A review of environmental and host factors in relation to equine respiratory disease

Does housing system affect horse welfare? The AWIN welfare assessment protocol applied to horses kept in an outdoor group-housing system: The 'parcours'

Outdoor group housing is generally reported as being beneficial to the welfare of horses compared to single boxes, being considered to show greater similarities with the living conditions of feral horses, allowing full expression of behaviours such as grazing, social interactions and free movement. However, concerns persist regarding the ability to maintain a good nutritional state and the possibility of acquiring injury. No data reporting a comprehensive assessment of welfare for horses in outdoor group-housing systems are currently available. The present study aimed at applying a scientifically valid welfare assessment protocol to group-housed outdoor horses in 'parcours', a particular management system used in the south of France. 'Parcours' are semi-natural areas, grazed by domestic herbivores located in lowland, mountain, or marsh. One hundred and seventy-one horses older than a year pertaining to six farms and kept on 'parcours' were evaluated by a trained veterinarian using a modified version of the second level Animal Welfare Indicators (AWIN) welfare assessment protocol for horses. No major welfare issues were detected. Horses in 'parcours' displayed few abnormal behaviours, they could move freely for most of the day and interact with conspecifics, maintaining a healthy state of nutrition and a good relationship with humans. The main welfare concerns were related to the presence of superficial integument alterations such as alopecia, difficulty in reaching quality controlled water sources and a lack of shelter. As the number of facilities involved in this study is relatively limited, further harmonised data collection should aim to enlarge the sample size and allow comparison with different outdoor group-housing conditions.

Nicoletella semolina in the airways of healthy horses and horses with severe asthma

Background

Nicoletella semolina was identified in the airways of horses and its low prevalence could be because of its difficult differentiation from other Pasteurellaceae.

Objectives

To develop a molecular method for the identification of N. semolina and to evaluate its prevalence in the mouth and the airways of healthy and severe asthmatic horses.

Animals

Six healthy and 6 severely asthmatic horses in phase I, 10 severely asthmatic horses in phase II, and 10 healthy horses in phase III.

Methods

Cohort (phases I and II) and cross‐sectional (phase III) studies. Quantitative polymerase chain reaction primers targeting the sodA gene were optimized. N. semolina was quantified in oral and nasal washes and in bronchoalveolar lavage fluid (BALF; phase I, sampled twice), in nasal washes and BALF (phase II, sampled twice), and in nasal washes (phase III).

Results

N. semolina was found in the nose of 5, 10, and 9 horses in phases I, II, and III, respectively (first sampling for phases I and II). Six BALF from 5 different horses were positive for N. semolina in phase II. In phase I, there was no significant difference in the nasal loads of healthy horses (median (range): 2.04 × 10⁴ copies/mL (0‐2.44 × 10⁵)) and asthmatic horses in exacerbation (3.75 × 10² (0‐4.84 × 10⁶); Wilcoxon's rank sum test, P = .57).

Conclusions and Clinical Importance

N. semolina is commonly found in the airways of horses. The potential pathogenicity of N. semolina remains to be elucidated, but the molecular technique we developed will facilitate future studies.

Case-Control Study of Risk Factors for Equine Asthma in Texas

Equine asthma is a common condition in horses, for which few host-related risk factors have been identified. The objective of this study was to identify host-related risk factors for the development of equine asthma. A retrospective, case-control study was performed, utilizing horses presented to the Texas A&M University, Veterinary Medical Teaching Hospital from January 2014 December 2018. Incident cases of mild to severe equine asthma (n = 37), diagnosed clinically with cytologic support of disease were examined. For each case, two control populations were identified, including one temporal control (n = 37) and one age-matched control (n = 37). Data collected included signalment, dietary and stable management, prior medical history, metabolic status, physical examination findings, and results of cytologic evaluation via bronchoalvelolar lavage or tracheal wash. Conditional logistic regression was used to compare data on equine asthma cases with data from each set of controls. Results indicated that obesity (Body Condition Score ≥ 7) was the only statistically significant risk factor for equine asthma in this population of horses. These results may aid in identification of targets for management, prevention, and further investigation into the pathogenesis of equine asthma. Early identification and intervention of horses at risk of lower airway disease could ameliorate the impact of disease.

Effect of air temperature and humidity in a stable on basic physiological parameters in horses

The aim of the study was to analyse selected air parameters in a stable (microclimate) and the basic physiological parameters of horses housed in the stable in different seasons of the year. The research material was 12 adult hot-blooded horses kept in a brick stable with stalls. Air parameters in the stable (temperature in the passageway, temperature in the stall at two points, relative humidity in the passageway, and relative humidity in the stall at two points) were determined four times in one year, in summer, autumn, winter and spring. Measurements were made with a Bluetooth BLE-LOGGER LB-518 battery-operated cordless thermo-hygrometer at 12 noon at five points in the stable located 300 cm apart. Physiological parameters of the horses, i.e. internal body temperature (Veterinär SC 12 veterinary thermometer), heart rate (Polar ELECTRO OY RS800CX with PolarProTrainer 5.0. software), and respiratory rate (with a manual stopwatch) were measured at 6 a.m. and 6 p.m. on each day of the study. The season of the year was found to have a significant influence on the microclimate of the stable. To ensure optimal air humidity, airing of the stable should be limited only in winter and periodically in autumn. It is also worth emphasizing that the stable microclimate has a marked effect on the basic physiological parameters of horses. High temperature and relative humidity in the stable can cause unfavourable changes in the form of an increase in evening body temperature in the summer and a decrease in the winter. The remaining parameters, i.e. heart rate and respiratory rate, can also unfavourably increase, mainly in the summer. Horses should have fewer problems maintaining normal physiological parameters in winter, even fewer in autumn, and the fewest in spring.

Prevalence of upper respiratory diseases and associated factors in Colombian Creole horses

ABSTRACT To determine the prevalence of diseases of the upper respiratory tract and associated factors in the Colombian Creole Horse Valley Aburrá in 2015, a random sampling of 15 farms in southern Aburrá Valley under different management conditions was performed. A total of 105 CCC underwent general clinical examination, respiratory endoscopic evaluation and a detailed inspection of housing conditions and management. A low prevalence of upper respiratory tract diseases was observed, including Pharyngeal Lymphoid Hyperplasia 38.1%, Recurrent Laryngeal Neurophaty 12.38%, Dorsal Displacement of the Soft Palate 7.62%, and presence of tracheal secretions not associated with a specific pathology. A bivariate analysis showed association between tracheal secretions and frequency of training per week (OR = 9.86), duration of the training sessions (OR = 5.55) and inadequate ventilation of the stable (OR = 10.52). Association between HLR and inadequately ventilated barns was also observed (OR = 14.9). Logistic regression showed association between tracheal secretions and inadequate ventilation (OR = 7.18). We conclude that inadequate ventilation was the most important factor for the incidence of upper respiratory tract diseases in horses at the southern area of the Aburrá Valley.

Reducing exposure to pathogens in the horse: a preliminary study into the survival of bacteria on a range of equine bedding types

AIMS

To compare the rate of growth of four microbial strains that cause disease in the horse, on four commonly used types of bedding. The moisture-holding capacity of each bedding type was also tested.

METHODS AND RESULTS

Microbial strains included Streptococcus equi, Streptococcus zooepidemicus, Fusobacterium necrophorum, Dichelobacter nodosus and Dermatophilus congolensis. The bedding types tested were Pinus sylvestris (Scots pine shavings), Pinus nigra (Corsican pine shavings), Picea sitchensis (Sitka spruce shavings), Cannabis sativa (hemp) and chopped wheat straw. A suspension of each microbial strain was spread in triplicate on agar media and incubated in its optimal growth conditions. The viable count (colony-forming unit per ml) was determined for each bacterial strain for the five different bedding types. Pinus sylvestris bedding resulted in significantly less (P = 0·001) bacterial growth of all strains tested.

CONCLUSIONS

Factors resulting in the inhibition of bacterial growth include the antibacterial effects reported in the Pinacea family and the physical properties of the bedding substrate. Research is currently focussed on the diagnosis and management of disease. Prevention of disease is also important for matters of biosecurity. Strategies should include the provision of a hygienic environment and the use of specific types of bedding.

SIGNIFICANCE AND IMPACT OF THE STUDY

Bedding choice has implications for global equine health and disease prevention as well as potential benefits in other animal species.

Thoroughbred bedding preferences, associated behaviour differences and their implications for equine welfare

Choice tests are an effective means of assessing the short-term environmental preferences of captive animals. The preferences shown by eight thoroughbred horses (Equus caballus) for three commonly used bedding materials (paper, straw and shavings) were investigated. For each preference test two choices were presented in separate boxes joined by an unbedded corridor. Time spent in each compartment and associated behaviours were recorded. Despite a positional bias, horses clearly showed a preference for straw bedding (42·9 (s.e. 3·6) %) over shavings (35·2 (s.e. 3·4) %, P < 0·05), straw (42·0 (s.e. 37) %) over paper (29·3 (s.e. 3·4) %, P < 0·05) and shavings (41·6 (s.e. 4·3) %) over paper (27·7 (s.e. 3·7) %, P < 0·001) based on percentage of observed time spent on the substrate. Straw bedding increased the occurrence of bedding related activities, with more of these activities in choices where straw was available (P < 0·001) and in these choices the activities being preferentially expressed in the straw alternative (P < 0·001). Straw may therefore be preferred as it allows the expression of a wider number of motivationally significant activities.

Can insecticide-treated netting provide protection for Equids from Culicoides biting midges in the United Kingdom?

Background

Biting midges of the genus Culicoides Latreille, 1809 (Diptera: Ceratopogonidae) cause a significant biting nuisance to equines and are responsible for the biological transmission of African horse sickness virus (AHSV). While currently restricted in distribution to sub-Saharan Africa, AHSV has a history of emergence into southern Europe and causes one of the most lethal diseases of horses and other species of Equidae. In the event of an outbreak of AHSV, the use of insecticide treated nets (ITNs) to screen equine accomodation is recommended by competent authorities including the Office International des Épizooties (OIE) in order to reduce vector-host contact.

Methods

Seven commercially avaliable pyrethroid insecticides and three repellent compounds, all of which are licensed for amateur use, were assessed in modified World Health Organization (WHO) cone bioassay trials in the laboratory using a colony line of Culicoides nubeculosus (Meigen), 1830. Two field trials were subsequently conducted to test the efficiency of treated net screens in preventing entry of Culicoides.

Results

A formulation of cypermethrin (0.15 % w/w) and pyrethrins (0.2 % w/w) (Tri-Tec 14®, LS Sales (Farnham) Ltd, Bloxham, UK) applied to black polyvinyl-coated polyester insect screen (1.6 mm aperture; 1.6 mm thickness) inflicted 100 % mortality on batches of C. nubeculosus following a three minute exposure in the WHO cone bioassays at 1, 7 and 14 days post-treatment. Tri-Tec 14® outperformed all other treatments tested and was subsequently selected for use in field trials. The first trial demonstrated that treated screens placed around an ultraviolet light-suction trap entirely prevented Culicoides being collected, despite their collection in identical traps with untreated screening or no screening. The second field trial examined entry of Culicoides into stables containing horses and found that while the insecticide treated screens reduced entry substantially, there was still a small risk of exposure to biting.

Conclusions

Screened stables can be utilised as part of an integrated control program in the event of an AHSV outbreak in order to reduce vector-host contact and may also be applicable to protection of horses from Culicoides during transport.

Risk factors associated with health disorders in sport and leisure horses in the Netherlands

Horses are used for a wide variety of purposes from being used for recreational purposes to competing at an international level. With these different uses, horses have to adapt to numerous challenges and changes in their environment, which can be a challenge itself in continuously safeguarding their welfare. The objective of this study was to assess the prevalence of health disorders with clinical examination and identify possible risk factors of health disorders affecting horse welfare in professional husbandry systems in the Netherlands. With the use of fixed protocols for recording health aspects in horses, 150 horse farms voluntarily participating in the study were assessed by trained assessors. On each farm, 20 horses were clinically examined, in total almost 3,000 animals. This study recorded on the basis of the clinical examinations: the respiratory system (i.e., abnormal breathing [1%], coughing [1%], nasal discharge [1.9%]), body condition (i.e., 18.8% fat body condition and 6.4% poor body condition), locomotion (14.5% exhibited irregularity of locomotion and 4.8% were lame), back palpation (a light response [22.6%] and moderate to severe response [8.4%]), mouth (i.e., irregularities on mouth corners [3.4%] and bars [3.4%]), and ocular discharge (12%). Risk factor analysis, stepwise using mixed model regression, demonstrated several risk factors for health aspects. Horses used for instruction (riding lessons) were almost two times more at risk to develop moderate to severe back pain compared to horses used for recreation (odds ratios [OR] = 0.54) or for competition (OR = 0.61). Horses used for instruction (riding school lessons), breeding, or recreation all had a higher risk for irregular locomotion or lameness compared to competition horses (OR = 0.42, OR = 0.55, OR = 2.14, respectively). Horses used for recreation were more prone to have a higher BCS compared to horses used for breeding (OR = 3.07) and instruction (OR = 2.06). The prevalence of health problems and the identified risk factors are valid for the horses in the present study in which farms voluntarily participated. Furthermore, the results may provide the basis for horse welfare and health programs on farm and horse industry levels. With the development of a valid welfare monitoring system for the horse industry, the welfare of horses can be increased through improving awareness and stimulating changes in management.

Effects of soaking hay fodder for horses on dust and mineral content

Four bales of hay were chosen from a stack of hay, barn-stored for 6 months. Each bale was subdivided into four 2·5 kg sections and one section from each bale was subjected to one of four water soaking treatments: 0, 0·5, 3 or 12 h. Post treatment, the samples were shaken for 9 min under a Negretti LS45F personal dust sampler which sampled the surrounding air. The samples were than analysed for levels of respirable particules < 5 μm in size and for amounts of sodium (Na), potassium (K), phosphorus (P), magnesium (Mg), calcium (Ca) and nitrogen (N). Soaking for 30 min reduced the number of respirable particles by about 90% but also reduced the Na, K and P content of the hay. Soaking for a longer period, at least up to 12 h, did not give a significant further reduction in number of respirable particles but there was loss of Mg and further losses in Na, K, and P. These results clearly indicate that soaking for 30 min is sufficient to reduce the respirable challenge with minimum nutrient loss.

Hay for horses: the effects of three different wetting treatments on dust and nutrient content

Five bales were randomly chosen from a stack of 6-month-old barn-stored hay. Four 2·5-kg sections were taken from each bale and subjected to one of four different water wetting treatments, 0-min soak, 10-min soak, 30-min soak and 80-min steaming. Post wetting, the sections were shaken for 9 min under a Negretti LS45F personal dust sampler which sucked-in any particles released into the surrounding air. The sampler contents were then analysed for respirable particle numbers (particles < 5um), and the hay subsampled and analysed for water-soluable carbohydrate, N, Na, K, Ca, P, Mg, Zn, Mn, Fe and Cu. The steaming and soaking treatments all proportionately reduced respirable particle numbers by more than 0·93 of those present in the dry hay. Soaking for 10 min and 30 min significantly reduced levels of P, K, Mg, Na and Cu, whereas the steamed samples showed no loss of nutrients from the levels present in the dry hay. Thus in terms of reducing respirable particle numbers and conserving nutrient levels, steaming for 80 min is the most effective treatment when preparing hay fodder for horses.

Suitability of biocompost as a bedding material for stabled horses: respiratory hygiene and management practicalities

REASONS FOR PERFORMING STUDY

Bedding material in stables has an important influence on air hygiene and information on the suitability of biocompost and wood shavings is incomplete.

OBJECTIVES

To compare the suitability and benefit of biocompost and wood shavings as bedding in horse stables and to determine key air factors for the evaluation of the potential impact of these materials on respiratory health.

METHODS

The study was conducted in a naturally ventilated stable with 4 horses. Air hygiene parameters were measured 24 h/day for 7 days with each bedding type: ammonia (NH3), inhalable and respirable dust, endotoxins, colony forming units (CFU) of total mesophilic bacteria, fungi, actinomycetes and thermophilic actinomycetes. Both bedding materials were analysed for general chemical composition, particle size distribution and natural microbial content. The animals' behaviour was monitored by video cameras, and their health and cleanliness status determined by clinical and visual examination.

RESULTS

Concentrations of NH3, dust, endoxins and fungi were significantly higher during the monitoring period with wood shavings than with biocompost. In contrast concentrations of mesophilic bacteria, mesophilic actinomycetes and thermophilic actinomycetes microbial pollutants were highest with biocompost. The water content of bulk biocompost was considerably higher than that of wood shavings. Particles < or = 0.4 mm were not detectable in bulk wood shavings. The concentration of thermophilic actinomycetes by weight in raw biocompost was 639 times higher than in raw wood shavings. No significant differences were observed in the time spent by the horses lying down. The biocompost material tended to adhere more intensively to the animals' hair coat. Horses showed no clinical signs indicating any adverse effects of the biocompost material during the trials.

CONCLUSIONS

Biocompost cannot be recommended as bedding material for horses in stables, because the concentration of thermophilic actinomycetes and other agents that elicit and maintain recurrent airway obstructions was significantly higher with biocompost than with wood shavings. To ensure the well-being of horses, any new bedding material must be tested very carefully before it is introduced to the market.

Climatic and aeroallergen risk factors for chronic obstructive pulmonary disease in horses

OBJECTIVE

To estimate the association between climate and airborne pollen and fungal factors and chronic obstructive pulmonary disease (COPD) in horses.

SAMPLE POPULATION

Data from 1,444 horses with a diagnosis of COPD.

PROCEDURE

The Veterinary Medical Database was used to identify records of horses admitted to veterinary teaching hospitals in the United States and Canada between 1990 and 1999. Rainfall, mean minimum and maximum temperature, and maximum monthly pollen and fungal spore (mold) counts recorded at the city closest to where the hospital is located were identified for each month data were reported to the Veterinary Medical Database. Associations between climatic and aeroallergen data and monthly prevalence of COPD were estimated by use of cross-correlation and logistic regression models.

RESULTS

Significant positive correlations were found between prevalence of COPD and rainfall 3 months previously, minimum temperature 1 and 2 months previously, total pollen counts measured 3 months previously, and total mold counts measured during the same month and 1 month previously.

CONCLUSIONS AND CLINICAL RELEVANCE

Outdoor aeroallergens and climatic factors may contribute to the occurrence of COPD in horses.

A preliminary analysis of the process of protein secretion and the diversity of putative secreted hydrolases encoded inAspergillus fumigatus: insights from the genome

The genome sequence of Aspergillus fumigatus has enabled the annotation of genes likely to encode secreted enzymes that may be important in underpinning the natural lifestyle of the fungus and its pathogenicity. We summarize the data from the genome sequence relevant to both the process of protein secretion and the predicted hydrolase enzymes secreted by A. fumigatus.

Analysis of risk factors for recurrent airway obstruction in North American horses: 1,444 cases (1990-1999)

OBJECTIVE

To identify risk factors for recurrent airway obstruction (RAO) among horses examined at veterinary teaching hospitals in North America.

DESIGN

Retrospective case-control study.

ANIMALS

1,444 horses with RAO and 1,444 control horses examined for other reasons.

PROCEDURE

The Veterinary Medical Database was searched for records of horses in which RAO was diagnosed. A control group was identified by randomly selecting a horse with a diagnosis other than RAO that matched the institution and year of admission for each of the horses with RAO. Information obtained included hospital, admission year and month, age, sex, breed, and discharge status. The association between risk factors and diagnosis of RAO was estimated with logistic regression models.

RESULTS

The risk of RAO increased significantly with age, with horses > or = 7 years old being 6 to 7 times as likely to have RAO as were horses < or = 4 years old. Thoroughbreds were 3 times as likely to have RAO as were ponies. Horses were 1.6 and 1.5 times as likely to be examined because of RAO during winter and spring, respectively, than they were during summer.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that RAO was more likely to be diagnosed in females, horses > or = 4 years old, and Thoroughbreds and that RAO has a seasonal distribution.

Comparison of tracheal aspirates and bronchoalveolar lavage in racehorses 2. Evaluation of the diagnostic significance of neutrophil percentage

OBJECTIVE

To determine whether diagnosis of airway inflammation, using cut-off percentages for neutrophils, differs when based on samples from tracheal aspirate (TA) and bronchoalveolar lavage (BAL) collected concomitantly from the same racehorse.

DESIGN

Retrospective case series of 48 young Thoroughbred and Standardbred racehorses in race training, but showing poor performance. PROCEDURE TA and BAL samples were collected from all horses 1 to 2 h after high-speed treadmill exercise. Aliquots of the retrieved fluid were cytocentrifuged and smears stained with Diff-Quik. The mean percentage of neutrophils was calculated. Diagnostic cut-off points were set at 20% for TA samples and 5% for BAL samples. Agreement in the interpretations between the two techniques was analysed.

RESULTS

In 19 of 51 paired samples (37%) there were differences in diagnostic interpretation between TA and BAL samples. Of these, airway inflammation was indicated only by the TA sample in 13 and only by the BAL in 6.

CONCLUSION

TA and BAL samples give important information about different regions of the airway, but neither should be used alone for the diagnosis of inflammation of the entire lung. The limitations of these procedures mean that both samples should be collected when it is desired to cytologically evaluate the entire lower airway.

Nutrition and feeding of the geriatric horse

Little is known regarding nutrient requirements and feeding of geriatric horses, and more effort should be placed on this area of equine nutrition research. That which is known suggests that some geriatric horses may not have different requirements than other mature horses, whereas others affected by disease or poor dentition may have special nutritional needs. In general, rations for geriatric horses should be based on high-quality roughage supplemented with complementary minerals and vitamins. The need for additional energy aside from that provided by the forage can be supplied by adding energy concentrates, such as cereal grains or fat, to the ration. Processing techniques involving heat, such as pelleting and extruding, are advised when cereal grains are included in the ration so as to improve starch digestibility in the small intestine and avoid starch overload in the hindgut and it subsequent problem (ie, colic, laminitis). In addition, the environment in which geriatric horses are fed should be one that promotes ease of ration consumption and eliminates factors thar impair feed consumption, such as competition from other horses and the need to travel relatively long distances (eg, grazing marginal pastures). Finally, strict attention should be paid to the body condition of geriatric horses so as to evaluate adequacy of the ration and the general health of the horse.

Environmental control to maintain stabled COPD horses in clinical remission: effects on pulmonary function

The objective of this study was to test the hypothesis that stabled COPD horses can be maintained in clinical remission by replacing hay by grass silage and bedding made of wood shavings (Period B) and of wheat straw (Period C) during 6 weeks, respectively. At the end of these different periods, the pulmonary function of the horses was assessed by mechanics of breathing and arterial blood analyses. These results were compared to those measured in clinical remission obtained after 2 months in pasture (Period A). No significant difference was observed between these 3 periods neither to values obtained for healthy horses placed during 6 weeks in a hay environment. For all that, COPD horses placed in contact with hay in the same barn developed within mean +/- s.d. 8+/-3 days clinical signs of heaves and significant alterations of pulmonary function parameters.

The use of Baypamun N in crowding associated infectious respiratory disease: efficacy of Baypamun N (freeze dried product) in 4-10 month old horses

The efficacy of an immunomodulator, Baypamun N, was tested in 4-10-month-old horses which were exposed to stress by weaning, transport and commingling with yearlings from different breeders (crowding). Verum (n = 26) and placebo animals (n = 27) received three intramuscular injections of the investigational preparations (days 0, 2, 9) starting at the day of commingling in one stable. The incidence of acute respiratory disease was high during the first 4 weeks after commingling. Approximately 50% of all horses showed seroconversion due to field infection by EHV1 and EHV4 during the observation period. The clinical scores in the Baypamun N group were significantly reduced by 40.3% (P < 0.05) compared to the placebo group. The proportion of horses with purulent nasal discharge during the observation period (4 weeks) was also significantly reduced by 58.7% (P < 0.01) in the Baypamun N group. Fifty per cent of the horses injected with Baypamun N showed no purulent nasal discharge and therefore no signs of complicated disease of the upper respiratory airways in contrast to only 14.8% in the non-protected placebo group. The challenge conditions studied in this investigation were rather severe because of the permanent exposure of Baypamun N treated individuals to the non-separated and untreated horses (n = 51). This indicates that treatment with Baypamun N is a successful tool to avoid severe clinical consequences of stress in young horses.

Equine pulmonary disease: a case control study of 300 referred cases. Part 2: Details of animals and of historical and clinical findings

Examination of historical and clinical details of 270 adult horses suffering from a variety of mainly chronic pulmonary diseases showed that the chronic obstructive pulmonary disease (COPD) group (median age 9 years) were the oldest, and that the COPD, chronic idiopathic hypoxaemia and exercise induced pulmonary haemorrhage (EIPH) groups had the longest duration of disease (median durations 7, 12 and 9 months, respectively) with a median disease duration of 2 months for the remaining horses. A history of antecedent respiratory infection was present in 24.3% of all horses. Six out of 12 horses that grazed with donkeys suffered lungworm infection. Silage was fed to 11.3% of all horses, nonstraw beddings were utilised by 28.7% of horses and 8.7% of horses were maintained permanently outdoors. Environmental control had been unsuccessfully attempted in 47% of COPD cases prior to referral. Histories of poor athletic performance or of excessive post exercise dyspnoea were found to be less definitive indicators of pulmonary disease. Coughing was the most sensitive clinical indicator of pulmonary disease, being present in 71.1% of horses with pulmonary disorders. Nasal discharge was present in 50.4% of these horses and coughing or nasal discharge was present in 86.7% of horses with respiratory disorders. Unilateral nasal discharge was inexplicably present in 3.3% of horses with pulmonary disease. Other clinical findings, including the presence of increased breathing effort, abnormal thoracic or tracheal auscultatory findings were less sensitive diagnostic parameters with pulmonary diseases, and were frequently absent unless severe pulmonary disease was present.

Equine pleuropneumonia

Pleuropneumonia is a clinically important equine disease, predisposed by a number of identifiable factors. Successful management is largely dependent on early identification and prompt initiation of appropriate treatment strategies. Rapid resolution of the disease process is associated with appropriate treatment commenced within 48 h of the causative insult. Lower airway contamination by oropharyngeal organisms and subsequent extension into the pulmonary parenchyma results in respiratory dysfunction and systemic toxaemia. Acute disease is associated with the isolation of facultatively anaerobic organisms, especially beta-haemolytic Streptococcus spp. and Pasteurellaceae. Delayed or inappropriate treatment is likely to result in chronic disease characterized by the involvement of anaerobic bacteria and a poor response to therapy. The primary mode of treatment for anaerobic infection of the human thorax is surgical drainage and resection of necrotic tissue but whilst such techniques have been described for the management of equine pleuropneumonia, the size of the equine thoracic cavity hinders accurate diagnostic evaluation and successful completion of such intervention. The chronic nature and cost of ongoing treatment and limitations on choice of antimicrobial agents warrant a poor prognosis for survival and a poorer prognosis for return to athletic endeavour.

Airborne dust and aeroallergen concentration in a horse stable under two different management systems

Airborne dust concentration (ADC) was measured in 2 different horse management systems using an Andersen cascade impactor in the box-stall, and a personal Marple cascade impactor attached to the halter to measure ADC in the breathing zone. The levels of aeroallergens implicated in chronic obstructive pulmonary disease were measured by radioallergosorbent-inhibition immunoassay. A conventional management system (System C) utilising hay feed and straw bedding, and a recommended environment (System R) utilising wood shaving bedding and a complete pelleted diet were studied. In the stall, total and respirable ADC (geometric mean) were significantly higher in System C (2.55 mg/m3; 0.44 mg/m3, respectively) than in System R (0.70 mg/m3; 0.20 mg/m3, respectively). In System C, the total and respirable ADC in the breathing zone (17.51 mg/m3; 9.28 mg/m3) were much higher than in the stall, but values in both regions were similar in System R (0.52 mg/m3; 0.30 mg/m3). Major aeroallergens were significantly higher in System C than in System R: Micropolyspora faeni (1423 ng/m3 and 705 ng/m3), Aspergillus fumigatus (1823 ng/m3 and 748 ng/m3), and mite allergens (1420 ng/m3 and 761 ng/m3). Measurement of ADC with personal samplers indicates that the very high inhalation challenge in the breathing zone is not reflected in measurements of stall air quality. When compared with System C, System R produced only 3% of the respirable dust burden in the breathing zone and a decreased aeroallergen challenge.

The genetic basis of equine allergic diseases. 1. Chronic hypersensitivity bronchitis

The genetic influence on chronic hypersensitivity bronchitis (CB) was investigated in families at two studs and among half-siblings of three affected and three non-affected sires at several farms. The family members at the two studs were born and raised under the same conditions, whereas the half-siblings were kept individually under very different conditions and were exposed to various environmental factors. The diagnosis was based on long-term observations and multiple clinical examinations at each of the two studs. In the half-sibling group, the diagnosis was based on the individual history and on a thorough clinical examination. The history of all horses suggested the disease was caused by allergies (symptoms provoked by hay). Statistical analysis of the data in the first study showed that a greater percentage of off-spring of two affected parents developed CB (9 of 13) than those with only one affected parent (23 of 48) and those with two healthy parents (5 of 29). The distributions of the affected offspring in these three categories (none, one or both parents affected) differed significantly (P less than 0.005) from what would have been expected without a genetic effect. The tendency to develop the disease was inherited equally from dams or sires. In the second stud fewer animals (n = 42) were included in the study, but the results were similar. Parents without a history of CB produced off-spring with a low incidence of disease (1 of 16) compared with a higher incidence among descendants of one or two affected parents (10 of 26; P = 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

Environmental effects on thermoregulation and nutrition of horses

Horses are reared in all types of weather. Temperatures as diverse as -40 degrees C to 40 degrees C are tolerated by horses. The nutrient requirement most influenced by cold weather is energy. In cold weather, feeding good quality hays free-choice is usually sufficient for mature horses in good body condition. Grain may have to be fed when poor quality hays are used. Hot weather (greater than 30 degrees C) necessitates heat loss to maintain body core temperature. Horses sweat to reduce body heat. Heat stress can be minimized by feeding diets that reduce the heat increment. Use of grain and fat in the diet, which have a lower heat increment than fibrous feeds such as hays, may benefit horses in hot climates. Wind or precipitation necessitate protection to minimize chilling in cold weather and discomfort in hot weather. However, it is a moot point whether horses will use shelters under these circumstances.