Derek C. Knottenbelt

Headshaking in horses: possible aetiopathogenesis suggested by the results of diagnostic tests and several treatment regimes used in 20 cases

Twenty mature horses with typical headshaking of 2 week-7 year duration were studied. Clinical examinations included radiography of the head and nasopharyngeal endoscopy. All were assessed at rest and at exercise, both before and after fitting an occlusive nasal mask, application of tinted contact lenses and the perineural anaesthesia of the infraorbital and posterior ethmoidal branches of the trigeminal nerve. Infraorbital anaesthesia had no effect in 6/7 cases but 11/17 (65%) cases showed a 90-100% improvement following posterior ethmoidal nerve anaesthesia. Tinted contact lenses had no apparent long-term benefit, although 2 cases showed a transient improvement. We found no other evidence to suggest a photic aetiology in the current series of cases. Treatment regimens based on the results of the diagnostic investigative methods included sclerosis of the posterior ethmoidal branch of the trigeminal nerve. This was effective in some cases but the benefits were temporary. Cyproheptadine alone was ineffective but the addition of carbamazepine resulted in 80-100% improvement in 80% of cases. Carbemazepine alone was effective in 88% of cases but results were unpredictable at predefined dose rates. The positive response to carbamazepine, combined with the clinical features is consistent with involvement of the trigeminal nerve, particularly the more proximal branches such as the posterior ethmoidal nerve. Headshaking has some clinical features in common with trigeminal neuralgia in humans. As a result of the findings detailed in this paper, we conclude that a trigeminal neuritis or neuralgia may be the basis of the underlying aetiopathology of equine headshaking. Initial observations of the positive response of headshakers to carbamazepine therapy is encouraging. However, future studies will include a more detailed investigation of dosages, duration of effectiveness (in some cases it appears short-lived) and other effects. In practice there is a realistic possibility of controlling but not curing headshaking with carbamazepine therapy at the present time. Other future investigations will include details of the functional anatomy of the trigeminal nerve and the role of the P2 myelin protein in headshaking and other neurological disease.

Microbiology of equine wounds and evidence of bacterial biofilms

Horse wounds have a high risk of becoming infected due to their environment. Infected wounds harbour diverse populations of microorganisms, however in some cases these microorganisms can be difficult to identify and fail to respond to antibiotic treatment, resulting in chronic non-healing wounds. In human wounds this has been attributed to the ability of bacteria to survive in a biofilm phenotypic state. Biofilms are known to delay wound healing, principally due to their recalcitrance towards antimicrobial therapies and components of the innate immune response. This study describes the presence of bacterial biofilms within equine wounds. Thirteen 8-mm diameter tissue samples were collected from (n=18) chronic wounds. Following histological staining, samples were observed for evidence of biofilms. Fifty one wounds and control skin sites were sampled using sterile swabs. Control skin sites were on the uninjured side of the horse at the same anatomical location as the wound. The isolated bacteria were cultured aerobically and anaerobically. The biofilm forming potential of all the isolated bacteria was determined using a standard crystal violet microtitre plate assay. Stained tissue samples provided evidence of biofilms within 61.5% (8 out of 13) equine wounds. In total 340 bacterial isolates were identified from all the equine wound and skin samples. Pseudomonas aeruginosa and Enterococcus faecium were the most predominantly isolated bacterial species from equine wound and skin samples respectively. Staphylococcus was the most commonly isolated genus in both environments. Bacteria cultured from chronic and acute wounds showed significantly (P<0.05) higher biofilm forming potential than bacteria isolated from skin. This paper highlights preliminary evidence supporting the presence of biofilms and a high microbial diversity in equine chronic wounds. The presence of biofilms in equine wounds partly explains the reluctance of many lower limb wounds to heal. Non-healing limb wounds in horses are a well documented welfare and economic concern. This knowledge can be used to shape future treatments in order to increase the healing rate and decrease the costs and suffering associate with equine wounds.

Caudal anaesthesia of the infraorbital nerve for diagnosis of idiopathic headshaking and caudal compression of the infraorbital nerve for its treatment, in 58 horses

REASONS FOR PERFORMING STUDY Idiopathic headshaking is often a facial pain syndrome, but a diagnostic protocol has not been described. In a previous study, caudal compression of the infraorbital nerve for treatment offered a fair success rate, but low case numbers and short follow-up time were limitations. OBJECTIVES To describe a diagnostic protocol for headshaking, examining the role of bilateral local analgesia of the posterior ethmoidal nerve (PET block). To report longer-term follow-up after surgery of the original cases and further cases and to determine whether changes to the technique influence success rates and complications. METHODS Records of horses that had undergone PET block and caudal compression surgery at 3 hospitals were reviewed. Modifications to the surgical technique included placing additional coils into the infraorbital canal and/or performing concurrent laser cautery of the nerve. Follow-up information was obtained by telephone contact with owners. RESULTS The PET block was performed in 27 horses, with a positive result in 23 of 27 (85%). Surgery was performed in 58 horses. A successful outcome was initially achieved in 35 of 57 (63%) horses, but recurrence occurred between 9 and 30 months later in 9 (26%). Surgery was repeated in 10 of 31 (32%) horses. Final success rate, considering only response to the last performed surgery, was 28 of 57 (49%) horses with median follow-up time of 18 months (range 2-66 months). Nose-rubbing was reported post operatively in 30 of 48 (63%) horses. This resolved in all but 4 horses, which were subjected to euthanasia. Response to PET block or change in surgical technique did not appear to influence outcome or complications. CONCLUSIONS AND POTENTIAL RELEVANCE The diagnostic protocol described is recommended for the investigation of headshakers. Caudal compression offers the best prognosis for a successful outcome compared with other treatments, for horses in which the only alternative is euthanasia. Surgical treatment of the disorder requires refinement, and the pathogenesis of the disorder requires investigation.

Mitomycin C, with or without surgery, for the treatment of ocular squamous cell carcinoma in horses

Ocular lesions in horses, confirmed as squamous cell carcinoma, were treated topically with mitomycin C. Fourteen horses with confirmed ocular squamous cell carcinoma, three of which were affected bilaterally, were included in the study. Eight of the affected eyes were treated topically with mitomycin C alone; in the other nine eyes, the tumours were surgically removed and topical treatment with mitomycin C was then applied. The treatment protocol consisted of 0.2 ml of 0.04 per cent mitomycin C instilled into the conjunctival sac of the affected eye, every six hours, in rounds of seven days of treatment followed by seven days without treatment. This was repeated until full regression of the tumour occurred (up to four rounds of treatment with mitomycin C). Of the eight eyes treated with mitomycin C alone (without surgery), clinical resolution occurred in six cases. Of the nine eyes treated with a combination of surgery and topical mitomycin C, clinical resolution occurred in seven cases. No complications were observed.

Application of an in vitro model to evaluate bioadhesion of fibroblasts and epithelial cells to two different dressings

The cellular component of a healing wound consists of many cell types and the environment in which these cells grow is important to the rate and quality of healing which can be influenced by the type of dressing used. The most commonly used dressings are traditional gauze-type dressings. In many cases these dressings may adhere to the wound surface, and subsequent removal is often traumatic, causing pain and tissue reinjury. Some modern gelling dressings have been developed to overcome this adherence problem. In order to evaluate in more detail cell-dressing interactions, an in vitro model has been developed utilising wound fibroblasts and epithelial cells. Quantitative evaluation of adherence of cells cultured with a traditional gauze or a new gelling dressing has been undertaken using radiolabel and manual counting techniques. Scanning electron microscopy has been used to visualise the cells adherent to dressings allowing evaluation of their adhesion-morphology. The results show differential attachment of cells to viscose and gelling fibres of the dressings; considerably reduced cell adhesion to the gelling fibre was evident, and it was apparent that cells adhered predominantly to the viscose component of the dressing. This model can be used to investigate and compare the adhesion of cells to different dressings and their components.

VESTIBULAR DISEASE IN TWO HORSES : A CASE OF MYCOTIC OTITIS MEDIA AND A CASE OF TEMPOROHYOID OSTEOARTHROPATHY

ELLIS, W. A. & McNULTY, M S. (1995) Pathogenesis of porcine circovirus; experimental infections of colostrum deprived piglets and examination of pig foetal material. Veterinary Microbiology 44, 49-64 ALLAN, G. M., McNEILLY, F., KENNEDY, S., DAFT, B., CLARK, E. G., ELLIS, J. A., HAINES, D. M., MEEHAN, B. M. & ADAIR, B. M. (1998a) Isolation of porcine circovirus-like viruses from pigs with a wasting disease in the USA and Europe. Journal of Veterinary Diagnostic Investigation 10, 3-10 ALLAN, G., MEEHAN, B., TODD, D., KENNEDY, S., McNEILLY, F., ELLIS, J., CLARK, E. G., HARDING, J., ESPUNA, E., BOTNER, A. & CHARREYRE, C. (1998b) Novel porcine circoviruses from pigs with wasting disease syndromes. Veterinary Record 142,467-468 CLARK, E. G. & HARDING, J. C. (1998) The pathology of post-weaning multisystemic wasting syndrome. Proceedings of the 15th International Pig Veterinary Society Congress. p 212 DAFT, B., NORDHAUSEN, R. W., LATIMER, K. S. & NIAGRO, F. D. (1996) Interstitial pneumonia and lymphadenopathy associated with circoviral infection in a six-week-old pig. Proceedings of the American Association of Veterinary Laboratory Diagnosticians. p 32 DULAC, G. C. & AFSHAR, A. (1989) Porcine circovirus antigens in PK15 cell line (ATCC CCL-33) and evidence of antibodies to circovirus in Canadian pigs. Canadian Journal of Veterinary Research 53,431-433 EDWARDS, S. & SANDS, J. J. (1994) Evidence of circovirus infection in British pigs. Veterinary Record 134,680-681 ELLIS, J., HASSARD, L., CLARK, E., HARDING, J., ALLAN, G., WILLSON, P., STROKAPPE, J., MARTIN, K., McNEILLY, F., MEEHAN. B., TODD, D. & HAINES, D. (1998) Isolation of circovirus from lesions of pigs with postweaning multisystemic wasting syndrome. Canadian Veterinary Journal 39, 44-51 HAMEL, A. L., LIN, L. L. & NAYAR, G. P. S. (1998) Nucleotide sequence of porcine circovirus associated with postweaning multisystemic wasting syndrome in pigs. Journal of Virology 72, 5262-5267 HARDING, J. C. (1997) Post-weaning multisystemic wasting syndrome (PMWS): preliminary epidemiology and clinical presentation. Proceedings of the American Association of Swine Practitioners. p 503 HARDING, J. C. S. & CLARK, E. G. (1997) Recognizing and diagnosing postweaning multisystemic wasting syndrome (PMWS). Swine Health and Production 5,201-203 HINES, R. K. & LUKERT, P. D. (1995) Porcine circovirus: a serological survey of swine in the United States. Swine Health and Production 2,71-73 KENNEDY, S., ALLAN, G., McNEILLY, F., ADAIR, B. M., HUGHES, A. & SPILLANE, P. (1998) Porcine circovirus infection in Northern Ireland. Veterinary Record 142, 495-496 LAROCHELLE, R., ANTAYA, M., MORIN, M. & MAGAR, R. (1999) Typing of porcine circovirus in clinical specimens by multiplex PCR. Journal of Virological Methods (In press) LAROCHELLE, R. & MAGAR, R. (1997) Evaluation of the presence of porcine reproductive and respiratory syndrome virus in packaged pig meat using virus isolation and polymerase chain reaction (PCR) method. Veterinary Microbiology 58, 1-8 LECANN, P., ALBINA, E., MADEC, F., CARIOLET, R. & JESTIN, A. (1997) Piglet wasting disease. Veterinary Record 141, 660 MEEHAN, B. M., CREELAN, J. L., McNULTY, M. S. & TODD, D. (1997) Sequence of porcine circovirus DNA: affinities with plant circoviruses. Journal of General Virology 78, 221-227 MORIN, M., GIRARD, C., ELAZHARY, Y., FAJARDO, R., DROLET, R. & LAGACE, A. (1990) Severe proliferative and necrotizing pneumonia in pigs: a newly recognized disease. Canadian Veterinary Journal 31, 837-839 MURPHY, E A., FAUQUET, C. M., BISHOP, D. H. L., GHABRIAL, S. A., JARVIS, A. W., MARTELLI, G. P., MAYO, M. A. & SUMMERS, M. D. (1995) Virus Taxonomy. Sixth Report of the International Committee on Taxonomy of Viruses. Wien & New York, Springer-Verlag. pp 166-168 NAYAR, G. P. S., HAMEL, A. & LIN, L. (1997) Detection and characterization of porcine circovirus associated with postweaning multisystemic wasting syndrome in pigs. Canadian Veterinary Journal 38, 385-386 ROSSOW, K. D. (1998) Porcine reproductive and respiratory syndrome. Veterinary Pathology 35, 1-20 SEGALES, J., SITJAR, M., DOMINGO, M., DEE, S., DEL POZO, M., NOVAL, R., SACRISTAN, C., DE LAS HERAS, A., FERRO, A. & LATIMER, K. S. (1997) First report of post-weaning multisystemic wasting syndrome in pigs in Spain. Veterinary Record 141, 600-601 TISCHER, I., BODE, L., PETERS, D., POCIULI, S. & GERMANN, B. (1995) Distribution of antibodies to porcine circovirus in swine populations of different breeding farms. Archives of Virology 140, 737-743 TISCHER, I.,GELDERBLOM, H.,VETTERMANN,W. & KOCH, M.A. (1982) A very small porcine virus with circular single-stranded DNA. Nature 295, 64-66 TISCHER, I., MIELDS, W., WOLFF, D., VAGT, M. & GRIEM,W. (1986) Studies on epidemiology and pathogenicity of porcine circovirus. Archives of Virology 91, 271-276 Vestibular disease in two horses: a case of mycotic otitis media and a case of temporohyoid osteoarthropathy

Identification of a mutation associated with fatal foal immunodeficiency syndrome in the fell and dales pony.

The Fell and Dales are rare native UK pony breeds at risk due to falling numbers, in-breeding, and inherited disease. Specifically, the lethal Mendelian recessive disease Foal Immunodeficiency Syndrome (FIS), which manifests as B-lymphocyte immunodeficiency and progressive anemia, is a substantial threat. A significant percentage (∼10%) of the Fell ponies born each year dies from FIS, compromising the long-term survival of this breed. Moreover, the likely spread of FIS into other breeds is of major concern. Indeed, FIS was identified in the Dales pony, a related breed, during the course of this work. Using a stepwise approach comprising linkage and homozygosity mapping followed by haplotype analysis, we mapped the mutation using 14 FIS–affected, 17 obligate carriers, and 10 adults of unknown carrier status to a ∼1 Mb region (29.8 – 30.8 Mb) on chromosome (ECA) 26. A subsequent genome-wide association study identified two SNPs on ECA26 that showed genome-wide significance after Bonferroni correction for multiple testing: BIEC2-692674 at 29.804 Mb and BIEC2-693138 at 32.19 Mb. The associated region spanned 2.6 Mb from ∼29.6 Mb to 32.2 Mb on ECA26. Re-sequencing of this region identified a mutation in the sodium/myo-inositol cotransporter gene (SLC5A3); this causes a P446L substitution in the protein. This gene plays a crucial role in the regulatory response to osmotic stress that is essential in many tissues including lymphoid tissues and during early embryonic development. We propose that the amino acid substitution we identify here alters the function of SLC5A3, leading to erythropoiesis failure and compromise of the immune system. FIS is of significant biological interest as it is unique and is caused by a gene not previously associated with a mammalian disease. Having identified the associated gene, we are now able to eradicate FIS from equine populations by informed selective breeding.

Anaemia, diarrhoea and opportunistic infections in Fell ponies

This report summarises clinical and pathological observations on Fell pony foals with a range of signs that included ill thrift, anaemia, respiratory infection, glossal hyperkeratosis and diarrhoea. Some of the foals had normochromic, normocytic anaemia and some had low levels of plasma proteins, including immunoglobulin G. Antibiotic and supportive treatment was ineffective and all affected foals died or were killed on humane grounds. Postmortem examination of 12 foals and tissues from 2 other foals revealed a range of lesions that included glossal hyperkeratosis, typhlocolitis, intestinal cryptosporidiosis, granulomatous enteritis, proliferative and necrotising bronchiolitis consistent with adenovirus infection; lesions similar to those in the respiratory tract were present in the salivary gland and pancreas of individual foals. Lymphoid tissue was judged to be smaller than expected. These observations suggest the possibility of opportunistic infections secondary to some form of undefined immunocompromised state.

Caudal compression of the infraorbital nerve: A novel surgical technique for treatment of idiopathic headshaking and assessment of its efficacy in 24 horses

UNLABELLED REASONS FOR DESIGNING AND REPORTING TECHNIQUE: Idiopathic headshaking has remarkable similarities to human neuropathic facial pain syndromes associated with post herpetic and trigeminal neuralgia. These derive from abnormal sensory function within the peripheral or central pathways of the trigeminal nerve (TgN). Limiting input from the TgN can be helpful in controlling the perception of pain. Rhizotomy of the infraorbital branch of the TgN as it emerges from the infraorbital canal has been reported but has a poor efficacy. A novel technique involves compression of the nerve at a more caudal location within the infraorbital canal and the technique requires validation. HYPOTHESIS Caudal compression of the infraorbital nerve with platinum coils, performed in horses diagnosed with idiopathic headshaking, results in a decrease in clinical signs. METHODS Caudal compression of the infraorbital nerve, using platinum embolisation coils, was performed under fluoroscopic guidance. Clinical records of 24 idiopathic headshakers that had undergone this procedure were reviewed. Follow-up information was obtained by telephone questionnaire with the owner or referring veterinary surgeon. RESULTS All 24 horses had at least one surgical procedure. Median follow-up time was 6 months. There were 2 horses which had surgery 2 weeks before follow-up and these were excluded from the analysis of outcome. Following one surgery, 13/22 horses (59.0%) had a successful outcome. Of the 9 horses that did not improve, surgery was repeated in 6 cases. Two of these horses had a successful outcome. Overall, a successful outcome was obtained in 16/19 horses (84.2%). CONCLUSIONS This surgical technique is likely to prevent input from the TgN at a more caudal location then the previously described infraorbital neurectomy. The technique requires refinement.

A randomised, blinded, crossover study to assess the efficacy of a feed supplement in alleviating the clinical signs of headshaking in 32 horses.

REASONS FOR PERFORMING STUDY Feed supplements are commonly used by owners to alleviate headshaking; however, randomised, controlled trials are required to assess their efficacy. OBJECTIVE To determine the efficacy of a feed supplement for alleviation of the clinical signs of headshaking using a randomised, blinded, placebo-controlled trial. METHODS Using a crossover design, 44 horses previously diagnosed with chronic idiopathic headshaking received both the supplement and a matching placebo per os for 28 days with a washout period between of 14 days. Video recordings were taken at rest and exercise prior to the study and at the end of both periods of treatment. The degree of headshaking was assessed in a blinded, randomised manner by 2 veterinary surgeons. At the same time points, owners completed a questionnaire to assess the severity of headshaking signs. A Wilcoxon signed rank test was used to compare the scores while on supplement and placebo. RESULTS Using the video assessments, there was no significant difference between scores while on supplement compared with placebo (P = 0.7). Using the questionnaire responses, there was no significant difference between scores for any activity when the placebo and the supplement were compared with each other. However, owners reported significant improvement during all activities for both placebo and supplement compared with pretreatment scores. CONCLUSIONS AND POTENTIAL RELEVANCE The supplement offered no benefit over a placebo in alleviating the clinical signs of headshaking. There appeared to be a significant proxy placebo effect when the outcome was based on subjective owner perception of clinical signs. This study demonstrated no beneficial effect of this supplement on the clinical signs of headshaking. The study did show a significant placebo effect, thereby highlighting the necessity of properly conducted, randomised controlled trials, with blinding, to assess true treatment effects in trials in animals.