Effect of corticosteroid and bronchodilator therapy on bronchoalveolar lavage cytology following intrapulmonary blood inoculation

REASON FOR PERFORMING STUDY

Intrapulmonary blood causes an inflammatory response. Modifying this inflammatory response may be useful in the treatment of exercise induced pulmonary haemorrhage (EIPH).

OBJECTIVES

To evaluate the efficacy of 3 treatments, an oral bronchodilator, inhaled steroid and oral steroid in modifying the cellular response to intrapulmonary blood inoculation.

MATERIALS AND METHODS

Experimental design was a randomised block divided into 4 experimental segments of 2 weeks. Eight normal horses were randomly assigned to pairs and treatments. Autologous blood was inoculated into the lungs on 4 occasions over an 8 week period. For each treatment, a bronchoalveolar lavage (BAL) sample was collected on Day 0 and then 2 randomly selected segmental bronchi (one in each lung) were inoculated with blood (50 ml). BAL fluid was collected from one inoculated bronchus on Day 3 and from the other on Day 10. From BAL samples, total RBC and total and differential WBC were determined. Results for percentages and absolute cell counts were expressed as mean +/- s.e. and analysed using one, 2 and 3 way analysis of variance.

RESULTS

All treatments significantly reduced the number of erythrophages at Day 3 (P = 0.02) Treatment with oral prednisolone resulted in a significantly higher percentage of macrophages (P = 0.03) and also reduced the relative and absolute number of haemosiderophages in BAL compared to the other 2 treatments at Day 10 (P = 0.07).

CONCLUSION

We concluded that treatments altered the dynamics of cell populations in BAL following blood inoculation. Whether this alters the evolution of lung lesions following episodes of EIPH and indeed whether there are benefits for equine lungs following episodes of EIPH, remain to be determined.

POTENTIAL RELEVANCE

Future studies into treatments for EIPH may benefit from incorporating a variety of dose rates for oral prednisolone and a longer period of evaluation. Such studies may also benefit from the use of cell activation markers. The concomitant use of pulmonary function testing and cytology in the field may assist in ascertaining whether treatments influence the performance and welfare of athletic horses subsequent to episodes of EIPH.

Is improved high speed performance following frusemide administration due to diuresis-induced weight loss or reduced severity of exercise-induced pulmonary haemorrhage?

REASONS FOR PERFORMING STUDY

Prerace administration of frusemide to horses has been linked with a significant improvement in racing performance, but the basis for this improvement is unclear.

OBJECTIVE

To test whether improved performance with prerace administration of frusemide is due to the drug's diuresis-induced weight loss rather than its apparent alleviation of exercise-induced pulmonary haemorrhage (EIPH).

METHODS

Eight thoroughbred horses underwent 3 trials in a random order, 2 or 3 weeks apart: control (C), frusemide/unburdened (FU), and frusemide/burdened (FB). None of the horses were known to have exhibited post-exercise epistaxis or endoscopic evidence of EIPH. Endoscope-guided bronchoalveolar lavages (BALs) were performed before and after each horse completed a standardised exercise test (SET) on an inclined treadmill to assess semi-quantitatively the volume of EIPH. For C, horses received an i.v. saline placebo injection (5 ml) and were unburdened while performing the SET. With FU, horses received frusemide (0.5 mg/kg) and were also unburdened. For FB, horses received frusemide and were burdened with weight equal to that lost during the 4 h post frusemide injection period. Erythrocyte number in BAL fluid, mass specific VO2max, time and distance for the entire SET as well as at maximum speed were recorded. A one-way repeated measures analysis of variance was conducted on all results.

RESULTS

Mass specific VO2max was significantly higher for the FU than for FB or C. Mass specific VO2max for FB and C were not different. More RBCs were found in BAL samples after C runs than after both FU and FB trial runs. Horses with the frusemide treatment (either burdened or unburdened) produced less EIPH than in the C trial, but their mass specific VO2max values were higher on the FU trial alone. For FU, horses ran longer at 115% VO2max than under C or FB conditions.

CONCLUSION AND POTENTIAL RELEVANCE

Improvement of performance in the furosemide trials was due more to the weight-loss related effects of the drug than its apparent alleviation of EIPH. Further research is warranted with the same or similar project design, but with a larger sample size and with horses known to have more severe EIPH.

Pharmacological studies of bronchial constriction inhibited by parasympatholytics and cilomilast using equine precision-cut lung slices

Equine precision cut lung slices (PCLS) were used to evaluate the ability of several pharmacologic compounds, parasympatholytics atropine, ipratropium, tiotropium and phosphodiesterase (PDE) 4-inhibitor cilomilast, to inhibit methacholine (MCh) induced bronchial constriction. The study war performed using vital lung samples from 20 horses, harvested immediately after euthanasia and lung examination.Tissue samples from the cranial, caudal and accessory lobe were taken for histological examination. Viability in PCLS of 250 +/- 20 microm was confirmed by observation of cilia movement and bronchial contraction in response to the addition of increasing concentrations of MCh (10(-8) to 10(-4) mol/l). Washing in pure RPMI-medium resulted in bronchial reopening. After incubation (20 minutes in an RPMI-solution containing cilomilast (10(-5) mol/l), atropine, ipratropium or tiotropium (10(-7) mol/l) each group (randomized, placebo controlled) was treated with MCh again. After reopening the unaffected viability of the PCLS was confirmed by the addition of MCh. EC50 values were calculated from bronchial cross-sections for each contraction. EC50 values significantly increased after atropine, ipratropium and tiotropium addition. No difference was found for cilomilast and in control slices. Statistical analysis showed a large interindividual, but a small intraindivual variability. No correlation was found between the clinical examination, histological findings and PCLS' responsiveness. We were able to confirm Vietmeier's (2007) values for the responsiveness of equine PCLS to MCh and to proof the effect of several new bronchodilatators using a new technique that allows the assessment of several substances in the same horse.

West Nile Virus: is a vaccine needed?

West Nile virus (WNV) is a neurotropic Flavivirus that was associated with sporadic outbreaks of meningoencephalitis in Africa and the Middle East until 1999, when a more virulent strain emerged in the US that caused thousands of infections among humans and horses, with reported fatality rates between 10 and 50%. Although the epidemiology of WNV is changing into a more endemic pattern in the US, and the incidence of neuroinvasive disease is decreasing, the long-term effects of resolved WNV infections in humans, characterized as persistent movement disorders and various functional disabilities, are a significant cause of morbidity. In addition, the horse industry is also negatively impacted by WNV infections, resulting in significant economic losses. Together with the fact that WNV is a potential bioterrorism agent, these factors suggest that there is a need for the development of a safe and effective vaccine against WNV. The increased understanding of WNV pathogenesis and correlates of protection enables the rational design of such a vaccine. Several experimental vaccines have been tested in preclinical models and some have undergone clinical trials. The challenges related to the development of cheaper, safer and more effective vaccines for use in both humans and horses are likely to be overcome by new technological developments in the field of vaccinology.

Post anaesthetic colic in horses: a preventable complication?

REASONS FOR PERFORMING STUDY

There is little information on the prevalence of, and risk factors associated with, post anaesthetic colic (PAC) in horses undergoing nonabdominal operations.

OBJECTIVES

To undertake the first prospective study of prevalence of PAC and identify risk factors in its development in nonabdominal procedures.

METHODS

A multicentre prospective case-control study was conducted, on every horse undergoing anaesthesia for a nonabdominal procedure between April 2004 and June 2005. Colic cases were defined as any horse with recognised signs of abdominal pain within 72 h of general anaesthesia that could not be attributed to any concurrent disease. Five control horses per case were selected randomly from the study population at all hospitals. Multivariable logistic regression analysis was used to examine the relationship between predictor variables and the risk of developing PAC.

RESULTS

The estimated mean prevalence of PAC in the study population was 5.2% (95% CI, 2.8, 8.0). However, the prevalence of colic varied between each centre. The most commonly diagnosed cause of colic was impaction. Multivariable analyses showed that the centre involved and the type of surgery performed were associated with an increased risk of PAC. Preoperative food deprivation and the use of opioid drugs were confounding factors.

CONCLUSIONS

Prevalence of PAC varied significantly between the 4 hospitals studied; there may be hospital-related covariates that account for this. The type of surgery performed influenced the risk of PAC.

POTENTIAL RELEVANCE

Identifying the risk factors for PAC is a prerequisite for its prevention. This study indicates horses at increased risk of PAC that might benefit from a more critical evaluation of post anaesthetic gastrointestinal function and/or the provision of preventative measures. Further investigation is required to explain the variation in prevalence of PAC between centres.

Multivariable analysis of factors influencing outcome of 2 treatment protocols in 128 cases of horses responding positively to intra-articular analgesia of the distal interphalangeal joint

REASONS FOR PERFORMING STUDY

There is limited knowledge available of factors influencing response to treatments of the DIP-joint in horses with lameness responding to diagnostic analgesia of the DIP-joint. For this reason a multivariable statistical analysis was performed.

HYPOTHESIS

Horses with lameness reduced by > or = 75% 10 min after intra-articular analgesia of the DIP-joint, can be treated successfully by intra-articular medication of the joint. Multiple factors influence the response to treatment.

METHODS

The study was performed retrospectively based on clinical records of horses treated with either polysulphated glycosaminoglycan (PSGAG) or methylprednisolone acetate (MPA) in the DIP-joint between January 1996 and January 2003. Information was collected from clinical records and from the owners of the horses via a detailed questionnaire, in which they described their perception of the outcome a minimum of one year after treatment. Allocation of the horses to the 2 treatment groups was done mainly because of a change in treatment policy. In Regime A all horses received 3 intra-articular injections of PSGAG approximately 8 days apart, whereas in Regime B all horses received a single intra-articular injection of MPA as a first treatment. If the horse did not improve sufficiently to return to work by 4 weeks, a series of 3 intra-articular PSGAG injections was administered.

RESULTS

Of the horses receiving Regime A, 67% had a successful outcome, compared with 46% of the group receiving Regime B. A significantly better result was obtained in dressage horses than in jumping horses (eventing and showjumping). Other variables such as age, duration of lameness, distribution of lameness, degree of lameness, response to DIP-joint analgesia and radiographic observations were also associated with success of treatment.

CONCLUSIONS AND POTENTIAL RELEVANCE

There is a rationale for using either PSGAG or MPA intra-articularly in the treatment of lameness, reduced > or = 75% within 10 min of analgesia of the DIP-joint.

Effect of GastroGard and three compounded oral omeprazole preparations on 24 h intragastric pH in gastrically cannulated mature horses

REASONS FOR PERFORMING STUDY

Ulceration of the squamous gastric mucosa is commonly associated with intensive training programmes in horses, but only one compound ('Gastrogard') has been subjected to controlled scrutiny as to therapeutic efficacy.

OBJECTIVES

To compare the gastric acid inhibitory efficacy of one manufactured ('GastroGard') and 3 generic pharmacy-compounded preparations of the proton pump inhibitor omeprazole (OME) in the mature horse.

HYPOTHESIS

All OME preparations tested would induce a clinically acceptable effect.

METHODS

Six healthy mature gastrically cannulated horses of various breeds, 3 mares and 3 geldings, were used. Each product was administered per os once daily (0730 h) at an equivalent dose of 4 mg OME/kg bwt, in a randomised complete repeated measures design for sequence of individual preparation treatment per horse. There was a minimum of 14 days between treatment regimens. A portable unit that recorded pH continuously was attached to a recording electrode fixed within the gastric lumen via the gastric cannula. Three 24 h recordings were made one day before and during Days 2 and 7 after commencement of a 7 day treatment with each of the 4 individual preparations. The horses were fed as usual throughout the study.

RESULTS

Only the GastroGard and one other preparation induced a significant increase over baseline in mean percentage of time that the pH was > 4.0 and mean median intragastric pH, during the first 14 and 12 h post treatment respectively, for both Days 2 and 7 post treatment. Both these products had a vehicle pH > 8.0, in contrast to the 2 less effective products, where the vehicle pH was < 6.0.

CONCLUSIONS

OME at 4 mg/kg per os s.i.d. can effectively maintain intragastric pH at an accepted anti-ulcerogenic level for at least 12 h post administration in mature horses. In contrast to GastroGard, it should not be expected that all compounded preparations of OME are equally effective in achieving this performance. It appears that vehicle pH might play an important part in determining preparation efficacy.

POTENTIAL RELEVANCE

Optimal timing for daily dosing of athletic horses with an effective OME preparation, in order to suppress gastric squamous ulceration, might be 4-8 h prior to a training session.

Preliminary study of mucosal IgA in the equine small intestine: specific IgA in cases of acute grass sickness and controls

REASONS FOR PERFORMING STUDY

There is much evidence to suggest that group III Clostridium botulinum (types C and D) are involved in the aetiology of equine grass sickness (EGS). Antibodies have been detected previously in the blood and high levels associated with resistance to disease. Specific mucosal antibodies in the gastrointestinal (GI) tract are likely to be important in protection, and this study was performed to ascertain if such antibodies could be detected and if their levels were related to disease state.

OBJECTIVES

To develop a method for quantifying IgA antibodies to C. botulinum types C and D in the GI tract of horses and to relate antibody levels to disease status.

METHODS

Samples of tissue (n = 25: 6 duodenum, 7 jejunum and 12 ileum) were taken from acute grass sickness (AGS) cases and from control horses (n = 12; 4 samples from each site) at post mortem. They were extracted with the detergent saponin in the presence of protease inhibitors and assayed for total IgA, for specific IgA against botulinum neurotoxins types C and D (BoNT/C or BoNT/D), and against surface antigens of a BoNT/C negative strain of C. botulinum type C (SA) and of Clostridium tetani (TetSA), as a control. Specific IgA was expressed as percentage total IgA.

RESULTS

Compared to controls, significantly higher levels of specific IgA against BoNT/C were detected in the jejunum (P = 0.04) and ileum (P = 0.02) of AGS cases. Similarly, higher specific levels against BoNT/D were demonstrated in duodenum (P = 0.01) and jejunum (P = 0.02). Significantly higher levels of IgA against SA were demonstrated only in duodenal samples (P = 0.01).

CONCLUSIONS

Levels of IgA antibody to BoNTs in control horses were at near undetectable levels, suggesting no recent exposure to toxins. In AGS cases, significantly higher levels of specific IgA were detected predominantly in jejunum and ileum.

POTENTIAL RELEVANCE

If specific IgA is protective then any successful vaccine for EGS should induce a mucosal response.

Effective removal of equine arteritis virus from stallion semen

REASONS FOR PERFORMING STUDY

A method of removing equine arteritis virus (EAV) from equine semen used for artificial insemination is urgently needed. Recent medical studies suggest that a double semen processing technique of density gradient centrifugation followed by a 'swim-up' can provide virus-free sperm preparations for assisted reproduction.

OBJECTIVES

To investigate the use of the double semen processing technique to obtain virus-free sperm preparations from stallion semen containing EAV.

METHODS

Aliquots of an ejaculate from an uninfected stallion were spiked with virus and processed by the double processing technique. The sperm preparations were tested by PCR for the presence of EAV. The procedure was repeated using an ejaculate from a known shedding stallion, testing processed and unprocessed aliquots by PCR and virus isolation.

RESULTS

Virus-free sperm preparations were obtained using the double sperm processing technique. The 'swim-up' step is apparently required to ensure complete virus removal.

CONCLUSIONS

The double semen processing technique is potentially a useful and simple tool for the removal of EAV from the semen of shedding stallions.

POTENTIAL RELEVANCE

The inclusion of density gradient centrifugation and 'swim-up' in protocols for the processing of semen for artificial insemination could help prevent the transmission of viral diseases carried in semen, such as EAV.

Prevention of ischaemia-induced small intestinal adhesions in foals

REASONS FOR PERFORMING STUDY

Treatments addressing variously theorised pathophysiological mechanisms of small intestinal adhesions have been reported. This study applied those classes of treatments to the most clinically relevant aetiology of post operative adhesions.

HYPOTHESIS

Treatments addressing the pathophysiology of ischaemia-reperfusion induced adhesions would accordingly reduce the incidence of adhesions from this model.

METHODS

Four classes of treatments were administered for 72 h to 16 foals subjected to complete ischaemia followed by reperfusion to create peritoneal adhesions. These groups were: 1) FPG group--flunixin meglumine (1.1 mg/kg bwt i.v., divided q.i.d.), potassium penicillin G (22,000 iu/kg bwt i.v., q.i.d.) and gentamicin (2.2 mg/kg bwt i.v., t.i.d.); 2) HEP group--heparin (80 iu/kg bwt subcut., b.i.d.); 3) DMSO group--dimethylsulphoxide (DMSO) (20 mg/kg bwt [diluted in 500 ml normal saline] i.v., b.i.d.); and 4) SCMC group--sodium carboxymethylcellulose (500 ml 3% sterile solution intraperitoneally, administered only at the beginning of surgery).

RESULTS

Post operative intestinal obstruction did not occur in any foal. After 10 days, necropsy revealed bowel-to-bowel adhesions in none of the FPG or DMSO groups, in 2/4 of the SCMC group, in 3/4 of the HEP group and 5/6 foals subjected to the procedure without treatment (UIR group).

CONCLUSIONS

Inhibition of the inflammation associated with ischaemia and reperfusion in foals treated with FPG or DMSO decreased small intestinal adhesions in foals.

POTENTIAL RELEVANCE

Although anti-inflammatory therapy was shown to eliminate bowel-bowel adhesions in this controlled study, it must be remembered that clinical cases are without control. These therapies are advised to improve the result but are unlikely to eliminate the problem.

The efficacy of dantrolene sodium in controlling exertional rhabdomyolysis in the Thoroughbred racehorse

REASONS FOR PERFORMING STUDY

Dantrolene sodium (Dantrium) has been used extensively for the treatment of myopathies in man and anecdotal evidence suggests it is of clinical benefit in the control of exercise-induced rhabdomyolysis (ER) in racehorses, although data to support this are currently lacking.

OBJECTIVES

To investigate the efficacy of oral dantrolene sodium in controlling ER in a randomised, double-blind, placebo-controlled crossover trial involving 77 Thoroughbred racehorses in Newmarket, UK.

METHODS

Horses were treated on 2 occasions 1 week apart, with treatment days coinciding with a return to exercise following 2 days box rest on each occasion. For the first treatment, each horse was randomly selected to receive either 800 mg dantrolene sodium or a colour-matched placebo administered orally 1 h before exercise. This was followed by crossover to the other treatment on the second occasion, with each horse thereby acting as its own control. Degree of ER was assessed using rising serum creatine kinase (CK) levels, by subtracting pre-exercise blood CK levels from those measured in 6 h post exercise blood samples. For each horse, the difference in change between pre- and post exercise CK values between placebo and dantrolene treatments was calculated, with positive values indicating a greater rise with placebo than with dantrolene sodium treatment.

RESULTS

The overall mean difference for all horses was +104.8 iu/l and the null hypothesis, that there was no true difference in non-normally distributed post exercise rises in CK values between placebo and dantrolene treatments, was rejected (P = 0.0013) using the nonparametric Wilcoxon signed rank test. Additionally, no horses given dantrolene sodium showed clinical signs of ER, whereas 3 horses given the placebo developed ER following exercise. The incidence of ER in the study was 4% (3/77).

CONCLUSIONS

The results confirmed that oral administration of dantrolene sodium, 1 h before exercise, had a statistically significant effect on reducing the difference between pre- and post exercise plasma CK levels compared with a placebo in the same animals, and preventing clinical ER in susceptible individuals.

POTENTIAL RELEVANCE

This study suggested that dantrolene sodium is of use in controlling ER in the Thoroughbred racehorse. Further investigation into pre- and post exercise myoplasmic calcium levels and the repeat of the study late in the season when horses receive a much higher energy ration and more strenuous exercise would appear to be warranted.

Increased expression of MAIL, a cytokine-associated nuclear protein, in the prodromal stage of black walnut-induced laminitis

REASONS FOR PERFORMING STUDY

The mediators and signalling cascades important in the initiation of laminitis remain unclear. We therefore wanted to explore the genes and overall signalling mechanisms that play an important role in the developmental stage of laminitis.

OBJECTIVE

To use a broad genomic screening technique to identify novel genes that are differentially regulated in the equine lamellae during the developmental period of laminitis.

METHODS

Differential mRNA display (DRD) was performed to discover regulated genes, and real-time quantitative polymerase chain reaction (RT-qPCR) was then used to evaluate lamellar mRNA levels of a regulated gene (MAIL) and mediators related to that gene (IL-1beta and IL-6) in control horses (n = 5) and horses administered black walnut extract (BWE; n = 5).

RESULTS

Using DRD, MAIL was identified as a regulated gene. RT-qPCR indicated a 4-fold increase in expression of the MAIL mRNA in BWE lamellae compared to controls. A 30-fold increase in IL-1beta, and a 160-fold difference in IL-6 mRNA expression was present in BWE lamellae. Differences in MAIL, IL-1beta and IL-6 mRNA expression were statistically significant between groups (P < 0.05).

CONCLUSIONS AND POTENTIAL RELEVANCE

The data strongly support a role for inflammatory cytokines in the developmental stages of laminitis, possibly inducing the vascular and metabolic alterations reported to occur in the affected digit. These results potentially support the use of anti-inflammatory drugs in horses at risk of laminitis, and warrant further investigation of the link between systemic disease processes associated with laminitis and the reported digital inflammation.

Endotoxin-induced digital vasoconstriction in horses: associated changes in plasma concentrations of vasoconstrictor mediators

REASONS FOR PERFORMING STUDY

Lipopolysaccharide (LPS) infusion reduces digital perfusion, but the mediators responsible remain undetermined.

OBJECTIVES

To identify vasoconstrictor mediators released following LPS infusion and relate their appearance in plasma to digital blood flow alterations.

METHODS

Blood flow in the lateral digital vessels of 6 Thoroughbred horses, following a 30 min infusion of LPS (E. coli 055:B5; 30 ng/kg), was measured using Doppler ultrasonography. Concomitant measurements of hoof wall and coronary band surface temperatures (HWST and CBST) were made. Serial blood samples were collected and plasma LPS, tumour necrosis factor alpha (TNFalpha), 5-HT, thromboxane B2 (TxB2) and endothelin measured.

RESULTS

Plasma LPS concentrations reached a maximum of 13.2 pg/ml during the infusion, followed by an increase in plasma TNFalpha concentration. Digital arterial and venous blood flow decreased by 43 and 63%, respectively; HWST and CBST similarly decreased. Systemic blood pressure remained unaltered. Plasma concentrations of TxB2 and 5-HT increased, coinciding with the onset of digital hypoperfusion. Plasma endothelin concentrations remained unchanged.

CONCLUSIONS

The temporal relationship between the onset of digital hypoperfusion and increases in plasma 5-HT and TxB2 concentrations is consistent with these platelet-derived mediators being associated with LPS-induced laminitis.

POTENTIAL RELEVANCE

These experimental data support the use of anti-platelet therapy in the prevention of laminitis associated with endotoxaemic conditions.

Transarterial coil embolisation in 31 horses (1999-2002) with guttural pouch mycosis: a 2-year follow-up

REASONS FOR PERFORMING STUDY

There have been no previously published large case series describing short- and long-term outcome of transarterial coil embolisation (TCE) in horses with guttural pouch mycosis (GPM).

OBJECTIVES

To describe the clinical and surgical features of horses with GPM presented at the Veterinary School of Lyon during a 28 month period; and to evaluate immediate to long-term results of TCE as a treatment.

METHODS

Medical records of all horses with GPM treated with TCE between February 1999 and July 2002 were analysed. To be included in the study, no other surgical or medical treatment for the mycosis was administered. Subject details, case history and results of initial clinical examination and endoscopy were reviewed. For all individuals, evaluation of long-term complications and case evolution was based on owner or trainer interviews between 24 and 41 months after surgery.

RESULTS

Thirty-one horses were identified with unilateral (n = 25) or bilateral (n = 6) GPM affecting only the medial (n = 28), only the lateral (n = 2) or both compartments simultaneously (n = 7). Of the 23 individuals presented with epistaxis, 20 showed complete resolution of the problem. Of the 19 horses presented with neurological signs, 2 were subjected to euthanasia for persistence of severe dysphagia. Prognosis for survival was excellent (84%) and prognosis for return at the level expected by the owner or trainer was good (71%).

CONCLUSIONS AND POTENTIAL RELEVANCE

TCE of horses affected with GPM is an effective method of preventing haemorrhage and resolving the majority of mycotic lesions without further specific treatment. Treated horses did not present relapse of mycosis during the follow-up period.

Can an external device prevent dorsal displacement of the soft palate during strenuous exercise?

REASONS FOR PERFORMING STUDY

Dorsal displacement of the soft palate (DDSP) is a common condition in racehorses for which various surgical treatments are often performed. In light of recent findings that suggested the position of the larynx may influence the occurrence of DDSP, we investigated whether a noninvasive mean of affecting the position of the larynx could be effective in the management of DDSP.

HYPOTHESIS

An external device (laryngohyoid support; LHS) positioning the larynx in a more rostral and dorsal location and preventing caudal displacement of the basihyoid bone would be effective in preventing DDSP during strenuous exercise.

METHODS

Ten horses were exercised on a high-speed treadmill under 4 different treatment conditions: control (n = 10); control with external device (n = 10); after bilateral resection of thyrohyoid (TH) muscles (n = 7); and after bilateral resection of TH muscles with external device (n = 7). Two trials were performed randomly for each of the 4 conditions. In Trial 1, videoendoscopic images of the upper airway, pharyngeal and tracheal static pressures, and arterial blood gases were collected. In Trial 2, airflow measurement combined with mask and tracheal static pressure was obtained, and upper airway impedance calculated. The trials allowed calculation of airway impedance and respiratory frequency, and assessment of ventilation using arterial PO2 and PCO2.

RESULTS

Under control conditions, none of the 10 horses developed DDSP. There was no statistically significant effect from the LHS on airway impedance or respiratory frequency, nor on arterial PO2 and PCO2. Seven of the 10 horses developed DDSP during exercise after resection of the TH muscles. None of these 7 horses continued to experience DDSP during exercise with the external device. In the latter group and condition, the LHS significantly improved inspiratory and expiratory flow and impedance.

CONCLUSIONS

The LHS helped prevent experimentally induced DDSP at exercise, probably by statically positioning the larynx in a more rostral and dorsal position.

POTENTIAL RELEVANCE

Field studies are required to investigate whether the LHS can successfully prevent DDSP in horses with naturally occurring disease.

Training-related factors associated with dorsometacarpal disease in young Thoroughbred racehorses in the UK

REASONS FOR PERFORMING STUDY

Dorsometacarpal disease (DMD) is common in young Thoroughbred (TB) racehorses, often interfering with their training programme. No reports exist on incidence rate or associated risk factors in the UK.

OBJECTIVES

To estimate the incidence rate of DMD in TB horses in training for flat racing in the UK and identify associated risk factors, particularly in relation to training regimens.

METHODS

Data were drawn from a large prospective study in which TB horses in 13 training yards were monitored for a period of up to 2 years, recording daily training information and details of musculoskeletal injury, including DMD. The incidence of DMD was calculated and survival analysis performed to determine features of the training regimen related to the risk of disease.

RESULTS

A total of 335 horses provided 4235 months at risk of DMD. Seventy-nine first episodes were recorded, resulting in an incidence rate of 1.87/100 horse months (95% confidence interval 1.50-2.33). Increasing exercise distances at canter and high speed in short periods (up to 1 month) were associated with an increasing risk of DMD. However, increasing cumulative exercise distances since entering training were associated with a decreasing risk of the disease.

CONCLUSIONS

The risk of DMD in young TBs decreases with accumulation of distances exercised at canter and high speed; this reflects the adaptive response of the third metacarpal bone to the loads placed upon it. However, increasing exercise distances in short periods (up to 1 month) increases the risk of DMD, probably as a consequence of microdamage and its associated remodelling response, and should therefore be avoided.

POTENTIAL RELEVANCE

Training regimens for young TBs can be adjusted to prevent the occurrence of DMD. Early but gradual introduction of small amounts of high-speed exercise may be beneficial. Canter exercise should be kept minimal on high-speed work days and large amounts of both cantering and high-speed work per week, 2 weeks or per month should be avoided, particularly during the early stages of training, in order to minimise the risk of DMD.

Determination of the stiffness of the equine spine

REASONS FOR PERFORMING STUDY

Mechanical properties of the equine back are the bases for realistic modelling of the back, which is recognised as an important step towards improved understanding of the pathogenesis of equine back conditions.

HYPOTHESIS

The stiffness of the equine back depends on the direction of the applied force and on the position of the spine.

METHODS

Fourteen dissected spines were tested in a tensile testing machine. In 3 different positions, simulating dorsoventral, laterolateral and dorsoventral-30 degree rotated movement, force was applied on the dorsal spinous process of T12 to reach an excursion of 4 cm in each direction. The normal distribution of the stiffness coefficients was tested with a Kolmogorov-Smirnov test and the stiffness coefficients were compared with paired t tests.

RESULTS

Mean +/- s.d. dorsoventral stiffness was 2093 +/- 611 N/m for the nonrotated spine and 2182 +/- 459 N/m for the 30 degree rotated spine. Mean laterolateral stiffness was significantly lower than dorsoventral stiffness at 1454 +/- 156 N/m.

CONCLUSIONS

The stiffness of the spine depends on the direction of loading.

POTENTIAL RELEVANCE

The stiffness of the spine under loading may be a relevant factor in the development of back disorders.

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.

Equine laminitis: cryotherapy reduces the severity of the acute lesion

REASONS FOR PERFORMING STUDY

The hypometabolic and vasoconstrictive effects of cryotherapy could prevent the development of laminitis.

OBJECTIVES

To use distal limb cryotherapy to prevent laminitis induced by alimentary carbohydrate overload.

METHODS

Laminitis was induced in 6 Standardbred horses that had one front limb continuously cooled in an ice/water mixture. Lameness evaluation, blinded lamellar histological grading and analysis for lamellar matrix metalloproteinase-2 (MMP-2) mRNA expression were used to evaluate the severity of laminitis.

RESULTS

Cryotherapy was well tolerated and effective in cooling the feet. In each horse no lameness was observed in the treated limbs. Laminitis histology scores in the treated limbs were significantly less than those of the corresponding untreated forelimbs (P < 0.05). Laminitis histology scores in the treated limbs were also significantly less than those of the untreated limbs (fore- and hind) as a group (P < 0.05). Expression of MMP-2 mRNA in the iced feet was significantly (P < 0.05) less than that detected in the untreated feet.

CONCLUSIONS

Cryotherapy, when applied to one foot, markedly reduced the severity of acute laminitis in this study. We propose that vasoconstriction (preventing delivery of haematogenous trigger factors) and hypometabolism (reduction in lamellar MMP activity) were the primary therapeutic mechanisms.

POTENTIAL RELEVANCE

Although further research is needed, we suggest cryotherapy as a potentially effective prophylactic strategy in horses at risk of developing acute laminitis.

Pilot immunization of mice infected with an equine strain of Corynebacterium pseudotuberculosis

This pilot study evaluated protection of an equine autogenous bacterin-toxoid vaccine against Corynebacterium pseudotuberculosis infection. Twenty-four BALB/c mice were inoculated with two doses of bacterin-toxoid vaccine or two injections of a placebo. Clinical, microbiologic, and pathologic outcomes were assessed after intradermal infection with one of two equine-origin C. pseudotuberculosis strains. Mice receiving bacterin-toxoid from fast-growing C. pseudotuberculosis showed significant protection from challenge infection, as evidenced by a higher survival rate, fewer gross and histopathologic lesions, and lower bacterial levels on culture. Successful protection via a vaccine against equine internal abscesses might provide supplementary management options against an important, potentially fatal disease.

Concurrent use of veterinary drugs and herbal medicines in racing standardbreds

Standardbred trainers from 1 racetrack and 7 off-track training facilities were surveyed to determine the most common drugs, and prevalence of concurrent herb administration. Furosemide (on-track) and anti-inflammatory drugs (off-track) were the most common drugs administered. Among horses on-track, 9.8% received herbs compared with 13.8% off-track horses; 67% and 58% of these horses, respectively, received concurrent drugs.

Impact of drought-related vaccination on livestock mortality in pastoralist areas of Ethiopia

Under a national Livestock Policy Forum in Ethiopia the impact of livestock vaccination during drought was assessed in order to inform the development of a best-practice guideline. For each of the different types of vaccine used during drought years there was no significant difference in livestock mortality, for any species, in vaccinated compared with non-vaccinated herds. The limited impact of vaccination on livestock mortality was attributed to weaknesses in the design and implementation of vaccination programmes, including use of inappropriate vaccines, low vaccination coverage, problems with vaccine dosing, incorrect timing of vaccination and problems with vaccine storage. If these weaknesses could be overcome vaccination could be a useful means to protect livestock assets, with considerable benefit-cost ratios. Vaccination should be conducted as a standard preventive measure during normal years, and programme design should be informed by participatory epidemiological studies.

Getting to grips with strangles: an effective multi-component recombinant vaccine for the protection of horses from Streptococcus equi infection

Streptococcus equi subspecies equi (S. equi) is a clonal, equine host-adapted pathogen of global importance that causes a suppurative lymphodendopathy of the head and neck, more commonly known as Strangles. The disease is highly prevalent, can be severe and is highly contagious. Antibiotic treatment is usually ineffective. Live attenuated vaccine strains of S. equi have shown adverse reactions and they suffer from a short duration of immunity. Thus, a safe and effective vaccine against S. equi is highly desirable. The bacterium shows only limited genetic diversity and an effective vaccine could confer broad protection to horses throughout the world. Welsh mountain ponies (n = 7) vaccinated with a combination of seven recombinant S. equi proteins were significantly protected from experimental infection by S. equi, resembling the spontaneous disease. Vaccinated horses had significantly reduced incidence of lymph node swelling (p = 0.0013) lymph node abscessation (p = 0.00001), fewer days of pyrexia (p = 0.0001), reduced pathology scoring (p = 0.005) and lower bacterial recovery from lymph nodes (p = 0.004) when compared with non-vaccinated horses (n = 7). Six of 7 vaccinated horses were protected whereas all 7 non-vaccinated became infected. The protective antigens consisted of five surface localized proteins and two IgG endopeptidases. A second vaccination trial (n = 7+7), in which the IgG endopeptidases were omitted, demonstrated only partial protection against S. equi, highlighting an important role for these vaccine components in establishing a protective immune response. S. equi shares >80% sequence identity with Streptococcus pyogenes. Several of the components utilized here have counterparts in S. pyogenes, suggesting that our findings have broader implications for the prevention of infection with this important human pathogen. This is one of only a few demonstrations of protection from streptococcal infection conferred by a recombinant multi-component subunit vaccine in a natural host.

Numerous research groups have vaccinated, using recombinant antigens, against streptococcal infections in mouse model systems and shown protection. We have here demonstrated efficient protective vaccination of the natural host, the horse, using recombinant antigens. Streptococcus equi subspecies equi (S. equi) is an equine host-adapted and highly contagious pathogen of global importance. Six out of seven Welsh mountain ponies vaccinated with a combination of seven recombinant S. equi proteins were protected from experimental infection as assessed by clinical examination, pyrexia, lymph node swelling, inflammation, bacterial recovery, and post mortem examination. The protective antigens consisted of five surface localized proteins and two endopeptidases that are specific for IgG; the latter were shown to be of major importance for efficacy. Several of the antigens used here have similarities in Streptococcus pyogenes, implying that our findings are of importance for development of a vaccine against this important human pathogen.

Evidence that antibodies against recombinant SnSAG1 of Sarcocystis neurona merozoites are involved in infection and immunity in equine protozoal myeloencephalitis

Sarcocystis neurona is the principal etiologic agent of equine protozoal myeloencephalitis (EPM). An immunodominant protein of S. neurona, SnSAG-1, is expressed by the majority of S. neurona merozoites isolated from spinal tissues of horses diagnosed with EPM and may be a candidate for diagnostic tests and prophylaxis for EPM. Five horses were vaccinated with adjuvanted recombinant SnSAG1 (rSnSAG1) and 5 control (sham vaccinated) horses were vaccinated with adjuvant only. Serum was evaluated pre- and post-vaccination, prior to challenge, for antibodies against rSnSAG1 and inhibitory effects on the infectivity of S. neurona by an in vitro serum neutralization assay. The effect of vaccination with rSnSAG1 on in vivo infection by S. neurona was evaluated by challenging all the horses with S. neurona merozoites. Blinded daily examinations and 4 blinded neurological examinations were used to evaluate the presence of clinical signs of EPM. The 5 vaccinated horses developed serum and cerebrospinal fluid (CSF) titers of SnSAG1, detected by enzyme-linked immunosorbent assay (ELISA), post-vaccination. Post-vaccination serum from vaccinated horses was found to have an inhibitory effect on merozoites, demonstrated by in vitro bioassay. Following the challenge, the 5 control horses displayed clinical signs of EPM, including ataxia. While 4 of the 5 vaccinated horses did not become ataxic. One rSnSAG-1 vaccinated horse showed paresis in 1 limb with muscle atrophy. All horses showed mild, transient, cranial nerve deficits; however, disease did not progress to ataxia in rSnSAG-1 vaccinated horses. The study showed that vaccination with rSnSAG-1 produced antibodies in horses that neutralized merozoites when tested by in vitro culture and significantly reduced clinical signs demonstrated by in vivo challenge.

Diseases in neonatal foals. Part 1: the 30 day incidence of disease and the effect of prophylactic antimicrobial drug treatment during the first three days post partum

REASONS FOR PERFORMING STUDY

Neonatal diseases have been grouped and analysed but up-to-date statistically significant information about the incidence and prevalence of diseases in foals is limited. Since the 1950s it has been a common management practice to administer a 3 day course of antimicrobial drugs to neonatal foals. This was shown to significantly reduce the incidence of infections (Platt 1977). Since then management practices have improved and it is widely believed that prophylactic antimicrobial drugs are no longer necessary in foal rearing.

OBJECTIVES

To determine the 30 day incidences or prevalences (depending on case definition) of various diseases and conditions in the neonatal foal and ascertain the influence of a prophylactic 3 day treatment on the frequency of infections.

METHODS

The population consisted of Thoroughbred foals born on stud farms in the Newmarket (UK) area in 2005 (n = 1031). Depending on the stud farm's practice in the use of prophylactic antimicrobial drugs, 2 groups of newborn foals (treated and untreated) were identified and followed for 30 days.

RESULTS

The 30 day incidences of infectious diseases under study were between 0.2% (osteomyelitis) and 5.85% (systemic disease with diarrhoea). The overall incidence for 'total infectious diseases' was 8.27%. The most commonly observed noninfectious condition was limb deformities (12.11% of all foals). There was no significant difference in the incidence of infectious diseases between the 2 groups.

CONCLUSION

Infectious diseases are still an important problem in neonatal foals requiring further investigation as to which factors other than antimicrobial prophylaxis are relevant for disease prevention.

POTENTIAL RELEVANCE

The results provide an up-to-date overview about the frequencies of various neonatal foal diseases. They do not support the traditional prophylactic use of antimicrobials to prevent infectious diseases in healthy newborn foals. However, it should be noted that this study was not a randomised controlled trial and therefore does not provide the strongest possible evidence for this conclusion.

Influenza A viruses with truncated NS1 as modified live virus vaccines: pilot studies of safety and efficacy in horses

REASONS FOR PERFORMING STUDY

Three previously described NS1 mutant equine influenza viruses encoding carboxy-terminally truncated NS1 proteins are impaired in their ability to inhibit type I IFN production in vitro and are replication attenuated, and thus are candidates for use as a modified live influenza virus vaccine in the horse.

HYPOTHESIS

One or more of these mutant viruses is safe when administered to horses, and recipient horses when challenged with wild-type influenza have reduced physiological and virological correlates of disease.

METHODS

Vaccination and challenge studies were done in horses, with measurement of pyrexia, clinical signs, virus shedding and systemic proinflammatory cytokines.

RESULTS

Aerosol or intranasal inoculation of horses with the viruses produced no adverse effects. Seronegative horses inoculated with the NS1-73 and NS1-126 viruses, but not the NS1-99 virus, shed detectable virus and generated significant levels of antibodies. Following challenge with wild-type influenza, horses vaccinated with NS1-126 virus did not develop fever (>38.5 degrees C), had significantly fewer clinical signs of illness and significantly reduced quantities of virus excreted for a shorter duration post challenge compared to unvaccinated controls. Mean levels of proinflammatory cytokines IL-1beta and IL-6 were significantly higher in control animals, and were positively correlated with peak viral shedding and pyrexia on Day +2 post challenge.

CONCLUSION AND CLINICAL RELEVANCE

These data suggest that the recombinant NS1 viruses are safe and effective as modified live virus vaccines against equine influenza. This type of reverse genetics-based vaccine can be easily updated by exchanging viral surface antigens to combat the problem of antigenic drift in influenza viruses.

Pressure on the horse's withers with three styles of blanket

The objective of this study was to compare total force and localised pressure on horses' withers with three blanket styles (straight cut, V-shaped insert, cutback withers). Three pressure recordings, each of 5s duration, were taken in order to determine blanket pressure on the withers during standing and walking in 12 horses. Means+/-SD were calculated for the following variables and compared across blankets: total force, mean pressure, maximal pressure, and area with pressure >4 kPa. For standing trials, the blanket with the V-shaped insert had the lowest total force and smallest area with pressure >4 kPa (P<0.05). For walking trials, the straight cut blanket had the highest total force, maximal pressure, mean pressure, and largest area with pressure >4 kPa (P<0.05). The results indicate that blanket style affects force and pressure on the horse's withers and that blankets may exert sufficient pressure on the withers to induce the formation of pressure sores.

Immunoprophylaxis against important virus disease of horses, farm animals and birds

Since the refinement of tissue culture techniques for virus isolation and propagation from the mid 1960s onwards, veterinary virology has received much academic and industrial interest, and has now become a major global industry largely centred on vaccine development against economically important virus diseases of food animals. Bio-tech approaches have been widely used for improved vaccines development. While many viral diseases are controlled through vaccination, many still lack safe and efficacious vaccines. Additional challenges faced by academia, industry and governments are likely to come from viruses jumping species and also from the emergence of virulent variants of established viruses due to natural mutations. Also viral ecology is changing as the respective vectors adapt to new habitats as has been shown in the recent incursion by bluetongue virus into Europe. In this paper the current vaccines for livestock, horses and birds are described in a species by species order. The new promising bio-tech approaches using reverse genetics, non-replicating viral vectors, alpha virus vectors and genetic vaccines in conjunction with better adjuvants and better ways of vaccine delivery are discussed as well

Early pathogenesis of equine Streptococcus equi infection (strangles)

REASONS FOR PERFORMING STUDY

Little is known about entry and subsequent multiplication of Streptococcus equi following exposure of a susceptible horse. This information would have value in design of intranasal vaccines and understanding of shedding and protective immune responses.

OBJECTIVES

To determine entry points and sites of subsequent replication and dispersion of S. equi at different times after intranasal infection or commingling exposure.

METHODS

Previously unexposed horses and ponies were subjected to euthanasia 1, 3, 20 or 48 h following intranasal inoculation with biotin labelled or unlabelled S. equi CF32. Some ponies were inoculated with suspensions of equal numbers of CF32 and its mutants lacking capsule, S. equi M-like protein or streptolysin S. Others were infected by commingling exposure and subjected to euthanasia after onset of fever. Tonsils and lymph nodes were cultured for S. equi and tissues sectioned for histopathological examination and fluorescent microscopy.

RESULTS

Tonsillar tissues of both the oro- and nasopharynx served as portals of entry. Entry was unexpectedly rapid but involved few bacteria. Small numbers of organisms were detected in tonsillar crypts, in adjacent subepithelial follicular tissue and draining lymph nodes 3 h after inoculation. By 48 h, clumps of S. equi were visible in the lamina propria. At onset of fever, tonsillar tissues and one or more mandibular and retropharyngeal lymph nodes were heavily infiltrated by neutrophils and long chains of extracellular S. equi. Mutant S. equi lacking virulence factors were not seen in draining lymph nodes.

CONCLUSIONS

Although very small numbers of S. equi entered the lingual and nasopharyngeal tonsils, carriage to regional lymph nodes occurred within hours of inoculation. This observation, together with visual evidence of intracellular and extracellular multiplication of S. equi in tonsillar lymphoid tissue and lymph nodes over the following days, indicates involvement of potent antiphagocytic activity and failure of innate immune defences.

RELEVANCE

Future research should logically address the tonsillar immune mechanisms involved including identification of effector cell(s) and antigens.

Retrospective study of perioperative antimicrobial use practices in horses undergoing elective arthroscopic surgery at a veterinary teaching hospital

Perioperative antimicrobial administration practices were evaluated retrospectively in 97 horses undergoing elective arthroscopy, and antimicrobial use was compared with standard recommendations for perioperative prophylaxis. Parenteral antimicrobials were administered perioperatively to 95/97 (98%) horses, 88 of which received intravenous sodium penicillin. Time from 1st dose until 1st incision ranged from 30 to 390 min [142 +/- 55.6 min, mean +/- standard deviation (s), median 135 min], and the first incision was performed greater than 2 half-lives after administration of sodium penicillin in 86/95 (91%) cases. Overall duration of therapy was 30.8 +/- 24.2 h (mean +/- s). Six (6.3%) horses received only a single preoperative dose, while 63 (66%) horses were treated for 24 h or less. While objective data regarding optimal perioperative antimicrobial prophylaxis are limited, the antimicrobial use practices observed here commonly deviated from standard recommendations for perioperative prophylaxis.

Effects of a MAPK p38 inhibitor on lung function and airway inflammation in equine recurrent airway obstruction

REASONS FOR PERFORMING STUDY

It has been suggested that many of the beneficial effects of corticosteroids are mediated through mitogen-activated protein kinase (MAPK) p38 inhibition.

OBJECTIVE

To investigate the efficacy of the MAPK p38 inhibitor compound MRL-EQ1 to either prevent (Phase 1) or treat (Phase 2) recurrent airway obstruction (RAO) in horses.

METHODS

MRL-EQ1 was administered i.v. at a dosage of 0.75-1.5 mg/kg bwt q. 12 h. In Phase 1, susceptible horses in clinical remission were divided into 2 groups (n = 5/group), based on historical values of respiratory mechanics. All horses were entered in the study in pairs (one control, one treated horse) and exposed to the same environmental challenge (stabling, mouldy hay and dusty conditions). The treatment group received MRL-EQ1 for 14 days while the control horses were untreated during the same period. In Phase 2, affected horses were ranked by severity of respiratory dysfunction and split randomly into either dexamethasone or MRL-EQ1 treatment groups (n = 5/group). Bronchoalveolar lavage fluid, respiratory mechanic measurements, MRL-EQ1 plasma concentration and tumour necrosis factor (TNF) whole blood activity were evaluated sequentially.

RESULTS

In Phase 1, MRL-EQ1 did not prevent the occurrence of clinical signs and pulmonary inflammation. However, treatment was associated with a reduction in severity and a delay in the onset of signs and a reduction in pulmonary neutrophilia. In Phase 2, plasma concentrations achieved resulted in ex vivo suppression of lipopolysaccharide-induced TNF production in equine blood. MRL-EQ1 did not improve airway inflammation or lung function and was associated in a dose dependent manner with behavioural (depression, excitability) and blood changes (neutrophilia, increased serum muscle enzyme concentrations).

CONCLUSIONS

Inhibition of p38 in the horse was partially effective in reducing clinical signs and airway inflammation when administered prior to, but not during clinical exacerbation in RAO.

POTENTIAL RELEVANCE

Inhibitors of p38 MAPK with a better toxicity profile may be effective in the prevention or treatment of RAO.

The effect of a topical insecticide containing permethrin on the number of Culicoides midges caught near horses with and without insect bite hypersensitivity in the Netherlands

Insect bite hypersensitivity (IBH) in horses is most likely caused by Culicoides species, although other insects may also play a role. Until now no effective cure has been found for this condition, although numerous therapeutic and preventive measures have been used to control insect hypersensitivity. One such method is to apply a topical insecticide to horses. In this study, the effect of a topical insecticide containing permethrin (3.6%) was examined in seven pairs of horses. The horses were placed inside a tent trap to collect Culicoides spp. and other insects attracted to the horses on two subsequent evenings. On the first evening, both horses were untreated. After the end of this session, one horse of each pair was treated with the pour-on insecticide; treated horses were kept separate from untreated horses. The next evening the pairs of horses were again placed inside the tent trap and insects were collected. Similar percentages of Culicoides were trapped as in earlier studies (C. obsoletus 95.34% and C. pulicaris 4.54%), with healthy horses attracting more Culicoides than horses affected by IBH. The number of Culicoides, the percentage of blood-fed Culicoides obsoletus, and the total number of insects attracted to horses 24 hours after treatment with permethrin were reduced but the reduction was not statistically significant. No negative side effects of permethrin administration were observed.

Distribution of the neurokinin-1 receptor in equine intestinal smooth muscle

REASON FOR PERFORMING STUDY

Tachykinins have profound effects on equine intestinal motility, but the distribution of the neurokinin receptors (NKRs) through which they act is unknown. This study reports the distribution of one of these receptors, the neurokinin-1 receptor (NK1R), in smooth muscle throughout the equine intestinal tract.

OBJECTIVES

To quantify the distribution of the NK1R, based upon mRNA expression, in smooth muscle of different regions of the equine intestinal tract.

METHODS

Nine regions of the intestinal tract were sampled in 5 mature horses. Total RNA was isolated from smooth muscle and reverse transcribed; NK1R mRNA was then quantified using real-time PCR.

RESULTS

NK1R mRNA was found at all levels of the sampled intestinal tract. The smooth muscle of the proximal small intestine and the ventral colon exhibited the highest level of NK1R mRNA expression in the equine intestinal tract.

CONCLUSIONS

Tachykinins probably affect intestinal contractility and propulsion in the proximal small intestine and in the ventral colon.

Attenuation of ischaemic injury in the equine jejunum by administration of systemic lidocaine

REASONS FOR PERFORMING STUDY

Absorption of endotoxin across ischaemic-injured mucosa is a major cause of mortality after colic surgery. Recent studies have shown that flunixin meglumine retards mucosal repair. Systemic lidocaine has been used to treat post operative ileus, but it also has novel anti-inflammatory effects that could improve mucosal recovery after ischaemic injury.

HYPOTHESIS

Systemic lidocaine ameliorates the deleterious negative effects of flunixin meglumine on recovery of mucosal barrier function.

METHODS

Horses were treated i.v. immediately before anaesthesia with either 0.9% saline 1 ml/50 kg bwt, flunixin meglumine 1 mg/kg bwt every 12 h or lidocaine 1.3 mg/kg bwt loading dose followed by 0.05 mg/kg bwt/min constant rate infusion, or both flunixin meglumine and lidocaine, with 6 horses allocated randomly to each group. Two sections of jejunum were subjected to 2 h of ischaemia by temporary occlusion of the local blood supply, via a midline celiotomy. Horses were monitored with a behavioural pain score and were subjected to euthanasia 18 h after reversal of ischaemia. Ischaemic-injured and control jejunum was mounted in Ussing chambers for measurement of transepithelial electrical resistance (TER) and permeability to lipopolysaccharide (LPS).

RESULTS

In ischaemic-injured jejunum TER was significantly higher in horses treated with saline, lidocaine or lidocaine and flunixin meglumine combined, compared to horses treated with flunixin meglumine. In ischaemic-injured jejunum LPS permeability was significantly increased in horses treated with flunixin meglumine alone. Behavioural pain scores did not increase significantly after surgery in horses treated with flunixin meglumine.

CONCLUSIONS

Treatment with systemic lidocaine ameliorated the inhibitory effects of flunixin meglumine on recovery of the mucosal barrier from ischaemic injury, when the 2 treatments were combined. The mechanism of lidocaine in improving mucosal repair has not yet been elucidated.