH be considered a disease and a weak recommendation for use of furosemide in management of racehorses with EIPH.

Factors associated with likelihood of horses having a high serum Streptococcus equi SeM-specific antibody titer

OBJECTIVE To identify factors associated with an increased likelihood that horses would have a serum Streptococcus equi SeM-specific antibody titer > or = 1:1,600. DESIGN Cross-sectional study. ANIMALS 188 healthy client-owned horses. PROCEDURES A single serum sample from each horse was tested for SeM-specific antibody titer with an ELISA. Multivariate logistic regression was used to identify factors associated with having a titer > or = 1:1,600. RESULTS Age, breed, and vaccination status were significantly associated with the likelihood of having a titer > or = 1:1,600. The odds of having a titer > or = 1:1,600 increased by a factor of 1.07 with each 1-year increase in age. Quarter Horses and horses of other breeds were 4.08 times as likely as were Thoroughbreds and warmbloods to have a titer this high. Horses that had previously received an intranasal S equi vaccine were 4.7 times as likely as were horses without any history of vaccination to have a titer this high. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that older horses, horses other than Thoroughbreds and warmbloods, and horses that had been vaccinated with an attenuated-live intranasal S equi vaccine between 1 and 3 years previously had an increased likelihood of having a serum SeM-specific antibody titer > or = 1:1,600.

An assay to quantitate the binding of Rhodococcus equi to macrophages

A Rhodococcus equi radiobinding assay has been developed using organisms labeled with 3H-uracil. These labeled organisms resemble their unlabeled counterparts with respect to colony morphology, viability, and buoyant density. Bacteria routinely incorporate between 5 x 10(-3) and 5 x 10(-2) counts per minute per colony forming unit (cfu) which in this assay allows the detection of fewer than 0.2 cfu per macrophage. Once incorporated, greater than 90% of the label remains bacterial associated for at least 4 h postlabeling. The majority of the label is trichloroacetic acid precipitable, partitions into the aqueous phase following phenol/chloroform extraction and is ethanol precipitable. RNAse treatment of the ethanol precipitate abolishes label trichloroacetic acid precipitation. This radiolabeling technique has been used to quantitate the attachment of R. equi to both murine peritoneal and equine alveolar macrophages adherent to 13 mm glass coverslips. R. equi binding is dose dependent, saturable, and specific to macrophages. Further, binding is enhanced in the presence of fresh serum. Inhibition of radiolabeled bacterial binding can be obtained by competition with cold R. equi. This radiolabeled binding assay represents a crucial step in identifying the receptors on macrophages involved in the recognition of R. equi and may help to provide information on how macrophages recognize intracellular bacteria in general.