C.E. Wylie

Equine Grass Sickness: Epidemiology, Diagnosis, and Global Distribution

Equine grass sickness (EGS) is recognized as a debilitating and predominantly fatal neurodegenerative disease affecting grazing equids. The gastrointestinal tract is the most severely affected body system, resulting in the main clinical signs of colic (acute grass sickness), weight loss, or dysphagia (chronic grass sickness). EGS predominantly occurs within Great Britain, although it is also recognized in regions of mainland Europe, and mainly affects young horses with access to pasture in the springtime. There is strong evidence of an association between EGS and the type C toxins produced by the bacterium Clostridium botulinum. This article covers the clinical aspects, epidemiology, and global distribution of EGS, along with comparisons with botulism and developments in disease prevention.

Preventive health care and owner-reported disease prevalence of horses and ponies in Great Britain

This study aimed to describe the provision of preventive health care and owner-reported disease prevalence in horses and ponies within Great Britain (GB), and to assess geographical variations in health care provision. A cross-sectional survey was conducted, using a postal questionnaire administered to a random sample of veterinary-registered owners of horses and ponies in GB (n=797). The majority of animals received regular preventive health care: 95.6% had regular hoof care; 71.3% were vaccinated for both influenza and tetanus and median time since last anthelmintic administration was 8.7 weeks. Thirty-one percent of owners indicated their animal was overweight/obese. A new health problem within the previous 7 days was reported for 7.4% of animals, 59.3% of which were veterinary-diagnosed. Thirty-two percent of animals were reported to have a long-term/recurrent condition, of which osteoarthritis (13.9%) was the most prevalent. Obesity, musculoskeletal disorders, and dermatological conditions were the most prevalent conditions affecting veterinary-registered horses/ponies.

Frequency of equine laminitis: a systematic review with quality appraisal of published evidence.

Equine laminitis is a highly debilitating disease of the foot. Despite its perceived importance, epidemiological characteristics are poorly understood and the true frequency of the disease remains unclear. The objective of this study was to retrospectively assess previous research to identify publications which provide the best evidence of the frequency of naturally-occurring equine laminitis. A systematic review of English language publications was conducted using MEDLINE (1950-2010), CAB Direct (1910-2010) and IVIS (1997-2010). Additional publications were included by searching bibliographies. Search terms included laminitis, equine, frequency, prevalence and incidence. Studies that allowed frequency estimations to be made for naturally-occurring equine laminitis were included. Information was extracted using predefined data fields, including 13 study quality indicators. Sixty-nine publications were appraised. Ten were considered to provide the most reliable information, estimating the frequency of equine laminitis ranging from 1.5% to 34%. Previous publications estimating laminitis frequency were generally poor quality. Laminitis frequency varied across publications however the publications included in this review focussed on many of the different underlying laminitis aetiologies and comparison of the frequencies between groups would be inappropriate. High-quality evidence-based studies are needed to estimate the true disease frequency in different equine populations.

Demographics and management practices of horses and ponies in Great Britain: A cross-sectional study

The objectives of this study were to describe the demographic characteristics and management practices undertaken by owners of horses/ponies within GB and assess seasonal and geographical variations in management practices. A cross-sectional study was conducted, surveying a random sample of veterinary-registered owners in GB, using a self-administered postal questionnaire. A total of 797 useable responses were received. Only 4.0% of animals were stabled 24h/day, this proportion being greater in winter compared to other seasons (p<0.001). Shavings (45.7%) and straw (35.3%) were the most frequently used bedding. Ninety-two percent of animals had access to pasture (median 91 h/week). The majority of animals received forage (82.6%) and concentrate/supplementary feeding (86.1%). Retired/companion animals and ponies received supplementary feed less frequently and most animals were used for pleasure riding (60.6%). Seasonal and regional differences in management practices were identified, of relevance to practitioners and researchers in the investigation and management of disease conditions.

Risk factors for equine laminitis: a case-control study conducted in veterinary-registered horses and ponies in Great Britain between 2009 and 2011.

Laminitis is a highly debilitating disease of the foot known to have a complex and multifactorial aetiology of metabolic, inflammatory, traumatic or vascular origin. The disease has major welfare implications due to unrelenting pain associated with degenerative changes, which often necessitate euthanasia on welfare grounds. Despite this, there have been few high-quality studies investigating risk factors for equine laminitis, and only a limited number of risk factors have been previously investigated. The aim of this study was to conduct a case-control study of risk factors for active episodes of veterinary-diagnosed laminitis in horses and ponies attended by veterinary practitioners in Great Britain, based on multivariable statistical analyses. Questionnaires were received for 1010 animals, comprising 191 laminitis cases and 819 controls. Factors associated with an increased risk of laminitis were weight gain in the previous 3 months, summer and winter months compared to spring, new access to grass in the previous 4 weeks, box rest in the previous week, owner-reported history of laminitis, lameness or foot-soreness after shoeing/trimming, existing endocrinopathic (pituitary pars intermedia dysfunction and equine metabolic syndrome) disease and increasing time since the last anthelmintic treatment. Factors associated with a decreased risk of laminitis were increasing height (cm), feeding of additional supplements in the previous week and transportation in the previous week. Novel associated factors were identified that may aid in the management and prevention of the disease in the veterinary-registered equine population.

Laminitic pain: parallels with pain states in humans and other species.

Laminitis poses a threat to all horses, and is widely considered as being one of the most important diseases of horses and a global equine welfare problem. The effects of laminitis lead to debilitation, development of pronounced digital pain, and great suffering in the afflicted animal. The precise pathophysiological processes that result in laminitic pain are poorly defined, and hence the delivery of effective palliative care is clinically challenging. Knowledge and understanding of pain states in other animal species may further aid the elucidation of equine laminitic pain mechanisms, guide the search for treatable causes of this multifactorial problem, and thereby help achieve enhanced therapeutic and palliative care. However, parallels drawn from pain states in other animals must consider species differences in both anatomy and physiology, and the specific nature of the laminitic disease process.

Making use of equine population demography for disease control purposes: preliminary observations on the difficulties of counting and locating horses in Great Britain.

Detailed knowledge of horse populations can better facilitate effective control of equine diseases. Preliminary studies were undertaken to ascertain the type of information held on the UKs National Equine Database (NED) and to determine the geographical resolution at which mandatorily recorded owner addresses might be a suitable proxy for predicting horse locations. Results indicated that relatively few UK passport-issuing organisations requested details of where horses were kept in addition to owner address details. Examination of data on 1440 horses held on an Animal Health Trust syndromic surveillance database showed that 90% of them were kept within 10 km of their owners. While owner location may provide an indication of where most horses are kept, further work is also needed to evaluate the usefulness of NED as an epidemiological resource in future equine disease control measures.

A systematic review of the efficacy of prophylactic control measures for naturally occurring canine leishmaniosis. Part II: topically applied insecticide treatments and prophylactic medications.

The objective of this study was to systematically review the efficacy of topically applied insecticide treatments of dogs (impregnated collars, spot-ons), and prophylactic medications to prevent natural Leishmania infantum (L. infantum) infection in dogs. Randomised controlled trials (RCT), non-randomised clinical trials, cohort studies and case-control studies that investigated preventive efficacy for natural L. infantum infection in dogs were eligible for inclusion. Two review authors independently assessed each study against the inclusion criteria, independently extracted relevant data from all included studies and assessed the risk of methodological shortcomings in each individual study. The odds ratio (OR) and absolute risk reduction (ARR) for dichotomous outcomes and mean difference for continuous outcomes were calculated. Meta-analysis was not performed due to heterogeneity of the studies identified. The search yielded 937 articles, from which 84 full text articles were selected for second stage screening. Eleven eligible studies were included; four on collars (two RCTs), three on spot-ons (two RCTs - one looking at two different dosing regimens), three on prophylactic medications (all RCTs) and one on both collars and spot-ons summarised in this paper. All of the studies were considered to be at a high risk of methodological shortcomings, with the exception of one spot-on study which was considered to be at an unclear risk of methodological shortcomings. Deltamethrin collars, 65% permethrin, 10% imidacloprid with 50% permethrin spot-ons and domperidone prophylactic medication tended to significantly reduce the proportion of dogs infected with L. infantum based on either parasitological or serological evidence.

A systematic review of the efficacy of prophylactic control measures for naturally-occurring canine leishmaniosis, part I: Vaccinations

Canine leishmaniosis (CanL) is an important zoonotic disease; however, the efficacy of available vaccines for the prevention of naturally-occurring Leishmania infantum (L. infantum) infection in dogs remains unclear. The objective of this review was to determine the efficacy of currently available vaccines to prevent naturally-occurring L. infantum infection in dogs. Four bibliographic databases (CAB Direct 2011, Web of Science 2011, U.S. National Library of Medicine 2011 and Literatura Latino Americana e do Caribe em Ciências da Saúde) were searched along with eight sets of conference proceedings and the International Veterinary Information Service (IVIS) database, from 1980 to November 2012. Randomised controlled trials (RCTs), non-randomised clinical trials (NRCTs), cohort studies and case-control studies that investigated vaccine efficacy for natural L. infantum infection in dogs were eligible for inclusion. Two review authors independently assessed each study against the inclusion criteria, independently extracted relevant data from all included studies and assessed the risk of methodological shortcomings in each individual study. The odds ratio (OR) and absolute risk reduction (ARR) for dichotomous outcomes and mean difference for continuous outcomes were calculated. Meta-analysis was not performed due to heterogeneity of the studies identified. The search was conducted for all mitigations for CanL and yielded the title and abstract of 937 articles, from which 84 articles were screened based on full text. Twelve studies on vaccinations (five RCTs, seven NRCTs) were identified. Ten studies were at a high risk of methodological shortcomings, whilst two were at an unclear risk. The use of 200 μg ALM protein, Leishmune(®), CaniLeish(®), LiESAp with MDP, and ALM with BCG tended to significantly reduce the proportion of dogs infected with L. infantum based on either parasitological or serological evidence. The use of lyophilized protein vaccine significantly increased the proportion of dogs infected with L. infantum based on either parasitological or serological evidence. There is peer-reviewed evidence that control measures are effective in preventing CanL with the results suggesting that between 6 and 54% of infections could be prevented with vaccination. However, this evidence is based on a small number of RCTs, all of which are either at high or unclear risk of methodological shortcomings. Well-designed, adequately powered and properly reported randomised clinical trials are needed to clearly establish efficacy of vaccines as CanL control measures.

A cohort study of equine laminitis in Great Britain 2009–2011: estimation of disease frequency and description of clinical signs in 577 cases

REASONS FOR PERFORMING STUDY A previous systematic review highlighted a lack of good evidence regarding the frequency of equine laminitis in Great Britain. OBJECTIVES To estimate the frequency of veterinary-diagnosed active laminitis in the general horse population of Great Britain and to describe the clinical signs present in cases. STUDY DESIGN Prospective cohort study. METHODS Data on active episodes of equine laminitis were collected from veterinary practitioners. RESULTS The prevalence of veterinary-diagnosed active laminitis was 0.47% (95% confidence interval [CI] 0.42-0.52%) for the veterinary-attended population and 0.49% (95% CI 0.43-0.55%) for the veterinary-registered population, suggesting that active episodes of laminitis accounted for nearly one in 200 equine visits and occurred in nearly one in 200 horses registered with veterinary practices. The incidence of veterinary-diagnosed active laminitis was 0.5 cases per 100 horse-years at risk (95% CI 0.44-0.57). Laminitis occurred in all limbs, but most commonly affected the forelimbs bilaterally (53.5%, 95% CI 49.4-57.7%) and was most severe in the front feet. The most common clinical signs were increased digital pulses, difficulty turning and a short, stilted gait at walk. CONCLUSIONS AND POTENTIAL RELEVANCE The frequency of veterinary-diagnosed active laminitis was considerably lower than previously published estimates, which is probably due to differences in geographical setting, study period, case definition, study design and study populations.