Phenylbutazone and the horse--a review.

The clinical uses and side-effects of phenylbutazone in man, horses, and other animals are reviewed. The blood dyscrasias commonly described in man have not been reported in the horse, although several of the more minor side-effects have occasionally been seen (e.g. water retention, depression, transient staggering and phlebitis). Despite the lack of documented evidence, the toxicity of phenylbutazone in the horse is considered to be lower than that in man. This may be associated with the lower dose rates normally used, the more rapid plasma clearance rate and the comparatively younger age of most horses under treatment. The following guidelines for the use of phenylbutazone in practice are put toward. It should only be used under strict veterinary control and then only if there are clear clinical indications. It should not be given if there are signs of gastro-intestinal ulceration, clotting defects or any cardiac, renal or hepatic dysfunction. Dose rates should be kept to a minimum and the drug withdrawn immediately if any side-effects occur or if there is no clinical response within 4 days. If prolonged therapy is necessary, periodic haematological analyses should be carried out.     

Cross-sectional study of antimicrobial-resistant bacteria in horses. Part 2: Risk factors for faecal carriage of antimicrobial-resistant Escherichia coli in horses

Reasons for performing study: The increasing prevalence of antimicrobial resistant bacteria such as antimicrobial‐resistant and extended spectrum β‐lactamase (ESBL)‐producing Escherichia coli represents a significant problem for human and veterinary medicine. Despite this, the risk factors for faecal carriage of such bacteria by horses in the UK, particularly those in the wider community, have not been well described. Objectives: To characterise the risk factors for faecal carriage of antimicrobial‐resistant E. coli amongst horses in the mainland UK. Methods: A cross‐sectional study of horses recruited by 65 randomly selected equine veterinary practices was conducted, with a faecal sample collected and self‐administered questionnaire completed by the horse owner. Faecal samples were cultured for antimicrobial‐resistant E. coli, with isolates confirmed as E. coli having their antimicrobial resistance profile determined. Multilevel, multivariable logistic regression models were used to investigate risk factors for the carriage of antimicrobial‐resistant E. coli in the sample population. Results: Faecal samples and completed questionnaires were obtained for 627 horses located on 475 premises. Recent hospitalisation, contact with specific types of nonequid animals, the type of premises, the surrounding land use, the reason for veterinary treatment received in the last 6 months and antimicrobial treatment in the previous 10 days were identified as risk factors for many of the antimicrobial‐resistance outcomes considered. Being stabled on the same yard as a recently hospitalised horse was identified as a risk factor for increased risk of carriage of ESBL‐producing E. coli. Conclusions and potential relevance: Increasing antimicrobial resistance may have significant health implications for the horse population of Great Britain. This form of epidemiological investigation highlights potential risk factors that may be controlled to limit the extent of the problem.     

Fistulous withers in horses: 24 cases (1984-1990).

Between Jan 1, 1984 and Aug 1, 1990, 27 horses were admitted to the veterinary medical center for evaluation of fistulous withers. Nine (37.5%) of 24 horses tested for antibody to Brucella abortus were seropositive. Horses that tested seropositive were significantly (P = 0.046) more likely to have been pastured with cattle that were seropositive for B abortus, and were significantly (P = 0.010) more likely to have had radiographic evidence of vertebral osteomyelitis than were horses that tested seronegative. Five horses that were seropositive for B abortus were administered strain 19 brucella vaccine sc (n = 1) or iv (n = 4). The horse treated by sc injection of vaccine improved during hospitalization, but was lost to follow-up evaluation. Three (75%) of 4 horses treated by iv injection died, but 1 horse recovered within 4 weeks of treatment.     

Clinicopathologic evidence of disseminated intravascular coagulation in horses with acute colitis

OBJECTIVE: To detect subclinical disseminated intravascular coagulation (DIC) in horses with colitis and to determine any association between the diagnosis of subclinical DIC and outcome or occurrence of complications in horses with colitis. DESIGN: Prospective study. ANIMALS: 37 horses admitted to a veterinary teaching hospital for treatment of acute colitis. PROCEDURE: Coagulation profiles were obtained on each horse 0, 24, and 48 hours after admission. Six tests were performed: platelet count, plasma fibrinogen concentration, prothrombin time, activated partial thromboplastin time, antithrombin activity, and serum fibrin degradation products concentration. RESULTS: A clinicopathologic diagnosis of subclinical DIC was made if 3 of the 6 tests had abnormal results at any 1 sample period. No horse had clinical signs of DIC at the time of sampling. Twelve of 37 (32%) horses met the criteria for diagnosis of subclinical DIC within a 1-year period. Outcome was defined as survival or nonsurvival. Five of 12 horses with subclinical DIC and 2 of 25 horses without subclinical DIC did not survive. Crude odds ratio analysis revealed a horse with acute colitis was 8 times as likely to die or be euthanatized if a diagnosis of subclinical DIC was made. CONCLUSIONS AND CLINICAL RELEVANCE: Clinicopathologic evidence of DIC is common and is significantly associated with a poor outcome in horses with acute colitis. Treatment of subclinical DIC may influence outcome in horses with acute colitis.     

Evaluation of changes in microbiota after fecal microbiota transplantation in 6 diarrheic horses

The purpose of this study was to characterize the fecal microbiota of horses with acute and chronic diarrhea before and after fecal microbiota transplantation (FMT). Six client-owned horses with acute and chronic diarrhea received FMT from 2 healthy donor horses. Microbiota analysis using next-generation sequencing was performed on fecal samples collected before and 2 and 7 d after FMT. Signs of diarrhea improved in 4 horses, whereas the remaining 2 horses did not survive. There was a significant difference in the number of bacterial species between donors and recipients (P < 0.05). The Order Lactobacillales and the genera Lactobacillus, Intestinimonas, and Streptococcus were increased in the microbiota of diarrheic horses, and Saccharofermentans genus increased in healthy donors. The results suggest that FMT from the healthy donors was not effective over a 7-day period as it did not change the fecal microbiota of the diarrheic horses. Further research to improve the efficacy of FMT in horses is needed.     

Extracorporeal shock wave therapy for treatment of osteoarthritis in the horse: clinical applications.

Veterinarians have begun using extracorporeal shock wave therapy (ESWT) for treatment of osteoarthritis (OA) in horses, although relatively little information has been published about its efficacy or mechanism of action. As a clinician, it can be difficult to know if and when ESWT should be recommended. Case studies in which ESWT is used to treat advanced OA in horses are discussed. ESWTseems to be a valuable adjunct for management of equine OA. It is the purpose of this article to discuss indications and techniques as well as to share clinical experiences using ESWT in the treatment of OA in the horse.     

Lack of Cyathostomin sp. reduction after anthelmintic treatment in horses in Brazil

The increase of anthelmintic resistance in the last years in the nematode population of veterinary importance has become a major concern. The objective of the present study was to evaluate the efficacy of the main anthelmintic drugs available in the market against small strongyles of horses in Brazil. A total of 498 horses from 11 horse farms, located in the states of Paraná, São Paulo, Rio de Janeiro and Minas Gerais, in Brazil, were treated with ivermectin, moxidectin, pyrantel and fenbendazole, orally at their recommended doses. The fecal egg count reduction test (FECRT) was used to determine the product's efficacy and fecal culture was used to determine the parasite genus. Reduction on anthelmintic efficacy was found for fenbendazole in all horse farms (11/11), pyrantel in five yards (5/11) and ivermectin had low efficacy in one of the yards studied (1/11). Multidrug resistance of up to 3 drugs classes was found in one of the tested farms (1/11). Cyathostomin were the most prevalent parasite. The results showed that resistance to fenbendazole is widespread; the efficacy of pyrantel is in a critical situation. Although the macrocyclic lactones compounds still showed high efficacy on most farms, suspected resistance to macrocyclic lactones is of great concern.     

An evidence‐based approach to equine parasite control: It ain't the 60s anymore

Most veterinarians continue to recommend anthelmintic treatment programmes for horses that derive from knowledge and concepts more than 40 years old. However, much has changed since these recommendations were first introduced and current approaches routinely fail to provide optimal or even adequate levels of parasite control. There are many reasons for this. Recent studies demonstrate that anthelmintic resistance in equine parasites is highly prevalent and multiple‐drug resistance is common in some countries, but few veterinarians take this into account when making treatment decisions or when recommending rotation of anthelmintics. Furthermore, the current approach of treating all horses at frequent intervals was designed specifically to control the highly pathogenic large strongyle, Strongylus vulgaris. But this parasite is now quite uncommon in managed horses in most of the world. Presently, the cyathostomins (small strongyles) are the principal parasitic pathogens of mature horses. The biology and pathogenesis of cyathostomins and S. vulgaris are very different and therefore require an entirely different approach. Furthermore, it is known that parasites are highly over‐dispersed in hosts, such that a small percentage of hosts harbour most of the parasites. The common practices of recommending the same treatment programme for all horses despite great differences in parasite burdens, recommending prophylactic treatment of all horses without indication of parasitic disease or knowing what species of parasites are infecting the horses, recommending use of drugs without knowledge of their efficacy and failing to perform diagnostic (faecal egg count) surveillance for estimating parasite burdens and determining treatment efficacy, are all incompatible with current standards of veterinary practice. Consequently, it is necessary that attitudes and approaches to parasite control in horses undergo a complete overhaul. This is best achieved by following an evidence‐based approach that takes into account all of these issues and is based on science, not tradition.     

Hypothermia prevention in long-standing equine dental procedures

Hypothermia is a common, detrimental post-operative complication in man and veterinary medicine. Active warming strategies are paramount for prevention and treatment. Duration of operations, administered drugs and their adverse effects put horses undergoing procedures requiring long-standing sedation in danger of hypothermia. The aim of this study was to investigate whether an air warming device would be helpful to avoid severe hypothermia in adult horses. Twenty client-owned horses undergoing dental/sinusoidal procedures were divided into two equal groups. The treatment group was covered with a warming blanket connected to the warming device with the temperature set to 43°C. Horses in the control group were not blanketed. Temperature was measured at the time of first sedation (T0) and every hour throughout the length of the procedure. Use of the warming blanket was straightforward and caused no adverse reactions. The mean decrease in body core temperature in the treatment group was significantly less than the mean temperature decrease in the control group, beginning at the second hour of the procedure. No horse in the treatment group reached a body temperature below 36°C. Overall loss of temperature in the control group was more than double when compared with the treatment group (1.5°C and 0.7°C respectively). The use of an active air warming blanket in horses is an easy technique to prevent hypothermia in horses undergoing long-standing sedation procedures.     

Combined decongestive therapy including equine manual lymph drainage to assist management of chronic progressive lymphoedema in draught horses

Equine chronic progressive lymphoedema (CPL) is a disabling disorder of draught horse breeds. Combined decongestive therapy (CDT) is the treatment of choice for lymphoedema in man and has been adapted for use in horses. Equine CDT, which includes manual lymph drainage (MLD) and subsequent bandaging with short stretch bandages, was expected to improve the signs of CPL in draught horses because CPL resembles primary lymphoedema in man. Five affected horses ‐ Gypsy cob (n = 1), Clydesdale (n = 1), Shires (n = 3) ‐ were included. Lesions were documented pre‐ and post treatment. Percentage volume loss of the distal legs was calculated using the disc model. Initial plans for daily CDT had to be adapted; intermittent treatment of Chorioptes infections required alternating between CDT and MLD in 4/5 horses. Concurrent pyoderma (1/5 horses) was treated throughout the study. Development of unrelated lameness (hoof abscess) allowed limited CDT treatment only in one horse. Marked softening of previously firm tissue indicated the change from ‘brawny’ to pitting oedema in 2/5 horses. Fibrotic nodules and folds in the pasterns became markedly softened and smaller in 2/5 horses. Skin surface notably improved in all horses: hyperkeratosis decreased, erosions and ulcerations healed completely and crusts disappeared. After 2 weeks, a mean volume reduction of 11.25% was seen, ranging from 4.75–21.74% and quality of movement improved. This pilot study documents evidence that CDT assists management of CPL. Current CPL management is limited to palliative treatments of secondary infections. Whilst not a permanent treatment, CDT offers a promising tool to manage horses with CPL, improving their quality of life and potential usefulness. More extensive and prolonged studies with a larger number of horses are warranted to evaluate the full potential of CDT.     

Effect of ‘tongue tie’ use on racing performance of Thoroughbreds in the United Kingdom

Reasons for performing study: There is contradictory published evidence on the potential efficacy of ‘tongue ties’ (TTs) for treatment of intermittent dorsal displacement of the soft palate (DDSP) in racehorses. Objectives: To evaluate the effect of TTs on racing performance in Thoroughbred racehorses in the UK using a retrospective cohort study. Methods: Data on individual horses' lifetime racing performance and TT use were retrieved from the Racing Post Online Database. Exposed cases were horses that ran with a TT in randomly chosen race meetings on one of 60 randomly chosen dates from 2001–2003. Unexposed (control) horses were matched to each exposed horse. Various measures of racing performance were analysed both within and between exposed and unexposed groups. Subsets of exposed horses that ran for 3 or 5 consecutive starts wearing TTs and their matched controls were analysed separately to examine the effect of repeated TT use. Results: The inclusion criteria were fulfilled by 108 horses. The odds ratio for ‘improvement’ in race earnings between exposed and unexposed horses was 1.85 for horses that ran at least once with a TT, and 3.60 and 4.24, respectively, for horses that ran in 3 or 5 consecutive races wearing a TT. After instigation of TT use, horses that ran in 3 or 5 consecutive races wearing a TT had a significant increase in earnings when they ran wearing a TT compared to their pre‐TT races. Conclusions and potential relevance: The use of a TT appears to have a beneficial effect on racing performance in a selected population of Thoroughbred racehorses.     

Use of a jugular vein model for the instruction of equine intravenous catheter placement by third-and fourth-year veterinary students

Successful placement of an i.v. catheter in horses is a core competency required by the AVMA COE accreditation policy (section 7.11, #2,#3,#5). Therefore, we determined whether the use of a novel intravenous (i.v.) catheter placement training tool would improve confidence, time to successful placement and accuracy with which third- and fourth-year veterinary students acquire competence regarding this skill in adult horses. Students lacking earlier experience with i.v. catheter placement in horses were randomly assigned to either Group 1 (n = 15) or 2 (n = 10). Students with prior experience with the technique were assigned to Group 3 (n = 14). Group 1 students were instructed on i.v. catheter placement using the model and then assessed using a live horse. Group 2 students were instructed on i.v. catheter placement using a live horse and then assessed using a live horse. Group 3 students were assessed using a live horse. Assessments included number of placement attempts, number of redirects and time needed to achieve correct intraluminal placement. Student perceptions regarding the use of this model for the purpose of learning i.v. catheter placement in horses were evaluated using a questionnaire. Results of this study demonstrated that students receiving initial instruction with the model achieved better scores in terms of both time to accomplish the task and accuracy for catheter placement in a live horse when compared with students that received their first instruction on a live horse. The use of this i.v. catheter placement training tool therefore served to lessen the cost of training and to minimise animal discomfort during this component of veterinary student training.     

Hendra Virus Infection in Horses: A Review on Emerging Mystery Paramyxovirus

Hendra virus (HeV) is a zoonotic paramyxovirus which causes acute and deadly infection in horses (Equus caballus). It is a rare and unmanaged emerging viral infection in horses which is harbored by bats of the genus Pteropus (Australian flying foxes or fruit bats). The virus is pleomorphic in shape and its genome contains nonsegmented negative-stranded RNA with 18234 nucleotides in length. The virus is transmitted from flying foxes to horses, horse to horse, and horse to humans. Human-to-human transmission of HeV infection is not reported yet. The infection of HeV in horses is highly variable and shows broad range of signs and lesions including distinct respiratory and neurological disorders. Currently, there are no specific antiviral drugs available for the treatment of HeV infection in horses. Vaccination is considered as prime option to prevent HeV infection in horses. A subunit vaccine, called as “Equivac HeV vaccine” has been approved recently for preventing this viral infection in horses. In addition, a plethora of common preventive strategies could help restrict the inter- and intra-species transmission of HeV. Considering the scanty but severe fatality cases of this mystery virus as well as lack of proper attention by veterinary scientists, this review article spotlights not only on the clinical signs, transmission, epidemiology, biology, pathogenesis, and diagnosis of HeV but also the preventive managements of this uncommon infection in horses by vaccination and other precautious strategies.     

Arthroscopic treatment of meniscal cysts in the horse

Reasons for performing study: To describe the clinical symptoms, treatment, and outcome of meniscal cysts in horses. These structures have not been previously described in the literature as a potential cause of lameness in the horse. Hypothesis: Meniscal cysts are an uncommon condition of the femorotibial joint but can be a significant cause of lameness. Symptoms can be resolved by arthroscopic excision. Methods: Records of horses diagnosed with meniscal cysts and treated by cyst excision and meniscal debridement at 2 surgical practices were reviewed. Clinical outcome was determined by repeat veterinary examination and contact with owner. Results: Seven cases of meniscal cyst were treated with arthroscopic cyst excision and meniscal debridement. Five of 7 horses had lameness attributable to femorotibial joint pathology, while the remaining 2 horses had meniscal cysts found incidentally during diagnostic arthroscopy for the treatment of osteochondritis dissecans of the lateral trochlear ridge of the femur. Five of 6 horses with long‐term follow‐up were sound and a 7th horse was improved 11 months after surgery. Conclusions and potential relevance: Meniscal cysts, while uncommon, can be associated with progressive lameness in the horse. Surgical excision of the cysts results in resolution or improvement of symptoms, without evidence of recurrence on follow‐up examination.     

Demographics and costs of colic in Swedish horses

BACKGROUND: Colic is an important cause of morbidity and mortality in horses. In Sweden, an insurance database with diagnostic medical information is maintained on >30% of the nation's horse population. HYPOTHESIS: The objective was to describe the occurrence of colic, defined by costly veterinary care and life claims, in horses at 1 insurance company during 1997-2002. HORSES: All horses (<21 years of age) with complete insurance for veterinary care and life during the period 1997-2002 were included. METHODS: Colic was defined as conditions where the main clinical sign was abdominal pain and the problem was related to the gastrointestinal system. The analyses included measures of incidence by sex, breed group, age categories, geographical location (urban/other), survival to and survival after colic, medical cost for colic, and multivariable modeling of risk factors related to the event of colic. RESULTS: In all, 116,288 horses contributed to 341,564 horse years at risk (HYAR). There were 3,100 horses with a colic diagnosis, of which 27% were settled for life insurance. The median gross cost for veterinary care was 4,729 Swedish Kronor (SEK). The overall occurrence and mortality rate of colic was 91 and 24 events per 10,000 HYAR. Survival after colic at 1 month was 76% (95% confidence interval: 75-78%). CONCLUSIONS AND CLINICAL IMPORTANCE: The occurrence of colic varied with breed group, age, and season. The mortality rates probably reflected the true mortality of colic. The veterinary care rates most likely underestimated of the risk colic because they represent relatively costly events.     

Pharmacology and therapeutics in donkeys

Therapeutics are often administered to donkeys based on dosage and intervals recommended for horses because very few drugs have donkey‐specific label indications. Yet differences between donkeys and horses in drug distribution, metabolism and elimination have been noted for most therapeutic agents studied. These differences can be partially explained by the donkey's unique physiology. Since their ancestors evolved in a desert environment, the modern donkey exhibits qualities that allow them to tolerate dehydration better than the horse and recover more quickly from its effects. Fluid balance and body water compartment partitioning differ from the horse and may have implications regarding drug distribution. Since donkeys are preferential browsers, differences in diet may have influenced evolutionary differences in metabolic disposition of drugs. It is important to acknowledge these differences when designing dose regimes for donkeys based on horse protocols in order to avoid either lack of efficacy or toxicity.     

A randomised, double-blinded, placebo-controlled study on the efficacy of a unique extract of green-lipped mussel (Perna canaliculus) in horses with chronic fetlock lameness attributed to osteoarthritis

Reasons for performing study: Lyophilised products from green‐lipped mussel (Perna canaliculus[LPPC]) are used to orally treat horses with osteoarthritis (OA). However, no randomised, controlled or double‐blinded studies on the efficacy of this treatment in horses have been reported to date. Objective: To investigate the effects of a unique LPPC (Biolane) ¹ in improving clinical signs of OA in the fetlock. Methods: Data were analysed from 26 horses with primary fetlock lameness in a controlled, randomised and double‐blinded, multi‐centre clinical trial. The study design was a partial crossover with a washout period and consisted of 19 horses treated with LPPC and 20 with a placebo. Horses were dosed orally with 25 mg/kg bwt/day LPPC or placebo for 56 days. Efficacy was evaluated by clinical assessment of lameness, passive flexion, pain, swelling and heat in the affected joint. Relationships between variables were analysed using an ordinal logistic model with random effects for horse and horse x treatment according to a modified intention‐to‐treat analysis. Results: Clinical evaluation of horses with a fetlock lameness treated with LPPC showed a significant reduction in severity of lameness (P<0.001), improved response to the joint flexion test (P<0.001) and reduced joint pain (P = 0.014) when compared with horses treated with placebo. Conclusions: The LPPC significantly alleviated the severity of lameness and joint pain and improved response to joint flexion in horses with lameness attributable to OA in the fetlock.     

Photodynamic therapy for the treatment of periocular squamous cell carcinoma in horses: a pilot study

Objective  Local photodynamic therapy (PDT) is a novel cancer therapy in veterinary ophthalmology. A prospective pilot study seeking to demonstrate proof of principle and safety for the treatment of equine periocular squamous cell carcinoma (PSCC) was therefore conducted. We hypothesized that surgical excision with adjunctive local PDT is an effective and safe treatment for equine PSCC.
Procedures  Nine horses (10 eyes) with PSCC were treated with surgical resection, local infiltration of resulting wound beds with 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a (HPPH) and irradiation with 665-nm wavelength diode laser. Regular follow-up ophthalmic examinations were performed.
Results  Surgical resection and PDT yielded disease-free intervals of 25–68 months in our study horses as of January, 2008. These results were obtained following a single treatment in seven horses and two treatments in one horse. In one horse, carcinoma in situ developed 2.5 months after partial surgical excision and PDT, requiring local excision under standing sedation.
Conclusions  Preliminary results suggest that surgical resection and adjunctive local PDT is a safe and effective novel treatment for PSCC in horses. More research is needed before PDT for the treatment of equine PSCC can be adequately compared with other current modalities. Important to future investigations regarding PDT, tumor recurrence rate, length of hospitalization, number of treatment episodes required to effect tumor remission, and total treatment costs should be examined in a controlled manner. Our present results and experiences suggest that this treatment may be useful in the treatment of equine PSCC.     

Pharmacokinetics of azathioprine following single-dose intravenous and oral administration and effects of azathioprine following chronic oral administration in horses

OBJECTIVE: To determine pharmacokinetics of azathioprine (AZA) and clinical, hematologic, and serologic effects of i.v. and oral administration of AZA in horses. ANIMALS: 6 horses. PROCEDURE: In study phase 1, a single dose of AZA was administered i.v. (1.5 mg/kg) or orally (3.0 mg/kg) to 6 horses, with at least 1 week between treatments. Blood samples were collected for AZA and 6-mercaptopurine (6-MP) analysis 1 hour before and at predetermined time points up to 4 hours after AZA administration. In study phase 2, AZA was administered orally (3 mg/kg) every 24 hours for 30 days and then every 48 hours for 30 days. Throughout study phase 2, blood samples were collected for CBC determination and serum biochemical analysis. RESULTS: Plasma concentrations of AZA and its metabolite, 6-MP decreased rapidly from plasma following i.v. administration of AZA, consistent with the short mean elimination half-life of 1.8 minutes. Oral bioavailability of AZA was low, ranging from 1% to 7%. No horses had abnormalities on CBC determination or serum biochemical analysis, other than 1 horse that was lymphopenic on day 5 and 26 of daily treatment. This horse developed facial alopecia from which 1 colony of a Trichophyton sp was cultured; alopecia resolved within 1 month after the study ended. CONCLUSIONS AND CLINICAL RELEVANCE: Overall, no adverse effects were observed with long-term oral administration of AZA to horses, although 1 horse did have possible evidence of immunosuppression with chronic treatment. Further investigation of the clinical efficacy of AZA in the treatment of autoimmune diseases in horses is warranted.