Evaluating chronic pain in horses - podcast

In a podcast recorded recently, Dr. Kelly Diehl, Senior Director of Science and Communication at the Morris Animal Foundation spoke to Drs. Janny de Grauw and Diane Howard about the challenges associated with the detection and measurement of chronic pain in horses. 

Osteoarthritis, a leading cause of chronic pain in horses, is often not recognized by owners and so goes undertreated. 

 

Dr. de Grauw and Dr. Howard also discussed how they developed their pain assessment tool and how they hope this will help thousands of horses suffering from chronic pain.

Under Dr. de Grauw’s supervision, Howard developed a 15-item questionnaire based on changes in horse behaviour through interviews with owners of horses diagnosed with osteoarthritis. The questions cover posture, facial expressions, movement and behaviour.

“As veterinarians, we want to treat horses with painful and debilitating conditions like OA as effectively as possible,” said de Grauw. “How well we can manage their condition critically relies on recognition of subtle signs of (worsening) pain by owners and caregivers, who can then seek help.”

Listen to the podcast here:

https://podcasts.apple.com/us/podcast/evaluating-chronic-pain-in-horses/id1440087311?i=1000541242539

Alternative approach to colic ops

 

Standing flank laparotomy may be a suitable option for surgical treatment of some cases of equine colic, a recent study has concluded.

The standard surgical approach for colic is through an incision in the ventral midline, with the horse under general anaesthesia. General anaesthesia poses additional risks over and above those of the surgery itself, and the personnel and equipment required increases the cost.

 

Operating through a flank incision would avoid the need for general anaesthesia and should be less expensive.

 

Marco Lopes and co-workers conducted a retrospective analysis of clinical records of 37 equids (horses, ponies and a donkey) treated using a standing flank laparotomy at five hospitals, between 2003 and 2020. Their findings are published in the Equine Veterinary Journal.

 

They did not include cases of small colon impaction in their analysis, as previous work had already shown that such cases could be dealt with using a flank incision.

 

Financial considerations were the main reason for the choice of technique. However, in ten cases of nephrosplenic entrapment the surgeon preferred a flank incision.

 

In seven animals the decision for euthanasia was taken immediately as they were found to have an untreatable condition, or the likelihood of survival was very poor.

 

Twenty of the 30 horses found to have a treatable condition survived. These conditions included small intestine inflammation or impaction, large colon displacement (especially nephrosplenic ligament entrapment) and sand impaction, 

 

The authors identify limitations of the technique:

• the horse must stand still during the operation, so standing flank laparotomy cannot be performed in horses with severe colic that cannot be adequately controlled medically
• additional peritoneal analgesia may be needed
• access to the peritoneal cavity and the abdominal organs is not as good as with a ventral midline incision.
• a second incision on the opposite flank may be needed
• surgeons are not as familiar with standing flank laparotomy 
•  scars in the flank are more likely to be seen than those in the ventral midline.

 

They conclude that this series of cases indicates that standing flank laparotomy is a viable approach for abdominopelvic exploration in some horses with colic attributed to conditions of the small intestine, caecum, large colon and peritoneum.

 

For more details, see: 

 

Standing flank laparotomy for colic: 37 cases

Marco A. F. Lopes, Joanne Hardy, Kelly Farnsworth, Raphael Labens, W. Y. Eunice Lam, Erik Noschka, Tiago Afonso, Claudia Cruz Villagrán, Luiz C. P. Santos, Montague Saulez, Gal Kelmer

Equine Vet J (2021)

 

https://doi.org/10.1111/evj.13511

 

Investigating a possible treatment for melanoma

Initial indications are that betulinic acid may prove to be a useful topical treatment for early-stage melanomas in horses. 

Melanomas are tumours of the pigment-producing melanocytes, and are among the most common equine tumours, occurring particularly in grey horses. Typically, they first appear as small, pigmented nodules, often under the tail. They usually grow slowly for years, but may infiltrate surrounding tissues, or appear elsewhere in the body.

 

Betulinic acid (BA) is a natural compound, found in the bark of several species of plants, such as the

white birch (Betula pubescens) after which it was named. It has been shown to have several potentially-useful pharmacological effects. Previous work has shown that BA can induce death (apoptosis) of melanocytes in cell culture. 

 

Research conducted in Austria looked at whether topical treatment with betulinic acid, or NVX-207, (a betulinic acid derivative) could be used to treat early cases of melanoma.

 

Lisa A. Weber and colleagues conducted a small, pilot study involving eighteen Lipizzaner mares with cutaneous melanomas (all having a diameter of no more than 15mm).

 

The horses, on a stud farm in Austria, were divided into three treatment groups: placebo cream; 1% BA cream; and 1% NVX-207 cream.

 

The research team treated a maximum of two tumours per horse. After topical application of the cream, the melanomas were covered to prevent it being rubbed off. The study extended over 13 weeks.

 

The researchers assessed progress with clinical examinations, measuring the tumours, monitoring them and the surrounding clinically normal skin, assessing the horses’ behaviour during cream application, and monitoring haematologic and blood biochemistry profiles. 

 

All horses tolerated the topical drug application well and did not object to it being applied. Two horses had mild colic during the study, which resolved with medical treatment. Both horses had a previous history of colic and the authors consider it very unlikely that the colic was related to the topical melanoma treatment.

 

The topical therapy resulted in part in clinically visible and measurable changes in small melanocytic lesions, which were reflected in skin depigmentation and reduction in tumour diameters and volumes. 

 

The researchers found a beneficial effect after treatment with BA towards the end of the treatment period. A few tumours in the placebo group also showed a decrease in size.

 

They conclude: “The results presented in this pilot study indicate that topical treatment of early-stage equine melanoma with 1% BA and 1% NVX-207 twice a day over a period of 13 weeks is feasible and safe.” 

 

“Especially after BA application, positive effects were observed toward the end of the treatment interval. This suggests that this approach might be a potential therapy for early-stage equine melanoma and, thus, reduce the health risks associated with the possible malignant degeneration of the tumours.”

 

However, the authors are unable to recommend the current treatment protocol for general use as the long treatment duration could lead to poor owner compliance. They suggest that modification of the pharmaceutical formulations may improve the clinical outcome and reduce treatment periods.

 

 

For more details, see:

 

Effects of Topically Applied Betulinic Acid and NVX-207 on Melanocytic Tumors in 18 Horses.

Weber, L.A.; Delarocque, J.; Feige, K.; Kietzmann, M.; Kalbitz, J.; Meißner, J.; Paschke, R.; Cavalleri, J.-M.V. 

Animals 2021, 11, 3250. 

https://doi.org/10.3390/ani11113250

 Looking for adverse effects of pergolide

 

Pergolide is widely used in the treatment of PPID (Pituitary Pars Intermedia Dysfunction, or equine Cushing’s disease). The drug is also used in humans, where it has been associated with side effects, involving fibrotic lesions of the atrio-ventricular valves in the heart.

 

Heidrun Gehlen and colleagues in the Department of Veterinary Medicine, at the Free University of Berlin, conducted a study to see if pergolide causes similar problems in horses. 

 

Twenty-three horses of various breeds, aged between 19 and 30 years old, were included. All had been diagnosed previously with PPID, based on ACTH (adrenocorticotrophin hormone) concentration.

 

Twelve horses had been receiving pergolide for between 14 days and 6 years before the start of the study. These comprised the treatment group and continued to receive pergolide. Eleven other horses received no pergolide.

 

The researchers performed a complete echocardiographic exam on all horses, which showed that they were free of cardiovascular diseases, including the absence of valvular defects. 

 

Follow up examinations were performed on nine horses in the treatment group and five of the non-treatment group between 3 and 8 months later.

 

The researchers compared the findings in PPID horses being treated with pergolide with the untreated PPID horses.

 

They found that treatment with pergolide did not affect the ventricular function nor induce valvular disease. Measurements taken in the follow-up exam did not differ from those taken initially in both groups. None of the 12 pergolide-treated horses developed valvular regurgitation. 

 

The work is reported in the Journal of Veterinary Science. The authors conclude: “The main result of our small orientation study was that treatment with pergolide of a duration between 3 and 8 months in a horse population with confirmed PPID did not seem to affect the left ventricular function assessed by TDE and STE [tissue Doppler and two-dimensional speckle tracking echocardiography]. Furthermore, none of the horses developed valvular regurgitation in the observation period.”

 

They add that further studies are needed, with a larger population and longer follow-up period. 

 

For more details, see:

 

Preliminary study on the effects of pergolide on left ventricular function in the horses with pituitary pars intermedia dysfunction

Heidrun Gehlen,  Judith Fisch,  Roswitha Merle and Dagmar S. Trachsel

J Vet Sci. 2021 Sep;22(5):e64. 

https://doi.org/10.4142/jvs.2021.22.e64