Equine infectious disease and microbiology, accompanied by a Special Collection on the equine microbiome are in the spotlight for the March 2026 issue of the Equine Veterinary Journal (EVJ), which is free to view for 12 weeks. Consisting of reports which span a diverse array of disciplines and pathogens, many of the manuscripts covering infectious diseases involve international collaborations.
Equine infectious disease remains a consistent area of research interest for equine clinicians and scientists. Science in brief: Equine Infectious Disease and Microbiology, edited by Julia Kydd and Celia Marr with guest editors Macarena Sanz, Tessa LeCuyer and Laura Peachey, brings together 30 papers that cover three key themes, across multiple body systems and diseases. These include: the value of national level disease surveillance programmes; the importance of obtaining a definitive diagnosis for certain infectious diseases; and the use of cross-species comparisons for understanding pathogens that affect multiple animal species.
Diagnostics
Several studies report advances in diagnostic techniques for equine fever, equine influenza and equine gastrointestinal parasites. Such developments should all serve to speed up the implementation of biosecurity measures, to limit disease transmission.
Gastrointestinal system
A series of studies expand knowledge of gastrointestinal system diseases, including the use of metabolic profiling for earlier insights into equine proliferative disease in foals, the potential aetiology of colitis and the importance of additional testing for chronic hepatitis and liver failure in cases of hepacivirus.
Multiple body systems
One review in the Special Focus issue provides an update on the management of cases of equine botulism as a differential diagnosis.
Antimicrobials
Two papers report on the increasingly important challenge of antimicrobial resistance. A survey on the use of antibiotics concludes that almost 40% of hospitalised horses received at least one antimicrobial and in relation to colic surgery suggests that antimicrobial prophylaxis beyond 24 hours is unnecessary to prevent post-surgical complications.
Haemopoietic system
Two systematic reviews focus on prevalence, morbidity and disease management of equine trypanosomiasis to guide more robust, evidence-based disease control strategies. Another study reports on a novel diagnostic tool for differential detection of T. haneyi which is a main cause of Equine Piroplasmosis, as well as providing the first evidence of T. haneyi in China.
Regional diseases
A study of Hendra virus analyses government horse datasets and field surveys to examine the distribution and density of domestic horses as bridging hosts for Hendra virus and models to study emergence of zoonotic pathogens.
Another paper on regional diseases demonstrates that horses infected with African Horse Sickness Virus develop a severe consumptive coagulopathy that manifests clinically as a bleeding phenotype.
In terms of obtaining a definitive diagnosis for certain infectious diseases, one study reports that an important differential diagnosis for African Horse Sickness in endemic regions is infection with equine encephalosis virus.
Reproductive system
Two studies report on infectious disease and reproductive loss. One shows that isolation of E.coli, but not other bacteria is associated with decreased fertility in Thoroughbred broodmares. The other applies in vivo multi-omics to explore the pathophysiology of nocardioform placentitis, proposing that because of the broad range of bacteria identified, it should be renamed mucoid placentitis.
Respiratory system
Seven studies on respiratory health are included in the Special Focus. Several report on strangles, conclude that effective strangles prevention requires investment in thorough screening, consistent quarantine practices, close monitoring and interconnected reporting. It suggests that as novel vaccines emerge, the equine community will become better equipped to prevent strangles and reduce its impact.
Identification of foals potentially requiring antimicrobial treatment, when resident on a farm where pneumonia attributed to endemic Rhodococcus equi is present was attempted. The paper provides valuable and detailed characterisation of age-associated changes in cytokines, vitamin D and steroid hormones from birth to weaning, albeit that none of the measured immune or hormonal parameters effectively predicted future respiratory disease.
On the topic of vaccination against type A equine influenza virus, a study shows the promise of a combined adjuvant approach to optimise immune responses to commercially available vaccine formulations.
From a surveillance perspective in relation to equine herpesvirus myeloencephalopathy, a report concludes that sampling of air space within stables for EHV-1 DNA may be useful as a non-invasive surveillance tool for these pathogens.
A further study involving racehorse and sport horse populations, which were assumed to be functionally separate, confirms some overlap, with limited but highly concentrated windows for local or indirect pathogen spread, such as aerosolised transmission of respiratory diseases. Inconsistent horse identification across non-racing disciplines remains an obstacle, impeding the industry's disease preparation strategy.
Integument
A case of progressive necrotising skin ulceration, which is a rare diagnosis in horses, fills gaps in knowledge about disease processes. It highlights the importance of obtaining a definitive diagnosis for non-resolving infectious processes, and comparing data on similar infectious agents in other host species, particularly when novel approaches to treatment are necessary and data in horses are sparse.
Multisystemic
Two studies highlight the importance of gathering information on disease processes in other animals, but also the need to verify findings in equids and thus better understand the pathophysiology of disease across host species. A further paper reports on the importance of recognising differences in disease presentation across host species.
“The considerable and diverse research efforts within this Special Focus will ultimately improve the detection, diagnosis, treatment and control of many pathogens,” said Julia Kydd. “The eventual aim is to prevent or minimise the impact of future outbreaks. This will help the equine industry internationally but very importantly improve equine welfare and the quality of life for those people who rely on working equids for their daily survival.”
The Special Focus section also includes a Special Collection on the equine microbiome. It updates EVJ’s 2019 collection of manuscripts reporting early developments on the equine microbiome, highlighting the considerable progress in unravelling its complex mysteries and their application to the horse over the past 7 years.
The Special Focus Issue is available here.