Development of novel Streptococcus equi vaccines with an assessment of their immunizing potentials and protective efficacies.

Strangles is a highly contagious disease of the equine upper respiratory tract caused by Streptococcus equi subspecies. Streptococcus equi subsp. equi (S. equi) and Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) was isolated, as local, hot, and field strains, from horses clinically suffering from respiratory distress. The isolated Streptococci were identified using bacteriological and molecular techniques. Four formulations of inactivated S. equi vaccines were developed and evaluated. The first formulation was prepared using the S. equi isolates, adjuvanted with MONTANIDE GEL adjuvant, while the second formulation was adjuvanted with MONTANIDE ISA-70 adjuvant. The other 2 formulations were inactivated combined vaccines prepared from both S. equi and S. zooepidemicus isolates. The 3rd formulation was the combined isolates adjuvanted with MONTANIDE GEL while the 4th formulation was the combined isolates adjuvanted with MONTANIDE ISA-70. The developed vaccines' physical properties, purity, sterility, safety, and potency were ensured. The immunizing efficacy was determined in isogenic BALB/c mice and white New Zealand rabbits using the passive hemagglutination test. Also, the antibodies' titer of the combined S. equi and S. zooepidemicus vaccine adjuvanted with MONTANIDE ISA-70 in foals was tracked using an indirect enzyme-linked immunosorbent assay. The protective efficacy of the developed vaccines was determined using a challenge test in both laboratory and field animal models, where a 75% protection rate was achieved. The combined vaccine proved to be more efficacious than the monovalent vaccine. Also, the MONTANIDE ISA-70 adjuvant provided significant protective efficacy than the MONTANIDE GEL. The current work is introducing a very promising mitigative and strategic controlling solution for strangles.

Arthrospira platensis enriched with Cr(III), Mg(II), and Mn(II) ions improves insulin sensitivity and reduces systemic inflammation in equine metabolic affected horses.

Equine metabolic syndrome (EMS) is a critical endocrine condition in horses, characterized by hyperinsulinemia, hyperlipidemia, and insulin resistance, posing a significant threat to their health. This study investigates the efficacy of supplementing EMS-affected horses with Arthrospira platensis enriched with Cr(III), Mg(II), and Mn(II) ions using biosorption process in improving insulin sensitivity and glucose tolerance, reducing inflammation, and mitigating obesity-related fat accumulation. Our results demonstrate that Arthrospira supplementation reduces baseline insulin and glucose levels, contributing to decreased adipose tissue inflammation. Furthermore, Arthrospira supplementation results in a decrease in body weight and improvements in overall body condition scores and cresty neck scores. Additionally, administration of Arthrospira leads to reduced levels of triglycerides and aspartate aminotransferase, indicating a decrease in hepatic adiposity and inflammation. These findings suggest that Arthrospira, enriched with essential micro- and macroelements, can be an advanced feed additive to enhance insulin sensitivity, promote weight reduction, and alleviate inflammatory processes, thereby improving the overall condition of horses affected by EMS. The use of Arthrospira as a feed additive has the potential to complement conventional management strategies for EMS.

Surgical Closure of Equine Abdomen, Prevention, and Management of Incisional Complications.

Although rarely fatal, complications of ventral midline laparotomy incision in equine patients increase hospitalization cost and duration and may jeopardize return to athletic function. Therefore, many techniques have been developed to reduce their occurrence and expedite their resolution when they occur. Our technique of celiotomy incision closure includes the use of tension sutures (vertical U mattress) of polyglactin 910 on the linea alba, which is then apposed by polyglactin 910 interrupted sutures or a simple continuous pattern suture with a stop midway before routine closure of the superficial layers. The celiotomy incision is protected by an elastic bandage during the immediate postoperative period. This technique has been associated with favorable results: 5.3% confirmed incisional infections after a single celiotomy and 26.7% after repeat celiotomy. The overall incisional complication (serous/sanguineous discharge, hematoma, infection, hernia formation, and complete wound breakdown) occurrence was 9.5% and 33.3% after single and repeat laparotomy, respectively. In cases considered more susceptible to infection (early relaparotomy or laparotomy incisions longer than 30 cm), negative pressure therapy was found easy to apply on closed incisions. No detrimental effects were observed. However, the potential prophylactic benefit of this therapy needs to be confirmed in a larger group. In infected laparotomy wounds requiring drainage, the use of negative pressure therapy seemed to have a positive effect on the formation of granulation tissue. However, there was no control group to allow statistical confirmation. Finally, one case of complete breakdown of the laparotomy incision was managed by stainless steel retention sutures, the application of negative pressure therapy, and a hernia belt. At re-evaluation 15 months post-surgery, several small hernias were detected, but the horse had returned to his previous level of sports performance and had not shown any episode of colic.

Lessons Learned from West Nile Virus Infection:Vaccinations in Equines and Their Implications for One Health Approaches.

Humans and equines are two dead-end hosts of the mosquito-borne West Nile virus (WNV) with similar susceptibility and pathogenesis. Since the introduction of WNV vaccines into equine populations of the United States of America (USA) in late 2002, there have been only sporadic cases of WNV infection in equines. These cases are generally attributed to unvaccinated and under-vaccinated equines. In contrast, due to the lack of a human WNV vaccine, WNV cases in humans have remained steadily high. An average of 115 deaths have been reported per year in the USA since the first reported case in 1999. Therefore, the characterization of protective immune responses to WNV and the identification of immune correlates of protection in vaccinated equines will provide new fundamental information about the successful development and evaluation of WNV vaccines in humans. This review discusses the comparative epidemiology, transmission, susceptibility to infection and disease, clinical manifestation and pathogenesis, and immune responses of WNV in humans and equines. Furthermore, prophylactic and therapeutic strategies that are currently available and under development are described. In addition, the successful vaccination of equines against WNV and the potential lessons for human vaccine development are discussed.

Development and preclinical evaluation of equine-derived hyperimmune serum against SARS-CoV-2 infection in K-18 hACE2 transgenic (Tg) mice.

This study aimed to develop an equine-derived hyperimmune serum against SARS-CoV-2 and evaluate its efficacy as a potential immunotherapy tool for the treatment of known and potential variants of COVID-19 in preclinical trials. The novelty of this study is the whole virus and ALUM gel adjuvant formula. The horses were immunized using a whole inactivated SARS-CoV-2 antigen, and the final purified hyperimmune serum showed high plaque reduction neutralization (PRNT 50) neutralizing titers. The efficacy of the hyperimmune serum was evaluated histopathologically and biochemically in the lungs, hearts, and serum of K18 hACE2 transgenic mice (n=45), which is an accepted model organism for SARS-CoV-2 studies and was challenged with live SARS-CoV-2. Serum treatment improved the general condition, resulting in lower levels of proinflammatory cytokines in the blood plasma, as well as reduced viral RNA titers in the lungs and hearts. Additionally, it reduced oxidative stress significantly and lessened the severity of interstitial pneumonia in the lungs when compared to infected positive controls. The study concluded that equine-derived anti-SARS-CoV-2 antibodies could be used for COVID-19 prevention and treatment, especially in the early stages of the disease and in combination with antiviral drugs and vaccines. This treatment will benefit special patient populations such as immunocompromised individuals, as specific antibodies against SARS-CoV-2 can neutralize the virus before it enters host cells. The rapid and cost-effective production of the serum allows for its availability during the acute phase of the disease, making it a critical intervention in preventing the spread of the disease and saving lives in new variants where a vaccine is not yet developed.

Monophosphoryl lipid A and poly I:C combination enhances immune responses of equine influenza virus vaccine.

Equine influenza is a contagious respiratory disease caused by H3N8 type A influenza virus. Vaccination against equine influenza is conducted regularly; however, infection still occurs globally because of the short immunity duration and suboptimal efficacy of current vaccines. Hence the objective of this study was to investigate whether an adjuvant combination can improve immune responses to equine influenza virus (EIV) vaccines. Seventy-two mice were immunized with an EIV vaccine only or with monophosphoryl lipid A (MPL), polyinosinic-polycytidylic acid (Poly I:C), or MPL + Poly I:C. Prime immunization was followed by boost immunization after 2 weeks. Mice were euthanized at 4, 8, and 32 weeks post-prime immunization, respectively. Sera were collected to determine humoral response. Bone marrow, spleen, and lung samples were harvested to determine memory cell responses, antigen-specific T-cell proliferation, and lung viral titers. MPL + Poly I:C resulted in the highest IgG, IgG1, and IgG2a antibodies and hemagglutination inhibition titers among the groups and sustained their levels until 32 weeks post-prime immunization. The combination enhanced memory B cell responses in the bone marrow and spleen. At 8 weeks post-prime immunization, the combination induced higher CD8+ central memory T cell frequencies in the lungs and CD8+ central memory T cells in the spleen. In addition, the combination group exhibited enhanced antigen-specific T cell proliferation, except for CD4+ T cells in the lungs. Our results demonstrated improved immune responses when using MPL + Poly I:C in EIV vaccines by inducing enhanced humoral responses, memory cell responses, and antigen-specific T cell proliferation.

Updated ACVIM consensus statement on equine herpesvirus-1.

Equine herpesvirus-1 (EHV-1) is a highly prevalent and frequently pathogenic infection of equids. The most serious clinical consequences of infection are abortion and equine herpesvirus myeloencephalopathy (EHM). The previous consensus statement was published in 2009 and considered pathogenesis, strain variation, epidemiology, diagnostic testing, vaccination, outbreak prevention and control, and treatment. A recent survey of American College of Veterinary Internal Medicine large animal diplomates identified the need for a revision to this original consensus statement. This updated consensus statement is underpinned by 4 systematic reviews that addressed key questions concerning vaccination, pharmaceutical treatment, pathogenesis, and diagnostic testing. Evidence for successful vaccination against, or effective treatment of EHV-1 infection was limited, and improvements in experimental design and reporting of results are needed in future studies of this important disease. This consensus statement also updates the topics considered previously in 2009.

Effect of hay nets on horse bodyweight, body condition score, hay usage, and dental health in mature adult horses.

Hay nets are a commonly used management practice to increase intake time and reduce hay waste but may impact horse health. The objectives were to compare hay usage, dental wear, and dental conditions between horses fed with (NET) or without (CON) hay nets during a 2-year cross-over study. In September 2021, 13 mature adult horses were blocked by bodyweight (BW) and randomly assigned to the NET or CON treatments for one year. After one year (September 2022), horses switched treatments and the trial concluded in September 2023. Horses were housed in adjacent dry lots with shelter, ad libitum water, and free choice access to round bales with or without hay nets (4.45 cm openings). Blinded dental work, including incisor length measurements and recording of dental abnormalities and conditions, and recording of horse BW and body condition score (BCS) were completed in September 2021, 2022, and 2023. Digital images were taken monthly to determine rostral oral cavity scores (ROCS). Round bales were weighed prior to being placed in the dry lot and the date fed was recorded to calculate hay usage. Significance was set at P≤0.05. Horse BW, BCS, and hay usage were greater in horses consuming hay without hay nets (P<0.05). No differences were observed in incisor length, presence of incisor bevels, ROCS, or dental abnormalities and conditions (P>0.05). These data suggest that hay nets do not result in negative impacts on dental health but can reduce hay usage and help to control horse BW and BCS.

Evaluation of immunogenicity and protective efficacy of bacteriophage conjugated haemagglutinin based subunit vaccine against equine influenza virus in a murine model.

Equine influenza (EI) is a highly contagious acute respiratory disease of equines caused by the H3N8 subtype of Influenza A virus i.e. equine influenza virus (EIV). Vaccination is an important and effective tool for the control of EI in equines. Most of the commercial influenza vaccines are produced in embryonated hen's eggs which has several inherent disadvantages. Hence, subunit vaccine based on recombinant haemagglutinin (HA) antigen, being the most important envelope glycoprotein has been extensively exploited for generating protective immune responses, against influenza A and B viruses. We hypothesized that novel vaccine formulation using baculovirus expressed recombinant HA1 (rHA1) protein coupled with bacteriophage will generate strong protective immune response against EIV. In the present study, the recombinant HA1 protein was produced in insect cells using recombinant baculovirus having cloned HA gene of EIV (Florida clade 2 sublineage) and the purified rHA1 was chemically coupled with bacteriophage using a crosslinker to produce rHA1-phage vaccine candidate. The protective efficacy of vaccine preparations of rHA1-phage conjugate and only rHA1 proteins were evaluated in mouse model through assessing serology, cytokine profiling, clinical signs, gross and histopathological changes, immunohistochemistry, and virus quantification. Immunization of vaccine preparations have stimulated moderate antibody response (ELISA titres-5760 ± 640 and 11,520 ± 1280 for rHA1 and rHA1-phage, respectively at 42 dpi) and elicited strong interferon (IFN)-γ expression levels after three immunizations of vaccine candidates. The immunized BALB/c mice were protected against challenge with wild EIV and resulted in reduced clinical signs and body weight loss, reduced pathological changes, decreased EIV antigen distribution, and restricted EIV replication in lungs and nasopharynx. In conclusion, the immune responses with moderate antibody titer and significantly higher cytokine responses generated by the rHA1-phage vaccine preparation without any adjuvant could be a novel vaccine candidate for quick vaccine preparation through further trials of vaccine in the natural host.

The efficacy of N-acetylcysteine in decreasing airway inflammation and mucus accumulation in horses with 18 hours of head confinement.

BACKGROUND: During transportation many horses develop post-transportation infection, which can be life-threatening and end their sport career. Preventing mucus accumulation and inflammation during transportation is vital, emphasizing the need for effective strategies to enhance overall horse health welfare. OBJECTIVES: Assess the impact of N-acetylcysteine (NAC) on mucus accumulation and inflammation in horses subjected to 18 hours of head confinement. ANIMALS: Six healthy crossbred horses, 5.3 ± 2.1 years of age and weighing 387 ± 30 kg. METHODS: Prospective placebo-controlled cross-over design study. The horses' heads were restrained in their stalls for a period of 18 hours. They were studied under 4 conditions: Not confined (NC): before head confinement, placebo (P), and confined head (CH): 18 hours of head confinement without treatment, and N-Acetylcysteine (NAC): 18 hours of head confinement treated with NAC before confinement (15 mg/kg/day NAC PO for 3 days). Bronchoalveolar lavage (BAL) was performed in each condition. Mucus accumulation along the trachea was evaluated by endoscopy. RESULTS: Endoscopic scores were significantly different between CH and other conditions, whereas no significant differences were found among NC, P, and NAC. The BAL cell count (34 291 ± 2624 cells/µL), neutrophil and lymphocyte count (18 601 ± 3193 cells/µL and 3337.4 ± 593 cells/µL, respectively) in CH were significantly higher compared to NAC. Neutrophil percentage was significantly higher in CH (53.8 ± 8%) compared to horses that received NAC (20.08 ± 8%). Conversely, in comparison to NAC (66.33 ± 9%), the percentage of macrophages was significantly lower in CH (35.7 ± 10%). CONCLUSIONS: N-acetylcysteine was found to significantly decrease mucus accumulation and inflammatory cell counts in horses with head confinement.

Worm control practices used by Thoroughbred horse managers in Australia: A national survey.

This study assessed worm control practices used by Australian Thoroughbred farm managers with an online questionnaire survey. The questionnaire comprised 52 questions (close-ended: 44; open-ended: 8) about farm demography and general husbandry practices, farm managers' knowledge of gastrointestinal nematodes (GIN) and their importance, diagnosis, worm control strategies and anthelmintics, anthelmintic resistance (AR) and grazing management. Following the pilot survey, the link for the questionnaire survey was sent to all (n = 657) registered members of the Thoroughbred Breeders Australia on 12th April 2020. The response rate for the questionnaire was 18.5% (122 of 675). The farm managers reported a good understanding of GIN and their importance in different age groups of horses as most respondents (70% of 122) perceived worm-related illness to be more important in young (i.e., foals, weanlings and yearlings) than adult (> 3 years old) horses. Although most respondents (93%, 113 of 122) used anthelmintics prophylactically to control GIN, only 15% (18 of 122) observed worm-related illness in their horses. Just under 40% of respondents were performing faecal egg counts, with less than 20% using the results of faecal egg counts to guide deworming decisions. The interval-based deworming strategy was the most common method (≥55% of 122 respondents) to control GIN in all age groups of horses. Macrocyclic lactones were the first choice of anthelmintics for all age groups of horses. Although the majority of respondents (88%, 107 of 122) perceived resistance in GIN against commonly used anthelmintics as an important issue in managing worms in horses, only 29% assessed the efficacy of anthelmintics and 91% (111 of 122) were unaware of AR on their properties. Grazing management practices, such as manure removal, were more frequently performed on smaller paddocks (<0.20 ha: 58%) than on larger paddocks (>0.20 ha: 18%). Multiple correspondence analyses showed that the likelihood of suboptimal worm control practices on small farms (n = ≤50 horses) was greater than that of medium (n = 51-100) and large (n = >100) farms. This study provides insights into the demography of Thoroughbred farms in Australia, husbandry practices used by stud managers and their knowledge about worms, control options and AR concerns, thereby paving the way for taking any initiatives to address the problem of AR in GIN of Australian Thoroughbred horses.

The effect of feeding a commercial feedstuff on gastric squamous gastric disease (ESGD) healing and prevention of recurrence.

Feedstuffs are often recommended to mitigate potential damage from acid associated with equine squamous gastric disease (ESGD). In acidic conditions, pectin alters its structure to one like mucus and binds the stomach mucosa, whilst alfalfa has a strong intrinsic acid buffering capacity. The study aimed to determine whether feeding a commercial beet pulp/alfalfa/oat fibre mix aids ESGD healing and/or prevention of recurrence. Ten adult horses with naturally occurring ESGD were included. All animals were treated with omeprazole as per the attending veterinarian's recommendation and randomly allocated to also be fed a commercial beet pulp/alfalfa/oat fibre mix (1Kg/horse divided into 2 meals/day; n=5) or no additional feed (n=5) for one month. Gastroscopy was then repeated to assess response to therapy. If the ESGD had healed, omeprazole therapy was discontinued, and the commercial feed given to all horses for a further month. Gastroscopy was repeated to determine ESGD recurrence. The mean (±SD) age of the horses was 11.6 (±3.8) years; 4 mares and 6 geldings; various breeds were represented; and the median (range) initial ESGD grade was 2 (2-4). ESGD had healed (grade 0/4) in all animals after one month. After a further month, ESGD had recurred in significantly (p=0.04) more animals that did not receive the commercial feed initially (3/5; 60%; mean [range] ESGD grade 3 [0,4]) compared to those that did (0/5; 0%; mean [range] ESGD grade 0 [0,0]). Thus, the commercial beet pulp/alfalfa/oat fibre mix aided prevention of ESGD recurrence when fed during the healing and prevention phases.

Isolation of lactic acid bacteria from the reproductive tract of mares as potentially beneficial strains to prevent equine endometritis.

Endometritis, the inflammation of the endometrium, is the leading cause of subfertility in mares, and therefore responsible for major economic losses in the horse industry worldwide. It is generally treated with uterine lavages combined with ecbolic agents and local or systemic antibiotics. However, since antibiotic overuse has been associated with antimicrobial resistance in mares with persistent endometritis, new prevention and treatment alternatives are needed. One such alternative could be the use of probiotic lactic acid bacteria (LAB) isolated from the host. Thanks to their species specificity, resident microbiota may restore ecological equilibrium within the host, and therefore, help prevent infections and improve physiological functions. In the present study, 257 bacterial strains were isolated from 77 healthy mares, and 88.76% (n = 228) of them were phenotypically classified as LAB. Within this group, 65.79% were able to inhibit at least one strain from each of the genera that most commonly cause equine endometritis (Streptococcus equi subsp. zooepidemicus, Escherichia coli, and Staphylococcus spp.). Five strains (RCE11, RCE20, RCE91, RCE99, and RCE167) were selected on the basis of their beneficial properties: ability to autoaggregate and adhere to equine epithelial cells, high inhibition of and co-aggregation with all the bacteria isolated from clinical cases of endometritis evaluated, and negative co-inhibition between one another. All five were finally identified as Enterococcus spp., namely E. faecium (two strains), E. hirae (two strains), and E. gallinarum (one strain). Further studies will assess their safety and biotechnological potential for the design of a multi-strain probiotic formula to prevent equine endometritis.

Antimicrobial prophylaxis is not indicated for horses undergoing general anaesthesia for elective orthopaedic MRI.

BACKGROUND: Post-anaesthetic fever is a known complication of general anaesthesia, however, its incidence in horses undergoing elective magnetic resonance imaging (MRI) is unknown. OBJECTIVE: To determine the incidence of post-anaesthetic fever in horses undergoing elective orthopaedic MRI and determine whether prophylactic antimicrobial therapy would be associated with a reduction in the incidence of post-anaesthetic fever. We hypothesised that prophylactic antimicrobials would be associated with a reduction in the incidence of post-anaesthetic fever. STUDY DESIGN: Retrospective cross-sectional study. METHODS: This retrospective study included 791 elective orthopaedic MRIs in systemically healthy horses between June 2006 and March 2020 that recovered from general anaesthesia and did not undergo surgery or intensive medical therapy soon after recovery. Potential factors associated with post-anaesthetic fever were evaluated using multivariable logistic regression. Case signalment, travel time, preanaesthetic haematology and fibrinogen abnormalities, use of prophylactic antimicrobials, peri-anaesthetic nonsteroidal anti-inflammatories, anaesthesia time and recovery time were all evaluated for association with post-anaesthetic fever. RESULTS: Of 791 MRI cases, 44 (5.6%) developed a post-anaesthetic fever. Horses that received prophylactic antimicrobials were [odds ratio (OR) 3.8, 95% confidence interval (CI) 1.98-7.46; p ≤ 0.001] more likely to develop a post-anaesthetic fever than those that did not receive antimicrobials. Young horses (1-4 years of age) were (OR 2.8, 95% CI 1.26-6.17; p = 0.01) more likely to develop fever compared with adult horses (≥5 years of age). MAIN LIMITATIONS: Limitations of this study pertain to retrospective analysis including nonrandomised case selection and incomplete data records. CONCLUSIONS: While fever may indicate infection, the majority of early post-anaesthetic fevers resolved before discharge from the hospital with no identified cause. The use of prophylactic antimicrobials to reduce the risk of post-anaesthetic fever for elective MRI is not supported by this study.

CONTEXTO: Febre é uma complicação comum após anestesia geral. Contudo, a incidência de febre em cavalos submetidos à ressonância magnética (RM) é desconhecida. OBJETIVO: Determinar a incidência de febre pós­anestésica em cavalos submetidos à RM devido à lesões ortopédicas e determinar se terapia antimicrobiana é necessária para reduzir a incidência de febre pós­anestésica. Nossa hipótese é que o uso de antimicrobianos é associado com a redução da incidência de febre pós­anestésica. DELINEAMENTO DO ESTUDO: Estudo retrospectivo transversal. METODOLOGIA: Esse estudo retrospectivo incluiu 791 equinos submetidos à RM por motivos ortopédicos, entre Junho de 2006 e Março de 2020, que recuperaram de anestesia geral, e não foram submetidos à cirurgia ou terapia intensa logo após a recuperação. Fatores que potencialmente poderiam ser associados com febre pós­anestésica foram avaliados utilizando regressão logística multivariada. Informações do paciente, como sexo e idade, tempo de viagem, anormalidades nos exames de sangue (hemograma e bioquímico) pré­anestésico, uso profilático de antimicrobianos, uso de anti­inflamatório não­esteroidal no período peri­anestésico, tempo de anestesia, e tempo de recuperação foram avaliados para possível associação com febre pós­anestésica. RESULTADOS: Dos 791 casos de RM, 44 (5.6%) desenvolveram febre pós­anestésica. Cavalos que receberam terapia antimicrobiana profilática foram (OR 3.8, 95% CI 1.98­7.46; p ≤ 0.001) vezes mais prováveis de desenvolverem febre pós­anestésica do que aqueles que não receberam antimicrobianos. Cavalos jovens (1­4 anos de idade) foram OR 2.8, 95% CI 1.26­6.17; p = 0.01) vezes mais prováveis de desenvolverem febre comparado com cavalos adultos (≥5 anos de idade). PRINCIPAIS LIMITAÇÕES: As limitações deste estudo são aquelas de uma análise retrospectiva, incluindo a seleção não randomizada dos pacientes e prontuários incompletos. CONCLUSÕES: Enquanto febre pode indicar a presença de infecção, a maioria das febres no período logo após anestesia se resolveram antes da alta do hospital e não tiveram nenhuma causa identificada. O uso profilático de antimicrobianos para reduzir a possível chance de febre pós­anestésica em casos de RM eletiva não é suportada por este estudo.

Clinical effects of a combination of phenylbutazone and omeprazole on chronic lameness in Mongolian horses.

BACKGROUND: Phenylbutazone (PBZ) is the most commonly used drug to treat symptoms of lameness in horses; however, it is associated with adverse effects such as gastric ulcer syndrome (EGUS). Interestingly, many practitioners prescribe omeprazole (OME) concurrently with PBZ to prevent the development of EGUS. However, the efficacy and safety of this practice in Mongolian horses with chronic lameness remain unknown. OBJECTIVES: To evaluate the clinical effects of a combination of PBZ and OME on chronic lameness in Mongolian horses. STUDY DESIGN: Randomised block experimental design. METHODS: Eighteen Mongolian horses with lameness score was ≥3 points, were divided into three treatment groups, with six horses in each group: placebo (CON), PBZ (4.4 mg/kg PO q. 24 h), or PBZ plus OME (4 mg/kg PO q. 24 h; PBZ + OME) in a randomised block design based on the initial lameness score. The horses were treated for 15 days. During this period, weekly gastroscopy, and physiological and biochemical tests were performed. RESULTS: Both PBZ (median 1.0, interquartile range [IQR]: 0.8-1.3; p = 0.01) and PBZ + OME (median 1.0, IQR: 1.0-1.0; p = 0.01) significantly decreased the lameness score compared with before administration. In addition, PBZ significantly increased the equine glandular gastric disease (EGGD) score (3.0 ± 0.6, p < 0.001), GT-17 content (293.4 ± 21.8 pg/mL, p < 0.001), and pepsinogen-1 (PG1) content (295.3 ± 38.3 ng/mL, p < 0.001) compared with CON or PBZ + OME. However, it significantly reduced the total protein (53.6 ± 1.5 g/L, p < 0.05) and albumin (25.5 ± 1.8 g/L, p < 0.05) contents. Nevertheless, compared with PBZ, PBZ + OME significantly decreased the EGGD score (0.3 ± 0.5, p < 0.001) and significantly increased the gastric fluid pH (7.3 ± 0.5, p < 0.001), total protein content (62.5 ± 4.6 g/L, p = 0.009), and albumin content (29.4 ± 1.1 g/L, p = 0.004). Meanwhile, they significantly diminished the gastrin 17 (GT-17) (162.0 ± 21.0 pg/mL, p < 0.001) and PG1 (182.4 ± 22.5 ng/mL, p < 0.001) contents. MAIN LIMITATIONS: Individual differences in horses were larger, but the sample size was small. There was larger interval between observations for each index. CONCLUSIONS: Compared with PBZ alone, PBZ + OME had no therapeutic effect on chronic lameness; however, it reduced the occurrence of EGGD in Mongolian horses. Horses may be protected against chronic lameness and PBZ-induced EGGD by increasing the pH value, decreasing serum PG1 and GT-17 content, and preventing the reduction of myeloperoxidase content.

Intramuscular but not nebulized administration of a mRNA vaccine against Rhodococcus equi stimulated humoral immune responses in neonatal foals.

OBJECTIVE: Design and evaluate immune responses of neonatal foals to a mRNA vaccine expressing the virulence-associated protein A (VapA) of Rhodococcus equi. ANIMALS: Cultured primary equine respiratory tract cells; Serum, bronchoalveolar lavage fluid (BALF), and peripheral blood mononuclear cells (PBMCs) from 30 healthy Quarter Horse foals. METHODS: VapA expression was evaluated by western immunoblot in cultured equine bronchial cells transfected with 4 mRNA constructs encoding VapA. The mRNA construct with greatest expression was used to immunize foals at ages 2 and 21 days in 5 groups: (1) 300 µg nebulized mRNA (n = 6); (2) 600 µg nebulized mRNA (n = 4); (3) 300 µg mRNA administered intramuscularly (IM) (n = 5); (4) 300 µg VapA IM (positive controls; n = 6); or (5) nebulized water (negative controls; n = 6). Serum, BALF, and PBMCs were collected at ages 3, 22, and 35 days and tested for relative anti-VapA IgG1, IgG4/7, and IgA activities using ELISA and cell-mediated immunity by ELISpot. RESULTS: As formulated, nebulized mRNA was not immunogenic. However, a significant increase in anti-VapA IgG4/7 activity (P < .05) was noted exclusively in foals immunized IM with VapA mRNA by age 35 days. The proportion of foals with anti-VapA IgG1 activity > 30% of positive control differed significantly (P = .0441) between negative controls (50%; 3/6), IM mRNA foals (100%; 5/5), and IM VapA (100%; 6/6) groups. Natural exposure to virulent R equi was immunogenic in some negative control foals. CLINICAL RELEVANCE: Further evaluation of the immunogenicity and efficacy of IM mRNA encoding VapA in foals is warranted.

Dynamics analysis of strangles with asymptomatic infected horses and long-term subclinical carriers.

Strangles is one of the most prevalent horse diseases globally. The infected horses may be asymptomatic and can still carry the infectious pathogen after it recovers, which are named asymptomatic infected horses and long-term subclinical carriers, respectively. Based on these horses, this paper establishes a dynamical model to screen, measure, and model the spread of strangles. The basic reproduction number $ \mathcal{R}_0 $ is computed through a next generation matrix method. By constructing Lyapunov functions, we concluded that the disease-free equilibrium is globally asymptotically stable if $ \mathcal{R}_0 < 1 $, and the endemic equilibrium exits uniquely and is globally asymptotically stable if $ \mathcal{R}_0 > 1 $. For example, while studying a strangles outbreak of a horse farm in England in 2012, we computed an $ \mathcal{R}_0 = 0.8416 $ of this outbreak by data fitting. We further conducted a parameter sensitivity analysis of $ \mathcal{R}_0 $ and the final size by numerical simulations. The results show that the asymptomatic horses mainly influence the final size of this outbreak and that long-term carriers are connected to an increased recurrence of strangles. Moreover, in terms of the three control measures implemented to control strangles(i.e., vaccination, implementing screening regularly and isolating symptomatic horses), the result shows that screening is the most effective measurement, followed by vaccination and isolation, which can provide effective guidance for horse management.

Effect of a blend of magnesium oxide on Equine Squamous Gastric Disease in young trotter horses under training.

BACKGROUND: Equine squamous gastric disease (ESGD), as part of the equine gastric ulcer syndrome (EGUS), are common in racing horses. The use of buffering feed supplements to treat and/or prevent gastric ulcers is an option to control this condition. OBJECTIVE: The purpose of this study was to evaluate the effect of a 30-day supplementation with a blend of magnesium oxide (MgO) on ESGD scores in trotters under training. METHODS: Forty-two young trotters were submitted to a gastroscopic evaluation to assess their ESGD score and were randomly assigned in a group supplemented with MgO or in a control group. After 30 days, a second evaluation by gastroscopy was performed. The effect of the MgO supplementation was assessed by comparing the evolution of the ESGD score in supplemented and control groups between day 0 and day 30. RESULTS: The results confirm the high prevalence of EGUS in young Trotters. The supplementation significantly decreased the ESGD scoring in the supplemented group whereas the control group remain unchanged. CONCLUSION: The oral MgO supplementation was efficient to control ESGD in the population studied.