Courses for horses: Rethinking the use of proton pump inhibitors in the treatment of equine gastric ulcer syndrome

Oral omeprazole has been the cornerstone of equine gastric ulcer syndrome (EGUS) treatment for nearly 20 years. However, approximately 15–30% of equine squamous gastric disease (ESGD) cases and 75% of equine glandular gastric disease (EGGD) cases fail to heal within current treatment guidelines. Recently, a number of factors that may affect the efficacy of oral omeprazole have been highlighted and the pharmacodynamics of a number of novel proton pump inhibitors (PPIs) have been described in the horse. The purpose of this article is to review the factors that affect oral omeprazole efficacy, with the goal of maximising therapeutic response, and the novel PPIs recently described.     

Incidence and monthly prevalence of Gasterophilus spp. larvae (Diptera: Gasterophilidae) in the stomach of donkeys (Equus asinus) in Egypt

The stomachs of 118 donkeys were examined at postmortem during the period from March 1982 to February 1983 for Gasterophilus spp. larvae. G. intestinalis larvae clustered in groups near the boundary of the glandular and non-glandular epithelium of the stomach and infested 98.3% of the donkeys with highest numbers in July and lowest numbers in October. G. nasalis larvae were mainly attached near the pylorus and first part of the duodenum and infested 87.3% of donkeys with highest incidence in December and lowest in October. The ratio of the second and third instars of G. intestinalis to G. nasalis ranged from 71% to 29%. The percentage of donkeys infested with 1-100, 101-200 and 201-300 larvae was 72.0, 18.6 and 4.3% for G. intestinalis and 76.3, 8.5 and 0.8% for G. nasalis.     

Parasites of the stomach in donkeys of the highveld of Zimbabwe

Summary

Fourteen donkeys from a communal area of the Zimbabwean highveld were examined for stomach parasites during July and November of 1986 and January and April of 1987. All 14 animals were infected. Habronema muscae occurred in 12, Draschia megastoma in 11, H. majus in 9, Trichostrongylus axei in 9, Gasterophilus intestinalis in 14 and G. nasalis in 1 donkey. The lowest level of infection was in January for the helminthes and in April for Gasterophilus larvae. The peak burdens of parasites were in July for Habronema spp. and in November for D. megastoma and Gasterophilus larvae. Infections with spirurid worms and Gasterophilus develop mainly from the middle of the rainy season to the beginning of the dry season (Januari to May/June). G. intestinalis seems to have an annual cycle.     

Parasites of the stomach in donkeys of the highveld of Zimbabwe

Fourteen donkeys from a communal area of the Zimbabwean highveld were examined for stomach parasites during July and November of 1986 and January and April of 1987. All 14 animals were infected. Habronema muscae occurred in 12, Draschia megastoma in 11, H. majus in 9, Trichostrongylus axei in 9, Gasterophilus intestinalis in 14 and G. nasalis in 1 donkey. The lowest level of infection was in January for the helminths and in April for Gasterophilus larvae. The peak burdens of parasites were in July for Habronema spp. and in November for D. megastoma and Gasterophilus larvae. Infections with spirurid worms and Gasterophilus develop mainly from the middle of the rainy season to the beginning of the dry season (January to May/June). G. intestinalis seems to have an annual cycle.     

The prevalence and anatomical distribution of equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark

Reasons for performing study: The prevalence (up to 93% in Thoroughbred racehorses) and severity of equine gastric ulceration syndrome (EGUS) have been correlated with the type of training and associated management practices. However, there have been few reports to confirm these findings in nonracehorses in Europe. Objectives: To describe the prevalence, anatomical distribution, severity and number of gastric ulceration lesions in a population of Danish pleasure horses; and to investigate differences for groups based on age, breed type and workload. Methods: A total of 201 horses not in active race‐training, age 7 months‐27 years, were evaluated, representing 23 different stables from all 5 regions of Denmark. These horses were considered to be healthy by the owner and not on veterinary treatment for EGUS. Endoscopically observed ulcer lesion scores were based on the number present (0–4) and severity (0–5). The presence or absence of ulcers in the glandular and/or nonglandular regions of the stomach was recorded and which site the most severe ulcers were found. Results: The prevalence of EGUS severity score ≥2 was 53%. The most severe lesions were commonly observed at the margo plicatus. Although older horses were not more likely to be affected by clinically significant EGUS they were more likely to have lesions in both the glandular and nonglandular regions. Differences in location of EGUS lesions were identified in different age groups, breed types and in horses exposed to different levels of work. Conclusion and potential relevance: This study confirms that gastric ulceration can be prevalent in a group of apparently clinically normal horses, not in intensive work. Further investigation of reasons for differences in EGUS location between different populations may aid toward the development of novel preventive measures.     

Gastrointestinal parasites of working donkeys of Ethiopia

The general prevalence and population composition of gastrointestinal and pulmonary helminths of working donkeys were studied. For the purpose 2935 working donkeys were coprologically examined for nematode and cestode, and 215 donkeys for trematode infections. Seven donkeys that died due to various health problems or were euthanased on a welfare ground were necropsied and the parasites were recovered and identified to the species level. The study was conducted during the periods 1996-1999. Coprological examination revealed 99% strongyle, 80% Fasciola, 51% Parascaris, 30% Gastrodiscus, 11% Strongyloides westeri, 8% cestodes and 2% Oxyuris equi infection prevalence. Over 55% of donkeys had more than 1000 eggs per gram of faeces (epg). Forty two different species of parasites consisting of 33 nematodes, 3 trematodes, 3 cestodes and 3 arthropod larvae were identified from postmortem examined donkeys. Among the nematodes 17 species of Cyathostominae and 7 species of Strongylinae were identified. Other parasites identified include, Habronema muscae, Draschia megastoma, Trichostrongylus axei, Strongyloides westeri, Anoplocephala perfoliata, Anoplocephala magna, Anoplocephaloides (Paranoplocephala) mamillana, Parascaris equorum, Fasciola hepatica, Fasciola gigantica, Gastrodiscus aegyptiacus, Dictyocaulus arnfieldi, Oxyuris equi, Probstmayria vivipara, Gasterophilus intestinalis, Gasterophilus nasalis, Rhinoestrus uzbekistanicus and Setaria equina. This study revealed that working donkeys in Ethiopia are infected with a range of helminths and arthropod larvae, which are representatives of the important pathogenic parasites found in equids worldwide.     

Prevalence of gastric ulcer syndrome in high-level endurance horses

Reasons for performing the study: Equine gastric ulcers syndrome (EGUS) prevalence studies are rare in the endurance horse and none has been carried out to date in horses competing at high level. Objectives: To determine the prevalence of EGUS in high‐level endurance horses. Methods: Thirty endurance horses competing at high level were selected and submitted to 2 gastroscopic examinations. The first gastroscopy was performed during the interseason period, and the second during the competition season within 2–3 days following a ride of 90–160 km. Data related to housing, feeding, training system as well as age, breed and gender were recorded for each horse. Results: The prevalence of squamous gastric ulcers was 48% during the interseason period (mean score 0.85 ± 0.13 on a scale from 0–4) and 93% during the competition season (mean score 1.60 ± 1.15) with a highly significant difference between the seasons (P = 0.001). Most of the lesions were situated in the squamous portion of the stomach but 33.3% of horses showed also glandular lesions. Significant influence of training and performance level on the gastric score (according to the distance of the ride preceding the second gastroscopy) was shown (P = 0.038). There was also a significant influence of housing on the gastric score (P = 0.002) showing higher scores in the horses kept totally on pasture (mean score: 2.14 ± 0.14) vs. horses housed in a mixed environment (stable + pasture, mean score: 1.43 ± 0.17). Both the pastured and (stabled + pastured) groups were receiving a grain supplement but the pastured group received a higher daily starch intake, which might explain the higher ulcer prevalence. There was no influence of age, breed or gender on the gastric scores. Conclusions: The high prevalence of gastric lesions observed in this study is probably related to the high level of training and performance of the horses examined compared to the population of horses included in the prior study. Potential relevance: This prevalence of EGUS in high‐level endurance horses is comparable to the prevalence established in racing horses. The equine veterinarians may take into consideration EGUS as a potential cause of poor performance.     

Pathomorphological study on gastroduodenal ulceration in horses: localisation of lesions

Gastroduodenal ulceration is a prevalent disease in foals and adult horses. Decreased performance as well as fatal complications relate to this syndrome. The objective of our study was to determine the prevalence of gastric ulceration in a mixed population of horses by postmortem examination and to evaluate a possible association between equine gastric ulcer syndrome (EGUS) and sex or age of the examined horses, to evaluate the localisation of lesions in the proximal part of the gastrointestinal tract and to determine the occurrence of gastric parasites. Postmortem examinations were performed on 71 horses over a period of 24 months. Gastric ulcers were found in 52 horses (73.2%). There was no significant association between age or sex and occurrence of gastric ulcers. In all horses the squamous mucosa lesions were localised near the margo plicatus (100% of the cases), whereas in 23 horses the lesions were near the margo plicatus and lesser curvature and in 7 horses at the greater curvature. In 18 horses the mucosa was affected in the whole extent of the margo plicatus and in 1 horse diffuse lesions of the squamous mucosa were noted. Lesions of the glandular mucosa were localised in 11 horses at the fundic area, in 1 horse they occurred in the pylorus, and in 10 horses diffuse lesions of the glandular mucosa were recorded. A low prevalence of Gasterophilus intestinalis infection was detected (1 horse, 1.4%). We have confirmed that gastric ulcers are a common problem in horses and duodenal or oesophageal ulceration is rare (not a single case of the latter was found in this study). Lesions in the glandular mucosa of the stomach are more frequent in suckling foals than in older animals. Lesions of the glandular mucosa are also common in adult horses, and a complete gastroscopic examination including examination of the pylorus is advisable to evaluate this syndrome.     

Risk factors associated with equine gastric ulceration syndrome (EGUS) in 201 horses in Denmark

Reasons for performing study: The prevalence (up to 93% in Thoroughbred racehorses) and severity of equine gastric ulceration syndrome (EGUS) has been associated with type of training and differing management practices. However, there have been few studies to confirm these findings in nonracehorses in Europe. Objectives: To investigate the prevalence of EGUS in a population of Danish horses, during winter when the horses had been housed and fed for at least 8 weeks and to analyse the influence of feed, work level and environment on the risk of EGUS of §grade 2 in severity. Methods: A total of 201 horses, not in active race‐training, were evaluated, representing 23 different stables from all 5 regions within Denmark. All horses were considered to be healthy and not on medical treatment for EGUS. Endoscopically observed ulcer lesion scores were based on the number present (0–4) and severity (0–5). Univariate and multivariable mixed effects logistic regression models were developed using EGUS score as the dependent variable. An ulceration severity score of §2 was regarded as being clinically significant. Separate models were developed for horses with ulcers in either the glandular or nonglandular regions of the stomach graded §2 (EGUS §2) and for those horses that had nonglandular ulcers graded §2 (NG §2). Results: In this population, 53% (107/201) of horses were graded as having EGUS §2 with 95 (47%) horses having NG §2. Three variables were significantly (P<0.05) associated with EGUS §2: straw being the only forage available; exceeding 2 g/kg bwt of starch intake/day or §1 g/kg bwt/meal; and water not being available in the turn out paddock. Risk of NG §2 significantly increased when straw was the only forage available, 1 g/kg bwt of starch/meal was exceeded, water was not available in the turnout paddock and the interval between forage feeding was <6 h. Conclusion and potential relevance: This study has confirmed that components of the diet, readily modifiable, may have an important impact on the risk of EGUS in the nonracehorse. Differences in the multivariable models produced for all ulcers and nonglandular ulcers support differences in the aetiology of ulcers in different locations of the stomach.     

Effects of supplements containing turmeric and devil’s claw on equine gastric ulcer scores and gastric juice pH

Supplements containing turmeric (Curcuma longa) and devil’s claw (Harpagophytum species) are commonly fed to horses to decrease inflammation and pain, but because these supplements contain spices and plant irritants, warning labels such as 'these supplements might cause gastric irritation' are required. The purpose of this study was to determine whether supplements containing turmeric and devil’s claw cause or worsen gastric ulcers in stall-confined horses, as suggested in required cautions that appear on the labels of these animal products. Twelve clinically healthy Thoroughbred horses with naturally occurring equine gastric ulcer syndrome (EGUS) scores >0 were included in a noncrossover study design. Horses were stratified by EGUS score and assigned to either the treatment (supplements containing turmeric and devil’s claw) or control (same supplements without active ingredients) group and fed the supplements for 28 days. Gastroscopy was performed on Days 0, 14 and 28. The EGUS score, nonglandular ulcer number (NGN) and severity (NGS) scores, and glandular number (GN) and severity (GS) scores were recorded during each gastroscopy by a masked investigator (F.M.A.). In addition, bodyweight, gastric juice pH, packed cell volume (PCV), total protein (TP) and blood biochemical results were measured on Day 0 and Day 28. Mean EGUS and NGS scores were significantly lower in both treatment and control groups by Days 14 and 28, when compared to Day 0. NGN score was not different among groups. Bodyweight, gastric juice pH and blood parameters did not change during the study. In conclusion, supplements containing turmeric and devil’s claw did not cause or worsen gastric ulcers or alter health parameters after 28 days of feeding.     

Analysis on the relationship between winter precipitation and the annual variation of horse stomach fly community in arid desert steppe,Northwest China (2007–2019)

Gasterophilus spp. have been found to be widespread in reintroduced Przewalski's horses in the Kalamaili Nature Reserve (Northwest China). However, data on the annual variation in Gasterophilus infections are lacking. To analyze the epidemiological features and determine the cause of the annual variation in Gasterophilus infections, we treated 110 Przewalski's horses with ivermectin and collected Gasterophilus larvae from fecal samples each winter from 2007 to 2019. All 110 Przewalski's horses studied were found to be infected by Gasterophilus spp., and a total of 141 379 larvae were collected. Six species of Gasterophilus were identified with the following prevalence: G. pecorum (100%), G. nasalis (96.36%), G. nigricornis (94.55%), G. haemorrhoidalis (56.36%), G. intestinalis (59.09%), and G. inermis (3.64%). The mean infection intensity of Gasterophilus spp. larvae in Przewalski's horses was 1285 ± 653. G. pecorum (92.96% ± 6.71%) was the most abundant species. The intensity of Gasterophilus spp. (r = –0.561, P < 0.046) was significantly correlated with winter precipitation. Our findings confirmed that, in the Kalamaili Nature Reserve, gasterophilosis is a severe parasitic disease in Przewalski's horses. Winter precipitation at the beginning of the year can indirectly affect the intensity and composition of Gasterophilus spp. in Przewalski's horses at the end of the year. Therefore, the water-related ecological regulation should be carried out to help reduce the parasite infection of Przewalski's horses.     

Efficacy of moxidectin equine oral gel against endoscopically-confirmed Gasterophilus nasalis and Gasterophilus intestinalis (Diptera: Oestridae) infections in horses

A 3 m, video gastroscope was used to screen 47 horses suspected of being naturally infected with equine bot larvae. 17 of 47 (36.2%) candidate horses harbored Gasterophilus nasalis larvae in the proximal duodenum and 46 of 47 (97.9%) had G. intestinalis larvae in the stomach. All horses infected with G. nasalis had concurrent infections with G. intestinalis. 14 horses with dual infections were allocated randomly to two treatment groups. Seven horses in Group 1 received 2% moxidectin oral gel once at a dosage of 0.4 mg/kg bodyweight (BW), and seven horses in Group 2 were untreated controls. 14 days after treatment, all horses were necropsied and the stomach and proximal duodenum harvested from each. Bot larvae were recovered, identified to species and instar, and counted. At the label dosage, moxidectin oral gel was 100 and 97.6% effective (P < 0.05) against third-instar G. nasalis and G. intestinalis, respectively. In addition to demonstrating the boticidal efficacy of moxidectin, this trial illustrated that gastroscopy/duodenoscopy is a feasible method for confirming infections with different species of bot larvae in the horse.     

Epidemiological observations on Gasterophilus intestinalis and G. nasalis in donkeys from Morocco.

During a 24 month period, 198 donkeys were examined for Gasterophilus intestinalis and Gasterophilus nasalis larvae. Gasterophilus intestinalis was found in 97.5% and G. nasalis in 95.5% of donkeys. The third instars (L3) of both species occurred during all months of the year and so did the second instars (L2), except in April (G. nasalis) and May (G. intestinalis). Over 75% of the animals had up to 200 larvae and 1.5% had over 600 larvae. The maximum number of both L2 and L3 larvae found in any animal was 418 G. intestinalis, 433 G. nasalis and 715 of both species combined. The seasonal variation in the numbers and development status of larvae indicated that the period of greatest activity of adult flies of G. intestinalis was from August/September to November, and that of G. nasalis from May to September. Consequently, the L2 larvae in the stomachs were in peak numbers between November and January for G. intestinalis and between July and September for G. nasalis. The L3 larvae of G. intestinalis had peak numbers between December and July, and those of G. nasalis between October and March. During January-March, most of the L2 larvae of G. nasalis were trapped in polypous nodules near the pyloric end of the stomach. It is concluded that the high-risk period for infection is during late spring and autumn, leading to the heavy larval burden of Gasterophilus in the stomach of donkeys during winter.     

规模化驴场中马流感病毒H3N8亚型感染情况调查

[目的]调查山东省聊城市规模化驴场中马流感病毒的感染情况,并分析其可能的来源。[方法]从聊城的规模化驴场采集病料和血清,通过HI试验检测驴血清中的马流感病毒H3N8亚型抗体的阳性率。使用RT-PCR技术扩增肺脏和鼻腔棉拭子样品中的马流感病毒M基因,对获得的马流感病毒M基因与不同流感病毒的M基因进行序列比对,推测其来源。[结果]HI试验表明,120个血清样品中马流感病毒H3N8亚型血清抗体阳性率为33.3%(40/120);其中,母驴的马流感病毒H3N8亚型血清抗体阳性率为42.5%(17/40)、公驴为32.5%(13/40)、驴驹为25.0%(10/40)。通过RT-PCR检测发现,32.3%(21/65)的样品可测出目的条带。通过序列比对得出,该试验获得的流感病毒M基因与马属动物的H3N8亚型流感病毒高度同源(CY032222、CY032318、CY028821等),同源性最高可达99.8%。[结论]马流感病毒在聊城周边的数个规模化养驴场发生流行。该研究从驴体内分离的流感病毒M基因属于马流感病毒H3N8亚型M基因。     

Gasterophilosis: a major cause of rectal prolapse in working donkeys in Ethiopia

A retrospective study was conducted to investigate the cause of rectal prolapse in working donkeys in Ethiopia. Analysis of data on rectal prolapse cases obtained from the Donkey Health and Welfare Project clinic at the School of Veterinary Medicine, Addis Ababa University, from 1995 to 2004 revealed that 83.6% (n = 177) of the cases were associated with Gasterophilus nasalis. The rest 10.7% and 5.7% were associated with work-related (overloading) cause and diarrhoea, respectively. The mean and median numbers of G. nasalis recovered from the rectum of infected donkeys were 66 and 64, respectively, with a range of 2–195. Over 100 G. nasalis larvae were recovered from the rectum of 22% of the donkeys. Circular demarcated ulcer-like and deep circumferential pits or ring-like mucosal lesions were found at the larval attachment sites. G. nasalis infection and the associated rectal prolapse were observed year round. However, the intensity of rectal larval infection and incidence of rectal prolapse were significantly higher during the rainy season (P < 0.01). Age and sex of the donkeys had no significant effect on the intensity of rectal larval infection and incidence of rectal prolapse (P > 0.05).     

Endoscopic findings of the stomach in pleasure horses in Poland

Background

This study was performed to determine the prevalence of ulcers in the gastric squamous and glandular mucosa in Polish pleasure horses.

Study design

Medical records from gastroscopic examinations of 108 pleasure horses of different breeds were reviewed. The study population consisted of two groups; group I (n = 48) with horses that expressed mild clinical signs of gastric ulcer syndrome (EGUS) including poor appetite, slight weight loss or poor body condition, and group II (n = 60) with horses that had no signs of gastrointestinal problems. The age range was 4–10 years, including 5 males, 34 castrated males (geldings) and 69 mares. The prevalence, distribution and severity of gastric ulcers were recorded. Lesions involving the squamous mucosa and the glandular mucosa of the antrum and pylorus were graded and compared between groups.

Results

Significant difference was found in the presence and severity of gastric ulcers between the two groups of horses. The overall prevalence of gastric ulcers in the first group of horses (n = 48) was 59% while in the group of clinically healthy horses (n = 60) the prevalence of gastric lesion was 40% (P = 0.004). Almost 19% of horses from group I had between 6–10 lesions (EGUS score III) and nearly 19% had either >10 localized lesions or very large diffuse lesions (EGUS number score IV). The number of ulcerations in affected horses were significantly lower in group II compared to group I (P = 0.016) as 10% of horses had 6–10 lesions (EGUS number score III) and nearly 14% had either >10 localized lesions or very large diffuse lesions (EGUS number score IV). Gastroscopy revealed that nearly 32% of horses from the second group had an ulceration EGUS score ≥ II.

Discussion and conclusions

This study confirms that gastric ulcerations can be prevalent in apparently clinically normal pleasure horses and a complete gastroscopic examination including the examination of the pylorus is advisable to evaluate this syndrome.     

Poor performance associated with equine gastric ulceration syndrome in four Thoroughbred racehorses

Equine gastric ulceration syndrome (EGUS) is commonly recognised in Thoroughbred racehorses. Although EGUS has previously been associated with reduced athletic performance, no objective studies have been reported. This case report describes 4 racehorses referred for investigation of poor athletic performance where EGUS was the only abnormal finding during a thorough investigation of all body systems. All horses showed considerable improvement in performance following treatment with omeprazole. Therefore, this is the first report in which evidence is presented suggesting a direct link between EGUS and decreased performance, other causes of poor performance having been excluded.     

The Contribution of Specific and Nonspecific Biomarkers in Diagnosis of Equine Gastric Ulcer Syndrome (EGUS) Under Field Condition

The aim of this study is to investigate the diagnostic efficiency of gastrin, pepsinogen, proinflammatory cytokines (TNF-α, IL-6), and oxidative stress biomarkers in horses with equine gastric ulcer syndrome (EGUS). Thirty horses diagnosed with gastroscopic EGUS and 15 clinically healthy horses were selected for this study. The serum levels of gastrin, pepsinogen showed nonsignificant changes in horses with EGUS when compared with healthy horses. The serum levels of TNF-α, IL-6 revealed a significant increase in horses with EGUS when compared with healthy ones. Oxidative stress is evident in horses with EGUS in comparison with healthy horses as detected by higher levels of malondialdehyde (MDA) and decreased serum levels of total antioxidant capacity (TAC), Superoxide dismutase (SOD), glutathione (GSH), and nitric oxide (NO). MDA and TNF-α showed better sensitivity and specificity than IL-6 in distinguishing horses with EGUS from control horses. Conclusively, examination of serum gastrin and pepsinogen levels had a limited value in diagnosis of EGUS in horses under investigation. Moreover, this study showed that oxidative stress is evident in horses with EGUS. Higher levels of TNF-α and IL-6 indicate their role in EGUS pathogenesis in horses. Finally, MDA, TNF-α, and IL-6 could be used as biological markers for preliminary screening of horses with EGUS. Gastroscopy still accredited as the “gold standard” for diagnosis EGUS.     

Seasonal Variations in the Abundance of Gasterophilus spp. Larvae in Donkeys in Northern Jordan

One hundred and five donkeys were examined over a 12-month period for the presence of Gasterophilus spp. larvae in their stomachs. G. intestinalis and G. nasalis were found, but there was a distinct seasonal variation in their abundance. The numbers of second-stage larvae (L₂) peaked during the early winter and early summer, but they were absent or at low levels during the early spring and early autumn. This suggests that there are two periods of adult fly activity (late autumn and late spring) for both G. nasalis and G. intestinalis. Third-stage larvae (L₃) were found throughout the year, but the lowest levels were seen in the late summer and autumn. The parasites also had an aggregated distribution, which may be due to host selection by the fly. The numbers of larvae did not vary significantly with age, which may be due to a lack of acquired protective immunity or to tolerance after repeated exposure.