New genetic discovery explains fatal neurological disease in Quarter Horse foals

   

© Rebecca Hermanson Dreamstime.com

Researchers at the UC Davis School of Veterinary Medicine have identified the genetic cause of Equine Juvenile Spinocerebellar Ataxia (EJSCA), a recently recognised and fatal neurological disease affecting American Quarter Horse foals. The discovery not only provides breeders with a genetic test to prevent affected foals from being born, but also advances scientific understanding of neurological disease in both horses and humans.

EJSCA is an inherited neurological disorder that affects foals within the first few weeks of life. Clinical signs typically develop between one and five weeks of age and progress rapidly. Affected foals initially appear uncoordinated and exhibit proprioceptive ataxia, meaning they have difficulty determining the position of their limbs in space. Within days, many develop severe weakness of the hind limbs, become unable to stand without assistance, and eventually require euthanasia on welfare grounds.

The disease results from degeneration of axons, the long nerve fibres that connect neurons and allow communication between the brain, spinal cord and limbs. As these pathways deteriorate, the nervous system can no longer accurately transmit information about movement and body position. Consequently, affected foals lose balance and coordination despite appearing normal at birth.

The first recognised case of EJSCA was identified in 2020 in a Quarter Horse filly known as “Curly Sue.” Veterinarians initially suspected another neurological condition, equine neuroaxonal dystrophy (eNAD), but further investigations revealed that the foal was suffering from a previously unrecognised disease.

To identify the genetic cause, researchers at UCDavis performed whole-genome sequencing on seven affected foals and compared their DNA with that of unaffected relatives and unrelated control horses. The investigation identified an 82-kilobase region on chromosome 11 that contained several candidate genetic variants. Further molecular studies demonstrated that the causative mutation was located within a non-coding region of the ferredoxin reductase (FDXR) gene.

Unlike many disease-causing mutations that alter the protein-coding sequence of a gene, this mutation affects how the gene is processed into messenger RNA. The variant causes the insertion of a cryptic exon - a segment of genetic material that is not normally included in the final RNA transcript. As a result, affected foals produce lower amounts of functional FDXR protein.

This finding is significant because FDXR plays an important role in cellular energy metabolism and nervous system function. Analysis of spinal cord and liver tissues showed that affected foals had substantially reduced FDXR protein concentrations compared with healthy controls. Importantly, mutations in the human FDXR gene are known to cause neurological disease, making EJSCA a potentially valuable natural model for studying similar disorders in people.

The researchers determined that EJSCA follows an autosomal recessive pattern of inheritance. This means that affected foals inherit two copies of the mutation, one from each parent. Horses carrying only one copy remain clinically normal but can pass the variant to their offspring. When two carrier horses are bred together, there is a 25% chance of producing an affected foal.

Screening of more than 1,000 Quarter Horses identified 25 carriers, indicating that the mutation currently occurs at a relatively low frequency within the breed. It has not yet been detected in other horse breeds. Because all known affected foals trace back to a single influential sire, researchers believe the mutation may have arisen relatively recently.

The development of a genetic test by the UC Davis Veterinary Genetics Laboratory now allows breeders to identify carrier animals before breeding. By avoiding carrier-to-carrier matings, breeders can effectively prevent the birth of affected foals while maintaining valuable bloodlines. This discovery represents the first non-coding neurological genetic variant identified in horses and the first known genetic cause of a degenerative axonal disease in the species, marking an important milestone in equine genetics and neurological research.

 

For more details, see:

Brown, B. N., Dahlgren, A. R., Ghosh, S., Durbin-Johnson, B., Willis, A., Olivas, C., York, D., Grahn, R., Bellone, R. R., Cortopassi, G. A., Miller, A. D., Brown, C. T., Woolard, K., & Finno, C. J. (2026).

An intronic variant in Ferredoxin Reductase (FDXR) creates a cryptic exon in Quarter Horses with Equine Juvenile Spinocerebellar Ataxia. 

PLoS genetics, (2026). 22(5), e1012158.

https://doi.org/10.1371/journal.pgen.1012158

Pseudomonas aeruginosa in horses and other animals

  

© CarolHancock Dreamstime.com

Pseudomonas aeruginosa is an environmentally widespread bacterium found naturally in soil and water. Although it
is often harmless in the environment, it is an important cause of disease in both human and veterinary medicine. The bacterium is particularly concerning because it possesses a high level of intrinsic resistance to many antibiotics, has a remarkable ability to adapt genetically, and can form resilient biofilms that protect it from both the host immune system and antimicrobial treatments.

 

The World Health Organisation (WHO) has designated P. aeruginosa as a "Priority Pathogen" due to its role in antimicrobial resistance. It is also one of the six bacterial species that make up the ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species). These bacteria are responsible for many hospital-acquired infections worldwide and are notorious for their ability to evade antibiotic treatment.

 

In horses, P. aeruginosa is associated with several important diseases, including genital tract infections, respiratory disease and ocular infections. In mares, infection can contribute to infertility and pregnancy-related problems, making it a significant pathogen in equine breeding operations.

 

To better understand the occurrence of P. aeruginosa in animal populations, Kellie Strickland and colleagues at the University of the Sunshine Coast, Australia, conducted a large-scale epidemiological study. The researchers analysed 1,669 DNA samples collected between 2010 and 2023 from a variety of healthy and diseased animals in South-East Queensland. The study included samples from wild birds, domestic animals, livestock, kangaroos and koalas.

 

Overall, the prevalence of P. aeruginosa was relatively low, with only 1.8% of all samples testing positive. However, livestock had the highest prevalence (4.5%), largely driven by horses, which showed a prevalence of 7.4%. This was considerably higher than the rates observed in wild birds (1.5%), koalas (1.6%) and other domestic animals (1.9%). No positive samples were detected in cattle or kangaroos.

 

Of particular concern was the detection of a genetic mutation known as GyrA Thr83Ile in two horse-derived P. aeruginosa samples. This mutation has previously been associated with resistance to fluoroquinolones, a class of antibiotics commonly used to treat P. aeruginosa infections in both humans and horses. Although the researchers were unable to confirm antibiotic resistance through laboratory culture and susceptibility testing, the presence of this mutation suggests that a resistant subpopulation may be emerging within the equine population.

 

The findings highlight the importance of ongoing surveillance of antimicrobial resistance in horses. While the overall prevalence of P. aeruginosa was low, the relatively high carriage rate in horses and the detection of a clinically important resistance-associated mutation warrant further investigation.

 

For more details, see:

Prevalence of Pseudomonas aeruginosa in Australian wild birds, native wildlife, livestock and domestic animals

Kellie R. Strickland, Martina Jelocnik, Erin P. Price & Derek S. Sarovich 

Scientific Reports (2026) vol 16, Article number: 15423 (2026) 

https://www.nature.com/articles/s41598-026-43853-6

Exercise, the gut microbiome and health

© MederPhotography Dreamstime.com

  

 The gut microbiome - the diverse community of bacteria, fungi, viruses and other microorganisms that inhabit the gastrointestinal tract - has become a major focus of research in both human and veterinary medicine.

 

Far from being passive inhabitants, these microorganisms play a crucial role in host health, influencing digestion, metabolism, immune function and even neurological processes. Growing evidence suggests that the composition and diversity of the gut microbiome can affect susceptibility to a wide range of conditions, including obesity, cardiovascular disease, autoimmune disorders and inflammatory diseases.

 

In human medicine, among the many factors that influence the microbiome, regular physical activity has emerged as one of the most important. Exercise is widely recognised for its benefits to digestive and systemic health, and research indicates that many of these effects may be mediated through changes in the gut microbiota. Regular moderate-to-vigorous exercise has been shown to increase microbial diversity, a characteristic strongly associated with better physical and mental health.

 

In contrast, reduced microbial diversity has been observed in individuals with obesity, cardiometabolic disease and certain autoimmune conditions.

 

While these effects are increasingly well documented in humans, less is known about the relationship between exercise and the gut microbiome in horses. A recent study, published in  Microbial pathogenesis, investigated this question by examining the effects of exercise on equine gut bacterial and fungal communities using 16S rDNA and ITS gene amplicon sequencing.

 

The results demonstrated that exercise significantly increased bacterial diversity, as reflected by higher ACE, Chao1 and Shannon diversity indices - commonly used measures of microbial diversity in ecological and microbiome studies. The increases in ACE and Chao1 suggest that exercise was associated with a greater number of bacterial taxa in the gut, while an increase in the Shannon index indicated that the bacterial community became both richer and more evenly distributed. Together, these findings suggest that exercise promoted a more diverse gut bacterial ecosystem.

 

Exercise also altered the overall composition of the bacterial community. Specifically, the relative abundance of eight bacterial phyla and 187 bacterial genera increased, while three phyla and 197 genera decreased significantly.

 

In contrast, exercise had little effect on the overall diversity and abundance of the fungal community, although significant changes were observed in the abundance of specific fungal taxa. Exercise increased the relative abundance of five fungal phyla and 105 genera, while reducing two phyla and 82 genera.

 

These findings indicate that exercise can substantially modify the composition and structure of the equine gut microbiota, particularly the bacterial component. The study supports the growing concept that exercise may promote health by shaping the gut microbial ecosystem.

 

Future research examining different exercise types and intensities may further clarify how physical activity can be used to optimise microbiome health and improve management strategies in both humans and horses.

 

For more details, see:

 

Ma, Rufei., & Wang, Chong.

Microbiome analysis reveals the positive effects of exercise on the gut microbiota in horse. 

Microbial pathogenesis (2026) , 216, 108501.

https://doi.org/10.1016/j.micpath.2026.108501

 

Could ertugliflozin reduce laminitis risk following corticosteroid joint injections?

© Silviu-florin Salomia Dreamstime.com

Intra-articular (IA) corticosteroid injections are widely used in equine practice to manage joint
pain and inflammation associated with conditions such as osteoarthritis. One commonly used corticosteroid is triamcinolone acetonide (TA), which can provide significant relief from lameness and improve performance. However, growing evidence suggests that even when corticosteroids are administered directly into a joint, they can have effects throughout the body, including alterations in blood glucose and insulin concentrations.

This is important because elevated insulin concentrations (hyperinsulinaemia) are strongly associated with endocrinopathic laminitis, one of the most common and serious causes of laminitis in horses. Horses with Equine Metabolic Syndrome (EMS) or insulin dysregulation (ID) are considered particularly vulnerable, but any horse experiencing a substantial increase in insulin may be at risk.

Researchers have recently investigated whether ertugliflozin, a member of the sodium-glucose co-transporter 2 inhibitor (SGLT2i) drug class, could help reduce these post-corticosteroid insulin increases. In human medicine, SGLT2 inhibitors are commonly used to treat Type 2 diabetes by promoting the excretion of glucose through the urine, thereby reducing blood glucose and insulin levels. More recently, these drugs have attracted attention in equine medicine as a treatment for severe insulin dysregulation.

Two independent studies have now examined the effects of ertugliflozin administration around the time of IA corticosteroid treatment in horses.

The first study, conducted by Page and colleagues at the University of Kentucky, used eight metabolically normal geldings in a controlled crossover design. Horses either received no treatment or were given ertugliflozin for seven days before and seven days after receiving a clinically relevant dose of triamcinolone acetonide. Researchers measured resting glucose and insulin concentrations and performed oral sugar tests to assess the horses' insulin responses.

The results showed that horses receiving ertugliflozin had significantly lower blood glucose and insulin concentrations following corticosteroid administration. Resting glucose concentrations remained lower for up to 48 hours after injection, while resting insulin concentrations were lower for up to 72 hours. Insulin responses during oral sugar testing were also reduced. Importantly, no obvious adverse effects were observed during the study.

A second study by Darch and colleagues produced similar findings. Using a randomised, blinded, placebo-controlled crossover design, eight Standardbred geldings received either ertugliflozin or a placebo before and after IA triamcinolone administration. The researchers monitored blood insulin, glucose and triglyceride concentrations over the treatment period.

Again, ertugliflozin substantially reduced the insulin response following corticosteroid injection. The peak insulin concentration (Cmax) was approximately 40 μIU/mL in the placebo group but only 17 μIU/mL in horses receiving ertugliflozin. Statistical analysis indicated a greater than 99% probability that the peak insulin concentration was lower when horses received ertugliflozin.

Together, these studies provide encouraging evidence that ertugliflozin can attenuate the increases in blood glucose and insulin that occur following IA corticosteroid administration. This finding is particularly relevant because corticosteroid-associated hyperinsulinaemia may contribute to laminitis risk.

However, both studies were conducted in horses that did not have insulin dysregulation. Consequently, the most important question remains unanswered: can ertugliflozin reduce post-corticosteroid insulin elevations in horses already suffering from EMS or ID, where the risk of laminitis is greatest?

Further research is now needed to determine whether this treatment strategy can safely protect high-risk horses. If successful, ertugliflozin could become an important tool that allows veterinarians to continue using corticosteroid joint injections while reducing the metabolic complications that may accompany them.

 

For more details,see:

1) Allen E Page,  Jenna L McPeek,  Ella McGreevy,  Sophia Carattini,  Emma N Adam.  

Treatment with ertugliflozin mitigates the hyperinsulinemic response to intra-articular triamcinolone acetonide. 

Equine Vet J.  2026.

https://doi.org/10.1002/evj.70150

 

2) Cara Darch, Timothy H. Hyndman, David Byrne, David Ian Rendle, Barny Fraser,

Ertugliflozin decreases the insulin spike in non-insulin dysregulated standardbred horses following intra-articular triamcinolone administration,

Domestic Animal Endocrinology, (2026) Vol 96,107016,

https://doi.org/10.1016/j.domaniend.2026.107016

Free webinar supports call for posters for Horses Inside Out Conference 2027

© ViktoriaMakarova Dreamstime.com

  

A call has been made for scientific posters centred on the theme of wellness and welfare for the
2027 Horses Inside Out Conference. Equine coaches, therapists, and industry professionals are being encouraged to contribute research, case studies, and practical observations as part of the conference programme.

The initiative provides an opportunity for professionals within the equine sector to present their expertise in a scientific format and contribute to ongoing discussions surrounding equine wellness and welfare. Contributors are invited to transform their practical experience and case studies into engaging scientific posters that may help advance understanding within the field.

To support participants through the process, Professor Meriel Moore-Colyer will host a free webinar entitled “Mastering Scientific Posters” on Monday 1st June. The webinar is designed to guide attendees through each stage of poster creation, including selecting an appropriate topic, developing ideas, and designing an effective and visually compelling scientific poster.

The webinar aims to make the process accessible and supportive for those who may feel unfamiliar with scientific poster presentation, while encouraging wider participation in equine science and welfare discussions.

For more details, see: 

https://www.horsesinsideout.com/webinars

 

Effects of a fibre-based forage feed on hindgut fermentation and microbiome

© Pimmimemom  Dreamstime.com

As understanding of equine gut health continues to evolve, increasing attention is being focused on the relationship between diet and the horse’s hindgut microbiome. The microbial community structure (MCS) within the hindgut plays a critical role in fibre digestion, nutrient utilisation, immune support, and overall gastrointestinal health. Although numerous commercial feeds and supplements are marketed to support digestive function and optimise nutrition, relatively little research has examined how these products influence the equine hindgut microbiome.

 

Newly published research conducted by K.J. Hart, M.J. Hegarty, E.H. Hart at Aberystwyth University sought to address this knowledge gap by investigating the effects of a complementary fibre-based forage feed* on hindgut fermentation and microbial community structure under controlled laboratory conditions.

 

The study aimed to evaluate how the feed influenced fermentation profiles and microbial populations when added to two contrasting basal diets: a forage-only diet (FOR) and a mixed forage-and-concentrate diet (MIX). Researchers used an in vitro hindgut fermentation model designed to simulate conditions within the equine large intestine.

 

While in vitro systems cannot replicate every aspect of the living horse, they provide valuable tools for studying microbial activity under carefully controlled conditions. These laboratory models allow researchers to isolate dietary effects without the many variables present in live-animal trials. However, the authors acknowledged that such systems cannot fully reproduce the complexity of the equine gastrointestinal tract, including immune responses, intestinal motility, hydration dynamics, stress, exercise, and long-term microbial adaptation.

 

Using a 2 × 2 factorial design, the researchers examined fermentation characteristics and microbial community changes in vessels receiving either the forage-only or mixed diet, with or without inclusion of the fibre-based feed. Each treatment was replicated three times. Artificial saliva was continuously infused into the fermenters, and feed bags were incubated for 24 and 48 hours to assess microbial community structure.

 

The study demonstrated clear differences between the two basal diets. The MIX diet produced a lower hindgut pH and higher total volatile fatty acid production compared to the forage-only diet, indicating altered fermentation activity. These findings reinforce existing knowledge that concentrate inclusion can significantly influence hindgut fermentation patterns.

 

Researchers also identified significant differences in microbial community composition between the two diet types at both 24 and 48 hours. In particular, an interaction involving Proteobacteria was observed at 24 hours, with levels highest in the MIX diet supplemented with the fibre-based feed. However, beyond this isolated interaction, the inclusion of the forage feed caused no substantial additional changes to the overall microbial community structure.

 

Importantly, the researchers concluded that the fibre-based feed produced “no negative effects” on fermentation parameters or microbial composition within the in vitro model. In practical terms, this suggests the feed was compatible with normal hindgut fermentation processes and did not disrupt microbial balance under the conditions tested.

 

The findings are significant because they contribute to a growing body of research examining how equine diets influence gut microbial ecology. However, the authors’ conclusions remained appropriately cautious. The study did not evaluate live horses, clinical health outcomes, performance measures, or long-term feeding effects. Instead, it provided an initial laboratory-based assessment of how a fibre-based feed interacts with hindgut fermentation systems.

 

Overall, the research suggests that inclusion of the tested fibre-based forage feed did not adversely affect hindgut microbial activity in vitro, while also highlighting the substantial influence that basal diet composition exerts on equine fermentation dynamics and microbial community structure.

 

*EquidGel®

 

For more details, see:

K.J. Hart, M.J. Hegarty, E.H. Hart,

An investigation into the impact of the inclusion of a commercial fiber-based feed, designed for both hydration and nutrition, on the equine hindgut microbiomes,

Journal of Equine Veterinary Science (2026) Vol 161, 105862,

https://doi.org/10.1016/j.jevs.2026.105862