Antimicrobial resistance changes in enteric Escherichia coli of horses during hospitalisation: resistance profiling of isolates.

The aim of this study was to determine whether hospitalisation of horses leads to increased antimicrobial resistance in equine faecal Escherichia coli isolates. E. coli were cultured from faecal samples of horses on admission and after 7 days of hospitalisation; antimicrobial susceptibility was determined for eight antimicrobial agents. Resistance profiles of E. coli isolates were grouped into clusters, which were analysed to determine resistance patterns. Resistance to 7/8 antimicrobial agents and multi-drug resistance (MDR; resistance to ≥3 antimicrobial classes) were significantly higher after 7 days of hospitalisation. Forty-eight resistance profiles were identified; 15/48 were present on day 0 only, 16/48 on day 7 only and 17/48 at both times of sampling. There was a significant association between day 7 profiles and resistance detected to an increased number of antimicrobial agents. Hospitalisation of horses for 7 days resulted in alterations in equine faecal E. coli antimicrobial resistance profiles.

A randomised, blinded, crossover study to assess the efficacy of a feed supplement in alleviating the clinical signs of headshaking in 32 horses.

REASONS FOR PERFORMING STUDY: Feed supplements are commonly used by owners to alleviate headshaking; however, randomised, controlled trials are required to assess their efficacy. OBJECTIVE: To determine the efficacy of a feed supplement for alleviation of the clinical signs of headshaking using a randomised, blinded, placebo-controlled trial. METHODS: Using a crossover design, 44 horses previously diagnosed with chronic idiopathic headshaking received both the supplement and a matching placebo per os for 28 days with a washout period between of 14 days. Video recordings were taken at rest and exercise prior to the study and at the end of both periods of treatment. The degree of headshaking was assessed in a blinded, randomised manner by 2 veterinary surgeons. At the same time points, owners completed a questionnaire to assess the severity of headshaking signs. A Wilcoxon signed rank test was used to compare the scores while on supplement and placebo. RESULTS: Using the video assessments, there was no significant difference between scores while on supplement compared with placebo (P = 0.7). Using the questionnaire responses, there was no significant difference between scores for any activity when the placebo and the supplement were compared with each other. However, owners reported significant improvement during all activities for both placebo and supplement compared with pretreatment scores. CONCLUSIONS AND POTENTIAL RELEVANCE: The supplement offered no benefit over a placebo in alleviating the clinical signs of headshaking. There appeared to be a significant proxy placebo effect when the outcome was based on subjective owner perception of clinical signs. This study demonstrated no beneficial effect of this supplement on the clinical signs of headshaking. The study did show a significant placebo effect, thereby highlighting the necessity of properly conducted, randomised controlled trials, with blinding, to assess true treatment effects in trials in animals.

Caudal anaesthesia of the infraorbital nerve for diagnosis of idiopathic headshaking and caudal compression of the infraorbital nerve for its treatment, in 58 horses.

REASONS FOR PERFORMING STUDY: Idiopathic headshaking is often a facial pain syndrome, but a diagnostic protocol has not been described. In a previous study, caudal compression of the infraorbital nerve for treatment offered a fair success rate, but low case numbers and short follow-up time were limitations. OBJECTIVES: To describe a diagnostic protocol for headshaking, examining the role of bilateral local analgesia of the posterior ethmoidal nerve (PET block). To report longer-term follow-up after surgery of the original cases and further cases and to determine whether changes to the technique influence success rates and complications. METHODS: Records of horses that had undergone PET block and caudal compression surgery at 3 hospitals were reviewed. Modifications to the surgical technique included placing additional coils into the infraorbital canal and/or performing concurrent laser cautery of the nerve. Follow-up information was obtained by telephone contact with owners. RESULTS: The PET block was performed in 27 horses, with a positive result in 23 of 27 (85%). Surgery was performed in 58 horses. A successful outcome was initially achieved in 35 of 57 (63%) horses, but recurrence occurred between 9 and 30 months later in 9 (26%). Surgery was repeated in 10 of 31 (32%) horses. Final success rate, considering only response to the last performed surgery, was 28 of 57 (49%) horses with median follow-up time of 18 months (range 2-66 months). Nose-rubbing was reported post operatively in 30 of 48 (63%) horses. This resolved in all but 4 horses, which were subjected to euthanasia. Response to PET block or change in surgical technique did not appear to influence outcome or complications. CONCLUSIONS AND POTENTIAL RELEVANCE: The diagnostic protocol described is recommended for the investigation of headshakers. Caudal compression offers the best prognosis for a successful outcome compared with other treatments, for horses in which the only alternative is euthanasia. Surgical treatment of the disorder requires refinement, and the pathogenesis of the disorder requires investigation.

Comparison of owner-reported health problems with veterinary assessment of geriatric horses in the United Kingdom.

REASONS FOR PERFORMING STUDY: Previous studies suggest that owners underestimate or incorrectly recognise or report health problems in geriatric horses. However, few studies have directly compared owner-reported and veterinary assessed disease. OBJECTIVES: To compare the findings of veterinary clinical examination of geriatric horses with owner-reported clinical signs and disease. METHODS: A total of 200 horses aged ≥ 15 years were randomly selected to receive a veterinary examination, from responses to a cross-sectional postal questionnaire survey. Veterinary examinations were performed within 2 months of questionnaire return, and agreement between owner-reported data and veterinary clinical findings was assessed. RESULTS: Owners under-reported many clinical signs and disease conditions detected on veterinary clinical examination. For example, dental abnormalities (detected in 95.4% of horses, reported by 24.5% of owners); cardiac murmurs (detected in 20% of horses, reported by 0.5% of owners); lameness (present in 50% of horses, reported by 23% of owners) and hoof abnormalities (detected in 80% of horses, reported by 27% of owners). Agreement between owner-reported and veterinary assessed respiratory disease (Kappa 0.02-0.2), body condition score (Kappa 0.24) and coat abnormalities (Kappa 0.42) was poor, fair and moderate, respectively. Range of motion (ROM) of the tarsal and metacarpophalangeal joints was lower in horses with owner-reported osteoarthritis (P = 0.005 and <0.001, respectively). CONCLUSIONS AND POTENTIAL RELEVANCE: The low prevalence and relatively poor agreement of owner-reported disease compared to that detected on veterinary examination suggests inaccurate or under-recognition, or inaccurate reporting of health problems by owners of geriatric horses, which could lead to a delay in presentation for veterinary treatment. Increased veterinary involvement and improved owner education in the care of geriatric horses should facilitate earlier identification of disease, particularly that which is not readily detectable by owners, and aid management of health and welfare problems.

Disease prevalence in geriatric horses in the United Kingdom: veterinary clinical assessment of 200 cases.

REASONS FOR PERFORMING STUDY: Geriatric horses (aged ≥ 15 years) represent a substantial proportion of the equine population, yet few studies have investigated the prevalence of diseases within this population in the UK. OBJECTIVES: To describe the findings of veterinary clinical examination of 200 geriatric horses and ponies in north west England and north Wales, and to assess the effect of animal age and type (horse or pony) on the presence or absence of clinical signs and veterinary diagnosed health problems. METHODS: From responses to a cross-sectional postal questionnaire survey of owners of geriatric horses (n = 918/1144), 200 horses were randomly selected to receive a veterinary clinical examination covering the major body systems. RESULTS: Twenty-six percent of animals were overweight (body condition score, BCS, >3/5) and 4.5% were underweight (BCS <2/5). Seventy-one percent had a dermatological abnormality and 22% displayed hirsutism or abnormal moulting. Ophthalmic lesions frequently identified included vitreous degeneration (66.0%), cataracts (58.5%) and senile retinopathy (33.7%). The prevalence of cardiac murmurs was 20%. Whilst only 7.5% of animals had a spontaneous cough during the examination, 18.5% had some form of nasal discharge and 22% had abnormalities on thoracic auscultation at rest. Following rebreathing, 13.6% developed marked abnormalities consistent with lower airway disease. When assessed at walk, 18.6% were lame on at least one limb, while 50.5% were lame in trot. The majority of animals (83.5%) had a reduction in range of motion in at least one joint. Eighty percent of animals had hoof abnormalities. Dental abnormalities were identified in 95.4% of animals, with cheek teeth diastemata, excessive wear/cupped out teeth and focal overgrowths the most frequently identified conditions. CONCLUSIONS AND POTENTIAL RELEVANCE: This study has identified many prevalent clinical signs of disease in geriatric horses. Description of the most prevalent health problems and further identification of risk factors for these conditions will aid in targeted improvements in veterinary care, owner education and welfare.

A cross-sectional study of geriatric horses in the United Kingdom. Part 1: Demographics and management practices.

REASONS FOR PERFORMING STUDY: With growing numbers of aged horses, geriatric medicine is becoming increasingly important in equine veterinary practice; however, there is a paucity of information on the UK equine geriatric population. OBJECTIVES: To describe the demographic characteristics of the equine geriatric population and to assess management practices undertaken by owners of geriatric horses (aged≥15 years). METHODS: A cross-sectional study was conducted, surveying a randomly selected sample of veterinary registered owners with horses aged≥15 years, using a self-administered postal questionnaire. RESULTS: Horses aged≥15 years represented 29% of the equine population in the study area. The response rate to the questionnaire survey was 80.2%. Management practices were similar to those previously described for the general equine population. However, the level of exercise and feeding practices changed significantly with increasing age. A summary of the demographic characteristics, feeding and management of horses in a sample of the geriatric equine population is presented. CONCLUSIONS AND POTENTIAL RELEVANCE: The management of geriatric horses has a direct effect on their health and welfare and this study has provided valuable information on the demographics and management of geriatric horses and ponies in the UK. The information can be used to form targeted owner education programmes for geriatric health and should aid in the investigation and prevention of disease.

A cross-sectional study of geriatric horses in the United Kingdom. Part 2: Health care and disease.

REASONS FOR PERFORMING STUDY: Geriatric horses (aged≥15 years) represent a substantial proportion of the equine population, yet very few studies have investigated the prevalence of diseases within the UK equine geriatric population. OBJECTIVES: To describe the provision of routine preventive health care measures, prevalence of clinical signs of disease and the prevalence of owner reported diseases. Additionally, the effect of increasing age on the provision of preventive health care and the presence or absence of clinical signs and disease was assessed. METHODS: A cross-sectional study was conducted, surveying a randomly selected sample of veterinary registered owners with horses aged≥15 years, using a self-administered postal questionnaire. RESULTS: As geriatric horses increased in age, there was a reduction in the provision of preventive health care measures, such as vaccination, farrier care and routine veterinary checks. Only 68.7% of horses had received a routine veterinary visit within the previous 12 months. Owners frequently observed clinical signs in their animals, with 77% reporting at least one clinical sign of disease. Increasing age was associated with increased reporting of many clinical signs of disease. Over half (58%) of horses had at least one episode of disease within the previous 12 months, yet only 31% of owners reported that their animal currently suffered from a known disease or disorder. CONCLUSIONS AND POTENTIAL RELEVANCE: Although owners frequently observed clinical signs in their aged horse, there may be incorrect or under recognition of many diseases and health problems. Reduced frequency of routine preventive health care measures, along with suboptimal owner recognition of health and welfare problems may lead to compromised welfare in the geriatric population.

Expression of lactate transporters MCT1, MCT2 and CD147 in the red blood cells of three horse breeds: Finnhorse, Standardbred and Thoroughbred.

REASONS FOR PERFORMING STUDY: In exercising horses, up to 50% of blood lactate is taken up into red blood cells (RBCs). Lactate transporter proteins MCT1, MCT2 and CD147 (an ancillary protein for MCT1) are expressed in the equine RBC membrane. In Standardbreds (SB), lactate transport activity is bimodally distributed and correlates with the amount of MCT1 and CD147. About 75% of SB studied have high lactate transport activity in RBCs. In other breeds, the distribution of lactate transport activity is unknown. OBJECTIVES: To study whether similar bimodal distribution of MCT1 and CD147 is present also in the racing Finnhorse (FH) and Thoroughbred (TB) as in the SB and to study the distribution of MCT2 in all 3 breeds and to determine if there is a connection between MCT expression and performance markers in TB racehorses. METHODS: Venous blood samples were taken from 118 FHs, 98 TBs and 44 SBs. Red blood cell membranes were purified and MCT1, MCT2 and CD147 measured by western blot. The amount of transporters was compared with TB performance markers. RESULTS: In TBs, the distribution of MCT1 was bimodal and in all breeds distribution of MCT2 unimodal. The amount of CD147 was clearly bimodal in FH and SB, with 85 and 82% expressing high amounts of CD147. In TBs, 88% had high expression of CD147 and 11% low expression, but one horse showed intermediate expression not apparent in FH or SB. Performance markers did not correlate with the amount of MCT1, MCT2 or CD147. CONCLUSIONS: High lactate transport activity was present in all 3 racing breeds, with the greatest proportion in the TB, followed by the racing FH, then SB. There was no significant statistical correlation found between lactate transporters in RBC membrane and markers of racing performance in the TB.

Experimental mild pulmonary inflammation promotes the development of exercise-induced pulmonary haemorrhage.

REASONS FOR PERFORMING STUDY: Histological studies of exercise-induced pulmonary haemorrhage (EIPH) reveals inflammatory infiltrates within areas of lung that contain haemorrhage. This has resulted in the hypothesis that pulmonary inflammation could cause EIPH or contribute to an increased risk or severity of EIPH. OBJECTIVES: To determine whether experimentally-induced pulmonary inflammation predisposes the lung to haemorrhage during exercise, by evaluating the bronchoalveolar lavage (BAL) cytology of normal and inflamed regions of lung following high speed treadmill exercise. MATERIALS AND METHODS: Transendoscopic airway inoculations of 0.01% acetic acid were used to induce mild localised inflammation within bronchopulmonary segments. Horses underwent high speed exercise 24 h after inoculation. Following exercise, inoculated sites and corresponding segments in the opposite lung underwent BAL. The cytology results from inflamed and control bronchopulmonary segments were compared, using paired t tests. RESULTS: Erythrocytes were present in BAL samples from 12.5% (1/8) control segments compared with 75% (6/8) inoculated segments following exercise, indicating a significant increase (P = 0.04) in the relative risk of EIPH following the development of pulmonary inflammation. Samples from inoculated segments had significantly higher percentages and numbers of neutrophils (12.1 ± 1.0% and 601 ± 98 cells/µl) than control samples (4.3 ± 0.3% and 214 ± 52 cells/µl). Significantly higher erythrocyte numbers were observed in samples from inoculated segments (14,304 ± 6862 cells/µl) compared with control samples (3.5 ± 3.5 cells/µl). CONCLUSIONS: The results showed inflammation increased the risk of developing pulmonary haemorrhage during exercise. These findings do not conflict with current theories on the common causes of EIPH, but suggest that care should be taken when recommending exercise in horses suspected to be suffering from pulmonary inflammatory disease. In addition, specific therapy to reduce pulmonary inflammation may benefit horses prone to the development of EIPH.

Caudal compression of the infraorbital nerve: a novel surgical technique for treatment of idiopathic headshaking and assessment of its efficacy in 24 horses.

UNLABELLED: REASONS FOR DESIGNING AND REPORTING TECHNIQUE: Idiopathic headshaking has remarkable similarities to human neuropathic facial pain syndromes associated with post herpetic and trigeminal neuralgia. These derive from abnormal sensory function within the peripheral or central pathways of the trigeminal nerve (TgN). Limiting input from the TgN can be helpful in controlling the perception of pain. Rhizotomy of the infraorbital branch of the TgN as it emerges from the infraorbital canal has been reported but has a poor efficacy. A novel technique involves compression of the nerve at a more caudal location within the infraorbital canal and the technique requires validation. HYPOTHESIS: Caudal compression of the infraorbital nerve with platinum coils, performed in horses diagnosed with idiopathic headshaking, results in a decrease in clinical signs. METHODS: Caudal compression of the infraorbital nerve, using platinum embolisation coils, was performed under fluoroscopic guidance. Clinical records of 24 idiopathic headshakers that had undergone this procedure were reviewed. Follow-up information was obtained by telephone questionnaire with the owner or referring veterinary surgeon. RESULTS: All 24 horses had at least one surgical procedure. Median follow-up time was 6 months. There were 2 horses which had surgery 2 weeks before follow-up and these were excluded from the analysis of outcome. Following one surgery, 13/22 horses (59.0%) had a successful outcome. Of the 9 horses that did not improve, surgery was repeated in 6 cases. Two of these horses had a successful outcome. Overall, a successful outcome was obtained in 16/19 horses (84.2%). CONCLUSIONS: This surgical technique is likely to prevent input from the TgN at a more caudal location then the previously described infraorbital neurectomy. The technique requires refinement.

Alveolar fibrosis and changes in equine lung morphometry in response to intrapulmonary blood.

Necropsy studies of horses suffering exercise-induced pulmonary haemorrhage (EIPH) have identified mild inflammatory lesions with evidence of alveolar fibrosis and bronchiolitis. These lesions were thought to be the result of viral infections that predisposed the affected regions of the lung to EIPH. We have shown previously that during erythrophagocytosis in the alveolar space, there is a prolonged period of macrophage influx and activation. This present study used morphometric analysis to quantify the effects of macrophage activity during erythrophagocytosis, on the alveolar cell population and physical structure of the alveolar walls. Segments of the bronchial tree were inoculated with either autologous whole blood or serum, at 15, 8, 3 days, 24 h and 30 min prior to euthanasia. Blood inoculation produced many significant changes in the alveolar morphometry including, increased numbers of alveolar macrophages, increased septal thickness, and a markedly increased percentage of collagen in the alveolar walls. Signs of chronic inflammation including increased macrophage activity and erythrophagocytosis coincided with increased alveolar macrophage numbers (10,688 +/- 1708 cells/mm3 to 30,957 +/- 6831 cells/mm3), septal thickness (4.1 +/- 0.4 microm to 6.1 +/- 0.5 microm) and alveolar septal collagen content (6.6 +/- 0.5% to 27.5 +/- 3.3%). The results suggest that intrapulmonary blood induces a macrophage dominated inflammatory response, septal thickening and the development of alveolar fibrosis. These changes are the probable cause of the observed alveolar fibrosis and bronchiolitis that was once suspected to be the originating cause of EIPH.

Effects of exogenous insulin on glucose tolerance in alpacas.

OBJECTIVE: To evaluate the effects of exogenous insulin on clearance of exogenous glucose in alpacas. ANIMALS: 7 adult castrated male alpacas. PROCEDURE: Prior to each of 2 trials, food was withheld for 8 hours. Glucose (0.5 g/kg of body weight) was then administered by rapid IV infusion. During 1 of the trials, regular insulin (0.2 U/kg, IV) was also administered 15 minutes later. Blood was collected immediately before (0 minutes) and 15, 20, 25, 30, 45, 60, 90, 120, 180, and 240 minutes after glucose administration. Plasma concentrations of glucose and lactate were determined, and glucose fractional turnover rate and plasma half-life were calculated. RESULTS: Insulin treatment caused a significant increase in fractional turnover rate of glucose and plasma lactate concentration. Plasma glucose concentrations were less in insulin-treated alpacas from 30 minutes after glucose administration (15 minutes after insulin administration) until the conclusion of each trial, compared with nontreated alpacas. In addition, plasma glucose concentration in insulin-treated alpacas returned to baseline values 1 hour sooner than in the nontreated group. CONCLUSIONS AND CLINICAL RELEVANCE: Glucose uptake in alpacas improves after insulin treatment, suggesting that administration of exogenous insulin will increase the therapeutic and decrease the pathologic effects of exogenous glucose administered to hypoglycemic alpacas. However, alpacas and other New World camelids should be monitored carefully during treatment with glucose or insulin, because these species appear to be partially insulin resistant.

Functional and compositional changes in pulmonary surfactant in response to exercise.

Pulmonary surfactant from bronchoalveolar lavages was obtained from 2 groups of horses. A control group consisting of 6 healthy racehorses that were paddock-rested and lavaged weekly for 6 consecutive weeks were compared with an experimental group of 10 healthy racehorses, lavaged weekly the same period, consisting of a 5 week incremental-intensity treadmill training programme and one week post training paddock rest. Phospholipid content of lavage fluid was determined indirectly by phosphorus assay, and surfactant functional activity was determined by bubble surfactometry. Total cell counts and differential cell percentages of lavage fluid were adjusted to reflect the dilution of alveolar epithelial lining fluid (ELF) using the lavage/serum urea ratio, and data were analysed per volume of ELF. There was no change in phospholipid content for either group, but some horses had consistently greater amounts than did others, ranging from 17.2-64.4 micrograms/microliter. From the exercised group ELF had both increased nucleated cell numbers due to increased macrophage numbers, and increased numbers of erythrocytes. Surface tension increased significantly over the exercise protocol, but not in controls. Functional activity of surfactant varied between horses, independent of phospholipid content, with average values for individuals ranging 10.5-29.5 mN/m. We conclude that exercise of sufficient intensity to induce intrapulmonary haemorrhage also leads to functional decrease in surfactant activity, without affecting phospholipid content. This study also indicates that functional differences in surfactant exist between horses and may be a risk factor for development of exercise-induced pulmonary haemorrhage.

Sequential changes in bronchoalveolar cytology after autologous blood inoculation.

Six horses, free of recent exercise-induced pulmonary haemorrhage (EIPH), each had 8 bronchial segments inoculated with 40 ml of autologous blood lavaged on Days 3, 5, 7, 10, 14 and 21 after inoculation. The bronchoalveolar lavage (BAL) fluid samples were analysed, and total leucocyte counts and differential cell percentages determined. Statistical analysis of the differences between the 8 post inoculation and 1 pre-inoculation (control) lavage sites demonstrated an early neutrophilic response, rising from < 5% of alveolar leucocytes to 10% by 24-48 h post inoculation. As this response waned, macrophage numbers increased and persisted at mildly elevated levels for the remainder of the experiment. Small numbers of erythrophagocytes were observed prior to 3 days post inoculation, but their numbers increased 10-fold by Day 10. In the first 3 days, blood was observed endoscopically streaming from inoculated lung regions, suggesting that mucociliary clearance is a major mechanism of early erythrocyte clearance. However, both free and phagocytosed whole erythrocytes were recovered in lavages 14 days after inoculation with small numbers of erythrocytes still present at 21 days. We conclude that intrapulmonary blood provokes a mild, but prolonged inflammatory reaction and that the removal of alveolar haemorrhage is dependent on a combination of mucociliary clearance and phagocytic mechanisms. Erythrophagocytosis is slow to commence and the removal of blood prolonged, suggesting that horses in fast work, sufficient to induce EIPH, are unlikely to recover fully if intervals between strenuous work are less than 14 days.

Comparison of bronchoalveolar lavage findings and measurements of gas exchange during exercise in horses with poor racing performance.

Twenty-four Thoroughbred and twelve Standardbred racehorses aged between 2 and 6 years, presented for reported poor racing performance, underwent clinical exercise testing. During the last 10 s of exercise at each speed throughout an incremental speed exercise test on a treadmill inclined at a 10% slope, samples of arterial blood and expired gases were collected. Maximum oxygen uptake and the partial pressures of oxygen and carbon dioxide in arterial blood were determined. These values were compared between the two breeds of horses and also with reference to cytological findings of bronchoalveolar lavage samples, including neutrophil, erythrocyte and haemosiderophage percentage and the total nucleated cell concentration. The results revealed an inverse relationship (Spearman R = -0.45, p < 0.05) between the total nucleated cell count in bronchoalveolar lavage samples and arterial oxygen partial pressure during exercise at 11 m.s(-1). This result suggests that subclinical pulmonary disease may be a more important cause of poor racing performance than previously thought. Also of note was a positive correlation (Spearman R = 0.50, p < 0.05) between maximum oxygen uptake and the percentage of erythrocytes.

Equine bronchoalveolar lavage cytology: survey of thoroughbred racehorses in training.

Sixty-two Thoroughbred horses aged between 1 and 7 years in training in Sydney had bronchoalveolar lavage (BAL) samples collected for cytological examination. All horses, except the yearlings and those with a cough, had raced at the time of the examination and the trainers reported satisfactory performance. Free erythrocytes were found in 73% of samples and haemosiderophages in 90% of the samples, indicating immediate or past occurrences of exercise-induced pulmonary haemorrhage (EIPH). Bronchoalveolar fluid from the yearlings contained significantly less (P < 0.05) erythrocytes and haemosiderophages than samples from horses in other age groups. In the older horses, there was also more haemosiderin within the macrophages. No differences in BAL cytology could be attributed to gender, and there was no relationship between BAL cytology and racing performance. The main cytological findings were (mean +/- sd): total nucleated cells--832 +/- 578/microL with the main cell types being: macrophages--59 +/- 10% (haemosiderophages--20 +/- 24%); neutrophils--9 +/- 6%; lymphocytes--31 +/- 9%. The erythrocyte count was 10.3 +/- 17.7% of the total cell count. Horses with chronic coughing had a higher proportion of macrophages and a lower proportion of lymphocytes in the leucocytes obtained from BAL. There was a higher occurrence of EIPH detected in BAL findings than that previously reported when endoscopic examination has been used to diagnose EIPH. The occurrence and severity of EIPH as indicated by the BAL findings was found to be related to exercise intensity. The cytological findings were similar to those reported in horses in the northern hemisphere.(ABSTRACT TRUNCATED AT 250 WORDS)