The effects of feeding sodium chloride pellets on the gastric mucosa, acid-base, and mineral status in exercising horses

BACKGROUND

Electrolyte supplementation may be a risk factor for gastric mucosal lesions, but relevant evidence is limited in horses.

HYPOTHESIS

Investigate the effects of PO sodium chloride (NaCl) supplementation on the gastric mucosa of exercising horses. We hypothesized that NaCl supplementation would neither cause nor exacerbate existing gastric mucosal damage.

ANIMALS

Fifteen 3-year-old healthy Warmblood stallions from a stud farm.

METHODS

Placebo-controlled study with a crossover design. Horses were fed either a NaCl pellet at a dosage adequate to replace the electrolyte losses in 10 L sweat or a placebo for 19 days with a washout period of 14 days between treatments. The gastric mucosa was evaluated by gastroscopy before and after treatment. Blood samples were collected for evaluation of acid-base status, packed cell volume (PCV), and total protein, creatinine and blood urea nitrogen concentrations. Urine was collected, and urine specific gravity, electrolyte, creatinine, and urea concentrations were measured.

RESULTS

The initial prevalence of gastric mucosal lesions was 85%. Sodium chloride pellets did not adversely affect the gastric mucosa and treatment did not significantly alter the hematologic and serum biochemical variables. Urine creatinine concentrations significantly decreased and urinary sodium concentrations significantly increased after supplementation with NaCl pellets. Water intake did not significantly differ between treatments.

CONCLUSIONS AND CLINICAL IMPORTANCE

Daily NaCl pellet supplementation is a palatable and safe way to replace electrolyte losses from sweating in exercising horses and has no negative effects on the gastric mucosa.

[Effects of oral manganese supplementation with different compounds on the manganese whole blood and serum concentrations of broodmares and their suckling foals]

OBJECTIVE

This study aimed to examine the effects of an oral supplementation on manganese (Mn) concentrations in the blood of lactating warm-blood broodmares. Furthermore, the potential relationship between Mn supply of the lactating mare and its suckling foal was investigated.

MATERIAL AND METHODS

During the 90-day trial, lactating mares were divided into 3 groups and daily received a daily dose of either a placebo (n = 11) or a Mn supplement of 560 mg Mn as Mn sulfate (n = 11) or Mn chelate (n = 11) in addition to the Mn intake from the basal ration (hay ad libitum, total mixed ration: Mn intake ~ 100 mg/kg dry matter). Blood samples were taken from the mares and their foals in 14-day intervals. The Mn determination in serum and whole blood as well as in the mare's milk was carried out by means of mass spectrometry with inductively coupled plasma. The Mn analysis in representative feed samples was performed by means of atomic absorption spectrometry. Data were assessed using the software IBM SPSS Statistics 27 (IBM Deutschland GmbH, Ehningen).

RESULTS

During the trial period, the mares showed Mn concentrations 10-fold higher in whole blood (median: 15.6 µg/l; 25-75 percentile: 12.8-18.5 µg/l) than in serum (median: 1.54 µg/l; 25-75 percentile: 1.20-1.90 µg/l). The foals had Mn whole-blood concentrations 16.4-fold higher (median: 21.3 µg/l; 25-75 percentile: 16.7-28.1 µg/l) compared to their serum (median: 1.50 µg/l; 25-75 percentile: 1.30-1.70 µg/l). The Mn whole-blood levels of the foals corresponded to 1.6-fold the Mn concentration of their dams. The milk contained a median Mn concentration of 0.012 mg/kg fresh matter. Mn supplementation had no effect on the Mn blood levels of mares and their foals.

CONCLUSION AND CLINICAL RELEVANCE

Blood Mn concentrations were not affected by the Mn supplementation. However, the Mn levels differed significantly between serum and whole blood. In addition, the Mn concentrations in whole blood of suckling foals were higher compared to their dams, although the Mn concentrations in the mare's milk were low regardless of Mn supplementation. Due to the low Mn content in milk, early Mn supply, preferably by forages, is necessary to ensure that the foals are supplied with Mn according to their requirement.

[Manganese concentrations in whole blood, plasma and serum of adult warmblood horses from 3 locations in Germany]

OBJECTIVE

This study aimed to establish reference intervals for Mn in whole blood, plasma and serum of healthy, adult warmblood horses with known dietary Mn intake and to compare 2 methods of analysis.

MATERIAL AND METHODS

Between May 2018 and November 2019 a single blood sample was taken from a total of 270 clinically healthy horses (age: 3-25 years) in 3 stud farms. In lithium-heparin (LH) whole blood, LH plasma and serum Mn concentrations were analyzed by means of atomic absorption spectrometry (AAS) and inductively coupled plasma mass spectrometry (ICP-MS). The reference intervals were calculated according to the recommendations of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and the Clinical and Laboratory Standards Institute (CLSI) comprising the range between 2.5 and 97.5 percentile of the analyzed Mn concentrations. Concurrent to blood sampling feed samples were taken and analyzed in order to determine the Mn content of the corresponding feeding ration.

RESULTS

The horses' whole-blood Mn levels were significantly (p < 0.0001) higher with a median Mn concentration of 12.4 μg/l (reference interval: 4.99-25.1 μg/l [AAS]; 5.99-25.3 μg/l [ICP-MS]) than in the corresponding serum (median: 1.65 μg/l, reference interval: 0.60-3.50 μg/l [AAS]; 1.11-2.96 μg/l [ICP-MS]) or LH plasma (median: 1.35 μg/l, reference interval: 0.22-2.68 μg/l [AAS]; 0.59-2.45 μg/l [ICP-MS]). In the comparison of methods, there were statistically significant differences in the Mn determinations for LH plasma and serum between AAS and ICP-MS, whereas they yielded comparable results for whole blood.

CONCLUSION AND CLINICAL RELEVANCE

Whole blood shows an average of 10-fold higher Mn concentrations than serum or LH plasma. When evaluating blood Mn concentrations, consideration must be granted to the sample material under analysis as well as to which method is employed since relevant differences were found between AAS and ICP-MS in serum and LH plasma.

Diagnostic imaging in acute interstitial pneumonia in foals: High variability of interpretation of chest radiographs and good conformity between ultrasonographic and post-mortem findings

Acute interstitial pneumonia (AIP) in foals is a rare but challenging syndrome. Diagnostic imaging is crucial for its diagnosis. While there are some reports on radiographic findings, ultrasound is sparsely described. Variability in the evaluation of radiographs in AIP has been well described in human literature. Part one of this study is a prospective, observational, observer agreement study investigating inter- and intraobserver agreement in the assessment of thoracic radiographs. Part two is a prospective, controlled, descriptive study on thoracic ultrasonography in foals with AIP. Eighteen foals with AIP were examined daily by thoracic ultrasound. Thoracic radiographs were taken on three successive occasions. Blinded radiographs were assessed by three observers based on two semi-quantitative scores (pattern recognition, subjective evaluation). Foals that died underwent postmortem examination (n = 9); postmortem findings were compared to ultrasound findings on the day of death. Ultrasonographic findings were consistent with postmortem findings. Comet tail scores in foals with AIP were significantly higher (p < 0.0001) than in control foals. Interrater agreement for the assessment of radiographs was none to moderate (κ = 0.07-0.65) for pattern recognition and weak to moderate (κ = 0.58-0.62) for subjective scoring. Intrarater agreement varied from minimal to strong (κ = 0.30-0.80) for pattern recognition but was strong (κ = 0.83) for subjective scoring. In conclusion, the diagnostic value of thoracic ultrasound in foals with AIP is high due to good conformity with postmortem findings. The evaluation of thoracic radiographs showed high variability in inter- and intra-agreement.

Primary vaccination in foals: a comparison of the serological response to equine influenza and equine herpesvirus vaccines administered concurrently or 2 weeks apart

This study compared concurrent and separate primary vaccination against equid alphaherpesviruses 1 and 4, genus Varicellovirus, subfamily Alphaherpesvirinae, family Herpesviridae, and equine influenza A virus, genus Alphainfluenzavirus, family Orthomyxoviridae. Their vernacular names are equine herpesvirus 1 and 4 (EHV1/4) and equine influenza virus (EIV). Infection with these respiratory pathogens is associated with loss of performance, interruption of training schedules, and on occasion, cancellation of equestrian events. Vaccination is highly recommended, and for some activities it is a mandatory requirement of the relevant authority. As there is a dearth of information relating to the impact of concurrent vaccination on the antibody response to EHV and EIV vaccines, they are usually administered separately, often 2 weeks apart. In a previous study of booster vaccination in Thoroughbred racehorses, concurrent vaccination with whole-virus inactivated carbopol-adjuvanted EHV and EIV vaccines did not impact negatively on the antibody response. In this study, investigations were extended to concurrent versus separate primary vaccination of warmblood foals. A field study was conducted to compare the immune response to a carbopol-adjuvanted EHV vaccine and an immune stimulating complex (ISCOM)-adjuvanted EI vaccine administered concurrently and 2 weeks apart. No adverse clinical reactions were observed, the pattern of EI and EHV antibody response was similar for both groups, and there was no evidence that concurrent primary vaccination compromised the humoral response. The results are of relevance to horse owners who wish to decrease veterinary costs, limit handling of young animals, and simplify record keeping by vaccinating concurrently.

Acute interstitial pneumonia in foals: A severe, multifactorial syndrome with lung tissue recovery in surviving foals

BACKGROUND

Acute interstitial pneumonia in foals has been sparsely described in literature, and the individual authors disagree on the underlying aetiology. Histopathological follow-up from surviving foals is not available.

OBJECTIVES

Description of clinical and histopathological findings in the course of acute interstitial pneumonia and in recovery. Investigating the aetiology and possible triggering factors of acute interstitial pneumonia.

STUDY DESIGN

Case series.

METHODS

Post-mortem examination of nine affected foals; seven died during the acute phase, and two had recovered from acute interstitial pneumonia. Data from clinical examinations on the day of death were recorded for all foals. Complete necropsy, special histological staining, virological and microbiological examinations were performed.

RESULTS

Seven foals died during the acute phase with severe respiratory distress, fever and increased numbers of comet tail artefacts in lung ultrasound. In post-mortem examination, a wide variety of possible triggering factors was identified. Microbiology revealed Escherichia coli, Rhodococcus equi and Klebsiella pneumoniae as the most common bacterial pathogens. Equine herpesvirus 2 was detected in all foals by PCR. Those with high viral loads also displayed histopathological changes suggestive of viral infections. Pneumocystis carinii was detected in all acutely affected foals. Histopathological changes in lung parenchyma clearly differed between the foals that had recovered from acute interstitial pneumonia and those dying in the acute phase. While lungs in acute phase featured marked parenchymal collapse and necrosis, the recovered foals revealed nearly normal ventilated lung parenchyma and alveolar structure.

MAIN LIMITATIONS

Small number of cases. Because all foals are from the same breeding farm with endemic occurrence of pathogens, it is not certain whether the results of this study can be transferred to other foals without restrictions.

CONCLUSIONS

Acute interstitial pneumonia seems to be based on a multifactorial aetiology. Lungs from foals that have survived acute interstitial pneumonia appear to be able to regenerate completely, leaving no permanent changes.

Markers of long term silent carriers of Streptococcus equi ssp. equi in horses

BACKGROUND

Difficulty in detection of silent carriers of Streptococcus equi is a key reason for its continued spread to immunologically naïve groups of horses.

OBJECTIVE

To determine whether clinical examination, markers of inflammation, or serology differentiate silent carriers of S. equi in recovered comingled horses.

ANIMALS

Ninety-eight warmblood yearlings and 72 unaffected mares on a large breeding farm (outbreak A), 38 mature Icelandic horses at a riding stable (outbreak B), and 27 mixed breed horses at a boarding stable (outbreak C).

METHODS

Prospective observational study 6 months to 2 years after strangles outbreaks. Carriers were defined as any animal positive on culture or qPCR to S. equi from nasopharyngeal lavage or guttural pouch endoscopy and lavage. Most horses had complete physical exams and 1 group included evaluation of white blood cell counts and serum amyloid A. Sera from all horses was tested for antibodies to antigens A and C of S. equi using an enhanced indirect ELISA. Descriptive statistics were calculated. Data were compared using paired t tests, Wilcoxon ranked test, chi square, or the Fishers exact test. Significance was set at P < .05.

RESULTS

Apart from weanlings at 6 months in outbreak A, there was no significant association between any clinical markers or serology with carrier state (P = .06-1). Moreover, 3/12 culture positive carriers were seronegative to S. equi.

CONCLUSIONS AND CLINICAL IMPORTANCE

Silent carriers of S. equi do not differ clinically or on markers of inflammation to their noncarrier herd-mates. Moreover, serology alone will not distinguish carriers in comingled horses.

Response of Sport Horses to Different Formulations of Equine Influenza Vaccine

The international governing body of equestrian sports requires that horses be vaccinated against equine influenza within 6 months and 21 days of competing. The aim of this study was to compare the antibody response of young sport horses to six-monthly booster vaccination with equine influenza vaccines of different formulations. An inactivated vaccine was allocated to 35 horses and subunit and recombinant vaccines were allocated to 34 horses each. After vaccination, all horses were monitored for evidence of adverse reactions. Whole blood samples were collected at the time of vaccination and on nine occasions up to six months and 21 days post vaccination. Antibodies against equine influenza were measured by single radial haemolysis. Transient fever and injection site reactions were observed in several horses vaccinated with each vaccine. Only two horses failed to seroconvert post booster vaccination but there was a delayed response to the recombinant vaccine. The antibody response to the recombinant vaccine was lower than that induced by the whole-inactivated and subunit vaccines up to three months post vaccination. Thereafter, there was no significant difference. By six months post vaccination, the majority of horses in all three groups were clinically but not virologically protected. There was minimal decline in antibody titres within the 21-day grace period.

Evaluation of Current Equine Influenza Vaccination Protocols Prior to Shipment, Guided by OIE Standards

To facilitate the temporary importation of horses for competition and racing purposes, with a minimum risk of transmitting equine influenza, the World Organisation for Animal Health (Office International des Epizooties, or OIE), formally engaged in a public-private partnership with the Federation Equestre Internationale (FEI) and the International Federation for Horseracing Authorities (IFHA) to establish, within the context of existing OIE standards, a science-based rationale to identify the ideal time period for equine influenza vaccination prior to shipment. Field trials using vaccines based on different technologies were carried out on three continents. The antibody response post-booster vaccination at intervals aligned with the different rules/recommendations of the OIE, FEI, and IFHA, was monitored by single radial haemolysis. It was determined that 14 days was the optimum period necessary to allow horses adequate time to respond to booster vaccination and for horses that have previously received four or more doses of vaccine and are older than four years, it is adequate to allow vaccination within 180 days of shipment. In contrast, the results indicate that there is a potential benefit to younger (four years old or younger) horses in requiring booster vaccination within 90 days of shipment, consistent with the current OIE standard.

Efficacy of the combination of doxycycline and azithromycin for the treatment of foals with mild to moderate bronchopneumonia

BACKGROUND

Given the importance of rifampin in treatment protocols for tuberculosis in people, its use in veterinary medicine is under increasing scrutiny in some countries and alternatives might be needed in the near future.

OBJECTIVES

This study was set up to evaluate whether azithromycin combined with doxycycline is effective for the treatment of bronchopneumonia in foals and noninferior to the combination of azithromycin and rifampin.

STUDY DESIGN

This is a controlled, randomised and double-blinded clinical trial. Two hundred and forty foals on a farm endemic for infections caused by Rhodococcus equi were involved.

METHODS

Foals with ultrasonographic pulmonary lesions (lesion score 10-15 cm) were allocated to 3 groups: azithromycin-doxycycline orally (n = 81); azithromycin-rifampin orally (n = 81); or untreated controls (n = 78). Physical examination and thoracic ultrasonography were performed by individuals unaware of treatment group assignment. Foals that worsened were considered treatment failures and removed from the study.

RESULTS

The proportion of foals that recovered was significantly higher for foals treated with azithromycin-doxycycline (80 of 81) or azithromycin-rifampin (81 of 81) compared with that of control foals (57 of 78). The difference in the percentage of efficacy of azithromycin-rifampin vs azithromycin-doxycycline was 1.2% (90% CI = -0.78% to 3.5%) which did not cross the predetermined noninferiority limit of 10%. Therefore, azithromycin-doxycycline was noninferior to azithromycin-rifampin within the predetermined noninferiority limit.

MAIN LIMITATIONS

The study was performed on a single farm, and recovery rates may differ in other locations.

CONCLUSION

Azithromycin-doxycycline was noninferior to azithromycin-rifampin for the treatment of bronchopneumonia in this farm.

Cephalometric Study of the Overjet Development in Warmblood Foals

Class II malocclusion is the most frequently occurring congenital malocclusion in horses. Radiographic cephalometric procedures adopted from human dentistry were used to study the development of overjet in a population of 650 Warmblood foals. Thirteen foals were diagnosed with measurable overjet at the beginning of the study. The malocclusion in nine foals resolved spontaneously and four foals without overjet at 2 weeks of age developed the condition during the first year of life. A cephalostat used in human orthodontics to immobilize the patient's head while being radiographed was replaced by a researcher-made head-holding device, whose size was based on the results of a pilot study. Laterolateral digital radiographs of each foal's head (cephalograms) were taken at five time points until the age of 12 months. Thirteen cephalometric points were identified and nine distances were measured on each radiograph. Additionally, the angle between the long axis of the upper and lower incisors was evaluated. Cephalometric measurements proved to be useful to identify foals that showed spontaneous regression of the malocclusion over the study time between 9 and 16 weeks of age.

Chronic severe pyloric lesions in horses: 47 cases

BACKGROUND

The clinical findings and outcome associated with chronic severe equine pyloric lesions have not been well described previously.

OBJECTIVES

To describe the history, clinical signs, endoscopic and ultrasound results, laboratory data, treatment, pathological findings and survival of horses with chronic severe pyloric lesions.

STUDY DESIGN

Retrospective case series.

METHODS

Medical records from horses treated at clinics in Czech Republic and Germany in which chronic severe pyloric lesions were confirmed endoscopically and/or on post-mortem examination were reviewed.

RESULTS

Forty-seven horses were identified, median age 3 years (range 0.8-16 years). There were 3 geldings, 23 mares and 19 stallions and the majority were Warmbloods (60%). The most common presenting signs were poor body condition (40; 87%), slow eating (39; 83%), recurrent colic (35; 74%) and selective appetite (30; 64%). The most consistent laboratory abnormality was hypoalbuminaemia (10; 36%). Slow gastric emptying was confirmed in 29 individuals during gastroscopy and/or ultrasonography. Endoscopy revealed distal oesophagitis in 9 of 47 horses, and severe equine squamous gastric disease in all cases. Pyloric lesions were depressed, flat or raised fibrinosuppurative pyloric ulcers and were seen in 45 (2 pylori were not seen endoscopically). Thirty-two cases were treated, with 28 responding well initially. All treated cases received anti-ulcer medication and four underwent gastrojejunostomy. Clinical signs recurred after medical treatment in at least 11 cases. Only 18 of 44 cases (41%) survived long term (3 were lost to follow-up). Horses diagnosed at 3 years of age or younger were significantly less likely to survive more than 6 months than older horses (27.8% vs. 72.2%, P<0.001).

MAIN LIMITATIONS

The study is retrospective, some records were incomplete and case identification was subjective.

CONCLUSIONS

Chronic severe pyloric lesions can be associated with delayed gastric emptying identified with ultrasonography and/or endoscopy. The prognosis is poor in young horses.

Long term silent carriers of Streptococcus equi ssp. equi following strangles; carrier detection related to sampling site of collection and culture versus qPCR

After strangles outbreaks, Streptococcus equi ssp. equi (S. equi) can persist in clinically normal silent carriers for months to years. Two naturally occurring outbreaks of strangles with 53 and 100% morbidity, respectively, were followed longitudinally to assess occurrence of carrier state and optimal detection methods Outbreak A involved 98 yearling warmbloods, and outbreak B 38 mature Icelandic horses. Fully recovered horses were sampled at least 6 months after index cases using nasal swabs (one sampling occasion only) nasopharyngeal lavage and guttural pouch visualisation and lavages for culture and qPCR to S. equi. Any horse with at least a single sample positive was deemed a carrier. Descriptive statistics and sensitivity and negative predictive values were calculated. Comparisons were made with McNemars and Fishers exact tests. Carrier rates in outbreak A were 3% based on culture and 15% based on qPCR and for outbreak B 13% based on culture and 37% based on qPCR. All culture positives were also qPCR positive. One carrier culture negative sampled after an additional 8 months was culture positive to S. equi, indicating that qPCR positives should be suspected to carry live bacteria. Findings indicate that reliance on guttural pouch sampling and appearance does not capture all silent carriers. All culture positives were identified by qPCR and even horses positive by qPCR but culture negative should be suspected carriers of live bacteria.

Decreased Clinical Severity of Strangles in Weanlings Associated with Restricted Seroconversion to Optimized Streptococcus equi ssp equi Assays

Background

Streptococcus equi ssp. equi causes characteristic clinical signs that are most severe in young horses, including fever, purulent nasal discharge, and lymph node abscessation in the head region.

Hypothesis/Objectives

Clinical, serologic, and microbiologic factors related to unexpectedly mild disease severity in a natural outbreak of strangles in immunologically naïve weanlings were investigated.

Animals

One‐hundred and twelve warmblood weanlings.

Methods

Prospective longitudinal observational study of a natural outbreak of strangles. The entire cohort was examined at the peak of the outbreak by deep nasal swabs for culture and quantitative PCR (qPCR) for the presence of S. equi and clinically and serologically in a sequential manner by an optimized ELISA from the index case throughout the outbreak until resolution. Descriptive statistics were calculated and comparisons made using a nondirectional Wilcoxon signed‐rank test.

Results

Outbreak morbidity was 53%, with 9 of 14 horses culture positive and 26 of 53 horses qPCR positive for S. equi lacking clinical signs characteristic of strangles. By resolution, 91 of 112 had seroconverted to Antigen A by ELISA but seroconversion to antigen C (part of the SeM protein) was minimal. Sequencing of the isolates detected no alterations in the SeM protein, but identified a 61 bp deletion in the gene SEQ_0402.

Conclusions and Clinical Importance

Absence of clinical signs alone in naïve horses may be an insufficient criterion to release horses from strangles quarantine measures. Restricted seroconversion to antigen C may have been associated with decreased clinical severity. The role of a minor gene deletion in SEQ_0402 in the virulence of S. equi warrants further investigation.

Study of the relationship between overjet development and some skull bone measurements in Warmblood foals

Overjet is defined as the projection of the maxillary incisors labial to their antagonists in a horizontal direction. This malocclusion in horses can lead to incorrect dental wear and is aesthetically undesirable. Whether lengthening of the maxilla or shortening of the mandible causes the condition has not yet been determined. Therefore, a measurement technique was developed to investigate the correlations between skull bone measurements in overjet-affected individuals. The position of the incisors in 650 Warmblood foals born in a private German stud was examined at two weeks of age, revealing the prevalence of overjet to be 2 per cent. Five measurements were made on each foal's head and comparisons with a second set of measurements that were made later in the foals first year showed a change in the presence or degree of overjet over time. Nine of 13 foals diagnosed with measurable overjet at the beginning of the study resolved spontaneously. Thirteen foals had no evidence of overjet at birth, of which four developed the condition during the first year of life. The methods used for measuring longitudinal changes in different skull bones and for the assessment of malocclusion in foals affected with overjet were considered effective.

Sarkoidose bei einer Warmblutstute

Gegenstand und Ziel: Darstellung klinischer und pathomorphologischer Untersuchungsbefunde bei einem adulten Warmblutpferd mit einer progredienten, generalisierten Hauterkrankung. Falldarstellung: Fallbericht einer sechs Jahre alten Hannoveraner Warmblutstute. Ergebnisse: Klinisch zeigte die Stute am ganzen Körper eine schmerzhafte Dermatitis mit Krusten und Pusteln ohne Pruritus. Weiterführende Untersuchungen ergaben keine Hinweise auf belebte Krankheitserreger. Pathomorphologisch bestand eine generalisierte, exfoliative und krustöse Dermatitis, die sich histologisch als überwiegend granulomatöse, teils lymphohistiozytäre und pustulöse Dermatitis superficialis et profunda darstellte. Granulomatöse Entzündungsprozesse wurden auch in Thymus, Herz, Lunge, Milz, Leber und in einzelnen Lymphknoten nachgewiesen. Mittels histologischer Spezialuntersuchungen ergaben sich keine Hinweise auf die Krankheitsursache. Schlussfolgerung: Aufgrund der vorliegenden Befunde wurde die Diagnose einer equinen Sarkoidose gestellt. Klinische Relevanz: Bei einer generalisierten exfoliativen Dermatitis mit dem Bild einer granulomatösen Entzündung ist die equine Sarkoidose differenzialdiagnostisch in Betracht zu ziehen.

Intestinal and hepatic contributions to the pharmacokinetic interaction between gamithromycin and rifampicin after single-dose and multiple-dose administration in healthy foals

BACKGROUND

Standard treatment of foals with severe abscessing lung infection caused by Rhodococcus equi using rifampicin and a macrolide antibiotic can be compromised by extensive inhibition and/or induction of drug metabolising enzymes (e.g. CYP3A4) and transport proteins (e.g. P-glycoprotein), as has been shown for rifampicin and clarithromycin. The combination of rifampicin with the new, poorly metabolised gamithromycin, a long-acting analogue of azithromycin and tulathromycin with lower pharmacokinetic interaction potential, might be a suitable alternative.

OBJECTIVES

To evaluate the pharmacokinetic interactions and pulmonary distribution of rifampicin and gamithromycin in healthy foals, and to investigate the cellular uptake of gamithromycin in vitro.

STUDY DESIGN

Controlled, four-period, consecutive, single-dose and multiple-dose study.

METHODS

Pharmacokinetics and lung distribution of rifampicin (10 mg/kg) and gamithromycin (6 mg/kg) were measured in nine healthy foals using LC-MS/MS. Enzyme induction was confirmed using the 4β-OH-cholesterol/cholesterol ratio. Affinity of gamithromycin to drug transport proteins was evaluated in vitro using equine hepatocytes and MDCKII-cells stably transfected with human OATP1B1, OATP1B3 and OATP2B1.

RESULTS

Rifampicin significantly (P<0.05) increased the plasma exposure of gamithromycin (16.2 ± 4.77 vs. 8.57 ± 3.10 μg × h/mL) by decreasing the total body clearance. Otherwise, gamithromycin significantly lowered plasma exposure of single- and multiple-dose rifampicin (83.8 ± 35.3 and 112 ± 43.1 vs. 164 ± 96.7 μg × h/mL) without a change in metabolic ratio and half-life. Gamithromycin was identified as an inhibitor of human OATP1B1, OATP1B3 and OATP2B1 and as a substrate of OATP2B1. In addition, it was extracted by equine hepatocytes via a mechanism which could be inhibited by rifampicin.

MAIN LIMITATIONS

Influence of gamithromycin on pulmonary distribution of rifampicin was not evaluated.

CONCLUSION

The plasma exposure of gamithromycin is significantly increased by co-administration of rifampicin which is most likely caused by inhibition of hepatic elimination.

Efficacy of Tulathromycin for the Treatment of Foals with Mild to Moderate Bronchopneumonia

BACKGROUND

There is conflicting data regarding the efficacy of tulathromycin for the treatment of foals with bronchopneumonia.

HYPOTHESES

Tulathromycin is effective for the treatment of bronchopneumonia in foals and noninferior to the combination of azithromycin and rifampin.

ANIMALS

A total of 240 foals on a farm endemic for infections caused by Rhodococcus equi.

METHODS

In a controlled, randomized, and double-blinded clinical trial, foals with ultrasonographic pulmonary lesions (abscess score 10-15 cm) were allocated to 3 groups: 1-tulathromycin IM q 7 days (n = 80); 2-azithromycin-rifampin, orally q24h (n = 80); or 3-untreated controls (n = 80). Physical examination and thoracic ultrasonography were performed by individuals unaware of treatment group assignment. Foals that worsened were considered treatment failures and removed from the study.

RESULTS

The proportion of foals that recovered was significantly higher for foals treated with tulathromycin (70 of 79) or azithromycin-rifampin (76 of 80) compared to that of control foals (22 of 80). The difference in the percentage of efficacy of azithromycin-rifampin versus tulathromycin was 6.4% (90% CI = -0.72-13.5%). Given that the confidence interval crossed the predetermined noninferiority limit of 10%, the null hypothesis that the response rate in the azithromycin-rifampin group is superior to that of the tulathromycin group could not be rejected. Resolution of ultrasonographic lesions occurred faster in foals treated with azithromycin-rifampin than in foals treated with tulathromycin.

CONCLUSION AND CLINICAL IMPORTANCE

Tulathromycin was effective for the treatment of bronchopneumonia in foals at this farm but not as effective as the combination of azithromycin-rifampin.

Effects of two alfalfa preparations with different particle sizes on the gastric mucosa in weanlings: alfalfa chaff versus alfalfa pellets

Background

Feeding alfalfa hay is often recommended for its buffering components, like protein and calcium, to prevent lesions of the gastric mucosa in horses. Until now, there has been no information regarding the influence of alfalfa particle size on the gastric mucosa. The aim of this study was to investigate the effects of feeding two alfalfa preparations with different particle sizes (alfalfa chaff vs alfalfa pellets) in comparison with grass hay on the gastric mucosa in weanling horses. We hypothesized that feeding a high proportion of fine alfalfa particles would negatively impact gastric mucosa and that feeding long alfalfa chaff would improve gastric mucosal health in weanlings.

Results

Before weaning, the prevalence of gastric mucosa lesions (one or more lesions considering all locations in the stomach) was 84.3 %; at 14 days after weaning, it was almost 100 %. Before and after weaning, most of the lesions were found at the greater curvature of the squamous mucosa and at the lesser curvature. After weaning, gastric mucosal lesions at the pylorus were significantly more severe in the group fed alfalfa chaff (p = 0.002). In the other regions, no differences related to the feeding regimes were observed.

Conclusions

Feeding alfalfa failed to improve gastric mucosal lesion scores in weanlings. Furthermore, foals fed alfalfa chaff had higher lesion scores at the pylorus. Alfalfa leaves contain a superior protein source and high amounts of calcium and magnesium, providing extra nutritional advantages in growing horses. At this time, either traditional grass hay rations or grass hay with alfalfa pellets can be recommended.

Efficacy of gamithromycin for the treatment of foals with mild to moderate bronchopneumonia

Background

Gamithromycin is active in vitro against the bacterial agents most commonly associated with bronchopneumonia in older foals. However, the clinical efficacy and safety of this drug have not been investigated.

Hypothesis

Gamithromycin is effective for the treatment of bronchopneumonia in foals.

Animals

One hundred and twenty‐one foals on a farm endemic for infections caused by Rhodococcus equi.

Methods

In a controlled, randomized, and double blinded clinical trial, foals with ultrasonographic evidence of pulmonary abscesses (abscess score 8.0–20 cm) were randomly allocated in 3 treatment groups: (1) gamithromycin IM q7 days (n = 40); (2) azithromycin with rifampin, PO q24h (n = 40); or (3) no antimicrobial treatment (controls; n = 41). Physical examination and thoracic ultrasonography were performed by individuals unaware of treatment group assignment. Foals that worsened were removed from the study.

Results

The proportion of foals that recovered without the need to be removed from the study was significantly higher for foals treated with gamithromycin (38 of 40) or azithromycin with rifampin (39 of 40) than for controls (32 of 41). Treatment with gamithromycin or with azithromycin‐rifampin resulted in a significantly faster decrease in the clinical score and abscess score compared to the controls. Adverse reactions characterized by colic (n = 18) and hind limb lameness (n = 14) were observed only in foals treated with gamithromycin.

Conclusion and Clinical Importance

Gamithromycin was noninferior to azithromycin with rifampin for the treatment of bronchopneumonia in the study population but had a higher frequency of adverse reactions.

An outbreak of Arthroderma vanbreuseghemii dermatophytosis at a veterinary school associated with an infected horse

We report a case of an outbreak of inflammatory dermatophytoses caused by Arthroderma vanbreuseghemii (formally Trichophyton mentagrophytes pro parte) that involved an infected horse, the owner and at least 20 students, staff and stablemen at a veterinary school in Bern (Switzerland) that presented highly inflammatory dermatitis of the body and the face. Transmission from human to human was also recorded as one patient was the partner of an infected person. Both the phenotypic characteristics and ITS sequence of the dermatophytes isolated from the horse and patients were identical, consistent with the conclusion that the fungus originated from the horse. Three infected persons had not been in direct contact with the horse. Although direct transmission from human to human cannot be ruled out, fomites were most likely the source of infection for these three patients. Inspection of the literature at the end of the nineteenth and beginning of the twentieth century revealed that this dermatophyte was frequently transmitted from horses to humans in contact with horses (stablemen, coachmen, carters and artillery soldiers). The rarity of the present case report at the present time is likely related to the transformation of civilisation from the nineteenth century to nowadays in Europe with the change of horse husbandry. In addition, the inadequate immune response of the horse and the high number of people in contact with it at the equine clinic may explain the exceptional aspect of this case report.