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Equine recurrent airway obstruction (RAO) is thought to result from an aberrant immune response to inhaled antigens, modulated by T lymphocytes via the secretion of pro-inflammatory cytokines. However data relating to the phenotypes of the T lymphocytes present in peripheral blood and bronchoalveolar lavage fluid of RAO horses and their cytokine profiles are contradictory. The aim of this study was to further investigate the cytokine (IL-4, IL-5, IL-13 and INF-gamma) mRNA expression profile in peripheral blood lymphocytes and bronchoalveolar lavage lymphocytes from RAO and control horses, before and at 48 h after horses were exposed to hay/straw. In contrast to previous studies, cytokine expression was quantified in populations of CD4 and CD8 T lymphocytes which were purified using magnetic bead antibody cell separation. Hay/straw exposure induced clinical airway obstruction, airway neutrophilia and airway lymphocytosis in RAO horses, and, induced a mild, but significant, airway neutrophilia in controls. However, hay/straw exposure had no significant effect on peripheral blood lymphocyte or bronchoalveolar lavage lymphocyte cytokine expression in either group. In conclusion, RAO was not associated with alterations in lymphocyte cytokine expression that are consistent with Th1 or Th2 responses, but rather with a general down-regulation in expression of the measured cytokines in peripheral blood lymphocytes and bronchoalveolar lavage lymphocytes.

Summary Reasons for performing study: Horses housed in conventional stable environments are exposed to high dust loads. Longterm exposure to inhaled dust may lead to subclinical airway disease. Hypotheses: Airway inflammation and mucus accumulation are 1) common in asymptomatic well-performing sport horses, 2) increased in older compared to younger individuals and 3) correlated. Methods: Mucus quantity and quality (endoscopic scoring) and BALF differential cytology were assessed in 13 younger horses (mean age 5 years) and 13 older horses (mean age 15 years), which had no historical or clinical evidence of lower airway disease, were performing well and were housed permanently in a conventional stable environment. Results: 1) Airway inflammation and/or mucus accumulation were very common. All sport horses showed evidence of subclinical inflammatory airway disease (IAD). 2) Older horses, having been exposed for 10 more years to a conventional stable environment, did not show increased subclinical airway inflammation or mucus accumulation. The only differences between the age groups were increased BALF total and lymphocyte cell counts in the younger horses. 3) Mucus quantity and quality scores were not significantly correlated with each other or with BALF neutrophil percentages and absolute numbers. Conclusions: Although clinically healthy and performing well, all of the examined horses housed in a conventional stable environment showed evidence of IAD. The degree of IAD was not increased in older horses that had not developed clinical signs. Potential relevance: The effect of subclinical degrees of IAD on performance in dressage and show jumping should be investigated further to better understand the clinical significance of IAD in sport horses.

Tidal breathing flow-volume loop (TBFVL) indices in healthy horses and in horses suffering from mild and moderate to severe recurrent airway obstruction (RAO) were measured. In addition, the ability of these indices to differentiate healthy controls from horses with mild RAO by separating the horses according to their usage was investigated. The horses were assigned to three sporting categories: 1 Leisure horses; 2 Horses competing at events with a duration of more than five minutes (eventing, coaching and endurance); and 3 Horses competing at events with a duration of less than five minutes (dressage and show jumping). Flow-volume curves were recorded with an ultrasonic spirometer and TBFVL indices were calculated with specially dedicated software. The sporting usage of the horses had a significant effect on the differentiating ability of TBFVL indices in diagnosing different degrees of RAO. The index TIF50 differentiated control horses from horses with minor RAO in all sporting categories.

The elimination of carbon dioxide from the lung can be used to monitor ventilation and perfusion, and 99mtechnetium-diethylenetriaminepentaacetate (99mTc-DTPA) clearance is a highly sensitive index of alveolar epithelial integrity, which is a presupposition for effective gas exchange. The aim of this study was to determine whether a correlation exists between indices of lung function derived from the single breath diagram for CO2, and 99mTc-DTPA clearance in horses with chronic obstructive pulmonary disease. The rate of 99mTc-DTPA elimination was negatively and substantially correlated with the dead space according to Bohr's formula, and the physiological and alveolar dead space. Strong and significant correlations existed between the three dead space indices and the alveolar fraction of CO2, and the ratio A1/A2 as an index of alveolar efficiency. The associations found were dependent on the clinical status of health and the mode of calculation of 99mTc-DTPA alveolar clearance.

The shape of the volumetric capnogram is modified by airway obstruction, and the evaluation of this deformation could allow an indirect measurement of bronchial patency. The study included 35 horses; five horses without evidence of pulmonary disease (group I) and 30 horses suffering from different degrees of chronic obstructive pulmonary disease (COPD) (groups II–IV). Data of recorded CO2 and volume curves were off-line plotted and statistically analysed using regression analysis. Analyses were performed separately for fractions 25–95 % (VTE25–95), 25–50 % (VTE25–50) and 50–95 % (VTE50–95) of expiratory tidal volume. For VTE25–95 estimates of linear and quadratic regression parameters were significantly different between groups. For VTE25–50 linear terms were significant in all clinical groups and decreased considerably from group I to group IV. Linear and quadratic terms for VTE50–95 were significant in all clinical groups and increased with the severity of COPD. The difference of total expiratory CO2 volume was significant between all groups. Statistical analysis of the volumetric capnogram is a precise method for description of shape deformities of the single breath diagram for CO2 (SBD-CO2) in horses with COPD and global models including phase II and III of the SBD-CO2 are helpful in the detection of pulmonary function impairment. However, although the model of the statistical shape analysis of the SBD-CO2 is precise, it may not necessarily be a useful test to discriminate horses with minor, moderate and severe COPD for clinical use.

The incidence of a new, yet unassigned toxin type of Clostridium perfringens containing the genes for the α-toxin and the recently described β2-toxin in horses with intestinal disorders is reported. The study included 18 horses suffering from typical typhlocolitis, 7 horses with atypical typhlocolitis, 16 horses with other intestinal disorders, and 58 horses without intestinal disease. In total, 20 samples of ingesta of the small and large intestines, five biopsy specimens of the intestinal wall, and 74 fecal samples were analyzed bacteriologically. C. perfringens isolates were typed for the presence of the α-, β-, β2-, and ɛ-toxin and enterotoxin genes by PCR, including a newly developed PCR for the detection of the β2-toxin gene cpb2 . β2-Toxigenic C. perfringens was detected in samples from 13 of 25 (52%) horses with typical or atypical typhlocolitis, with a particularly high incidence in specimens of ingesta and biopsy specimens (75%), whereas only 6 of 16 specimens from horses with other intestinal diseases yielded β2-toxigenic C. perfringens . No β2-toxigenic C. perfringens was found in the samples from the 58 control horses, of which only one fecal sample contained C. perfringens type A. Among the samples from the 15 horses with fatal cases of typical and atypical typhlocolitis 9 (60%) were positive for β2-toxigenic C. perfringens , whereas samples from only 4 of the 10 (40%) animals with nonfatal cases of infection were positive. We found an interesting correlation between the antibiotic-treated horses which were positive for β2-toxigenic C. perfringens and lethal progression of the disease. No C. perfringens strains isolated in this study contained genes for the β- and ɛ-toxins and enterotoxin. The high incidence of β2-toxigenic C. perfringens in samples of ingesta, biopsy specimens of the intestinal wall, and feces from horses suffering or dying from typhlocolitis together with the absence of this organism in healthy horses provides strong evidence that β2-toxigenic C. perfringens play an important role in the pathogenesis of typhlocolitis.

SUMMARY Lymphocytotoxic alloantibodies have been recognized in primiparous mare sera and colostra using the two-step microcytotoxicity test. The antigens detected on the leukocyte membrane do not occur on the erythrocytes. After testing on a cell panel from unrelated horses, absorptions with leukocytes were carried out. The subsequent retesting of the serum reagents on a cell panel including cells from 24 families rendered possible a grouping of preliminary monospecific reagents characterizing 18 antigen specificities on the cell membrane.

Muscle samples were taken from the superficial part of the semitendinosus muscle of four standardbred horses to compare the effects of three different fixation procedures on fiber size and capillarity. Infiltration fixation in an extended position of the muscle was compared to immersion fixation and infiltration fixation in a flexed position of the limb. The capillary length density was used to estimate muscle capillarity. Infiltration fixation was found to be a viable alternative to perfusion fixation of muscles for morphometry of fiber size and capillary length density allowing muscle tissue fixation at a defined sarcomere length without fiber kinking.

To investigate changes in the ultrastructure of the different muscle fiber types induced by endurance training ten sedentary subjects (five women and five men) were exercised on bicycle ergometers 5 times a week for 30 min. After 6 weeks of training there were significant changes in\(\dot V_{{\text{O}}_{{\text{2max}}} } \) (+14%), in the percentage of type I (+12%) and type IIB fibers (−24%) as well as in the volume densities of mitochondria. The latter increased 35% in type I, 55% in type IIA and 35% in type IIB fibers. The relative increase in subsarcolemmal mitochondria was larger than in interfibrillar mitochondria in all fiber types. There was also a significant increase in the volume density of intracellular lipid in type II fibres. It is concluded that high intensity endurance training leads to an enhancement of the oxidative capacity in all muscle fiber types.

The distribution of equine leucocyte antigens (ELA) in horses affected by equine sarcoid tumours was determined and compared with unaffected controls. ELA-haplotype W3,B1 occurred more frequently in affected riding horses of Irish, Swiss and French background. The combined data for the three breeds resulted in a chi 2 value of 20.35 (P less than 0.0005 after correction). Simultaneously, ELA-specificity W11 was more frequently found in horses of Irish background, while W5 was found in Swiss and French horses with sarcoids. The combined data for haplotype W3,B1 and/or W5 specificity demonstrated, in the genetically closely-related Swiss and French horses, a highly significant difference in the occurrence of these haplotypes between affected horses and healthy controls (chi 2 = 28.69, P less than 0.00001 after correction). Thus, the results strongly suggest that the predisposition of horses to sarcoid is associated with or linked to the major histocompatibility complex.