Common drug could increase risk of sudden death in racehorses

(c) Donald Blais Dreamstime.com

A drug that has been widely used in Thoroughbred racehorses in North America could increase the risk of sudden death according to a new study.  

The research also identified other risk factors associated with sudden death, relating to the circumstances of the race and individual histories of the horses.

 

Conducted by Dr Euan Bennett, of the University of Glasgow’s School of Biodiversity, One Health and Veterinary Medicine and Prof Tim Parkin of the University of Bristol Vet School, the study is the first large-scale study of sudden death in Thoroughbred racehorses.

 

The work was funded by the Grayson Jockey Club Foundation. A report is published in the Journal of the American Veterinary Medical Association.

 

The study analysed over four million starts in horse racing over a 12-year period, using data recorded in the Equine Injury Database (EID), which contains details of nearly all official race starts made in the USA and Canada. About one in 10,000 race starts resulted in a racing-related sudden death for a horse.

 

For this study, “sudden death” was taken to include any fatality occurring within three days of racing, where the cause of death recorded in the EID was sudden death, pulmonary haemorrhage, exercise-induced pulmonary haemorrhage (EIPH), post-exertional distress/heatstroke (PED), or cardiac arrhythmia. Fatalities due to catastrophic musculoskeletal injury were not included.

 

The researchers identified a notable risk factor related to race day medication. Horses that were recorded as being administered furosemide were 62% more likely to experience sudden death compared to horses that weren’t on furosemide.

 

Furosemide (also known as frusemide and by the trade name Lasix) has been used to prevent exercise-induced pulmonary haemorrhage (bleeding in the airways). It is also associated with enhanced racing performance. As a result, 94% of horse starts in the study were on furosemide.

The ethics of race day medication are controversial. Furosemide is already restricted or prohibited on the day of racing in certain circumstances, depending on jurisdiction.

 

The results also suggest that it might be possible to identify horses at risk of sudden death before they experience it – for example, due to previous injury and interruption to training/racing. 

 

Amongst other findings were that the risk of sudden death was greater for stallions compared with mares, and for horses five years or older compared with horses three years old or younger. Other risk factors identified include season and value of race and race distance.

 

Dr Bennett said: “Over the last 12 years, the overall risk of fatality within three days of racing has decreased by over 30%, but the incidence rate of sudden deaths has not changed significantly. This suggests that while interventions have been made which have contributed to a reduction in catastrophic injury, there are different sources of risk for sudden death which have not yet been identified.

 

“This study suggests that a risk profile, identifying which horses are at the greatest risk of sudden death, may be possible. Given how rare the outcome is, further work is required to establish any potential interventions which might contribute to a reduction in sudden deaths.

 

“On the association between furosemide use and sudden death, the fact that furosemide use is so common makes this result particularly remarkable given the statistical power of this large-scale study. Discussions around the ethics of race day administration of drugs should factor in potential risks such as those identified here, and further work is required to understand exactly why we identified this association.”

 

For more details, see:

 

Fifteen risk factors associated with sudden death in Thoroughbred racehorses in North America (2009–2021)

Euan D. Bennett and Tim D. H. Parkin

Journal of the American Veterinary Medical Association (2022)
https://doi.org/10.2460/javma.22.08.0358

Eye worm infection in Europe

(c) Anjajuli Dreamstime.com

Eye worm infection (Thelaziosis) may be a neglected disease in Europe, according to a recent report.  

Thelaziosis is a parasitic disease caused by nematodes (round worms) of the genus Thelazia (typically Thelazia lacrymalis in horses). 

 

In the United States, the infection rate for cattle and horses in has been estimated at 15% to 38%. In Europe, equine thelaziosis has been reported occasionally in countries such as Russian Federation, England, France, Germany, Sweden and Italy.

 

Eyeworms live in the tear glands, conjunctival sac, and under the eyelids. The intermediate hosts are non-biting flies, such as Musca autumnalis, which swallow the larvae as they feed on the lachrymal secretions. Larvae become infective within 2-4 weeks and are deposited on the horse’s eye when the fly feeds. In about 10 weeks the adult worms produce more larvae and the cycle continues. 

 

Infections may occur year-round, but disease outbreaks usually are associated with the warm season when the flies are more active.

 

Infections often produce no obvious signs. However, inflammation of the conjunctiva and eyelids can occur, and more severe cases may show inflammation, swelling, and cloudiness of the cornea.

 

A study in Romania, examined post-mortem specimens from 273 horses. The work, by Vlad-Dan Cotuțiu, and colleagues, is reported in Parasites & Vectors.

 

They found 12 infected horses (4.39%). They recovered 87 worms, which they identified as T. lacrymalis. They report that the intensity of infestation varied between one and 33 nematodes/animal. Five animals were infected in both eyes.

 

The numbers found were too low to reach statistically significant conclusions. However, the authors suggest that altitude may be a factor in the occurrence of thelaziosis. “In this study there were no infested animals originating from the alpine ecoregion (0 of 45); therefore, a plausible explanation could be the decreased vector abundance and shorter seasonal activity at higher altitudes.”

 

They also suggest that the widespread use of oral deworming protocols, including macrocyclic lactones or fenbendazole, probably contributed to the low prevalence. 

 

The authors conclude: “We consider equine thelaziosis a neglected disease in Europe, which requires more attention from veterinary practitioners mainly from an animal welfare point of view due to the potentially severe clinical impact.”

 

 

For more details, see:

 

Thelazia lacrymalis in horses from Romania: epidemiology, morphology and phylogenetic analysis. 

V-D Cotuțiu, A M Ionică, M Lefkaditis, C D Cazan, D H Alina, A D Mihalca.

Parasites Vectors 15, 425 (2022). 

https://doi.org/10.1186/s13071-022-05532-z

Horses Inside Out annual conference - Call for posters

 There’s still time to submit posters for presentation at the 2023 Horses Inside Out Conference.

Posters, relating to the theme “Upwards and Onwards’, will be displayed at the Horses Inside Out Conference on the 18^th and 19^thFebruary 2023 at the Holywell Conference Centre, Loughborough, LE11 3GR. The author or a representative should be on hand 11.00 – 11.45, 12.45 – 14.00 and from 15.00 – 15.30 on both Saturday and Sunday to answer delegates questions about their poster. 

Posters can be submitted by students, lecturers, research professionals or companies. They can be about research conducted by the author or literature reviews about the chosen subject. Posters that have been presented at previous conferences can be submitted.

A competition for the best scientific poster will be judged by Dr Andrew Hemmings and Dr Jessica Kidd.

To download the submission guidelines and an application form click here

For more details of the Horses Inside Out Conference 2023, go to:

https://www.horsesinsideout.com/annual-conference-2023

Funding available for PPID research

 Morris Animal Foundation is now accepting proposals for studies focused on all domesticated equid health topics, with a special interest in pituitary pars intermedia dysfunction (PPID also known as equine Cushing’s disease).

PPID is the most common endocrine disorder of older equids, affecting more than 20% of aged horses, ponies and donkeys. Applicants considering submitting a research proposal focused on this disease are directed to learn more about research questions of interest as identified during a PPID priority-setting partnership workshop.

 

Participants at the workshop reached a consensus on the top 10 questions of interest. These focused on long-term prognosis, diagnostic accuracy, efficacy of pergolide treatment, alternative treatment/management strategies and potential treatment options for poor responders to pergolide (see below.) 

 

A report* of the workshop is published in PLOS ONE. The quantity of questions generated indicates that there is still much to find out about the diagnosis, treatment and prognosis of PPID. 

 

All proposal topics should seek to advance the health and overall welfare of domesticated horses, ponies, mules, or donkeys. Applications are reviewed and rated based on impact and scientific rigor by the Foundation’s scientific advisory boards, made up of topic experts in the veterinary community.

 

Applications will be accepted until December 16, 2022. Interested researchers can find the proposal guidelines, proposal template, and other information at Morris Animal Foundation Apply for a Grant.

 

*For more details, see:

 

Equine pituitary pars intermedia dysfunction: Identifying research priorities for diagnosis, treatment and prognosis through a priority setting partnership. 

Tatum RC, McGowan CM, Dean RS, Ireland JL (2021) 

PLoS ONE 16(1): e0244784. 

https://doi.org/10.1371/journal.pone.0244784

Immune response to single housing

(c) Abby Khoriaty Dreamstime.com

Horses moved from group housing to individual stabling showed stress-related changes, recent research has found. 

The horses had shifts in their white blood cell counts typical of a stress response and higher levels of plasma cortisol. These changes could make them more vulnerable to infectious disease.

 

In the study, conducted at the University of Hohenheim in Stuttgart, Germany, Sonja Schmucker and colleagues followed a group of twelve horses through a series of management changes, and monitored alterations in their immune response and behaviour. The research is published in PLOS ONE.

 

Twelve warmblood geldings, aged 2-3 years old, completed the study. Before the start of the investigation, they had been living together in a group on pasture.

 

In the first phase of the study, the horses were divided into two groups, each maintained on two separate paddocks so that horses in one group could not see the others. After the eight days trial period both groups were returned to their original setting. 

 

After a further eight weeks on pasture, the horses entered the second part of the study. They were moved to individual stables, where they were able to see and touch their neighbours through barred windows. For the first week after housing, horses were allowed 30 minutes daily exercise in groups of 6 in an indoor area of the stable. From the second week onwards, the horses were exercised by lunging.

The research team collected blood samples for analysis of immune cell numbers and cortisol concentrations from all animals on days 1 and 8 after both changes in housing conditions. In addition, in the stabled group they collected samples 7 and 6 days before, and again immediately before, the beginning of the stabling phase.

 

They found that moving to individual stabling led to acute stress-induced immune changes but dividing the larger group into two smaller ones did not.

 

“The number of eosinophils, monocytes and T cells declined, whereas the number of neutrophils increased resulting in an increased N:L ratio. This pattern of change resembles the well-known picture of an immunomodulation induced by acute social stress.”

 

Plasma cortisol concentrations did not change after dividing the pasture group into two smaller groups However, moving the horses to individual stables was associated with an increase in cortisol concentrations one day after housing which had returned to previous levels after eight days.

 

The researchers report “Although cortisol concentrations returned to baseline level after 8 days, the alterations in most immune cell numbers persisted, pointing to a longer-lasting effect on the immune system of the horses.”

 

They also monitored the horses’ behaviour during the study and noticed that signs of stereotypical behaviour started to appear amongst the housed animals.

 

The authors conclude “relocation to individual stabling represented an intense stressor for the horses of the present study, leading to acute and lasting alterations in blood counts of various leukocyte types. In contrast, fission of the stable group did not result in behavioral, endocrine or immunological stress responses by the horses.”

 

“The results of the present study therefore strongly indicate that social isolation is a chronic stressor with negative impact on welfare and health of horses and highlight the advantage of group housing systems in view of immunocompetence.”

 

For more details, see:

Schmucker S, Preisler V, Marr I, Krüger K, Stefanski V (2022) 

Single housing but not changes in group composition causes stress-related immunomodulations in horses. PLoS ONE 17(8): e0272445. 

https://doi.org/10.1371/journal.pone.0272445

UK senior horses survey findings

Owners and carers of senior horses and ponies responded in their thousands to a survey,
organised by feed company Spillers.  

More than 12,000 participants completed the survey, displaying their loyalty to, and care for their precious equine oldies.

 

The survey revealed that 32.7% of respondents’ horses were 25 years old or more and that 65.6% of owners considered their horses became “senior” at 20+ years. The results will help the feed company understand more about supporting the growing sector of senior horses nutritionally, to help them live longer healthier lives.

 

The survey showed that the participants are faithful to their seniors with 58% having owned their senior for 11+ years and 5.7% having owned their oldie for more than 26 years. 99.3% intended to keep their senior horse for the rest of their life.

 

Senior horses were also shown to be predominantly healthy and active: 78% were considered to be in good condition, with 10% of the remainder being classified as overweight and 12% as underweight.

 

A total of 25.8% of seniors included in the survey had no known clinical issues or health-related problems. However, 44% showed signs of stiffness or arthritis. 15.2% were recorded as having Pars Pituitary Intermedia Dysfunction (PPID – “Cushings disease”), while dental issues were experienced by 15.2% of senior horses.

 

In terms of exercise 62.8% were still in ridden work but 72.9% of these were in light work or slowing down.

 

A diet designed specifically for older horses was fed to 37.2% of respondents’ horses were eating a senior specific feed and of these 53.7% had opted for a senior mash.

 

“Congratulations to all the owners and carers of senior horses as well as the equine industry as a whole for playing their part in helping our treasured senior horses and ponies grow old gracefully,” said Claire Dyett Marketing Manager for SPILLERS.

 

“It’s a real achievement that our seniors are ageing later and staying healthy and active in their older years. While almost a third are recorded as having PPID or dental issues, this is perhaps to be expected because horses are living longer. That more than a third of the respondents are opting for a senior specific feed, predominantly a mash, indicates that nutrition choices are helping to support health as horses age and encounter metabolic and dental problems. The results will help us in our perpetual mission to make the world a better place for horses.”