Peritoneal fluid values from healthy foals

Peritoneal fluid was analysed from 17 foals, aged 13 to 134 days with a mean age of 68 days. Cytologically, the peritoneal fluid was characterised by a mean total cell count of 0.45 x 10(9)/litre (range 0.06 to 1.42 x 10(9)/litre), rare eosinophils, rare cytophagia and variable percentages of neutrophils and mononuclear cells. These data indicate that peritoneal fluid nucleated cell counts over 1.50 x 10(9)/litre in the foal should be interpreted as elevated. Biochemical evaluation revealed a mean biuret protein level of 12 g/litre, mean refractive index protein level of 16 g/litre and urea nitrogen concentration of 1.96 mmol/litre. There was no correlation between the foals' white blood cell and peritoneal fluid nucleated cell counts. Results of this study indicate that adult horse reference values for evaluation of peritoneal fluid are of questionable validity for foals. Diagnostically, the most important observation was that maximum peritoneal fluid nucleated cell counts in healthy foals were much lower than reported maximal reference values for adult horses (1.5 x 10(9)/litre versus 5.0 x 10(9)/litre or 10.0 x 10(9)/litre).     

Exploratory celiotomy for suspected urinary tract disruption in neonatal foals: a review of 18 cases

The medical records of 18 neonatal foals, in which exploratory celiotomies were performed for suspected urinary tract lesions, were reviewed. Despite clinical signs and laboratory values indicative of disruption of the urinary tract, three foals did not have a site of urinary tract leakage at surgery. Eight foals had ruptured bladders and seven foals had urachal lesions. Ultrasonography was used as a pre-operative diagnostic procedure in eight foals to evaluate the presence of free peritoneal fluid and urinary tract integrity. Nine foals were alive six months after discharge. Seven of the nine non-surviving foals died or were destroyed because of fungal or bacterial infections.     

The use of clinical findings in the identification of equine peritonitis cases that respond favorably to medical therapy

Objective: To compare clinical findings in horses/foals with peritonitis that: (1) had no concurrent (NCA) versus a concurrent abnormality found during hospitalization, (2) survived to discharge versus did not survive to discharge, and (3) survived to discharge without surgery versus did not survive to discharge without surgery. Design: Retrospective study. Setting: George D. Widener Hospital for Large Animals at New Bolton Center. Animals: Horses/foals admitted between 1992 and 2002 with a diagnosis of peritonitis. A diagnosis of peritonitis within 4 days of presentation and peritoneal fluid nucleated cell count >10,000/μL were required for study inclusion. Horses/foals were excluded if the peritonitis was secondary to gastrointestinal or reproductive tract perforation, a complication of exploratory celiotomy, or if peritonitis was not diagnosed until surgery or necropsy. Interventions: None. Measurements and main results: Information obtained from the medical records included clinical findings at presentation and during the initial 4 days of hospitalization. Outcome was defined as: (1) NCA (yes/no), (2) survived to discharge (yes/no), and (3) survived to discharge without surgery (yes/no). Forty‐two percent (23/55) of horses/foals had NCA; 78% (43/55) survived to discharge, and 68% (36/55) survived to discharge without surgery. Horses/foals with peritonitis that had any one of the following clinical findings were likely to survive to discharge without surgery: no signs of abdominal pain, normal/improved rectal temperature, normal/improved intestinal borborygmi, normal fecal production, no abnormal findings on abdominal palpation per rectum, no nasogastric reflux, or yellow/orange peritoneal fluid. Conclusion: Clinical findings can be used to identify equine peritonitis cases that will respond favorably to medical therapy.     

Volvulus of the large colon in a neonatal foal

A one‐day‐old Thoroughbred colt foal was presented for assessment of abdominal pain and reduced urine output. Physical examination of the foal revealed marked abdominal distension, mild tachycardia, tachypnoea and congested mucous membranes. A marked anechoic peritoneal effusion, intestinal hypomotility and mural thickening of the large colon were detected sonographically. Serosanguinous fluid was obtained by abdominocentesis. After haemodynamic stabilisation, the foal underwent general anaesthesia and exploratory laparotomy and a 720° volvulus of the large colon at the sternal and diaphragmatic flexures was identified. After correction of the volvulus, the intraoperative findings were consistent with nonviability of the affected portion of the colon. The owner declined partial colon resection and elected for euthanasia of the foal. Although rare in neonatal foals, large colon volvulus should be considered in foals with signs of abdominal pain, abdominal distension and ultrasonographic findings of colonic mural thickening and luminal distension.     

Comparative pharmacokinetics of minocycline in foals and adult horses

The objective of this study was to compare the pharmacokinetics of minocycline in foals vs. adult horses. Minocycline was administered to six healthy 6‐ to 9‐week‐old foals and six adult horses at a dose of 4 mg/kg intragastrically (IG) and 2 mg/kg intravenously (i.v.) in a cross‐over design. Five additional oral doses were administered at 12‐h intervals in foals. A microbiologic assay was used to measure minocycline concentration in plasma, urine, synovial fluid, and cerebrospinal fluid (CSF). Liquid chromatography–tandem mass spectrometry was used to measure minocycline concentrations in pulmonary epithelial lining fluid (PELF) and bronchoalveolar (BAL) cells. After i.v. administration to foals, minocycline had a mean (±SD) elimination half‐life of 8.5 ± 2.1 h, a systemic clearance of 113.3 ± 26.1 mL/h/kg, and an apparent volume of distribution of 1.24 ± 0.19 L/kg. Pharmacokinetic variables determined after i.v. administration to adult horses were not significantly different from those determined in foals. Bioavailability was significantly higher in foals (57.8 ± 19.3%) than in adult horses (32.0 ± 18.0%). Minocycline concentrations in PELF were higher than in other body fluids. Oral minocycline dosed at 4 mg/kg every 12 h might be adequate for the treatment of susceptible bacterial infections in foals.     

Synovial fluid D-dimer concentration in foals with septic joint disease

Background: Increased synovial fibrinolytic activity (detected by increases in synovial D‐Dimer concentrations) has been observed in different joint diseases in humans and adult horses, presumably in order to minimize fibrin deposition within the joint and thus avoid its detrimental effects. Objective: To investigate fibrinolytic pathway activation in joint sepsis in foals by measuring synovial D‐Dimer concentrations. Animals: Eighteen septic foals with septic joints, 9 septic foals without septic joints, 9 systemically healthy foals with septic joint, and 3 controls are included. Methods: Prospective observational clinical study of foals admitted for septic arthritis. Synovial D‐Dimer concentration and routine synovial fluid analysis were performed. Diagnosis of joint sepsis was made whenever synovial total nucleated cell count was >30,000 cells/μL, synovial total protein >4 g/dL, and neutrophil percentage of >80%, or synovial fluid culture resulted positive. Results were compared among groups by general lineal models. Results: Synovial D‐Dimer concentration was significantly (P < .001) higher in the foals with septic joints compared with foals without joint disease (P < .001). Conclusions and Clinical Importance: Septic joint disease is associated with a marked increase of synovial D‐Dimer concentration (marked activation of the fibrinolytic activity) within the affected joint. Although further studies are needed, the measurement of synovial D‐Dimer concentration may be considered a complementary diagnostic marker of septic joint disease.     

Pharmacokinetics of clarithromycin and concentrations in body fluids and bronchoalveolar cells of foals

OBJECTIVE: To determine pharmacokinetics of clarithromycin and concentrations in body fluids and bronchoalveolar (BAL) cells of foals. ANIMALS: 6 healthy 2-to 3-week-old foals. PROCEDURES: In a crossover design, clarithromycin (7.5 mg/kg) was administered to each foal via IV and intragastric (IG) routes. After the initial IG administration, 5 additional doses were administered IG at 12-hour intervals. Concentrations of clarithromycin and its 14-hydroxy metabolite were measured in serum by use of high-performance liquid chromatography. A microbiologic assay was used to measure clarithromycin activity in serum, urine, peritoneal fluid, synovial fluid, CSF, pulmonary epithelial lining fluid (PELF), and BAL cells. RESULTS: After IV administration, elimination half-life (5.4 hours) and mean +/- SD body clearance (1.27 +/- 0.25 L/h/kg) and apparent volume of distribution at steady state (10.4 +/- 2.1 L/kg) were determined for clarithromycin. The metabolite was detected in all 6 foals by 1 hour after clarithromycin administration. Oral bioavailability of clarithromycin was 57.3 +/- 12.0%. Maximum serum concentration of clarithromycin after multiple IG administrations was 0.88 +/- 0.19 microg/mL. After IG administration of multiple doses, clarithromycin concentrations in peritoneal fluid, CSF, and synovial fluid were similar to or lower than concentrations in serum, whereas concentrations in urine, PELF, and BAL cells were significantly higher than concentrations in serum. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of clarithromycin at 7.5 mg/kg every 12 hours maintains concentrations in serum, PELF, and BAL cells that are higher than the minimum inhibitory concentration (0.12 microg/mL) for Rhodococcus equiisolates for the entire 12-hour dosing interval.     

Evaluation of postceliotomy peritoneal drain fluid volume, cytology, and blood-to-peritoneal fluid lactate and glucose differences in normal dogs

Objective: To describe peritoneal drain fluid volume, fluid cytology, and blood‐to‐peritoneal fluid lactate and glucose concentration differences after exploratory celiotomy in normal dogs. Study Design: Prospective study. Animals: Healthy Beagle dogs (n=10). Methods: After exploratory celiotomy, a peritoneal drain was placed, and peritoneal fluid was recorded every 6 hours for 7 days. Fluid was submitted for cytologic examination, and fluid and blood glucose and lactate concentrations were recorded every 12 hours. On day 7, drains were removed and drain tips submitted for aerobic bacterial culture. Results: Mean peritoneal fluid volume decreased from 2.8 mL/kg/day (day 1) to 0.6 mL/kg/day (day 7). All dogs had degenerate neutrophils in peritoneal fluid throughout the 7 days. Four dogs developed contaminated drains. Blood‐to‐peritoneal glucose concentration differences>20 mg/dL occurred after day 4. By day 7, 5 of 7 dogs with patent drains had blood‐to‐peritoneal lactate concentration differences70% of dogs had differences consistent with septic peritonitis each day. Postoperative blood‐to‐peritoneal fluid glucose and lactate difference may not be reliable indicators of septic peritonitis when evaluating abdominal fluid collected with closed suction drains.     

Factors associated with prognosis for survival and athletic use in foals with septic arthritis: 93 cases (1987-1994).

OBJECTIVE: To identify factors affecting the prognosis for survival and athletic use in foals with septic arthritis. DESIGN: Retrospective study. ANIMALS: 93 foals with septic arthritis. PROCEDURE: Medical records were reviewed to obtain clinical findings, laboratory test results, radiographic findings, treatment method, and outcome. Race records for Thoroughbreds and Standardbreds were evaluated to determine whether foals subsequently raced and whether they raced successfully. RESULTS: 43 foals had 1 affected joint, 44 foals had multiple affected joints, and number of affected joints was not recorded for 6 foals. The femoropatellar and tarsocrural joints were most commonly affected. Osteomyelitis or degenerative joint disease were detected in 59% (46/78) of foals. Failure of passive transfer, pneumonia, and enteritis were common. Foals were treated with lavage, lavage and intra-articular administration of antibiotics, lavage and arthroscopic debridement with or without partial synovectomy, or lavage and arthrotomy to debride infected bone and systemic administration of antibiotics. Seventy-three foals survived to be discharged from hospital, and approximately a third raced. Isolation of Salmonella spp from synovial fluid was associated with an unfavorable prognosis for survival and multisystem disease was associated with an unfavorable prognosis for survival and ability to race; other variables were not significantly associated with survival and ability to race. CONCLUSIONS AND CLINICAL RELEVANCE: With treatment, the prognosis for survival of foals with septic arthritis was favorable, whereas prognosis for ability to race was unfavorable. Multisystem disease, isolation of Salmonella spp from synovial fluid, involvement of multiple joints, and synovial fluid neutrophil count > or = 95% at admission may be of prognostic value.     

Pharmacokinetics of oral doxycycline and concentrations in body fluids and bronchoalveolar cells of foals

The objective of this study was to determine the disposition of orally administered doxycycline in foals. Six healthy 4- to 8-week-old foals were used. Doxycycline was administered to each foal via the intragastric (IG) route at dosages of 10 and 20 mg/kg, in a cross-over design. After the first 10 mg/kg dose, five additional doses were administered at 12-h intervals. A microbiological assay was used to measure doxycycline activity in serum, urine, peritoneal fluid, synovial fluid, cerebrospinal (CSF), pulmonary epithelial lining fluid (PELF), and bronchoalveolar (BAL) cells. Following administration at 10 mg/kg, mean+/-SD time to peak serum doxycycline activity (tmax) was 3.0+/-1.2 h, maximum serum activity (Cmax) was 2.54+/-0.27 microg/mL, and terminal half-life (t1/2) was 8.5+/-2.8 h. Administration at a dose of 20 mg/kg resulted in a significantly longer tmax (5.5+/-1.8 h) as well as a tendency toward higher Cmax (2.89+/-0.33 microg/mL) and longer t1/2 (11.9+/-2.6 h). After multiple IG doses, doxycycline activity in CSF was significantly lower than concurrent serum activity, whereas peritoneal fluid, synovial fluid, and BAL cell doxycycline activity was similar to concurrent serum activity. Doxycycline activity in urine and PELF was significantly higher than that found at other sites. Oral administration at a dosage of 10 mg/kg every 12 h would maintain serum, PELF, and BAL cell activity above the minimum inhibitory concentrations of Rhodococcus equi, beta-hemolytic streptococci, and other susceptible bacterial pathogens for the entire dosing interval.     

Plasma aldosterone, vasopressin and atrial natriuretic peptide in hypovolaemia: a preliminary comparative study of neonatal and mature horses

REASON FOR PERFORMING STUDY: Neonatal foals succumb rapidly to hypovolaemic shock in comparison to mature horses; they do not consistently increase their heart rate in response to hypotension and respond differently to fluid administration. The hormonal responses to hypovolaemia in the horse and foal require investigation. HYPOTHESIS: The hormonal responses to hypovolaemia and fluid administration differ between mature and neonatal horses. METHODS: Five mature horses and 5 neonatal foals fulfilling predetermined criteria for hypovolaemia, were included in the study. A blood sample was taken at admission and after normalisation of fluid balance. These were analysed for plasma aldosterone, vasopressin (AVP) and atrial natriuretic peptide (ANP). Normally distributed variables were compared using the Student's t test and nonparametric data using the Mann-Whitney U test. RESULTS: ANP, AVP and aldosterone were higher before fluid resuscitation than after fluid resuscitation in mature horses. Aldosterone was higher before than after fluid resuscitation in foals, and was higher in foals both before and after fluid resuscitation than in mature horses. ANP was lower in mature horses after fluid resuscitation than in foals. No other comparisons were significantly different. CONCLUSIONS: The hormonal responses of the mature and neonatal horses are different during hypovolaemia and following fluid resuscitation. POTENTIAL RELEVANCE: The differences in the hormonal responses to hypovolaemia and fluid resuscitation may be important when considering fluid resuscitation of hypovolaemic horses and foals, and warrants further investigation.     

Pharmacokinetics and pulmonary distribution of gamithromycin after intravenous administration in foals

The long‐acting azalide antibiotic gamithromycin is marketed for intramuscular treatment of bovine and swine infections. Off‐label use in foals leads to severe local lesions likely caused by hyperosmolality of the injected solution. We provide evidence from a pharmacokinetic study in 10 warm‐blooded healthy foals for intravenous bolus injection of gamithromycin diluted in distilled water to be a safe and well tolerated alternative. By intravenous dosing, markedly higher plasma exposure and better penetration into bronchoalveolar lavage cells but lower distribution into epithelial lining fluid are achieved as after intramuscular or subcutaneous administration. Intravenously injected gamithromycin was tolerated without any adverse drug reactions. The protocols for treatment of equine pulmonary infections caused by Rhodococcus equi should be revised accordingly.     

Presumed immune‐mediated hemolytic anemia in two foals with Rhodococcus equi infection

Objective – To describe the clinical presentation, case management, and outcome in 2 foals with Rhodococcus equi infection associated with presumptive severe immune‐mediated hemolytic anemia. Series Summary – Two foals diagnosed with R. equi pneumonia on the basis of tracheal wash cultures, thoracic radiographs, and thoracic ultrasonography were concurrently diagnosed with hemolytic anemia. Both foals required whole blood transfusions, and were treated with the antimicrobial combination of rifampin and a macrolide (eg, clarithromycin, erythromycin, or azithromycin). Dexamethasone was used to prevent further hemolysis in both foals, and to treat acute lung injury/acute respiratory distress syndrome in 1 of the foals. Both foals survived, and required prolonged antimicrobial therapy. New or Unique Information Provided – Although extra‐pulmonary disorders are commonly diagnosed in foals infected with R. equi, hemolytic anemia is rarely described. Dexamethasone is considered the treatment of choice for immune‐mediated hemolytic anemia, but may be contra‐indicated in foals with severe bacterial infections. In these foals, a relatively low dose and short duration of dexamethasone was utilized in an attempt to minimize immune suppression, although early discontinuation in 1 foal precipitated a second hemolytic crisis.     

Diseases in neonatal foals. Part 1: The 30 day incidence of disease and the effect of prophylactic antimicrobial drug treatment during the first three days post partum

Reasons for performing study: Neonatal diseases have been grouped and analysed but up‐to‐date statistically significant information about the incidence and prevalence of diseases in foals is limited. Since the 1950s it has been a common management practice to administer a 3 day course of antimicrobial drugs to neonatal foals. This was shown to significantly reduce the incidence of infections (Platt 1977). Since then management practices have improved and it is widely believed that prophylactic antimicrobial drugs are no longer necessary in foal rearing. Objectives: To determine the 30 day incidences or prevalences (depending on case definition) of various diseases and conditions in the neonatal foal and ascertain the influence of a prophylactic 3 day treatment on the frequency of infections. Methods: The population consisted of Thoroughbred foals born on stud farms in the Newmarket (UK) area in 2005 (n = 1031). Depending on the stud farm's practice in the use of prophylactic antimicrobial drugs, 2 groups of newborn foals (treated and untreated) were identified and followed for 30 days. Results: The 30 day incidences of infectious diseases under study were between 0.2% (osteomyelitis) and 5.85% (systemic disease with diarrhoea). The overall incidence for ‘total infectious diseases’ was 8.27%. The most commonly observed noninfectious condition was limb deformities (12.11% of all foals). There was no significant difference in the incidence of infectious diseases between the 2 groups. Conclusion: Infectious diseases are still an important problem in neonatal foals requiring further investigation as to which factors other than antimicrobial prophylaxis are relevant for disease prevention. Potential relevance: The results provide an up‐to‐date overview about the frequencies of various neonatal foal diseases. They do not support the traditional prophylactic use of antimicrobials to prevent infectious diseases in healthy newborn foals. However, it should be noted that this study was not a randomised controlled trial and therefore does not provide the strongest possible evidence for this conclusion.     

Study of crib-biting and gastric inflammation and ulceration in young horses

Nineteen young horses that had recently started to perform the stereotypy of crib-biting were compared with 16 non-stereotypic horses for 14 weeks. After initial observations of their behaviour and an endoscopic examination of the condition of their stomachs, the horses were randomly allocated to a control or an antacid diet At the start of the trial, the stomachs of the crib-biting foals were significantly more ulcerated and inflamed than the stomachs of the normal foals. In addition, the faecal pH of the crib-biting foals (6.05) was significantly lower than that of the normal foals (6.58). The antacid diet resulted in a significant improvement in the condition of the horses' stomachs. The crib-biting behaviour declined in most of the foals, regardless of their diet, but tended to decline to a greater extent in the foals on the antacid diet.     

Hydrallantois in the Mare – A Report of Five Cases

Hydrallantois in the mare is a very rare condition, and clinical reports help to gather information to elucidate its pathogenesis, treatment options and prognosis. Five different cases of hydrallantois in the mare are reported in this article, all with the involvement of placentitis. The five mares were presented because of acute distention of the abdomen, dyspnoea, stiff gait and a lack of appetite. After a gradual release of the excessive amount of allantoic fluid, an abortion was induced in all five mares. The foals were either born dead or euthanized. The mares recovered quickly. One mare conceived within the same season, one remained barren despite several cycles of natural breeding, and no data were available on the other three mares. In this series, the condition is reported for the first time in two Shetland ponies, both pregnant with foals sharing a close genetic background. In both cases, the condition led to hyperlipidemia. The condition as it occurs in nulliparous mares is also discussed. Finally, the possible involvement of placentitis in the pathogenesis is emphasized.     

Ascites in a 13‐year‐old miniature horse mare with an ovarian granulosa theca‐cell tumour: A manifestation of Meigs' syndrome?

A 13‐year‐old miniature horse mare presented for evaluation of ascites. Abdominal ultrasound showed severe free peritoneal fluid accumulation as well as a caudal abdominal mass. The peritoneal fluid was characterised as a transudate with no evidence of sepsis. Surgical exploration of the abdomen was performed; copious free peritoneal fluid and a large right ovarian mass were discovered. The abnormal ovary was removed, and the mass was determined histologically to be a benign granulosa theca‐cell tumour. Although there was mild peritoneal fluid accumulation in the immediate post operative period, the ascites effectively resolved with removal of the tumour, and the mare returned to a normal lifestyle. This is similar to reports of Meigs' syndrome in human women, in which a benign ovarian mass of significant size causes ascites that resolves once the mass is removed.     

Pharmacokinetics of azithromycin and concentration in body fluids and bronchoalveolar cells in foals.

OBJECTIVE: To determine the pharmacokinetics of azithromycin and its concentration in body fluids and bronchoalveolar lavage cells in foals. ANIMALS: 6 healthy 6- to 10-week-old foals. PROCEDURE: Azithromycin (10 mg/kg of body weight) was administered to each foal via i.v. and intragastric (i.g.) routes in a crossover design. After the first i.g. dose, 4 additional i.g. doses were administered at 24-hour intervals. A microbiologic assay was used to measure azithromycin concentrations in serum, peritoneal fluid, synovial fluid, pulmonary epithelial lining fluid (PELF), and bronchoalveolar (BAL) cells. RESULTS: Azithromycin elimination half-life was 20.3 hours, body clearance was 10.4 ml/min x kg, and apparent volume of distribution at steady state was 18.6 L/kg. After i.g. administration, time to peak serum concentration was 1.8 hours and bioavailability was 56%. After repeated i.g. administration, peak serum concentration was 0.63 +/- 0.10 microg/ml. Peritoneal and synovial fluid concentrations were similar to serum concentrations. Bronchoalveolar cell and PELF concentrations were 15- to 170-fold and 1- to 16-fold higher than concurrent serum concentrations, respectively. No adverse reactions were detected after repeated i.g. administration. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of pharmacokinetic values, minimum inhibitory concentrations of Rhodococcus equi isolates, and drug concentrations in PELF and bronchoalveolar cells, a single daily oral dose of 10 mg/kg may be appropriate for treatment of R. equi infections in foals. Persistence of high azithromycin concentrations in PELF and bronchoalveolar cells 48 hours after discontinuation of administration suggests that after 5 daily doses, oral administration at 48-hour intervals may be adequate.     

Outcome of surgical correction of meconium impactions in 8 foals

Meconium impactions are only rarely refractory to medical therapy. The purpose of this paper is to examine the outcome of 8 foals that required an exploratory celiotomy to correct a meconium impaction. Between 1984 and 1992, 24 foals were referred with a primary diagnosis of meconium impaction. All foals were treated medically prior to and following referral. Of the 24 foals, 8 had impactions requiring surgical intervention. Exploratory celiotomies were performed, and the impaction was reduced manually or by enterotomy. Follow up information was available on 7 foals. All survived surgery and were discharged. Four of the 8 foals matured and raced. Two foals were euthanatized due to extensive serosal adhesions and one foal was euthanatized due to an unrelated orthopedic condition. Our results support the decision for an exploratory surgery only after aggressive medical therapy has failed. Several treatment options have been developed in recent years that have reduced the number of foals that may require surgery.