K. J. Pickles

An investigation of anthelmintic efficacy against strongyles on equine yards in Scotland

REASONS FOR PERFORMING STUDYnCyathostomins comprise 50 helminth species, considered the most problematic equine endoparasites. Three classes of anthelmintic are currently licensed for their control, namely the benzimidazoles (fenbendazole), tetrahydropyrimidines (pyrantel) and macrocyclic lactones (ivermectin and moxidectin). Anthelmintic resistance in cyathostomins is common. With no new classes expected in the near future, it is essential to determine the efficacy of the available anthelmintics to inform future control programmes.nnnOBJECTIVESnTo determine the efficacy of all 3 anthelmintic classes against strongyles in equids on livery yards in east and central Scotland.nnnSTUDY DESIGNnAnthelmintic efficacy testing using the faecal egg count reduction test (FECRT).nnnMETHODSnFECRTs were performed on equids with initial strongyle faecal egg counts (FECs) of ≥50 eggs per gram. Efficacy was determined by comparing pretreatment (Day 0) and 14 days post treatment (Day 14) FECs. The following chemicals were tested: fenbendazole, pyrantel, ivermectin and moxidectin. Group arithmetic mean FECR of >90% for fenbendazole and pyrantel, and >95% for ivermectin and moxidectin, represented efficacy, whereas lower mean FECR indicated potential resistance.nnnRESULTSnA total of 447 FECRTs were performed on 15 yards, as follows (the numbers in parentheses represent the number of yards each anthelmintic was tested on): 55 equids (7 yards) fenbendazole, 111 (8 yards) pyrantel, 163 (13 yards) ivermectin and 118 (10 yards) moxidectin. Fenbendazole resistance was documented on all yards (range of mean FECR, 15.8-83.4%), whereas pyrantel (90.4-99.6%), ivermectin (99.5-100%) and moxidectin (99.4-100%) treatment had acceptable efficacy.nnnCONCLUSIONSnReduced efficacy of fenbendazole was widespread, whereas >90% efficacy was found after pyrantel, and >95% efficacy after ivermectin and moxidectin. Overall, efficacies were higher than reported previously in Europe and the USA, potentially reflecting differences in management and anthelmintic use on the yards surveyed.nnnPOTENTIAL RELEVANCEnThe use of fenbendazole for strongyle control in Scotland should be questioned. Targeted use of pyrantel should be encouraged to reduce reliance on macrocyclic lactones. Further work to correlate management practices with the presence of anthelmintic resistance is warranted.

A questionnaire study of equine gastrointestinal parasite control in Scotland

REASONS FOR PERFORMING STUDYnAnthelmintic resistance in equine gastrointestinal nematodes is a threat to equine health and welfare. Detailed knowledge of anthelmintic use and parasite control methods is a prerequisite to identification of potential risk factors for resistance.nnnOBJECTIVESnTo identify parasite control practices employed by equine owners in Scotland and investigate management factors associated with anthelmintic resistance.nnnSTUDY DESIGNnQuestionnaire study of equine parasite control in Scotland.nnnMETHODSnQuestionnaires were available electronically, distributed at a conference and mailed to clients. Key areas explored included general background, grazing management, anthelmintic treatment practices and use of diagnostic tests.nnnRESULTSnA total of 193 responses detailing information on parasite control programmes of 993 equids were analysed. Moxidectin (MOX) and ivermectin or related combination products were the most commonly administered anthelmintics in the preceding 12 months. Treatments licensed for use against cyathostomin encysted larvae and tapeworms were administered by 80% and 90% of respondents, respectively. This was often achieved through indiscriminate use of MOX and MOX-praziquantel products. Faecal egg count (FEC) analysis had been performed on 62% of yards and regular use of FECs reduced annual anthelmintic treatment frequency. Veterinarians had the greatest influence on control practices. While 40% of respondents believed that they practised targeted dosing, this was not associated with delaying treatment beyond the egg reappearance period of the anthelmintic used.nnnCONCLUSIONSnResponses indicated increasing veterinary involvement and use of FECs. The majority of respondents administered anthelmintics licensed against cyathostomin encysted larvae and tapeworms. However, responses suggested that owners did not understand the definition of targeted dosing regimens.nnnPOTENTIAL RELEVANCEnThe high frequency of MOX use represents a potential risk factor for macrocyclic lactone resistance. As veterinarians were the most influential factor in anthelmintic choice, awareness of macrocyclic lactone resistance and potential risk factors for its development and spread should be incorporated into client advice.

Sensory Nerve Conduction and Somatosensory Evoked Potentials of the Trigeminal Nerve in Horses with Idiopathic Headshaking

BACKGROUNDnIdiopathic headshaking (HSK) in horses is a distressing disorder in which the etiology and pathophysiology are unknown.nnnHYPOTHESISnDifferences in sensory function of the trigeminal nerve exist between healthy and affected horses.nnnANIMALSnSix healthy mature geldings and 6 mature geldings with idiopathic HSK.nnnMETHODSnProspective study. Sensory nerve action and somatosensory evoked potentials studies were performed. The stimulus site comprised the gingival mucosa dorsal to the maxillary canine. A pair of recording electrodes was placed along the sensory pathway of the trigeminal complex at the infraorbital nerve (R1), maxillary nerve (R2), spinal tract of trigeminal (R3), and somatosensory cortex (R4). Sensory nerve action potential latency (ms), amplitude (μV), duration (ms), area under the curve (μVms), and conduction velocity (m/s) were calculated.nnnRESULTSnThreshold for activation of the infraorbital branch of the trigeminal nerve was significantly different between 5 affected (≤ 5 mA) and 6 control horses (≥ 10 mA). After initiation of an action potential, there were no differences in all parameters measured and no differences between left and right sides. A horse with seasonal HSK tested during a time of no clinical manifestations showed a threshold for activation similar to control horses.nnnCONCLUSIONS AND CLINICAL IMPORTANCEnThis study confirms involvement of the trigeminal nerve hyperexcitability in the pathophysiology of disease. Further, results might support a functional rather than a structural alteration in the sensory pathway of the trigeminal complex that can be seasonal. The horse could serve as a natural animal model for humans with idiopathic trigeminal neuralgia.

Idiopathic headshaking: Is it still idiopathic?

The clinical syndrome of equine idiopathic headshaking (HSK) was first described in the veterinary literature over 100 years ago, and the disorder continues to be a cause of substantial distress for the horse, frustration for the owner and therapeutic challenge for the veterinarian. This review presents a summary of the current knowledge of clinical signs, signalment, aetiopathogenesis, anatomy, diagnosis and treatment of idiopathic HSK. Recent advances in understanding the pathogenesis of the disease will be discussed with reference to human trigeminal neuralgia, along with the implications this may have for potential therapies.

Latent equine herpesvirus-1 in trigeminal ganglia and equine idiopathic headshaking.

BACKGROUNDnTrigeminal neuralgia or neuropathic pain has been regarded as a putative cause of idiopathic headshaking in horses. Equine herpesvirus-1 (EHV-1) infection and resultant postherpetic pain have been suggested as a possible cause of such neuropathic pain.nnnHYPOTHESIS/OBJECTIVESnTo determine the presence of EHV-1 in the trigeminal ganglia of horses with idiopathic headshaking.nnnANIMALSnNineteen horses: control (n = 11, 9 geldings, 2 mares, median age 11 years) and headshaking (n = 8, all geldings, median age 11.5 years) horses were sourced from the equine research herd and caseload at the Veterinary Medical Teaching Hospital.nnnMETHODSnProspective study to determine the presence of EHV-1 latency in trigeminal ganglia of horses with idiopathic headshaking by real-time PCR detection of the glycoprotein B (gB) gene and the DNA polymerase (ORF 30) gene of EHV-1 in the absence of detectable late structural protein gene (gB gene) mRNA. Control horses were used for comparison. A house keeping gene (equine GAPDH) and positive and negative samples for EHV-1 were used for quality control.nnnRESULTSnAll samples from control horses and 7 of 8 headshaking horses were negative for EHV-1. One headshaking horse tested positive for a single copy of EHV-1 gene.nnnCONCLUSIONS AND CLINICAL IMPORTANCEnThis study does not support a role for EHV-1 infection and presumed postherpetic pain in the etiopathogenesis of equine headshaking.

Use of a gonadotrophin-releasing hormone vaccine in headshaking horses.

The aim of this study was to investigate the use of a gonadotrophin-releasing hormone (GnRH) vaccine in the treatment of headshaking in horses. Fifteen geldings received two doses of the GnRH vaccine four weeks apart. Serum was collected before and after vaccination to measure concentrations of luteinising hormone (LH) (10 horses) and follicle-stimulating hormone (FSH) (six horses). Owners recorded the frequency of seven common headshaking behaviours using a visual analogue scale (VAS) before vaccination and at two, four, eight, 12, 16 and 20 weeks after vaccination. Serum LH (P=0.008) and FSH (P=0.03) concentrations decreased significantly following vaccination. Although approximately one-third of the owners reported a subjective improvement in headshaking, serial scoring did not indicate a reduction in headshaking behaviours following vaccination with a commercial GnRH vaccine. Vaccination reactions were observed in four of 15 horses (27 per cent), including one case of severe, presumed immune-mediated, myositis.

Preliminary investigation of somatosensory evoked potentials in equine headshaking

The aim of this study was to develop a technique for recording electrical activity of the equine cerebral cortex following application of a noxious electrical stimulus to the maxillary branch of the trigeminal nerve in order to investigate trigeminal nerve neurophysiology in control and headshaking horses. Triphasic somatosensory evoked potentials (SEPs) were recorded using subcutaneous needle electrodes in four control and four headshaking horses under general anaesthesia. Dural electroencephalography electrodes were used to record SEPs in one further control and one further headshaking horse. Headshaking horses appeared to have decreased middle latency and inter-peak intervals following stimulation of the trigeminal nerve compared with control horses, supporting abnormal trigeminal nerve physiology in equine headshaking

Similar challenges, different approaches: a review of student support systems in UK veterinary schools

The characteristics of individuals pursuing a veterinary career, and the negative impact of undergraduate training, have been suggested as possible contributing factors to poor mental wellbeing in the profession (Bartram and Baldwin 2010). Therefore, veterinary students may be a vulnerable student population (Collins and Foote 2005, Hafen and others 2006, Sutton 2007). On-site counselling services were offered at approximately half the American veterinary schools in 2001 (Kogan and McConnell 2001). The aim of this study was to collate information on support systems in UK veterinary schools.nnA web-based questionnaire (Survey Monkey, Palo Alto, California, USA; freely available at www.surveymonkey.com) was electronically delivered to the Heads of Teaching at all UK Veterinary Schools in August 2011 which contained 16 closed (10 with additional free text option) and 13 open multiple choice questions. Questions included where on campus student teaching was undertaken, the distance of the school from the main campus, and the availability and types of counselling and other support services offered.nnResponses were received from all seven UK schools, although details of student support were received from only six schools. Veterinary teaching was undertaken at both the main university and a separate veterinary campus at four schools, exclusively at a separate veterinary campus at two schools and solely at the main university campus by one school. Two schools shared a campus with other schools/departments.nnCounselling services …