Objective—To evaluate whether bronchoalveolar lavage (BAL) alters respiratory mechanics of horses with recurrent airway obstruction (ie, heaves) over a 48-hour period.
Animals—6 horses affected with heaves.
Procedures—Horses were subjected to a complete BAL procedure, which included sedation with xylazine and butorphanol, intratracheal administration of lidocaine, and instillation and aspiration of two 250-mL boluses of saline (0.9% NaCl) solution through an endoscope (study 1). To evaluate the effects of saline solution, horses were subjected to the same procedure without saline solution instillation and aspiration (study 2). Lastly, the endoscope was similarly introduced into the lower airways, without sedation or saline instillation and aspiration (study 3). Respiratory mechanics were performed at baseline (time 0) and at 3, 6, 12, 24, and 48 hours after each procedure.
Results—In study 1, BAL induced a significant decrease in pulmonary resistance lasting up to 6 hours. This may have resulted from clearance of mucus in large airways. We also observed a significant increase in lung elastance and transpulmonary pressure at 12 hours after BAL in all 3 studies, which may be attributed to a circadian effect.
Conclusions and Clinical Relevance—Our results indicate that the temporal effects of BAL procedures on lung mechanics should be taken into account when designing research protocols involving horses with heaves. Future studies should address the immediate effects of BAL on lung function.
Objective—To evaluate effects of thrombophlebitis of 1 or both jugular veins on athletic performance of horses.
Design—Retrospective case series.
Animals—91 horses with jugular vein thrombophlebitis.
Procedures—Medical records of horses with jugular vein thrombophlebitis examined between 1988 and 2005 were reviewed for signalment, history, clinical signs, diagnosis, and treatment. Performance was evaluated in 2 ways. A questionnaire was used to obtain a subjective assessment from the owner or trainer of the horse's performance after thrombophlebitis, compared with the performance before thrombophlebitis. Racing records from before and after thrombophlebitis were also evaluated.
Results—Thrombophlebitis was diagnosed in 37 horses at the time of admission (group 1), and 54 horses developed thrombophlebitis during hospitalization for an unrelated medical condition (group 2). Twenty-seven of 81 (33%) owners answered the questionnaire, and racing records were available for 31 horses. Performance data were available for 48 horses. Owners reported that all nonracing horses, except 1, had equivalent or better performances after discharge. Twenty-six of 31 (84%) Standardbreds resumed racing; in these horses, there was no significant difference between racing times before and after thrombophlebitis. No significant difference in performance was detected regardless of the primary disease, whether a horse had unilateral or bilateral thrombophlebitis, or the treatment administered.
Conclusions and Clinical Relevance—Results suggested that the athletic performance of horses used for nonracing events was not affected by thrombophlebitis. Thrombophlebitis in racing Standardbreds was associated with a decreased chance of return to racing; however, performance was not impaired in those that resumed racing.
Objective—To determine variations in cytologic counts of bronchoalveolar lavage (BAL) fluid attributable to month of collection, first and second aliquots, and left and right lung sites in horses with recurrent airway obstruction (RAO).
Animals—5 horses with RAO and 5 healthy horses without respiratory tract disease.
Procedures—Horses were housed in a stable for 5 months prior to and throughout the study. Bronchoalveolar lavage fluid was collected from the right and left lung of each horse 3 times at monthly intervals (February, March, and April). Each BAL fluid collection was performed by use of 2 incremental instillations of 250 mL of isotonic saline (0.9% NaCl) solution in the same bronchial site. Analysis of BAL fluid included volume of BAL fluid recovered, a CBC, and differential cytologic counts.
Results—Volume of BAL fluid recovered and cytologic counts did not differ in horses with RAO across time or between right and left lungs, except for the number of mast cells. Horses with RAO had significantly lower volumes of BAL fluid recovered, significantly lower percentages of macrophages and lymphocytes, and significantly higher percentages of neutrophils than did healthy horses. Despite individual variation, all horses with RAO had > 25% neutrophils throughout the study period.
Conclusions and Clinical Relevance—Despite variation among horses, BAL fluid cytologic counts were repeatable over short and long periods and samples can be used for longitudinal studies as a diagnostic tool of pulmonary inflammation in horses with RAO.
Objectives—To determine the effects of pentoxifylline
(PTX) administration on lung function and
results of cytologic examination of bronchoalveolar
lavage fluid in horses affected by recurrent airway
Animals—10 RAO-affected horses.
Procedures—6 horses were orally administered PTX (16
g) mixed with corn syrup, and 4 horses were administered
corn syrup alone, twice daily for 14 days.
Pulmonary function was evaluated before administration
(day 0) and on days 8 and 15. Bronchoalveolar lavage
(BAL) was performed on days 0 and 15. Reversibility of
airway obstruction was assessed by measuring pulmonary
function before and after administration of
atropine (0.02 mg/kg, IV). Serum concentration of PTX
was measured in 4 horses 30 minutes and 2 and 4 hours
after administration of PTX on days 1, 2, 3, 7, and 14.
Results—Administration of PTX to RAO-affected
horses resulted in a decrease in elastance value on
day 8 and on elastance and resistance (RL) values on
days 8 and 15. Results for cytologic examination of
BAL fluid obtained on day 15 did not differ significantly,
compared with values for day 0. Values of RL
decreased in all horses following administration of
atropine. When mixed in corn syrup and administered
orally, PTX was poorly absorbed in horses, and there
was noticeable variation in serum PTX concentrations
over time and among horses.
Conclusions and Clinical Relevance—Based on
these results, it can be concluded that administration
of PTX at high doses improved respiratory function of
RAO-affected horses maintained in an unfavorable
environment. (Am J Vet Res 2002;63:459–463)
To investigate indicators of neutrophil activation in the blood of healthy and asthma-affected horses and assess associations between corticosteroid treatment and these variables.
48 horses (14 with severe equine asthma [SEA], 21 with mild to moderate equine asthma [MEA], and 13 healthy controls).
In a 3-part retrospective study, hematology analyzer data for horses included in previous studies were reviewed. Neutrophil size, neutrophil light absorbance (NLA), and myeloperoxidase (MPO) index were recorded. Data for each variable were compared among groups for the entire study sample (part 1). Changes in each variable were assessed for one subset of horses (5 SEA-affected and 6 controls) after treatment for 2 weeks with dexamethasone (0.06 mg/kg, PO, q 24 h; part 2) and for another subset (8 SEA-affected horses) after the same treatment and after a 1-week post-treatment washout period (part 3).
All 3 variables were significantly greater for the SEA group, compared with the MEA and control groups in part 1. Following dexamethasone treatment, the control- and SEA-group NLA and MPO index significantly decreased and SEA-group neutrophil size significantly decreased in part 2; immediate posttreatment results for SEA-affected horses were similar in part 3, with significantly increased neutrophil size and nonsignificant increases in NLA and MPO index following washout.
CONCLUSIONS AND CLINICAL RELEVANCE
Results suggested horses with exacerbated SEA have larger neutrophils that contain more MPO, compared with neutrophils of MEA-affected and healthy control horses. The clinical value of these variables for the diagnosis of equine asthma was deemed limited owing to data overlap among groups. (Am J Vet Res 2021;82:737–745)
OBJECTIVE To evaluate whether MgSO4 solution administered IV would improve the clinical signs and lung function of horses with severe asthma and potentiate the effects of salbutamol inhalation in those horses.
ANIMALS 6 adult horses with severe asthma.
PROCEDURES Asthmatic horses were used in 3 crossover design experiments (6 treatments/horse). Clinical scores for nasal flaring and the abdominal component associated with breathing and lung function were determined before and after administration of salbutamol (800 μg, by inhalation), MgSO4 solution (2.2 mg/kg/min, IV, over 20 minutes), and combined MgSO4-salbutamol treatment. The data were collected during experimental procedures to assess salbutamol inhalation versus mock inhalation, MgSO4 infusion versus infusion of saline (NaCl) solution (adjusted to the same osmolarity as the MgSO4 solution), and the combined MgSO4-salbutamol treatment versus salbutamol inhalation alone.
RESULTS Infusion of MgSO4 significantly improved clinical scores when administered alone or in combination with salbutamol inhalation. With the combination treatment, lung function improved, albeit not significantly. Tidal volume also increased following combined MgSO4-salbutamol treatment. Salbutamol alone significantly improved lung function, whereas saline solution administration and a mock inhalation procedure had no effect on the studied variables.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that MgSO4 infusion alone or in combination with salbutamol inhalation improved the clinical signs of severely asthmatic horses. The effects of MgSO4 were not associated with significant lung function improvement, which suggested that the changes observed were attributable to alterations in the horses' breathing patterns. Infusion of MgSO4 solution at the studied dose offers little advantage over currently used medications for the treatment of severe equine asthma.
To use a biopolymer delivery system to investigate the ability of interleukin (IL)-4 to recruit neutrophils into subcutaneous tissues of equids.
16 horses and 2 ponies.
Animals were assigned to 3 experiments (6/experiment). Effects of recombinant equine (Req) IL-4 (100, 250, or 500 ng/site) versus a positive control (ReqIL-8; 100 ng, 250 ng, or 1 μg/site) and a negative control (Dulbecco PBSS or culture medium) on neutrophil chemotaxis were assessed after SC injection into the neck with an injectable biopolymer used as the vehicle. Tissue samples including the biopolymer plug were collected by biopsy at various time points from 3 hours to 7 days after injection. Neutrophil infiltration was evaluated by histologic scoring (experiments 1, 2, and 3) or flow cytometry (experiment 3).
Histologic neutrophil infiltration scores did not differ significantly among treatments at most evaluated time points. On flow cytometric analysis, log-transformed neutrophil counts in biopsy specimens were significantly greater for the ReqIL-8 treatment (1 μg/site) than the negative control treatment at 3 but not 6 hours after injection; results did not differ between ReqIL-4 and control treatments at either time point. Negative control treatments induced an inflammatory response in most equids in all experiments.
CONCLUSIONS AND CLINICAL RELEVANCE
Flow cytometry was a more reliable method to estimate neutrophil migration than histologic score analysis. The ReqIL-4 treatment did not induce a detectable neutrophil response, compared with the negative control treatment in this study. Evidence of inflammation in negative control samples suggested the biopolymer is not a suitable vehicle for use in equids.
OBJECTIVE To develop a method to maintain the initial phenotype of airway smooth muscle (ASM) cells isolated from equine endobronchial biopsy specimens in long-term cell culture.
SAMPLE Endobronchial tissue specimens (8 to 10/horse) collected from the lungs of previously healthy horses at necropsy (n = 12) and endobronchial biopsy specimens collected from standing, sedated, heaves-affected horses in clinical remission of the disease (5) and control horses (4).
PROCEDURES A sampling protocol was developed to recover and maintain a contractile phenotype in ASM cells from endobronchial specimens from freshly harvested equine lungs and from healthy and heaves-affected horses. Immunologic techniques were used to evaluate the contractile phenotype of ASM cells in culture.
RESULTS Characteristic ASM cells were successfully cultured from endobronchial tissue or biopsy specimens from both healthy and heaves-affected horses, and their contractile phenotype was maintained for up to 7 passages. Moreover, the capacity of cells at the seventh passage to contract in a collagen gel in response to methacholine was maintained.
CONCLUSIONS AND CLINICAL RELEVANCE ASM cells isolated from equine endobronchial tissue and biopsy specimens were able to maintain a contractile phenotype in long-term cell cultures, suggesting they could be used for tissue engineering and in vitro studies of equine ASM cells.
OBJECTIVE To evaluate in vitro phagocytosis and bactericidal activity of circulating blood neutrophils in horses with severe equine asthma and control horses and to determine whether circulating blood neutrophils in horses with severe equine asthma have an increase in expression of the proinflammatory cytokine tumor necrosis factor (TNF)-α and the chemokine interleukin (IL)-8 and a decrease in expression of the anti-inflammatory cytokine IL-10 in response to bacteria.
ANIMALS 6 horses with severe equine asthma and 6 control horses.
PROCEDURES Circulating blood neutrophils were isolated from horses with severe equine asthma and control horses. Phagocytosis was evaluated by use of flow cytometry. Bactericidal activity of circulating blood neutrophils was assessed by use of Streptococcus equi and Streptococcus zooepidemicus as targets, whereas the cytokine mRNA response was assessed by use of a quantitative PCR assay.
RESULTS Circulating blood neutrophils from horses with severe equine asthma had significantly lower bactericidal activity toward S zooepidemicus but not toward S equi, compared with results for control horses. Phagocytosis and mRNA expression of TNF-α, IL-8, and IL-10 were not different between groups.
CONCLUSIONS AND CLINCAL RELEVANCE Impairment of bactericidal activity of circulating blood neutrophils in horses with severe equine asthma could contribute to an increased susceptibility to infections.
Objective—To evaluate whether the leukotriene (LT)
D4 receptor antagonist L-708,738 is therapeutically
beneficial in treating horses with recurrent airway
Animals—12 adult horses with heaves and healthy
lung lobes from 20 slaughtered horses.
Procedure—Lung lobes were used for smooth muscle
tension and radioligand binding studies. Horses
with heaves were given a placebo for 14 days and
administered L-708,738 (n = 6; 2.5 mg/kg PO, q 12 h)
or dexamethasone (6; 0.04 mg/kg, IV, q 24 h) from
days 14 to 28. Pulmonary function was measured
weekly for 36 days, and bronchoalveolar cells were
collected on days 0, 14, and 29 for cytologic examination.
Results—Nanomolar concentrations of L-708,738
were effective at antagonizing LTD4-induced bronchoconstriction
and LTD4-receptor binding in lung
lobes. Mean peak and trough L-708,738 plasma concentrations
during the treatment period were 1.54 and
0.28 μM, respectively. On days 21 and 29, lung
mechanics were significantly improved in the dexamethasone-
treated horses but not in the L-708,738-treated
horses. Neither dexamethasone nor
L-708,738 had a significant effect on cytologic findings.
Conclusions and Clinical Relevance—L-708,738
was bioavailable after oral administration and sustained
concentrations in plasma during the dosing
period that exceeded in vitro efficacy values.
However, airway function did not improve, suggesting
that either drug concentrations in the lungs were subtherapeutic
or that cysteinyl LT may not be important
mediators of airway inflammation in heaves. Results
provide the first evidence of cysteinyl LT1 receptors in
airways of horses. (Am J Vet Res 2002;63:579–585)