Foals of mares vaccinated for Hendra virus have a suboptimal response to HeV vaccination.

Hendra virus (HeV) is lethal to horses and a zoonotic threat to humans in Australia, causing severe neurological and/or respiratory disease with high mortality. An equine vaccine has been available since 2012. Foals acquire antibodies from their dams by ingesting colostrum after parturition, therefore it is assumed that foals of mares vaccinated against HeV will have passive HeV antibodies circulating during the first several months of life until they are actively vaccinated. However, no studies have yet examined passive or active immunity against HeV in foals. Here, we investigated anti-HeV antibody levels in vaccinated mares and their foals. Testing for HeV neutralising antibodies is cumbersome due to the requirement for Biosafety level 4 (BSL-4) containment to conduct virus neutralisation tests (VNT). For this study, a subset of samples was tested for HeV G-specific antibodies by both an authentic VNT with infectious HeV and a microsphere-based immunoassay (MIA), revealing a strong correlation. An indicative neutralising level was then applied to the results of a larger sample set tested using the MIA. Mares had high levels of HeV-specific neutralising antibodies at the time of parturition. Foals acquired high levels of maternal antibodies which then waned to below predictive protective levels in most foals by 6 months old when vaccination commenced. Foals showed a suboptimal response to vaccination, suggesting maternal antibodies may interfere with active vaccination. The correlation analysis between the authentic HeV VNT and HeV MIA will enable further high throughput serological studies to inform optimal vaccination protocols for both broodmares and foals.

Antibody reactions of horses against various domains of the EHV-1 receptor-binding protein gD1.

Equid alphaherpesviruses 1 (EHV-1) and 4 (EHV-4) are closely related and both endemic in horses worldwide. Both viruses replicate in the upper respiratory tract, but EHV-1 may additionally lead to abortion and equine herpesvirus myeloencephalopathy (EHM). We focused on antibody responses in horses against the receptor-binding glycoprotein D of EHV-1 (gD1), which shares a 77% amino acid identity with its counterpart in EHV-4 (gD4). Both antigens give rise to cross-reacting antibodies, including neutralizing antibodies. However, immunity against EHV-4 is not considered protective against EHM. While a diagnostic ELISA to discriminate between EHV-1 and EHV-4 infections is available based on type-specific fragments of glycoprotein G (gG1 and gG4, respectively), the type-specific antibody reaction against gD1 has not yet been sufficiently addressed. Starting from the N-terminus of gD1, we developed luciferase immunoprecipitation system (LIPS) assays, using gD1-fragments of increasing size as antigens, i.e. gD1_83 (comprising the first 83 amino acids), gD1_160, gD1_180, and gD1_402 (the full-length molecule). These assays were then used to analyse panels of horse sera from Switzerland (n = 60) and Iceland (n = 50), the latter of which is considered EHV-1 free. We detected only one true negative horse serum from Iceland, whereas all other sera in both panels were seropositive for both gG4 (ELISA) and gD1 (LIPS against gD1_402). In contrast, seropositivity against gG1 was rather rare (35% Swiss sera; 14% Icelandic sera). Therefore, a high percentage of antibodies against gD1 could be attributed to cross-reaction and due to EHV-4 infections. In contrast, the gD1_83 fragment was able to identify sera with type-specific antibodies against gD1. Interestingly, those sera stemmed almost exclusively from vaccinated horses. Although it is uncertain that the N-terminal epitopes of gD1 addressed in this communication are linked to better protection, we suggest that in future vaccine developments, type-common antigens should be avoided, while a broad range of type-specific antigens should be favored.

Development of a live attenuated vaccine candidate for equid alphaherpesvirus 1 control: a step towards efficient protection.

Equid alphaherpesvirus 1 (EqAHV1) is a viral pathogen known to cause respiratory disease, neurologic syndromes, and abortion storms in horses. Currently, there are no vaccines that provide complete protection against EqAHV1. Marker vaccines and the differentiation of infected and vaccinated animals (DIVA) strategy are effective for preventing and controlling outbreaks but have not been used for the prevention of EqAHV1 infection. Glycoprotein 2 (gp2), located on the envelope of viruses (EqAHV1), exhibits high antigenicity and functions as a molecular marker for DIVA. In this study, a series of EqAHV1 mutants with deletion of gp2 along with other virulence genes (TK, UL24/TK, gI/gE) were engineered. The mutant viruses were studied in vitro and then in an in vivo experiment using Golden Syrian hamsters to assess the extent of viral attenuation and the immune response elicited by the mutant viruses in comparison to the wild-type (WT) virus. Compared with the WT strain, the YM2019 Δgp2, ΔTK/gp2, and ΔUL24/TK/gp2 strains exhibited reduced growth in RK-13 cells, while the ΔgI/gE/gp2 strain exhibited significantly impaired proliferation. The YM2019 Δgp2 strain induced clinical signs and mortality in hamsters. In contrast, the YM2019 ΔTK/gp2 and ΔUL24/TK/gp2 variants displayed diminished pathogenicity, causing no observable clinical signs or fatalities. Immunization with nasal vaccines containing YM2019 ΔTK/gp2 and ΔUL24/TK/gp2 elicited a robust immune response in hamsters. In particular, compared with the vaccine containing the ΔTK/gp2 strain, the vaccine containing the ΔUL24/TK/gp2 strain demonstrated enhanced immune protection upon challenge with the WT virus. Furthermore, an ELISA for gp2 was established and refined to accurately differentiate between infected and vaccinated animals. These results confirm that the ΔUL24/TK/gp2 strain is a safe and effective live attenuated vaccine candidate for controlling EqAHV1 infection.

Tetanus prophylaxis in horses: guidelines for New Zealand and Australia based on a critical appraisal of the evidence.

Horses are exquisitely sensitive to tetanus neurotoxin and are exposed to the risk of infection with Clostridium tetani throughout life. The vaccine against tetanus is highly effective at preventing disease, whereas tetanus in unvaccinated populations is associated with high mortality rates. Current guidelines in New Zealand and Australia for the available vaccine contain contradictions and limitations surrounding the optimal tetanus immunisation protocols for both adult horses and foals. This review critically evaluates the scientific literature on tetanus prophylaxis in horses within the context of equine practice and available products in New Zealand and Australia. The review was conducted by a panel of industry and specialist veterinarians to obtain agreement on nine equine tetanus prophylaxis guidelines for practising veterinarians. The primary protocol for tetanus toxoid (TT) immunisation consists of a three-dose series IM for all horses ≥ 6 months of age, and a four-dose series IM is proposed if commencing vaccination in foals between 3 and 6 months of age. Tetanus prophylaxis in foals < 3 months of age relies on passive immunity strategies. Following the completion of the primary protocol, a TT booster dose IM should be administered within 5 years, and every 5 years thereafter. When followed, these protocols should provide adequate protection against tetanus in horses. Additional tetanus prophylaxis guidelines are provided for veterinarians attending a horse experiencing a known "risk event" (e.g. wound, hoof abscess, surgery, umbilical infection). When a correctly vaccinated horse experiences a risk event, pre-existing immunity provides protection against tetanus. When an unvaccinated horse or one with unknown vaccination status, or a foal born to an unvaccinated dam, experiences a risk event, TT IM and tetanus antitoxin (TAT) 1,500 IU SC should be administered simultaneously at separate sites, and the TT primary immunisation protocol should subsequently be completed for the horse's respective age. In previously immunised pregnant broodmares, a TT booster dose administered 4-8 weeks prior to parturition optimises the transfer of passive immunity against tetanus to the newborn foal via colostrum; provided that post-natal IgG concentration in serum is > 800 mg/dL (8 g/L), such foals should be passively protected against tetanus up to 6 months of age. Survivors of clinical tetanus must still receive the primary protocol for vaccination against tetanus. In summary, all horses in New Zealand and Australia should be vaccinated against tetanus with protection maintained throughout life via TT booster doses, facilitated by accurate medical record keeping and client education.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.