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Summary: It has been proposed that synaptophysin, an abundant integral membrane protein of synaptic vesicles, is an immunohistochemical marker for degenerating neurons in equine grass sickness (GS). In the present study, a statistically generated decision tree based on assessment of synaptophysin-immunolabelled ileal sections facilitated correct differentiation of all 20 cases of GS and 24 cases of non-GS disease (comprising eight horses with colic, six with neuroparalytic botulism and 10 controls). This technique also facilitated correct diagnosis of GS in all three cases that had been erroneously classified as having non-GS disease based on conventional interpretation of haematoxylin and eosin-stained cryostat sections of ileal surgical biopsies. Further prospective studies involving larger numbers of horses are required to fully validate this decision tree. In contrast to GS, botulism did not alter ileal neuron density or synaptophysin labelling, indicating that different mechanisms cause neuronal damage and/or dysfunction in GS and botulism. [Copyright &y& Elsevier]

Abstract: The effect of soaking hay to minimise equine breathing zone respirable dust concentration (RDC) is unknown, as is the duration of soaking required. Additionally, the influence of the bedding and forage used in one stable on the mean and maximum RDC in a neighbouring stable within a common airspace is unknown. Consequently, in the management of equine environmental respiratory disease uncertainty remains about the necessity for optimising conditions in neighbouring stables. Investigations using a real-time continuous particle monitor revealed that when feeding hay, horses’ mean breathing zone RDC was significantly reduced if the hay was immersed or soaked for a prolonged time, prior to feeding. There was no advantage in soaking for an extended time period. Implementing management changes in one stable (changing from straw bedding and hay feeding to wood shavings bedding and haylage feeding) significantly reduced mean and maximum background RDC in a neighbouring stable within a common airspace. [Copyright &y& Elsevier]

Abstract: Traditional methods of measuring airborne dust concentrations (ADC) in animal housing have included the collection of dust onto pre-weighed filters permitting the calculation of mean, not maximum, ADC. However real-time continuous particle monitors are advantageous in identifying short duration elevations in ADC which may be detrimental to equine respiratory health in the face of a relatively low mean ADC. These monitors have not previously been used to measure ADC in equine stables. Comparisons of a filter-based sampler and a real-time continuous particle monitor revealed no significant difference (P =0.079) and good agreement (⩾95% of the points fell within two standard deviations of the mean of the differences and the mean of the differences approximated zero) between the devices, with respect to mean respirable dust concentration (RDC) measurements. Investigations of the influence of various equine management systems on RDC revealed that both mean and maximum breathing zone RDC were significantly reduced (P <0.05) in equine stables by changing the environment from hay feed and straw bedding, to haylage feed and wood shavings bedding (reduction in mean – 0.0867mg/m3 to 0.0260mg/m3; reduction in maximum – 4.0758mg/m3 to 0.2182mg/m3, respectively). [Copyright &y& Elsevier]

Abstract: Serum from 12 horses suffering from chronic grass sickness (CGS) were assayed for IgG antibodies against botulinum neurotoxins C and D (BoNT/C and BoNT/D) and to a surface antigen extract of a neurotoxin negative strain of Clostridium botulinum type C. Collectively, the six surviving CGS cases demonstrated significantly higher initial IgG levels (P =0.05) against surface antigens than the six that were subsequently euthanased. The surviving animals also demonstrated higher initial IgG levels against the BoNT/C but not reaching significance (P =0.06). The two groups demonstrated no difference between IgG levels against BoNT/D. This study supports existing evidence of the involvement of C. botulinum type C in the aetiology of grass sickness. [Copyright &y& Elsevier]