Pharmacology in horses involves the study and application of drugs and medications to diagnose, treat, and prevent diseases and conditions in equine species. This field encompasses the understanding of pharmacokinetics and pharmacodynamics specific to horses, including how drugs are absorbed, distributed, metabolized, and excreted by the equine body. Commonly studied pharmacological agents in horses include non-steroidal anti-inflammatory drugs (NSAIDs), antibiotics, sedatives, and anthelmintics. Research in equine pharmacology focuses on determining appropriate dosages, understanding drug interactions, and minimizing adverse effects. This page compiles peer-reviewed research studies and scholarly articles that investigate the efficacy, safety, and regulatory aspects of pharmacological interventions in equine veterinary practice.
Symonds NE, Dart AJ, Keledjian J, Lau ML, Ennis LC, McIver VC, Tsang AS, Biasutti SA, Jeffcott LB.To quantify the time to clear dexamethasone from plasma and urine of horses following a single nebulisation. Methods: Experimental using six Standardbred mares. Methods: Dexamethasone sodium phosphate (0.04 mg/kg) diluted in 0.9% sodium chloride was administered as an aerosol using a Flexineb E2® nebuliser. Blood samples (0, 2, 4, 6, 8, 10, 12, 24, 32, 48, 72 and 96 h) and urine samples (0, 1, 4, 8, 24, 32, 48, 72 and 96 h) were collected for analysis using liquid chromatography mass spectrometry. Results: Maximum plasma concentrations (t ) were reached by the earliest detection point (...
Walshe N, Duggan V, Cabrera-Rubio R, Crispie F, Cotter P, Feehan O, Mulcahy G.The interactions between parasitic helminths and gut microbiota are considered to be an important, although as yet incompletely understood, factor in the regulation of immunity, inflammation and a range of diseases. Infection with intestinal helminths is ubiquitous in grazing horses, with cyathostomins (about 50 species of which are recorded) predominating. Consequences of infection include both chronic effects, and an acute inflammatory syndrome, acute larval cyathostominosis, which sometimes follows removal of adult helminths by administration of anthelmintic drugs. The presence of cyathosto...
Khan A, Hallowell GD, Underwood C, van Eps AW.Rectal fluid administration may offer a simple, safe and inexpensive alternative to intravenous or nasogastric fluid therapy in equine clinical cases. Objective: To evaluate the tolerance and effects of rectally administered fluid and compare the measurements of haemodilution and intravascular volume with those during nasogastric and intravenous fluid administration. Methods: Randomised controlled experimental trial. Methods: Six clinically normal Standardbred geldings were used in a 4-way crossover study: each received three different fluid treatments (intravenous, nasogastric and rectal) at ...
Ginther OJ, Domingues RR, Kennedy VC, Dangudubiyyam SV.An inhibitor of PGF2α biosynthesis (flunixin meglumine, FM) was used to study the role of endogenous PGF2α on the luteolytic effect of exogenous PGF2α in mares. A 2-h infusion of PGF2α at a constant rate (total dose, 0.1 mg) on Day 10 (ovulation = Day 0) was used to mimic the maximal concentrations of a spontaneous pulse of a PGF2α metabolite (PGFM). Treatment with FM (1.7 mg/kg) was done 1 h before and 5 h after the start of PGF2α infusion. In hourly blood samples beginning 1 h before the start of PGF2α infusion, progesterone decreased (P < 0.05) similarly by 5 h in each of t...
Nielsen MK, Sauermann CW, Leathwick DM.Anthelmintic resistance is widespread in equine cyathostomin populations across the world, and with no new anthelmintic drug classes in the pharmaceutical pipeline, the equine industry is forced to abandon traditional parasite control regimens. Current recommendations aim at reducing treatment intensity and identifying high strongylid egg shedders in a targeted treatment approach. But, virtually nothing is known about the effectiveness of these recommendations, nor their applicability to different climatic regions, making it challenging to tailor sustainable recommendations for equine parasite...
Lavoie JP, Bullone M, Rodrigues N, Germim P, Albrecht B, von Salis-Soglio M.Inhaled corticosteroids are effective for the treatment of equine asthma but they induce cortisol suppression with potential side effects. Objective: To study the efficacy of ciclesonide, an inhaled corticosteroid with an improved safety profile, on lung function, clinical signs related to airway obstruction, and serum cortisol levels in asthmatic horses exposed to a mouldy hay challenge. Methods: Cross-over placebo controlled, blinded, randomised experiment. Methods: Sixteen horses were enrolled in three subsequent dose-titration studies (8 horses/study) to investigate the effects of inhaled ...
Tessier C, Pitaud JP, Thorin C, Touzot-Jourde G.There are no data investigating the effect of systemic morphine on the size of the stomach or the food consumption in horses. Objective: To evaluate gastrointestinal side effects of morphine administered systemically in healthy horses by the means of clinical and ultrasonographic evaluations. Methods: In vivo experiment. Methods: On day 1 of the experiment, six healthy French Trotter mares were evaluated clinically and an abdominal ultrasonography was performed three times 4 h apart to record the size of the stomach, the number of contractions per minute of the duodenum, jejunum, caecum, left...
Mainguy-Seers S, Bessonnat A, Picotte K, Lavoie JP.Inhaled corticosteroids are effective in the treatment of equine asthma. A recent study reported that nebulisation of injectable dexamethasone had low systemic bioavailability in healthy horses and could represent a cost-effective therapy for equine inflammatory lung diseases. Objective: To determine the effects of dexamethasone nebulisation on lung function in severe asthmatic horses. It was hypothesised that dexamethasone administered by nebulisation would be more effective than the same dose administered orally. Methods: Randomised blinded experimental study in severe asthmatic horses. Meth...
Theurillat R, Sandbaumhüter FA, Gittel C, Larenza Menzies MP, Braun C, Thormann W.An enantioselective assay for the determination of methadone and its main metabolite 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine in equine plasma based on capillary electrophoresis with highly sulfated γ-cyclodextrin as chiral selector and electrokinetic analyte injection is described. The assay is based on liquid/liquid extraction of the analytes at alkaline pH from 0.1 mL plasma followed by electrokinetic sample injection of the analytes from the extract across a buffer plug without chiral selector. Separation occurs cationically at normal polarity in a pH 3 phosphate buffer containin...
Raftery AG, Jallow S, Rodgers J, Sutton DGM.Globally, working equines have a continued and growing socioeconomic role in supporting the livelihoods of between 300-600 million people in low income countries which is rarely recognised at a national or international level. Infectious diseases have significant impact on welfare and productivity in this population and equine trypanosomiasis is a priority disease due to its severity and prevalence. Strategies are required to improve the prevention, diagnosis, management and treatment of trypanosomiasis in equines and more data are required on the efficacy and safety of current trypanocidal dr...
Lindström H, Mazari AMA, Musdal Y, Mannervik B.Equine glutathione transferase A3-3 (EcaGST A3-3) belongs to the superfamily of detoxication enzymes found in all higher organisms. However, it is also the most efficient steroid double-bond isomerase known in mammals. Equus ferus caballus shares the steroidogenic pathway with Homo sapiens, which makes the horse a suitable animal model for investigations of human steroidogenesis. Inhibition of the enzyme has potential for treatment of steroid-hormone-dependent disorders. Screening of a library of FDA-approved drugs identified 16 out of 1040 compounds, which at 10 μM concentration afforded at ...
Thompson DL, Valencia NA, Walker NL, Oberhaus EL.Five experiments were performed to test the hypothesis that α-melanocyte-stimulating hormone (MSH) is secreted in response to various stressors in horses similar to prolactin, growth hormone, and adrenocorticotropin (ACTH). There was considerable variation in resting concentrations of MSH and in the degree of stimulation in responders; thus all data sets were tested for heterogeneity of variance and corrected for as needed before analysis. In experiment 1, 12 mares were used in a switchback design to test the effect of a 2-minute exercise bout on MSH secretion. Plasma MSH concentrations were ...
Subhahar MB, Singh J, Albert PH, Kadry AM.Celecoxib, a nonsteroidal anti-inflammatory drug, is frequently used to treat arthritis in humans with minimal gastrointestinal side effect compared to traditional NSAIDs. The primary aim of this study was to determine the pharmacokinetic profile of celecoxib-a selective cyclooxygenase-2 (COX-2) inhibitor in horses. Six horses were administered a single oral dose of celecoxib at 2 mg/kg (body weight). After oral dosing, the drug reached a maximum concentration (mean ± SD) in blood of 1,088 ± 324 ng/ml in 4.58 hr. The elimination half-life was 13.60 ± 3.18 hr, and the area under th...
Bozorgmanesh R, Magdesian KG, Sutton-Burges JW, Owens SD, Tablin F.Development of equine platelet concentrate (PC) would aid management of cases requiring transfused platelets (PLTs), where adminstration of whole-blood or platelet-rich plasma (PRP) might be contraindicated. Objective: To test and validate a method for production of an equine PRP-PC product. Methods: Six healthy Thoroughbred geldings from a research herd. Methods: In this prospective experimental study, whole blood was collected and processed through multiple centrifugation steps to yield 120 mL of PC. The PC was stored at 22°C and gently and continuously agitated. Measurements of PLT count...
Silva GB, De La Côrte FD, Brass KE, Palma HE, Gallio M, Cantarelli C, Bertolin K, Krause A, Wergutz J, Fontanari Krause LM, Antoniazzi AQ.Chondrocyte health is altered when exposed to local anesthetics, raising concerns as to the long-term effects of local anesthetics intra-articularly for diagnosis and analgesia. To investigate the drug with the lowest toxic potential, the effect of ropivacaine and mepivacaine on chondrocytes was evaluated. Articular cartilage from normal metacarpophalangeal joints of five equine cadaver specimens was used to establish chondrocyte cultures. Following seven days, chondrocytes were exposed to standard culture medium (DMEM), ropivacaine 7.5 mg/ml (ROP7.5), ropivacaine 10 mg/ml (ROP10), mepivacaine...
Rütten S, Schrödl W, Abraham G.Glucocorticoids are important drugs in the treatment of many inflammatory, autoimmune and allergic diseases in humans and animals. We investigated the effects of hydrocortisone and dexamethasone on TNF-α, IL-1Ra and INF-γ release in stimulated whole blood cell culture from healthy horses. Whole blood cell cultures proved to be useful for the characterization of the anti-inflammatory properties of new drugs. Diluted equine whole blood was exposed to lipopolysaccharide (LPS) and PCPwL (a cocktail consisting of phythemagglutinin E, concanavalin A, pokeweed mitogen and lipopolysaccharide) in the...
Caron JP, Gandy JC, Brown JL, Sordillo LM.Omega-3 fatty acid (n-3 PUFA) supplementation may have beneficial effects in certain chronic diseases, potentially including osteoarthritis. Favorable effects are attributed, in part, to downstream pro-resolving oxylipid metabolites. We investigated the role of n-3 PUFA and docosahexaenoic acid (DHA)-derived oxylipids (docosanoids) on equine synoviocyte metabolism. We hypothesized that n-3 PUFA and selected docosanoids would modulate inflammatory mediator gene expression by recombinant equine (re)IL-1β-stimulated synovial fibroblasts. Synoviocyte monolayer cultures were prepared from grossly ...
Morris LH, Colgan S, Leathwick DM, Nielsen MK.Parasite control in foals is complicated by the concurrent presence of biologically diverse parasites with differing levels of anthelmintic resistance. Several combination anthelmintic products are available for use in horses, but information on their efficacies against important equine parasites is scarce. Two trials were performed in New Zealand during 2008 and 2011 on four different farms with substantially different anthelmintic treatment histories. The first trial evaluated the efficacy of an ivermectin/praziquantel/oxibendazole combination, a single active oxibendazole, and a single-acti...
Mama KR, Hector RC.Many drugs and non-drug modalities are used to manage pain in horses, but evidence regarding efficacy and safety remains limited. This manuscript will first briefly review tried and tested techniques, e.g. the use of non-steroidal anti-inflammatory drugs, in the management of pain. Newer approaches to administering medications such as oral use of detomidine, which was previously only administered by injection, will also be discussed. Finally, introductory information on newer therapies, for example acupuncture and chiropractic manipulation, that the veterinarian may consider for the management...
Morresey PR, White GW, Poole HM, Hu T, Yin M, Sundman EA.OBJECTIVE To evaluate the effectiveness and safety of dipyrone to control pyrexia in horses with naturally occurring disease under field conditions. ANIMALS 138 horses with pyrexia and various infections evaluated at 14 veterinary sites in 12 states. PROCEDURES In the first (effectiveness) phase of this 2-phase study, horses were randomly assigned 3:1 to receive 1 dose of dipyrone (30 mg/kg [13.6 mg/lb], IV) or an equivalent amount of placebo. Effectiveness was defined as a decrease in rectal temperature ≥ 1.1°C (2°F), compared with the pretreatment value, or a rectal temperature of ≤ 38...
Meier A, de Laat M, Reiche D, Fitzgerald D, Sillence M.A previous six-week (wk) study demonstrated the potential of the sodium-glucose linked transport inhibitor velagliflozin as a novel treatment for equine insulin dysregulation. The present study examined the safety and efficacy of velagliflozin over 16 wk. of treatment, and over 4 wk. of withdrawal. Twenty-four insulin dysregulated ponies were selected, based on their hyper-responsiveness to a diet challenge meal containing 3.8 g non-structural carbohydrates (NSC)/kg bodyweight (BW). Ponies with serum insulin > 90 μIU/mL either 2 or 4 h after feeding were enrolled, and randomly allocated...
Rangel-Nava A, Ramírez-Uribe JM, Recillas-Morales S, Ibancovichi-Camarillo JA, Venebra-Muñoz A, Sánchez-Aparicio P.The objective of the study was to conduct a review of the pharmacological regulation and pharmacokinetic parameters of firocoxib when administered orally or intravenously in horses. A search for literature was done in SCOPUS and PubMed for studies that had to evaluate the pharmacological regulation as well as the pharmacokinetic parameters of firocoxib when administered in horses. The nonsteroidal anti-inflammatory drugs have analgesic, anti-inflammatory, antipyretics, and antiendotoxic effects. The newly developed is selective to COX2 characterized by less adverse effects in veterinary patien...
Schwarzbach SV, Melo CF, Xavier PLP, Roballo KC, Cordeiro YG, Ambrósio CE, Fukumasu H, Carregaro AB.Osteoarthritis (OA) is one of the main locomotor disorders in horses. Although nonsteroidal anti-inflammatory drugs are the first-line treatment for OA, opioids could also be used. In previous studies, opioids showed promising anti-inflammatory and analgesic effects. In this study, we aimed to investigate the effects of two opioids (morphine and methadone) against inflammation in lipopolysaccharide (LPS)-stimulated synoviocytes by analyzing microsomal prostaglandin E synthase-1 (mPGES-1) and prostaglandin-endoperoxide synthase 2 (PTGS2) expression. Synoviocytes were obtained from the joints at...
Durham AE, Frank N, McGowan CM, Menzies-Gow NJ, Roelfsema E, Vervuert I, Feige K, Fey K.Equine metabolic syndrome (EMS) is a widely recognized collection of risk factors for endocrinopathic laminitis. The most important of these risk factors is insulin dysregulation (ID). Clinicians and horse owners must recognize the presence of these risk factors so that they can be targeted and controlled to reduce the risk of laminitis attacks. Diagnosis of EMS is based partly on the horse's history and clinical examination findings, and partly on laboratory testing. Several choices of test exist which examine different facets of ID and other related metabolic disturbances. EMS is controlled ...
Gozalo-Marcilla M, Luna SP, Gasthuys F, Pollaris E, Vlaminck L, Martens A, Haspeslagh M, Schauvliege S.To determine the required rate of a detomidine infusion (loading dose 5 μg kg; initial rate 12.5 μg kg hour) added to a constant infusion of methadone (0.2 mg kg; 0.05 mg kg hour) for sedation in standing horses and ponies undergoing elective surgeries with appropriate local anaesthetic techniques. Methods: Prospective, clinical study. Methods: Adult, healthy, client-owned, non-food-producing horses or ponies sedated for elective standing surgeries longer than 45 minutes. Methods: At baseline (in the stables before administration of sedative agents), at 10 minutes after sedation and every 5 ...
Varegg MS, Kløverød KM, Austnes MK, Siwinska N, Slowikowska M, Zak A, Niedzwiedz A.Bronchoalveolar lavage (BAL) is a method for the recovery of respiratory secretion from the lower airways. Objective: To investigate if the administration of a single dose of a bronchodilatator in horses with a suspected or confirmed severe equine asthma could improve recovery of bronchoalveolar lavage fluid (BALF). Methods: Twenty-eight horses with severe equine asthma. Methods: Horses were divided into 2 groups: group "treated" was given salbutamol before endoscopic examination and BALF collection, whereas group "not treated" was not given. BAL was performed with BAL-catheter by instilling 3...
Müntener C, Kupper J, Naegeli H, Gassner B.A total of 306 reports of adverse reactions to veterinary medicinal products were received during the year 2017 representing an increase of 21% compared to the previous year. The majority of these reports described reactions concerning companion animals (180 dogs and 59 cats) as well as cattle (38 reports) and horses (14 reports). Most of the reported reactions were linked to the use of antiparasitics (158 reports), hormone products (30 reports) and anti-inflammatory products (25 reports). 40 reports were generated from consultations with Tox Info Suisse in Zürich and mainly involved the ex...
Sarnecky BA, Vanderwall DK, Mason HM, Kirschner SM, Ambrose B, Parker TL.Prolonging function of the corpus luteum (CL) is a method of suppressing estrus that relies on continued secretion of endogenous progesterone to keep mares out of heat naturally. The use of oxytocin treatment to prolong CL function is gaining increasing use, and the most common treatment protocol involves administration of 60 units of oxytocin intramuscularly (IM) once daily on days 7-14 after ovulation (eight daily treatments). Although that protocol induces prolonged CL function in ≥70% of treated mares, the need for daily administration is a drawback to its use. Therefore, the objective o...
Ansari Mood M, Rajaei SM, Faghihi H, Ghiadi A.This study was performed to evaluate the effect of topical 1% cyclopentolate hydrochloride on tear production (STT), intraocular pressure (IOP), and vertical pupil diameter (VPD) in healthy Turkman horses. Forty eyes of 20 clinically normal horses were used for this study, which were randomly assigned to two groups. Before instillation of 1% cyclopentolate, the baseline STT, IOP, and VPD of each group were recorded. Then, one drop of cyclopentolate was instilled randomly into one eye of each animal, and the contralateral eye served as control. Measurements were repeated at 20 minutes, 60 min...
Corado CR, McKemie DS, Young A, Knych HK.Metabolism is an essential factor in the clearance of many drugs and as such plays a major role in the establishment of dosage regimens and withdrawal times. CYP2D6, the human orthologue to equine CYP2D50, is a drug-metabolizing enzyme that is highly polymorphic in humans leading to widely differing levels of metabolic activity. As CYP2D6 is highly polymorphic, in this study it was hypothesized that the gene coding for the equine orthologue, CYP2D50, may also be prone to polymorphism. Blood samples were collected from 150 horses, the CYP2D50 gene was cloned and sequenced; and full-length seque...
Bourebaba L, Bedjou F, Röcken M, Marycz K.Equine metabolic syndrome (EMS) refers to a cluster of associated abnormalities and metabolic disorders, including insulin resistance and adiposity. The numerous biological properties of mesenchymal stem cells (MSCs), including self-renewal and multipotency, have been the subject of many in-depth studies, for the management of EMS; however, it has been shown that this cell type may be affected by the condition, impairing thus seriously their therapeutic potential. Therefore, an attempt to rescue EMS adipose-derived stem cells (ASCs) with calystegines (polyhydroxylated alkaloids) that are endow...
Rigotti C, De Vries A, Taylor PM.A prospective, randomised, blinded, clinical trial in 47 ponies compared butorphanol and buprenorphine administered intravenously with detomidine prior to castration under anaesthesia. Detomidine 12 μg/kg intravenously was followed by butorphanol 25 μg/kg (BUT) or buprenorphine 5 μg/kg (BUP) before induction of anaesthesia with intravenous ketamine and diazepam. Quality of sedation, induction and recovery from anaesthesia, response to tactile stimulation, and surgical conditions were scored. If anaesthesia was inadequate 'rescue' was given with intravenous ketamine (maximum three dose...
Durando MM, MacKay RJ, Linda S, Skelley LA.Polymyxin B and an antiserum against an Re mutant Salmonella typhimurium were evaluated for protective effect in an equine model endotoxemia. Six 3- to 5-month-old foals were given endotoxin (0.25 micrograms/kg of body weight) IV after no pretreatment, or pretreatment with polymyxin B (6,000 U/kg, IV) or S typhimurium antiserum (1.5 ml/kg, IV). When given without pretreatment, endotoxin caused transient recumbency and increases in rectal temperature, and heart and respiratory rates. In addition, leukopenia and increases in circulating tumor necrosis factor (TNF) and interleukin 6 (IL-6) activi...
Ruíz-López P, Morgaz J, Quirós-Carmona S, Navarrete-Calvo R, Domínguez JM, Gómez-Villamandos RJ, Granados MM.Autonomic nervous system (ANS) activity can modify cardiovascular parameters in response to nociceptive stimuli or drugs in anesthetized animals. The aim of this study was to determine if a surgical nociceptive stimulus and morphine, ketamine, and dobutamine administration would modify ANS activity observed as a change in the mean parasympathetic tone activity (PTAm) in anesthetized horses. In 20 anesthetized horses, heart rate (HR), mean arterial pressure (MAP), and PTAm were monitored before and 1, 3, and 5 min after surgical incision, and before and 10 min after the administration of morphi...
Delekta PC, Dobry CJ, Sindac JA, Barraza SJ, Blakely PK, Xiang J, Kirchhoff PD, Keep RF, Irani DN, Larsen SD, Miller DJ.Neurotropic alphaviruses, including western, eastern, and Venezuelan equine encephalitis viruses, cause serious and potentially fatal central nervous system infections in humans for which no currently approved therapies exist. We previously identified a series of thieno[3,2-b]pyrrole derivatives as novel inhibitors of neurotropic alphavirus replication, using a cell-based phenotypic assay (W. Peng et al., J. Infect. Dis. 199:950-957, 2009, doi:http://dx.doi.org/10.1086/597275), and subsequently developed second- and third-generation indole-2-carboxamide derivatives with improved potency, solub...
Piat P, Richard H, Beauchamp G, Laverty S.To assess the effects of an intra-articular (IA) lidocaine or bupivacaine injection on synovial fluid (SF) biomarkers of cartilage metabolism. Methods: Experimental. Methods: Horses (n = 6). Methods: The study had 2 components, each with an identical design: the first arm assessed the effects of bupivacaine (0.5%) IA in the intercarpal joints and, after a 2-week washout period, the second was conducted to evaluate the effects of IA lidocaine (2%) in the tarsocrural joints. The mares were randomly assigned to receive the test local anesthetic in the target joint or the placebo (0.9% NaCl) in th...
Bottoms GD, Johnson MA, Lamar CH, Fessler JF, Turek JJ.Dispersed equine vascular endothelial cells grown in tissue culture, and freshly isolated neutrophils were used to determine direct effects of endotoxin on cyclooxygenase and lipoxygenase products. Endothelial cells (10(7)/ml) or neutrophils (2 X 10(6)/ml) were incubated with (a) buffer, (b) endotoxin (10 micrograms/ml), (c) endotoxin + flunixin meglumine (10 micrograms/ml), or (d) calcium ionophore, A23187 (10 micrograms/ml). Thromboxane (TxB2), prostacyclin (6-keto-PGF1 alpha), and leukotriene C4 (LTC4) were determined in the incubation fluid by radioimmunoassay. Thromboxane and prostacyclin...
Combie J, Shults T, Nugent EC, Dougherty J, Tobin T.The locomotor responses of horses given morphine and fentanyl were blocked or lessened by administration of naloxone or acepromazine. Naloxone given at the dosage of 0.015 mg/kg completely blocked the locomotor activity induced in horses given fentanyl (0.020 mg/kg of body weight). The locomotor stimulation produced by morphine given at the dosage of 2.4 mg/kg was reduced by 75% of naloxone (0.020 mg/kg). Acepromazine partially blocked the locomotor responses to fentanyl and morphine. This blockade activity reached its peak about 30 minutes after acepromazine was given (IV) and lasted more tha...
de Albuquerque PPLF, Santos LHS, Antunes D, Caffarena ER, Figueiredo AS.Infections produced by hepaciviruses have been associated with liver disease in horses. Currently, at least three viruses belonging to the Flaviviridae family are capable of producing a chronic infection in equines: non-primate hepacivirus (NPHV), Theiler's disease-associated virus (TDAV), and equine pegivirus (EPgV). The RNA-dependent RNA polymerases of viruses (RdRp) (NS5 protein), from the flavivirus family, use de novo RNA synthesis to initiate synthesis. The two antiviral drugs currently used to treat hepatitis C (HCV), sofosbuvir and dasabuvir, act on the viral NS5B polymerase as nucleos...
Hoffman EP.The pathological genetic defects in the inherited myotonias and periodic paralyses were recently elucidated using molecular genetic studies. These disorders are usually transmitted as a dominant trait from an affected parent to a child. The many clinical symptoms include cold-induced uncontrollable contraction of muscle, potassium-induced contraction and paralysis, myotonia with dramatic muscular hypertrophy, muscle stiffness, and insulin-induced paralysis (in males). Horses afflicted with the disorder can suddenly collapse, despite an impressive physique. In the past three years, these clinic...
Nielsen MK, Branan MA, Wiedenheft AM, Digianantonio R, Scare JA, Bellaw JL, Garber LP, Kopral CA, Phillippi-Taylor AM, Traub-Dargatz JL.Equine strongyle parasites are ubiquitous in grazing equids across the world. Anthelmintic resistance is widely developed in cyathostomin populations, but very few surveys have evaluated anthelmintic efficacy in equine populations in the United States, and most of these are over 15 years old. The present study was carried out as part of the National Animal Health Monitoring Systems (NAHMS) Equine 2015-2016 study. The aims were to investigate anthelmintic treatment efficacy by means of the fecal egg count reduction test (FECRT) and identify parameters associated with decreased efficacy. Data we...
Tydén E, Dahlberg J, Karlberg O, Höglund J.The development of anthelmintic resistance (AR) to macrocyclic lactones in the equine roundworm Parascaris equorum has resulted in benzimidazoles now being the most widely used substance to control Parascaris infections. However, over-reliance on one drug class is a risk factor for the development of AR. Consequently, benzimidazole resistance is widespread in several veterinary parasites, where it is associated with single nucleotide polymorphisms (SNPs) in drug targets encoded by the β-tubulin genes. The importance of these SNPs varies between different parasitic nematodes, but it has been h...
Macpherson ML.Equine placentitis, and resultant preterm labor, are important sources of fetal and neonatal loss. The primary cause of equine placentitis is infection of the placenta with Streptococcus equi subspecies zooepidemicus, which ascends through the caudal reproductive tract. Current treatment protocols for mares affected with placentitis are empirical. This paper reviews treatment approaches for resolving placentitis and preterm labor in both equine and non-equine species. Specific therapies reviewed include antimicrobial, anti-inflammatory, tocolytic, and progestin agents.
Harrington DD, Page EH.Acute vitamin D toxicosis was diagnosed in 2 horses fed a grain ration containing 1,102,311 IU of cholecalciferol (vitamin D3)/kg (500,000 IU/lb) for about 30 days. Horse 1 died acutely with extensive mineralization of cardiovascular and other soft tissues. Horse 2, which had severe clinical signs and clinicopathologic changes of toxicosis, was treated with nonsteroidal antiinflammatory drugs and recovered in about 6 months. In an experimental study, the toxicity of ergocalciferol (vitamin D2) and cholecalciferol was compared in 2 horses (No. 3 and 4) given the respective vitamins at a daily d...
Meier A, de Laat M, Reiche D, Fitzgerald D, Sillence M.A previous six-week (wk) study demonstrated the potential of the sodium-glucose linked transport inhibitor velagliflozin as a novel treatment for equine insulin dysregulation. The present study examined the safety and efficacy of velagliflozin over 16 wk. of treatment, and over 4 wk. of withdrawal. Twenty-four insulin dysregulated ponies were selected, based on their hyper-responsiveness to a diet challenge meal containing 3.8 g non-structural carbohydrates (NSC)/kg bodyweight (BW). Ponies with serum insulin > 90 μIU/mL either 2 or 4 h after feeding were enrolled, and randomly allocated...
Davis JL, Posner LP, Elce Y.A 24-year-old 732-kg (1,610-lb) pregnant Belgian draft horse mare developed neuropathy and signs of intractable pain following colic surgery. Results: Following recovery from colic surgery to treat compression of the small and large intestines because of a large fetus, the mare was noticed to have signs of femoral neuropathy involving the left hind limb. Within 36 hours after recovery, the mare developed signs of severe pain that were unresponsive to conventional treatment. No gastrointestinal tract or muscular abnormalities were found, and the discomfort was attributed to neuropathic pain. Re...
Carlson KL, Kuskie KR, Chaffin KM, Libal MC, Giguère S, Lawhon SD, Cohen ND.This study determined the antimicrobial activity of tulathromycin against Rhodococcus equi in vitro. Ninety-eight virulent isolates of R. equi from equine clinical cases were examined, of which 20 isolates were macrolide resistant. A custom 96-well antimicrobial susceptibility testing plate was used, allowing 14 additional antimicrobials to be tested against R. equi. Isolates were cultured with various concentrations of antimicrobials, and minimal inhibitory concentration (MIC) values were determined. Tulathromycin was found to have poor activity in vitro against R. equi isolates susceptible o...
Simonsen U, Prieto D, Hernández M, Sáenz de Tejada I, García-Sacristán A.To study the influence of alpha-adrenergic stimuli on non-adrenergic non-cholinergic (NANC) neurogenic relaxation in isolated horse penile resistance arteries. Methods: Deep intracavernous penile arteries with an internal lumen diameter of 200-500 microns., isolated from the corpus cavernosum of young horses, were mounted in microvascular myographs for isometric tension recording and electrical field stimulation (EFS) of autonomic nerve terminals. Results: In the presence of guanethidine (10(-5) M) and atropine (10(-7) M) tone of the arteries was raised by the thromboxane analogue, U46619. EFS...
Bailey CS, Macpherson ML, Pozor MA, Troedsson MH, Benson S, Giguere S, Sanchez LC, Leblanc MM, Vickroy TW.The objective was to determine if long-term treatment with trimethoprim sulfamethoxazole (antimicrobial), pentoxifylline (anti-inflammatory/anti-cytokine) and altrenogest (synthetic progestin), would improve pregnancy outcome in mares with experimentally induced placentitis. Seventeen normal, pregnant pony mares were enrolled in the study at 280-295 d of pregnancy. Placentitis was induced in all mares by intra-cervical inoculation of Streptococcus equi subsp. zooepidemicus (10(7) CFU). Five mares served as infected, untreated control animals (Group UNTREAT). Twelve mares (Group TREAT) were inf...
Dabareiner RM, White NA.The cecum is an important site of water and electrolyte absorption, as well as microbial digestion of soluble and insoluble carbohydrates. These functions of the cecum and ascending colon require that ingesta be mixed constantly and retained long enough to complete the digestion of cellulose. Parasites, changes in regional blood flow, diet, and various pharmacologic agents are associated with alterations in normal cecal motility patterns.
Scare JA, Leathwick DM, Sauermann CW, Lyons ET, Steuer AE, Jones BA, Clark M, Nielsen MK.An alternative control regimen for drug-resistant parasites is combination deworming, where two drugs with different modes of action are administered simultaneously to target the same parasite. Few studies have investigated this in equine cyathostomins. We previously reported that an oxibendazole (OBZ) and pyrantel pamoate (PYR) combination was not sustainable against a cyathostomin population with high levels of OBZ and PYR resistance. This study consisted of a field study and two computer simulations to evaluate the efficacy of a moxidectin-oxibendazole (MOX-OBZ) combination against the same...
Galvão A, Wolodko K, Rebordão MR, Skarzynski D, Ferreira-Dias G.In the present report we describe the involvement of transforming growth factor B1 (TGF) in functional regression and structural luteolysis in the mare. Firstly, TGF and its receptors activin-like kinase (ALK) 5 and TGF receptor 2 were identified in corpus luteum (CL) steroidogenic, endothelial and fibroblast-like cells. Also, TGF and ALK5 protein expression were shown to be increased in Mid-, and Late-CL (p < 0.05). Subsequently, using an in vitro model with Mid-CL cells, we studied the role of TGF on secretory activity and cell viability. Cell treatment with TGF decreased progesterone...
Raftery AG, Jallow S, Rodgers J, Sutton DGM.Globally, working equines have a continued and growing socioeconomic role in supporting the livelihoods of between 300-600 million people in low income countries which is rarely recognised at a national or international level. Infectious diseases have significant impact on welfare and productivity in this population and equine trypanosomiasis is a priority disease due to its severity and prevalence. Strategies are required to improve the prevention, diagnosis, management and treatment of trypanosomiasis in equines and more data are required on the efficacy and safety of current trypanocidal dr...
Sriprapat S, Aeksowan S, Sapsutthipas S, Chotwiwatthanakun C, Suttijitpaisal P, Pratanaphon R, Khow O, Sitprija V, Ratanabanangkoon K.Therapeutic antivenom against snakes was first produced by Albert Calmette in 1894. Since then antivenoms have saved the life of countless snakebite victims. However, there are still many problems associated with antivenom production, for example variable percentage of responder horses, low neutralizing potency of antivenom, the large amount of snake venom needed for immunization and the difficulties encountered in producing potent polyvalent antivenoms. These problems have led to shortage and high cost of antivenom and, in some cases, failure of treatment. In 1997, a new immunization protocol...
Felippelli G, Cruz BC, Gomes LV, Lopes WD, Teixeira WF, Maciel WG, Buzzulini C, Bichuette MA, Campos GP, Soares VE, Bergamasco PL, de Oliveira GP....By means of parasitological necropsies, the present study aimed to evaluate, in six experiments, the degree of susceptibility or resistance of different helminth species which naturally infect horses to ivermectin 0.2 mg/kg, abamectin 0.2 mg/kg, moxidectin 0.4 mg/kg, trichlorfon 35 mg/kg, ivermectin 0.2 mg/kg+praziquantel 2.5 mg/kg, abamectin 0.2 mg/kg+praziquantel 2.5 mg/kg and ivermectin 0.2 mg/kg+6.6 mg/kg pyrantel. At experimental day zero, the horses were allocated to treatment groups based on average counts of strongylid eggs per gram of feces (EPG) obtained on days -3, -2 and -1. Oxyuri...
Foreman JH, Barange A, Lawrence LM, Hungerford LL.The objective was to test the hypothesis that phenylbutazone (PBZ) alleviates lameness in an adjustable heart bar shoe model of equine foot pain. Eight Quarter Horse mares underwent 4-weekly treatments randomly: 0.9% saline placebo (SAL: 1 mL/45 kg body weight i.v.) with no lameness; SAL with lameness; PBZ (4.4 mg/kg body weight i.v.) with no lameness; and PBZ with lameness. Blinded heart rate (HR) and lameness score (LS) were assessed every 20 min for 2 h and then hourly through 9 h. At 1 h SAL or PBZ was administered. Jugular venous samples were obtained at hours 0, 1, 2, 4, 6, and 8 and wer...
