Reducing deworming frequency without adverse health effects

Less intensive deworming strategies appear as effective in preventing disease as traditional more frequent treatment regimes

With the increasing problem of anthelmintic resistance, we are urged to adopt a more sustainable approach to deworming.

A study led by Martin Nielsen monitored egg count levels, bodyweight and equine health in mares and foals under different parasite control regimes. A report of the work has been published in the Equine Veterinary Journal.

Ninety-three foals and ninety-nine mares at two Standardbred and two Thoroughbred stud farms were included in the study. Faecal samples and bodyweight were monitored monthly, and any occurrence of colic or diarrhoea was recorded.

The foals were divided into two groups and wormed either monthly or on two occasions at two and five months of age. Mares were split into three groups and wormed monthly, twice a year, or when faecal egg counts exceeded 300 eggs per gram.

The research showed that, compared to foals treated monthly, foals dewormed at two and five months old had significantly higher strongyle and ascarid faecal egg counts. Despite that, there was no significant difference in body weight between the two groups.

Mares wormed twice a year weighed less than those in either of the other groups. However, there was no significant difference in faecal egg counts between the groups. 

The authors conclude that it was possible to reduce the frequency of anthelmintic treatment from traditional high intensity regimes without apparent negative health consequences.

Martin Nielsen has published a video summary of the work, which is available at:

https://vimeo.com/483033105

 

 

For more details, see:

Monitoring equine ascarid and cyathostomin parasites: Evaluating health parameters under different treatment regimens
Martin K. Nielsen, Erica K. Gee, Alyse Hansen, Tania Waghorn, Julie Bell, Dave M. Leathwick
Equine Veterinary Journal (2020)

https://doi.org/10.1111/evj.13374

Research funding announced

The Grayson-Jockey Club Research Foundation has announced funding of $1,638,434 towards 12 new projects, 12 continuing projects, and two career development awards each worth $20,000. 

New studies being supported this year include:

 

“Passive immunization of foals with RNA-AB against R equi.” Led by Jeroen Pollet, the project at Baylor College of Medicine will follow on from previous work that showed that poly-N-acetyl glucosamine (PNAG) anttibodies can protect foals against Rhodococcus equi (R. equi) infection. 

 

Currently, these protective antibodies can be acquired by foals drinking çolostrum from a vaccinated mare or by a blood transfusion. But now the research team want to develop a new vaccine to give newborn foals instant protection against R equi infection. 

 

They explain that the vaccine comprises lab-made messenger RNA molecules (mRNA), which are a blueprint that can be used to instruct cells to produce protective PNAG binding antibodies. “We intend to administer the mRNA therapy by using a nebulizer, to let the foals inhale the RNA. This way, we hope to make the procedure less invasive and have mRNA delivered to lung cells where the antibodies are most needed for protection against R. equi. The proposed project would be the first study developing an mRNA therapy for horses.”

 

A University of Minnesota project led by Molly McCue aims to use resting electrocardiograms (ECGs) to identify horses with irregular heart rhythms at exercise that can cause sudden cardiac death (SCD.  They anticipate that this should allow increased monitoring and improved understanding of SCD. 

 

Thomas Koch, at the University of Guelph, has gained funding for research that will assess the use of equine umbilical cord blood-derived mesenchymal stromal cells to treat joint injuries in horses. 

 

A Texas A&M University study led by Noah Cohen will look at developing a more accurate blood test to identify horses infected with the Streptococcus equi to improve control and prevention of strangles. 

 

Further details of these and all the other projects supported by this year’s Grayson Jockey Club research grants are available at:

 

http://www.grayson-jockeyclub.org/default.asp?section=2&area=Research&menu=2

Potential role of asthma in DDSP?

Upper respiratory tract conditions have received much attention in the causation and treatment of
dorsal displacement of the soft palate (DDSP). Recent research highlights the potential role played by lower airway conditions.

A study in Hungary has found DDSP was common in sport and pleasure horses with equine asthma.

In the normal horse, the soft palate fits snugly around the base of the epiglottis (the front part of the larynx). This allows inhaled air to pass directly from the nasal passages into the trachea. Normally, the horse does not breathe through the mouth.

Dorsal displacement of the soft palate occurs when the soft palate becomes dislodged from its normal position and comes to rest on top of the epiglottis, in the laryngeal opening. When this occurs during high-speed exercise, the high air flow causes the free border of the soft palate to vibrate. This causes significant obstruction to the horse’s breathing and produces a gurgling sound. The horse usually has to slow down and swallow to replace the soft palate in its normal position.

A study by Kinga Joó at the Szent István University, Kaposvár, Hungary and colleagues, reviewed the findings of pleasure and sport horses (competing at national level) presented for evaluation of suspected equine asthma.

Clinical examination of the horses included endoscopic examination, both at rest and during exercise. Tracheal wash and bronchoalveolar lavage (BAL) were used to collect mucus from the trachea and lower airway.

During the resting examination, a nasal occlusion test was performed to mimic pressure changes that might occur during intense exercise. In many horses this caused the palate to displace.

In all, 22 mild/moderate and 31 severe asthmatic cases were included in the study, a full report of which is published in the Journal of Equine Veterinary Science.

The authors found that 65% of pleasure and sport horses with mild equine asthma showed DDSP during the nasal occlusion test. In horses with severe equine asthma, 79% showed DDSP at rest and all of them had DDSP at exercise.

Horses showing DDSP tended to cough but did not make the typical gurgling sound heard in racehorses. The authors suggest this may be because of the lower rate of air flow in these horses compared with racehorses.

They emphasise the importance of treating the upper and lower respiratory tracts as a single unit, “as lower respiratory tract diseases can often cause upper respiratory functional disorders, whereas upper respiratory obstructions could be a factor in lower respiratory problems.”

They suggest that treatment of dorsal displacement of the soft palate has to be tailored to the cause.

For more details, see:

Asthmatic Disease as an Underlying Cause of Dorsal Displacement of the Soft Palate in Horses
Kinga Joó, Ágnes Povázsai, Zsófia Nyerges-Bohák, Ottó Szenci, Orsolya Kutasi
J Equine Vet Sci (2021) 96:103308.
 doi:10.1016/j.jevs.2020.103308.

Does omeprazole reduce side effects of phenylbutazone?

The authors of a recent report warn of risks associated with administering phenylbutazone and
omeprazole together.

Phenylbutazone, a non-steroidal anti-inflammatory drug (NSAID), is widely used in horses to treat lameness and other inflammatory conditions. It may cause adverse effects including kidney damage, and ulceration of the stomach and large intestine. To reduce the risk of these side effects, some clinicians have been administering omeprazole at the same time.

Omeprazole, is a proton-pump inhibitor that has been shown to be effective in preventing and treating equine gastric ulcer syndrome (EGUS). Similar drugs have been used in human medicine to treat and prevent NSAID-induced mucosal damage.

A study by Megan Ricord and others at Louisiana State University School of Veterinary Medicine at Baton Rouge, investigated the benefit of giving omeprazole at the same time as phenylbutazone in horses.

Horses from the University’s teaching herd with mild (<grade 2) gastric ulcers (involving either gastric (EGGD) or squamous (ESGD) mucosa) were involved in the study. They were divided into three groups and received a paste containing phenylbutazone (PBZ), phenylbutazone and omeprazole (PBZ/OME) or an inert control.

Horses were withdrawn from the study if adverse effects (colic, lethargy, diarrhoea) were identified that required medical management, or if ulceration (EGGD or ESGD) greater than grade 4 was seen.

The research team found that omeprazole did reduce EGGD formation, but did not influence development of ESGD.  The PBZ-treated group also showed a decrease in plasma protein concentrations compared to controls, which was likely associated with inflammation of the colon.

More intestinal complications occurred in the PBZ/OME group. These were mostly impactions, but two horses died and on post mortem examination they were found to have intestinal inflammation, ulceration and necrosis. 

The horses usually lived outside, but were housed for the duration of the study and this may have influenced the outcome. However, as the researchers point out, horses receiving non-steroidal treatment are often housed because of lameness issues.

“Importantly,” they point out, “concurrent administration of phenylbutazone and omeprazole, in association with change in management, led to an increase in clinical signs of intestinal complications.”

They advise that caution should be exercised when co‐prescribing phenylbutazone and omeprazole in horses.

For more details, see:

Impact of concurrent treatment with omeprazole on phenylbutazone-induced equine gastric ulcer syndrome (EGUS)
Megan Ricord, Frank M Andrews, Francisco J M Yñiguez, Michael Keowen, Frank Garza Jr, Linda Paul, Ann Chapman, Heidi E Banse
Equine Vet J (2021) 53:356-363.

doi:10.1111/evj.13323.

Online equine health talks

An online series of equine health seminars for Western Canada's horse community, is to be hosted by the Western College of Veterinary Medicine (WCVM)

Topics to be covered include Equine Asthma, foal care, cardiology, EMS and PPID and gastric ulcers. Talks take place on alternate Tuesday evenings starting February 23.

Although there is no charge, you need to register beforehand.

For more details, see:

https://wcvm.usask.ca/education/equine-seminars.php

Assessing welfare in working equids

Brooke, the international working horse and donkey charity, has unveiled an online collection of animal welfare indicators.

Their website explains: “Animal welfare indicators are scientific, non-invasive measurements of aspects that contribute to an animal’s overall welfare state, which help us to understand welfare from the animal’s perspective and include physical measures such as nasal discharge or body lesions, and behavioural measures, such as the animal’s response to contact or general attitude.”

Brooke introduced their first Working Equine Welfare Assessment protocol in 2003. Since then, they have refined how they assess animal welfare in the field.  In 2011, this resulted in them launching their Standardised Equine-Based Welfare Assessment Tool (SEBWAT), which is still widely used in their international country programmes with working equids.

Ashleigh Brown, global animal welfare advisor at Brooke, said: “Brooke benefits from many years of experience in assessing animal welfare in the field, in numerous countries around the world. We are excited to be able to share our resources and our learning to support others with their efforts to measure and improve animal welfare.”

Brooke hopes that the welfare indicators will be useful for scientists assessing welfare within a research context, animal health practitioners and veterinarians treating equids, and students of animal welfare assessment, equine science or animal welfare science. The tools may also be used to monitor the impact of welfare related regulation and provide welfare data in support of animal advocacy and welfare campaigns.

For more information and to access the repository, visit the Brooke website:

https://animalwelfareindicators.thebrooke.org