The Prevalence and Histopathology of Endocrinopathic Laminitis in Horses

Laminitis is a common, debilitating condition of equids that may have substantial effects on animal welfare. Laminitis may be related to endocrinopathic or inflammatory diseases, as well as uneven weight distribution. Until recently, research into the prevalence of endocrine disease amongst horses with laminitis has been overlooked, although it was anecdotally thought to be high. Most histological studies have been conducted on experimental carbohydrate overload or inflammatory models. However, more recently the histology of a hyperinsulinaemic model of laminitis was described with important differences apparent from the previous inflammatory models however, a more detailed study had not been performed. Furthermore, the histology of chronic, naturally occurring endocrinopathic laminitis has not been described and compared to that of healthy animals. The research presented in this thesis aimed to investigate endocrinopathic laminitis. In Study I, the prevalence of endocrine disease (either basal hyperinsulinemia or pituitary pars intermedia dysfunction, PPID) among horses that presented for laminitis at a first-opinion/referral equine hospital was shown to be 89%. In Study II, secondary epidermal lamellar elongation, narrowing and alteration in orientation were shown to be largely attributable to cell stretching in ponies with insulin-induced experimental laminitis (rather than proliferation as had been hypothesised), that occurred at the same time as an accelerated cell death-proliferation cycle. In Study III, the histomorphometry and pathological lesions of endocrinopathic laminitis were shown to be largely localized abaxially within the lamellar tissue including increased lamellar length and width, chronic abnormal keratinization, interlamellar epidermal bridging and apoptotic cell death with more acute lamellar tearing in some cases. Additionally, in all the laminitis cases, there were macroscopic pathological changes (divergent rings on the outer hoof wall and/or rotation of distal phalanx). However, both lamellar and macroscopic pathology varied in severity and were unrelated to the reported duration of laminitis. In Study IV, PPID animals with and without laminitis were compared. All the laminitic PPID animals also had hyperinsulinemia whereas all of the non-laminitic PPID animals were normoinsulinemic. In addition, all the PPID animals with laminitis had histological lesions in the lamellar region, but the lamellae of PPID animals without laminitis were normal when compared to the control group. In conclusion, endocrinopathic laminitis is by far the most common type of naturally occurring laminitis in horses and hyperinsulinemia is likely to be the primary cause in those horses, including those with PPID. In the acute phase, the pathophysiology behind the key lesion, SEL elongation, is proposed to be cellular (mechanical) compromise resulting in epidermal cellular stretching. In the chronic phase, the lamellar lesions are variable in severity in many cases allowing for a prolonged subclinical phase, and they are located predominantly abaxially close to the hoof wall.Kaviokuume eli kavion lamellikerroksen sairaus on yksi hevosen kivuliaimmista sairauksista, joka saattaa johtaa voimakkaaseen tai pitkittyneeseen kipuun ja jopa hevosen eutanasiaan. Kaviokuume voidaan jakaa syntymekanisminsa perusteella hormoniperäiseen ja tulehdukselliseen muotoon sekä tukeutumiskaviokuumeeseen, joka on kuitenkin hyvin harvinainen. Hormoniperäisen kaviokuumeen aiheuttajia voivat olla joko ylipainoisilla hevosilla esiintyvä metabolinen syndrooma (EMS, equine metabolic syndrome) tai vanhoilla hevosilla esiintyvä aivolisäkkeen toimintahäiriö (PPID, pituitary pars intermedia dysfunction). Tulehduksellinen kaviokuume voi puolestaan aiheutua esimerkiksi suolistotulehduksen tai muun vakavan tulehduksen seurauksena, kun taas tukeutumiskaviokuume on yleensä seurausta epätasaisesta painon jakautumisesta esimerkiksi vastakkaisen raajan murtuman vuoksi. Aiemmin tulehduksellista muotoa on pidetty yleisimpänä, minkä vuoksi kaviokuumetutkimukset ovat keskittyneet tämän muodon tutkimiseen. Tutkimukset on tehty pääosin kokeellisilla malleilla, mutta luonnostaan esiintyvää kaviokuumetta on tutkittu hyvin vähän. Tämän väitöskirjatyön tarkoituksena oli tutkia hormoniperäistä kaviokuumetta. Ensimmäisenä tavoitteena oli selvittää, kuinka yleisiä hormonaaliset syyt, EMS ja/tai PPID, ovat luonnostaan esiintyvän kaviokuumeen aiheuttajina. Yliopistolliseen eläinsairaalaan kaviokuumeen vuoksi vuosina 2007 ja 2008 tuoduista hevosista 89 % sairasti hormonaalista muotoa. Näistä kahdella kolmasosalla oli metabolinen syndrooma ja yhdellä kolmasosalla PPID. Toisena tavoitteena oli kuvailla hormoniperäisen kaviokuumeen aiheuttamia muutoksia kavioissa, etenkin niiden lamellikerroksessa. Sekä lamellikerroksen muutokset että kavion ulospäin näkyvät muutokset (rengasmuodostus kavion seinämässä ja/tai kavioluun kiertyminen) vaihtelivat vakavuudeltaan eikä niillä ollut yhteyttä kaviokuumeen kestoon. Osassa kavioita renkaat olivat todennäköisesti muodostuneet ennen oireiden alkamista, mikä viittaa oireettomiin kaviokuume-episodeihin ennen varsinaista sairautta. Väitöskirjan viimeisenä tavoitteena oli verrata kaviokuumetta sairastavien ja kavioistaan terveiden PPID-hevosten veren hormonipitoisuuksia sekä muutoksia kavioissa. Kaikilla kaviokuumetta sairastavilla PPID-hevosilla oli kohonnut veren insuliinipitoisuus, kun taas kavioistaan terveillä PPID-hevosilla ja kontrollihevosilla insuliinipitoisuus oli normaali. Lisäksi vain kaviokuumetta sairastavien PPID-hevosten kavioissa todettiin patologisia muutoksia, kun taas kavioistaan terveiden PPID-hevosten kaviot eivät poikenneet kontrollihevosten kavioista. Tämän perusteella ehdotamme, että myös PPID-hevosilla (kuten EMS-hevosilla) kaviokuumeen aiheuttaa veren kohonnut insuliinipitoisuus. Yhteenvetona tämän väitöskirjatutkimuksen pohjalta voidaan todeta, että hevosen luonnostaan esiintyvän kaviokuumeen taustalla ovat yleisimmin hormoniperäiset syyt, etenkin kohonnut veren insuliinipitoisuus. Koska kaviokuumeeseen ei ole olemassa tehokasta täsmähoitoa, tulee eläinlääkäreiden ja hevosten omistajien pyrkiä ehkäisemään kaviokuumeen synty. Etenkin lihavien hevosten sekä hevosten, joiden kavioissa on rengasmuodostusta, insuliinipitoisuutta tulee tarkkailla säännöllisesti. Mikäli herkkyys kaviokuumeelle havaitaan riittävän aikaisin, kliininen kaviokuume saatetaan pystyä ennaltaehkäisemään

Insulin dysregulation in a population of Finnhorses and associated phenotypic markers of obesity

Non peer reviewe

Pikkuvarsojen hoito ja ennuste Yliopistollisessa hevossairaalassa vuosina 2010–2013 : Treatment and prognosis of neonatal foals in Helsinki University Equine Teaching Hospital in 2010–2013

Peer reviewe

Effects of Bedding Material on Equine Lower Airway Inflammation : A Comparison of Two Peat Beddings, Wood Pellet, and Straw Pellet

The effects of bedding material on air quality are important amongst horses worldwide. Respiratory diseases, especially equine asthma, are highly prevalent with air hygiene playing a major role on the pathophysiology of these diseases. The objective of our study was to investigate the effects of four bedding materials on the respiratory signs, tracheal mucus score, and tracheal wash (TW) and bronchoalveolar lavage fluid (BALF) cytology in healthy adult horses. The study design was a prospective controlled cross-over study, and the subjects were healthy adult riding school horses (n = 32) from a single stable. Wood pellet, straw pellet, and loosely stored peat (Peat 3) were compared to peat packed in plastic-covered bales (Peat 2). Lower airway endoscopy and sampling (TW and BALF) for cytological examination were performed after each 35-day bedding period. The tracheal mucus scores (P = 0.014) and respiratory rate (P = 0.026) were higher during the straw pellet period compared to the Peat 2 period. The respiratory rate was lower during the wood pellet period compared to the Peat 2 period (P = 0.004). The TW neutrophil percentage during the straw pellet period was higher compared to the Peat 2 period (P = 0.0003). The BALF neutrophil percentage was higher during the straw pellet period (P = 0.005) and during the Peat 3 period compared to the Peat 2 period (P = 0.04). We conclude that baled peat (Peat 2) caused lower neutrophil percentages in the airway samples compared to straw pellet and loosely stored peat (Peat 3). No difference was observed between Peat 2 and wood pellet. The information gained from this study may assist veterinarians and horse owners in selecting appropriate bedding materials, especially for horses with equine asthma.Peer reviewe

Long-term follow-up on recovery, return to use and sporting activity : a retrospective study of 236 operated colic horses in Finland (2006-2012)

Background: Surgical treatment of colic is expensive and complications may occur. Information on the prognosis and the use of the horse after surgery for colic is important for surgeons and owners. Current literature on return to athletic function after celiotomy is limited. The present study reviewed surgical cases of the Veterinary Teaching Hospital, Helsinki, Finland for 2006-2012. The aim was to follow the population of horses of different breeds for surgical findings, postsurgical complications, long-term recovery and prognosis. The findings and their influence on survival, return to previous or intended use and performance were assessed. Results: Most of the operated horses (82.6%; 195/236) recovered from anesthesia and 74.9% (146/195) were discharged. The total follow-up time was 8 years and 10 months and the median survival time 79.2 months. Age of the horse, location of the abdominal lesion (small vs. large intestine), incidence of postoperative colic, surgical site infection, incisional hernia or convalescence time after surgery, did not significantly affect the probability of performing in the previous or intended discipline after the surgery. A majority of the discharged horses (83.7%) was able to perform in the previous or intended discipline and 78.5% regained their former or higher level of performance. Operated horses had 0.18 colic episodes per horse-year during the long-term follow-up. The incidence of colic was 20.0% within the first year after surgery. Horses operated for large intestinal colic were 3.3-fold more prone to suffer postoperative colic than horses operated for small intestinal colic. The majority of the owners (96.3%) were satisfied with the veterinary care and nearly all (98.5%) evaluated the recovery after the colic surgery to be satisfactory or above. Conclusions: If the horse survives to discharge, prognosis for long-term survival and return to previous level of sporting activity and performance was good after colic surgery in a population of horses of different breeds. None of the factors studied were found to decrease the probability of performing in the same or intended discipline after surgery. The majority of horses were able to return to their previous activity and perform satisfactorily for several years after surgery.Peer reviewe

Variation in insulin response to oral sugar test in a cohort of horses throughout the year and evaluation of risk factors for insulin dysregulation

Background The oral sugar test (OST) is commonly used to diagnose insulin dysregulation (ID) and equine metabolic syndrome; however, possible seasonal changes in OST results have not been evaluated. Objective To determine the possible variation in insulin response to OST throughout the year and risk factors associated with maximum insulin concentration (InsMax) and ID. Study design Prospective, longitudinal cohort study. Methods The OST was performed on 29 Finnhorses every other month six times. Serum total adiponectin concentration and phenotypic variables related to obesity were also measured. Changes in InsMax, adiponectin, scale weight, body condition score, cresty neck score (CNS), and fasting glucose concentration were assessed. Risk factor analyses were performed on InsMax and ID status, and ID groups were compared with each other. Results Fourteen horses were categorised with non-ID each time and 15 as having ID at least once during the follow-up period. The ID status of 12 horses varied throughout the year, but neither the insulin variables measured during the OST nor adiponectin expressed significant seasonal variation. Increasing age and CNS, and decreasing adiponectin were observed as risk factors for a high InsMax after OST. The risk of ID was higher in horses with no exercise compared to horses with exercise (OR 7.6, 95% CI 1.2-49.3, P = .03). Horses with ID had lower serum adiponectin concentrations, longer neck circumference and larger height than horses in the non-ID group. Main limitations The environmental conditions (feeding, exercise) were not constant for all horses throughout the study and only one breed was used. Conclusions Neither OST results nor adiponectin varies with season; however, there were a substantial number of horses with variable ID status throughout the year, in which repeated OSTs may be beneficial. Lack of exercise was a risk factor for ID.Peer reviewe

Insulin dysregulation in a population of Finnhorses and associated phenotypic markers of obesity

Background Obesity and insulin dysregulation (ID) predispose horses to laminitis. Determination of management practices or phenotypic markers associated with ID may benefit animal welfare. Objectives Determine ID status of a population of Finnhorses using an oral sugar test (OST) and compare phenotypes and management factors between ID and non-ID Finnhorses. Animals One hundred twenty-eight purebred Finnhorses >= 3 years of age. Methods Owners were recruited using an online questionnaire regarding signalment, history, feeding, and exercise of their horses. Selected contributing stables within a predefined area were visited. Phenotypic markers of obesity and the weight of each horse were recorded. After fasting overnight, horses received 0.45 mL/kg corn syrup PO. Serum samples before and at 60 and 90 minutes after syrup administration were analyzed for insulin by chemiluminescent assay. Horses met ID criteria if insulin concentrations were >= 33 mu IU/mL at T0, >= 66 mu IU/mL at T60 or T90 or some combination thereof. Associations between phenotypic markers, feeding and exercise variables, and ID were examined using mixed effects logistic regression modeling. Results Several phenotypic markers of obesity were significant on univariable analysis but in the final multivariable model, only obesity (body condition score >= 8) was associated with ID (P= .04). Over half of the horses (60% [95% confidence interval (CI), 51%-68%]) were considered overweight or obese whereas 16% (95% CI, 10%-23%) were classified as having ID. Conclusions and Clinical Importance Because obesity is associated with ID in cold-blooded type horses, objective monitoring of phenotypic markers by owners may be beneficial for health outcomes.Peer reviewe

Effects of Bedding Material on Equine Lower Airway Inflammation : A Crossover Study Comparing Peat and Wood Shavings

Bedding materials affect stable air hygiene, and thus the development and exacerbation of equine asthma. There is limited knowledge concerning the effects of different types of bedding material on equine lower airway inflammation. The objective of our study was to investigate the effects of bedding materials on respiratory signs, tracheal mucus score, and lower airway cytology in healthy adult horses. The study design was a prospective controlled study, and the subjects were healthy adult riding school horses (n = 32) from a single stable. Wood shavings were compared to peat, which was used as a reference bedding material. Lower airway endoscopy and sampling (tracheal wash and bronchoalveolar lavage fluid) for cytological examination were performed after each 35-day bedding period. No difference between bedding periods was observed in the respiratory rate or tracheal mucus score. Tracheal wash neutrophil percentage with the wood shavings was higher compared to the previous (P = 0.040) or following (P = 0.0045) peat period. Bronchoalveolar lavage fluid neutrophil percentage with the wood shavings was higher compared to the following peat period (P <0.001). We conclude that, between the two bedding materials used in this study, peat caused less neutrophilic lower airway inflammation in horses. The information gained from this study may assist veterinarians and horse owners in selecting bedding materials, especially for horses suffering from equine asthma.Peer reviewe

Relationships among Body Condition, Insulin Resistance and Subcutaneous Adipose Tissue Gene Expression during the Grazing Season in Mares

Obesity and insulin resistance have been shown to be risk factors for laminitis in horses. The objective of the study was to determine the effect of changes in body condition during the grazing season on insulin resistance and the expression of genes associated with obesity and insulin resistance in subcutaneous adipose tissue (SAT). Sixteen Finnhorse mares were grazing either on cultivated high-yielding pasture (CG) or semi-natural grassland (NG) from the end of May to the beginning of September. Body measurements, intravenous glucose tolerance test (IVGTT), and neck and tailhead SAT gene expressions were measured in May and September. At the end of grazing, CG had higher median body condition score (7 vs. 5.4, interquartile range 0.25 vs. 0.43; P=0.05) and body weight (618 kg vs. 572 kg +/- 10.21 (mean +/- SEM); P=0.02), and larger waist circumference (P=0.03) than NG. Neck fat thickness was not different between treatments. However, tailhead fat thickness was smaller in CG compared to NG in May (P=0.04), but this difference disappeared in September. Greater basal and peak insulin concentrations, and faster glucose clearance rate (P=0.03) during IVGTT were observed in CG compared to NG in September. A greater decrease in plasma non-esterified fatty acids during IVGTT (PPeer reviewe