Increased Parasite Resistance and Recurrent Airway Obstruction in Horses of a High‐Prevalence Family

Background: Equine recurrent airway obstruction (RAO) shares many characteristics with human asthma. In humans, an inverse relationship between susceptibility to asthma and resistance to parasites is suspected. Hypothesis/Objectives: Members of a high‐incidence RAO half‐sibling family (F) shed fewer strongylid eggs compared with RAO‐unaffected pasture mates (PM) and that RAO‐affected horses shed fewer eggs than RAO‐unaffected half‐siblings. Animals: Seventy‐three F and 73 unrelated, age matched PM. Methods: Cases and controls kept under the same management and deworming regime were examined. Each individual was classified as RAO affected or RAO unaffected and fecal samples were collected before and 1–3 weeks and 3 months after deworming. Samples were analyzed by combined sedimentation‐flotation and modified McMaster methods and classified into 3 categories of 0 eggs per gram of feces (EpG), 1–100 EpG, and >100 EpG, respectively. Results: PM compared with RAO‐affected F had a 16.7 (95% confidence interval [CI]: 2.0–136.3) times higher risk for shedding > 100 EpG compared with 0 EpG and a 5.3 (95% CI: 1.0–27.4) times higher risk for shedding >100 EpG compared with 0 EpG. There was no significant effect when RAO‐unaffected F were compared with their PM. RAO‐unaffected compared with RAO‐affected offspring had a 5.8 (95% CI: 0.0–1.0) times higher risk for shedding 1–100 EpG. Age, sex, breed, and sharing pastures with other species had no significant confounding effects. Conclusion and Clinical Importance: RAO is associated with resistance against strongylid parasites in a high‐prevalence family.     

Evaluation of Right Ventricular Myocardial Function in Healthy Horses With Recurrent Airway Obstruction Using Tissue Doppler Imaging

It has been described in humans that chronic obstructive bronchitis leads to pathologic changes, especially in the right ventricular myocardium due to hypoxia, which can be assessed by tissue Doppler imaging (TDI). In our study, different TDI techniques, that is, pulsed-wave TDI and color TDI, were evaluated for applicability in different scan planes (apical long-axis view and short-axis view) for the analysis of right ventricular myocardial function in six healthy horses (control) and six horses affected with recurrent airway obstruction (RAO) (RAO group). Tissue Doppler imaging was applicable to all scan planes described. Myocardial movement directions in general and the absolute values of TDI parameters were assessable. Significantly reduced early diastolic filling velocities (E), elevated late diastolic filling velocities (A), thereby decreased E/A quotient, prolonged electromechanical coupling periods between electrocardiograph Q-wave and maximal velocities, and compensatory elevated systolic strain as well as diminished displacement could be observed in horses with RAO compared with the control group. To conclude, equine right ventricular myocardial function is assessable by TDI. Significant changes of right ventricular myocardial function could be demonstrated by TDI in horses with RAO compared with matched healthy controls. The hypothesis that RAO potentially leads to right ventricular dysfunction detectable by TDI before conventional echocardiography changes are evident is supported by this explorative study.     

Cytokine Concentrations in Bronchoalveolar Lavage Fluid from Horses with Neutrophilic Inflammatory Airway Disease

Background

Multiple cytological patterns occur in bronchoalveolar lavage fluid (BALF) of horses with inflammatory airway disease (IAD). Only few data on BALF cytokine profiles are available for horses with IAD, and are limited to mRNA expression.

Hypothesis/Objective

Cytological profiles of IAD are associated with different BALF immunological pathways. To investigate BALF cytokine concentrations in a large number of horses with neutrophilic IAD.

Animals

One hundred and thirty‐eight client‐owned Standardbred racehorses in active training.

Methods

Prospective observational study. BALF samples were obtained from left and right lungs. Interleukin (IL)‐4, interferon (IFN)‐γ, and tumor necrosis factor (TNF)‐α concentrations were determined by ELISA.

Results

Fourteen horses had normal BALF cytological profiles and 56 exhibited evidence of bilateral neutrophilic IAD. Twenty‐four horses showed BALF with, respectively, IAD‐ and CTL consistent cytology and were excluded; as were 44 horses because of evidence of pulmonary hemorrhage. TNF‐α (56 ± 115 pg/mL; P = .034) and IFN‐γ concentrations (104 ± 247 pg/mL; P = .044) were significantly higher for IAD horses, compared with controls (respectively 19 ± 41 and 80 ± 116 pg/mL). Horses with ‘neutrophil’ subtype had significantly higher IFN‐γ concentrations (110 ± 154 pg/mL), than ‘neutrophil/metachromatic’ (56 ± 54 pg/mL; P = .028) and ‘neutrophil/metachromatic/eosinophil’ subtypes (44 ± 23 pg/mL; P = .012).

Conclusions and Clinical Importance

Cytokine concentrations in BALF suggested that neutrophilic IAD is associated with activation of the innate immune system and a possible T‐helper (Th)‐1 polarized response. This study also suggested that immunological pathways vary according to cytological IAD subtypes.     

Multiple Hypersensitivities Including Recurrent Airway Obstruction,Insect Bite Hypersensitivity,and Urticaria in 2 Warmblood Horse Populations

Background

Multiple hypersensitivities (MHS) have been described in humans, cats, and dogs, but not horses.

Hypotheses

Horses suffering from recurrent airway obstruction (RAO), insect bite hypersensitivity (IBH), or urticaria (URT) will have an increased risk of also being affected by another one of these hypersensitivities. This predisposition for MHS also will be associated with decreased shedding of strongylid eggs in feces and with a single nucleotide polymorphism (SNP BIEC2‐224511), previously shown to be associated with RAO.

Animals

The first population (P1) included 119 randomly sampled horses representative of the Swiss sporthorse population; the replication population (P2) included 210 RAO‐affected Warmblood horses and 264 RAO‐unaffected controls. All horses were Warmbloods, 14 years or older.

Methods

Associations between disease phenotypes (RAO, IBH, URT, MHS) fecal egg counts, the SNP BIEC2‐224511 as well as management and environmental factors were investigated.

Results

In P1, RAO‐affected horses had a 13.1 times higher odds ratio (OR) of also suffering from IBH (P = .004). In P2, the respective OR was 7.4 (P = .002) and IBH‐affected horses also showed a 7.1 times increased OR of concomitantly suffering from URT (P < .001). IBH, URT, and MHS phenotypes were significantly associated with the absence of nematode eggs in the feces.

Conclusions and Clinical Importance

This is the first report of MHS in horses. Specifically, an increased risk for IBH should be expected in RAO‐affected horses.     

Reproducibility of Airway Responsiveness in Horses Using Flowmetric Plethysmography and Histamine Bronchoprovocation

Background: Inflammatory airway disease has a high prevalence in horses, but is often a diagnostic challenge. Flowmetric plethysmography and histamine bronchoprovocation (FP/HBP) is a simple and effective tool for diagnosis, but reproducibility of these measurements made over time has not been established.
Hypothesis: We hypothesize that the measurement of airway responsiveness in horses using FP/HBP is consistent over both short and long periods of time.
Animals: Twenty-nine healthy adult horses from 2 university herds.
Methods: In this prospective experimental study, airway responsiveness was determined in each horse at day 0 (baseline [BL]) with FP/ HBP, using PC35 (provocative concentration of histamine needed to increase Δ_flow by 35%) as a measure of airway responsiveness. Each horse was re-tested 1–4 weeks after BL (short-term [ST]) and again at 3–12 months after BL (long-term [LT]).
Results: In the ST period, 23/27 (85%) of the horses had a PC35 that was within 1 doubling concentration of histamine of their BL value, with a mean change of 0.52 doubling concentrations (95% CI 0.26–0.79, range 0–2.06). For the LT data, 19/26 (73%) of horses were within 1 doubling concentration of their BL value, with a mean change of 0.81 doubling concentrations (95% CI 0.45–1.17, range 0.14–3.10). There was no significant difference in reproducibility between the 2 groups of subjects.
Conclusions and Clinical Importance: Repeated measurements of airway responsiveness obtained with FP/HBP show acceptable reproducibility over time periods up to a year. However, caution must be used when testing horses when ambient air temperature is low.     

Efficacy and safety of sound wave treatment of recurrent airway obstruction in horses

Background: One proposed nonmedical therapy for recurrent airway obstruction (RAO) in horses is a handheld acoustic device that propels sound waves from the nose down the tracheobronchial tree where it is intended to dislodge mucous and relax bronchospasm, permitting clearance of mucoid secretions. Objective: To evaluate the effectiveness and safety of this device when used as per the manufacturer's recommendations as a treatment for RAO. Animals: Nine adult horses previously diagnosed with RAO. Methods: Prospective, cross‐over clinical trial. Horses were exposed to a dusty environment until airway obstruction developed as defined by standard lung mechanics (SLM). Horses were randomly assigned to receive either acoustic therapy or a sham treatment for 4 weeks while being maintained in this environment. Horses were evaluated by clinical scores, SLM, and forced expiration regularly for 4 weeks. The opposite treatment was administered after a washout period. Results: Seven horses received the treatment; 9 received the sham. There were no changes (P > .05) in clinical score, maximal change in transpulmonary pressure (ΔP_Lmax), lung resistance (R_L), or the forced expiratory flow rate averaged over the last 75–95% of expiration (FEF_75?95%) over the study period. The device was determined to be safe, although several minor adverse effects were noted, including head tossing, coughing, and chewing during treatment. Conclusions and Clinical Importance: Treatment with this device did not improve clinical signs or lung function in horses with RAO kept in a dusty environment. Currently accepted treatments, including environmental management and medical therapy, should be recommended.     

Plasma Procalcitonin Concentration in Healthy Horses and Horses Affected by Systemic Inflammatory Response Syndrome

Background

The diseases most frequent associated with SIRS in adult horses are those involving the gastrointestinal tract. An early diagnosis should be the goal in the management of horses with SIRS.

Objective

The objective of this study was to evaluate the plasma procalcitonin (PCT) concentration in healthy and SIRS horses to assess differences between the two groups.

Animals

Seventy‐eight horses (30 healthy and 48 SIRS).

Methods

Prospective in vivo multicentric study. Horses were classified as SIRS if at least 2 of the following criteria were met: abnormal leukocyte count or distribution, hyperthermia or hypothermia, tachycardia, tachypnea. Healthy horses showed no clinical or laboratory signs of SIRS. Plasma PCT concentrations were measured with a commercial ELISA assay for equine species. Results were expressed as mean±standard deviation. T‐test for unpaired data was performed between healthy and SIRS group. SIRS group was divided in 4 subgroups and t‐test was performed between healthy versus each subgroup.

Results

PCT concentrations in healthy and SIRS horses were 18.28 ± 20.32 and 197.0 ± 117.0 pg/mL, respectively. T‐test showed statistical differences between healthy versus SIRS group and between healthy versus all subgroups.

Conclusions and Clinical Importance

Results showed an increase in PCT concentration in SIRS horses as previously reported in humans and dogs. PCT could be used as a single assay in equine practice for detection of SIRS.     

Clinical Features and Prognostic Variables in 109 Horses with Esophageal Obstruction (1992–2009)

Background: Esophageal obstruction is common in horses and can result in life‐threatening complications. Previous studies have described clinical findings in horses with esophageal obstruction, but there are no reports that attempt to make correlations of clinical findings with outcome. Hypothesis: Specific clinical features of horses with esophageal obstruction are associated with increased likelihood of complications. Animals: One hundred and nine horses with esophageal obstruction. Methods: Retrospective cross‐sectional study. All clinical records of horses admitted between April 1992 and February 2009 for esophageal obstruction were reviewed. The association among 24 clinical, hematological, biochemical, therapeutic variables and the likelihood of complications was investigated by a univariable logistic regression model, followed by multivariable analysis. Results: Multiple logistic regression analysis revealed that intact males (P= .02), age >15 years (P < .01), and a need for general anesthesia (P < .01) were associated with the development of complications after an episode of esophageal obstruction. Increased respiratory rate (>22 breaths/min) and moderate or severe tracheal contamination, although not associated with complications as a whole, significantly increased the risk of developing aspiration pneumonia (P≤ .01). Conclusions and Clinical Importance: Signalment, clinical variables, and endoscopic findings were confirmed as important tools in assessing the severity of the esophageal lesion and pulmonary involvement. Knowledge of risk factors for the development of complications will aid in making informed decisions to optimize treatment and assist in the assessment of prognosis.     

Comparison of Skin Prick Tests with In Vitro Allergy Tests in the Characterization of Horses with Recurrent Airway Obstruction

We intended to identify relevant immunoallergic factors and to compare skin prick tests (SPTs) and in vitro allergy tests in the characterization of horses with recurrent airway obstruction (RAO), so as to ascertain that SPTs perform better. Forty Lusitano/cross-Lusitano horses (30 RAO cases and 10 healthy control horses)—a very valuable autochthonous breed—were studied. Clinical history, thoracic radiography, respiratory tract endoscopy, and bronchoalveolar lavage were used for diagnosis. Serum samples of all 40 horses and undiluted bronchoalveolar lavage fluid samples of 21 RAO horses and 6 control horses were submitted for evaluation by an allergen-specific immunoglobulin E (IgE) enzyme-linked immunosorbent assay. SPTs were performed on the 40 horses. Sensitivity, specificity, positive predictive value, and negative predictive value were calculated for all diagnostic methods. Agreement between diagnostic methods was assessed by kappa statistic (Κ). Chi-square test with Yates correction showed SPT results from the RAO and control groups to be statistically different (P < .05). SPTs showed higher sensitivity, specificity, positive predictive value, and negative predictive value than both enzyme-linked immunosorbent assay tests. In human medicine, SPTs are considered to be the gold standard of allergy tests. Neither serum IgE nor bronchoalveolar lavage fluid IgE reliably detected allergen hypersensitivity, compared with SPT. SPTs performed significantly better overall than both in vitro tests. Low sensitivity of the in vitro assays indicates the need for continued study to elucidate a more sensitive specific IgE test.     

Evaluation of Equine Albumin Solution in Fluid Therapy in Horses with Colic

Equine albumin solution can be a good therapeutic option in fluid replacement for treatment of horses with colic. The purpose of this study was to evaluate the effects of initial fluid therapy with equine albumin solution in horses presenting with colic and mild-to-moderate dehydration, and to compare this therapy with fluid therapy based on crystalloids alone. Nineteen horses of both genders presenting with colic and mild-to-moderate dehydration were used. Animals were randomly assigned to one of two groups (control: fluid therapy based on crystalloid solutions; experimental: fluid therapy based on equine albumin and crystalloid solutions). Physical examination, hematocrit determination, blood gas analysis, serum biochemistry, blood and peritoneal lactate assessment, and measurement of colloid osmotic and arterial pressure were performed at predetermined times. Good results were obtained with equine albumin solution. More fluid is attracted into and maintained in the intravascular compartment, despite infusion of small volumes, as indicated by higher arterial pressure, lower capillary refill time, lower hematocrit and serum protein concentrations, lower colloid osmotic pressure, and better skin turgor. Equine albumin solution has good oncotic action and is a safe fluid therapy option for horses with colic and mild-to-moderate dehydration. Our results suggest it can be a good choice of fluid for correction of severe dehydration, although further research is necessary to determine the adequate dose in such cases.     

Efficacy of Hyperimmunized Plasma in the Treatment of Horses with Acute Colitis

Colitis in the adult horse is a life-threatening clinical condition that can be caused by any of several enteric pathogens. This study was conducted to determine whether treating horses with plasma obtained from donors that were hyperimmunized against the common equine diarrheal pathogens Clostridium difficile, Clostridium perfringens, and Salmonella sp shortens the duration of diarrhea in acute colitis. To evaluate the efficacy of plasma treatment, 42 horses with acute onset of diarrhea were studied. Horses were enrolled if they were of age >1 year, duration of diarrhea at presentation was <72 hours, and they had not received equine plasma within the last 3 months. In addition, the serum cortisol concentrations of horses with acute diarrhea were studied.Horses were randomized to receive hyperimmunized plasma, control plasma (collected from nonimmunized horses), or no plasma therapy. Clinical parameters and fecal consistency were observed until resolution, discharge, or death, and complete blood counts (CBCs) and biochemical profiles were collected throughout the study. A total of 38 horses completed the study. The mean duration of diarrhea was 40.7 ± 9.8 (mean ± SEM) hours, 119.2 ± 56.1 hours, and 72.0 ± 24.5 hours for the hyperimmunized plasma, normal plasma (NP), and control groups, respectively. Using survival analysis techniques, this difference did not achieve statistical significance (P = .374). Serum cortisol was found to be increased in all horses at presentation and to decrease with time in all treatment groups. There was no difference in cortisol concentrations between the three treatment groups studied (P = .237).     

Clinical Feasibility and Airway Deposition of Nebulized Voriconazole in Healthy Horses

Voriconazole (VRC) is a potential treatment for pneumomycosis in horses. The objectives of this study were to determine if the delivery of Vfend using a Flexineb nebulizer produced clinically significant [VRC] in lower airways. The hypothesis was that [VRC] after delivery by nebulization would be greater in the pulmonary epithelial lining fluid than plasma. A secondary objective was to determine [VRC] in upper airways through the collection of nasopharyngeal wash (NPW) samples. Voriconazole solution [Vfend-6.25 mg/mL, 100 (n = 2), 200 (n = 3), 500 (n = 1) mg] was nebulized once in 6 healthy geldings. Clinical responses, duration of nebulization, and [VRC] at various time points (up to 8 hours) in plasma, bronchoalveolar lavage fluid (BALF) supernatant and cell pellet, and NPW samples were recorded. Voriconazole (Vfend-6.25 mg/mL, 200 mg) was nebulized in 5 additional, healthy geldings, and [VRC] was measured in NPW samples pre- and postnebulization at time points up to 8 hours. The antifungal activity of BALF and NPW samples was determined using agar disk diffusion. Concentrations of voriconazole were below detection in plasma, BALF supernatant, and cell pellets for all time points and doses except the BALF cell pellet (0.4 μg/g) immediately after nebulization of 500 mg. For 5 horses, administered 200 mg of Vfend, mean [VCR] in NPW at the end of nebulization and 1, 6, and 8 hours postnebulization were: 30.8 ± 29, 1.0 ± 0.84, 0.2 ± 0.19, and 0.34 ± 0.67 μg/mL, respectively. Only NPW samples obtained immediately postnebulization showed antifungal activity. A nebulized Vfend solution is not recommended for the treatment of pneumomycosis in horses.     

Pulmonary Eosinophilia Associated with Increased Airway Responsiveness in Young Racing Horses

Horses are known to acquire small airway disease (SAD), an allergen-induced naturally occurring syndrome of reversible obstructive lung disease accompanied by airway hyperresponsiveness and increased inflammatory cell numbers on bronchoalveolar lavage (BAL). This disorder has received scant attention in young racehorses. The purpose of the present report was to examine the effect of BAL eosinophilia in young racehorses on clinical examination, BAL, hematology, airway responsiveness, and on pulmonary function at rest and after a standardized exercise challenge. Five (3 males, 2 females; age 2.6 ± 0.9 years) with a history of respiratory compromise and BAL eosinophil differential count <5% and 6 controls (4 males, 2 females; age 3.5 ± 1.0 years) training and performing to expectation with normal BAL cell differential (eosinophils < 1%) were studied. Respiratory system clinical examination was performed and expressed as a clinical score. Arterial blood gas measurements, CBC, and pulmonary function testing were performed at rest. Pulmonary mechanics measurements were repeated 1 hour and 20 hours after a standardized treadmill exercise challenge. Incremental histamine inhalation challenge was performed and the concentration of histamine effecting a 35% decrease in dynamic compliance (PC35C_Dyn) was determined. Significant differences were noted between and controls with regard to clinical score ( P = .01), blood eosinophils ( P = .04), BAL cell count ( P = .04), BAL macrophage differential ( P = .04), PC35C_Dyn ( P = .008), and tidal volume and respiratory rate at 20 hours following exercise challenge ( P = .05). We conclude that pulmonary eosinophilia and airway hyperresponsiveness are manifest in some young horses without overt airway obstruction at rest. We speculate that these may be early events in the natural progression of heaves.