Every Monday we gather the scientific papers about horses, ponies and donkeys that appeared in the past few weeks, keep the ones that matter to the people who look after them, and say in two plain sentences what each one found.
A preprint, not yet peer reviewed, describes two horses in Switzerland with brain and spinal cord inflammation linked to Shamonda virus, a virus that recently caused a large outbreak in cattle in Western Europe and had not been described in horses before. Virus genetic material was found in the brain tissue of both horses, and its sequence matched the virus from the Swiss cattle outbreak.
This review looks back over 20 years of research on medical treatments for osteoarthritis in horses, a joint disease that permanently damages cartilage, since a similar review in 2006. It describes how options have grown, including orthobiologic and cell-based therapies, and how treatment has shifted from mainly easing symptoms towards trying to change the course of the disease.
A preprint case report describes Shamonda virus, recently emerged in Central Europe, found in the brain and spinal cord tissue of two horses in Germany that had shown seizure-like episodes or fever and unsteadiness, and both had severe brain inflammation. The virus was not found in their blood or other organs, and the authors say diagnosing it in living horses is currently only possible to a very limited extent.
Two laboratory tests for the hormone ACTH, used to help diagnose PPID (equine Cushing's), were compared in 17 horses (4 young, 8 older and 5 with confirmed PPID), before and after a TRH stimulation test. Results differed widely: after TRH, one test flagged 2 of the 5 PPID horses and none of the older horses, while the other flagged all 5 PPID horses and 5 of the 8 older ones, so the choice of test could change whether a horse was classed as having PPID.
This preprint, not yet peer reviewed, used a climate-based model to map where West Nile virus and Usutu virus, both spread by mosquitoes, could transmit across England and Wales, and projected that suitability for both rises over time, more steeply under higher-emission scenarios. Cases of West Nile virus in horses were predicted to be most likely in southeast England, especially around Newmarket, because of its dense horse population.
Eight horses with a temporary, induced front-foot lameness were given intravenous phenylbutazone at 2.2, 4.4 or 8.8 mg/kg, or saline. The 4.4 and 8.8 mg/kg doses reduced lameness and heart rate for up to about 12 hours with no difference between them, while 2.2 mg/kg helped only briefly compared with saline.
Records of 123 horses treated for peritonitis (inflammation of the abdominal lining) at a UK referral hospital found that 74% survived to discharge, 90% when the peritonitis was primary versus 50% when it was secondary to another problem. A higher heart rate and blood-stained abdominal fluid on arrival were linked to lower survival, ponies did better than horses, and a third of survivors had complications such as colic or fever after going home.
Researchers tested whether an antibiotic eye ointment (erythromycin and colistin) applied after racing prevents eye surface inflammation (keratitis) in Thoroughbred racehorses, comparing it with eye flushing alone or a plain petroleum jelly ointment. After turf races, keratitis was less common with the antibiotic ointment (0.55% vs 6.25% with flushing alone, and 0% vs 8.18% in a randomised comparison of about 300 races), but after dirt races there was no significant difference.
Three horses in different parts of France had skin lesions, some resembling sarcoids, that turned out to be leishmaniasis caused by the parasite Leishmania martiniquensis, the first documented cases in the country. In all three the disease stayed limited to the skin: one healed on its own, one after surgical removal and one after injections of meglumine antimoniate into the lesion.
Seven healthy horses were given a bacterial toxin (LPS) that slows the gut, with and without the oral drug mosapride, in a blinded trial where each horse received every treatment. The toxin caused fever, a fast heart rate and a sluggish, swollen gut, while mosapride partly restored gut movement and reduced stomach distension and intestinal wall thickening.
Researchers cultured windpipe wash samples from 165 horses with equine asthma in Poland and grew bacteria in 117 of them (70.9%), most often Streptococcus zooepidemicus, Pseudomonas aeruginosa and Klebsiella pneumoniae. A positive culture was not linked to the season or month of sampling or clearly to airway neutrophil levels, and the authors note that finding bacteria does not by itself prove an infection.
Twenty-four healthy female donkeys were given a bacterial toxin to mimic endotoxaemia and then received flunixin, DMSO or no treatment; flunixin eased belly pain, kept gut movement going and brought appetite back sooner than DMSO, and reduced early signs of kidney stress. Two blood markers, NGAL and B2M, rose within 1–2 hours, before the standard kidney test (creatinine) changed, suggesting they may flag early kidney injury in donkeys.
Among 52 horses with signs of asthma (34 confirmed by lung-wash testing), neither allergy skin tests nor 23 inflammation markers in the blood helped diagnose asthma or tell its types apart. One type, mast-cell asthma, was found more often at locations with unhealthy air quality (24.1% versus 10.3% expected).
Blood samples taken in 2011 from 278 horses in four Indigenous communities of Costa Rica were tested for antibodies, a sign of past exposure, to several equine viruses. Antibodies were found to equine herpesvirus 4 in 91.2% of horses tested, West Nile virus in 58.9%, equine infectious anaemia in 16.6%, equine herpesvirus 1 in 6.6%, influenza in 5.1% and equine arteritis in 3.0%; these figures reflect 2011, not today.
Rabies test results from 204 cattle and 56 horses with neurological signs in Rio de Janeiro State, Brazil (2020–2024), were compared with local land use and livestock numbers. Most cases and positive results were in cattle, and municipalities with more pasture had more cases and positive tests, while those with more shrubland had fewer.
This preprint, not yet peer reviewed, reports that 15% of young Swedish trotting racehorses were passing roundworm (Parascaris) eggs, more often at 1–2 years than at 3–4, and that raised eosinophils (a type of white blood cell) in lung fluid were the most common airway finding, seen in 31.3% of two-year-olds versus about 10% of three- and four-year-olds. Only 1 of 10 horses with this lung inflammation had a roundworm infection, compared with 2 of 10 healthy horses, so no clear link was shown.
Pennsylvania horse owners checked their horses for ticks over two years and collected 413 ticks, including American dog, blacklegged and longhorned ticks, the last found for the first time in one county. In a trial with 50 horses, physical barriers, especially untreated fly boots and masks, were linked to fewer attached ticks.
This preprint, not yet peer reviewed, tested 1,414 horse samples from Punjab, Pakistan, over one year for Theileria equi, a tick-borne blood parasite, and found infection peaked in March (43.3%) and October (37.3%) and was lowest in April (6.5%). Infection was more common in areas with many horses and rose with temperature and humidity above 60%; among the tests compared, ELISA picked up the most cases and PCR gave the fewest false positives.
Eight Welsh Mountain ponies were switched between four haylages over a structured three-day changeover, and chemical markers in their urine and droppings were tracked. Their metabolism adapted to each new haylage within 5 days, with the changes driven by the forage's chemical make-up, most clearly for a young ryegrass haylage.
Thirty-two young Quarter Horses (2–3 years old) in moderate work were fed their grain either as two meals a day or as small automated portions every hour for 10 hours a day. In an 8-hour after-feeding test in 10 of these horses, those on hourly portions had lower blood sugar and insulin peaks and a lower overall insulin response than those fed twice daily.
Twelve healthy young horses were each offered plain water, water flavoured with sweet feed, and water containing a new additive, alongside a bucket of plain water. With the additive they drank about 52 litres a day, compared with roughly 30 litres with plain water and 32 litres with the sweet-feed flavouring, and no side effects were seen.
Six healthy adult crossbred horses were weighed weekly for 63 days on a calibrated scale, with a commercial weigh tape and with a body-measurement formula. Both methods overestimated weight, but the tape was closer (about 2.5% over on average) than the formula (about 9.9% over) and tracked the scale more consistently.
Researchers measured a fat-derived hormone linked to laminitis risk, called high molecular weight adiponectin, in 85 horses and ponies before and after an oral glucose test given in feed: its median level rose from 2.75 to 4.02 µg/mL two hours after the test, while total adiponectin did not change. In 31 ponies, grazing pasture or eating soyabean- or maize-based meals did not change this hormone over 4 hours.
Researchers followed 36 Thoroughbred racehorses in training for 90 days, with 23 going barefoot and 13 staying shod, and photographed their hooves before and after trimming. In the barefoot horses, the heel angle rose from about 30° to 35° and the gap between toe and heel angles narrowed, while the toe angle stayed stable; the shod horses showed no significant changes.
Using a sensor on one front heel, researchers measured heel movement in 15 healthy horses at walk and trot when barefoot, in aluminium nail-on shoes and in glue-on fabric cuff shoes. Heels moved most when barefoot (3.29 mm at the trot), glue-on shoes allowed more movement than nail-on shoes at the trot (2.56 vs 2.12 mm), and both shoe types limited heel movement compared with barefoot.
This preprint, not yet peer reviewed, used airway scope results from 2,721 Standardbred and 1,902 Thoroughbred racehorses in Canada to check whether air pollution is linked to bleeding in the lungs during exercise (EIPH). Higher ozone levels about a week before racing or training were linked with higher odds of bleeding (23% per 10 ppb rise) and of moderate or severe bleeding (41%); older horses were also more likely to bleed, and furosemide use was linked with lower odds of moderate or severe bleeding.
This preprint, not yet peer reviewed, compared two gaits of the Mangalarga Marchador breed, the marcha batida and the marcha picada, in 135 ridden horses. At the same speed (3.88 m/s) stride length and timing were the same, but the batida relied mostly on diagonal pairs of legs and the picada mostly on same-side pairs, and the authors report that the measurements did not match the current breed standard description.
Researchers looked back at 19 horses that had screws placed to repair slab fractures of the carpal (knee) bones other than the third carpal bone; 10 of these fractures came from falls, six of them while recovering from anaesthesia. Of these horses, 88% survived beyond a year, 53% returned to their previous level of work and 71% of owners were satisfied.
Stewards checked noseband tightness with the new FEI measuring device on 523 horses at the 2025 British Dressage Championships, and 95% of nosebands were loose enough to pass. The Swedish noseband was the most common type (39%), and 96% of horses stood calmly for the check.
Nine mares each received eight protocols, from the standard 250 µg dose of the ovulation drug histrelin down to 25 µg, injected into muscle or at two acupuncture points, or no treatment. Ovulation within 48 hours occurred in 87.5–100% of cycles with any histrelin dose, against 37.5% with no treatment; in this small pilot, injecting at acupoints showed no advantage over muscle injection of the same low dose.
The papers are found through Europe PMC, which indexes PubMed and the main preprint servers. Each title links to the paper itself; one marked “Open access” can be read for free.
Written by AI, so read the paper. Each summary is written by Claude Opus 5.5, an AI model made by Anthropic, from the paper’s abstract, and translated by it too. It can leave out what matters or get a detail wrong: open the paper before you rely on a finding, and talk to your vet before you change your horse’s care because of one study. A preprint has not yet been checked by other scientists. When Claude is unavailable, Mistral Small 3.1 writes the summary instead.
EquiDiary keeps each horse’s vaccinations, deworming, farrier visits, feeding and training in one history, shared with the people who look after it, and tells you when the next one is due.
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