Blue light treatment could help coat condition in horses with Cushing’s disease

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A large-scale study is investigating the use of blue light therapy in horses with PPID.
A large-scale study is investigating the use of blue light therapy in horses with PPID. © University College Dublin

A major study on both sides of the Atlantic will explore whether blue light therapy can help horses and ponies with Pituitary Pars Intermedia Dysfunction (PPID).

PPID, also known as Equine Cushing’s disease, is an endocrine disorder that affects one in five horses and ponies over the age of 15. It is a debilitating condition characterised by the growth of an abnormally long and curly hair coat, termed hypertrichosis.

In addition, the heavy winter coat frequently does not shed adequately in the spring. This can cause poor heat regulation which leads to sweating in affected horses, and some discomfort in hot weather or after exercise.

Results of a study led by Dr Amanda Adams at the University of Kentucky, published recently in the Domestic Endocrinology journal, suggest that blue light therapy may offer a potential treatment for reducing hypertrichosis in horses with Cushing’s.

The study found that PPID horses fitted with a blue light mask had lighter winter hair coats than untreated horses, and that hair coat growth was slowed.

The use of blue light masks, which simulate daylight, artificially mimics a long summer’s day. Now, more research is needed to confirm this finding, and also to evaluate other potential benefits for PPID horses of extending daylight using blue light.

To that end, a collaborative project between researchers at University College Dublin and the University of Kentucky’s Gluck Equine Research Centre will investigate the effects of blue light treatment in PPID horses over a 12-month period.

The research team will be led by Dr Barbara Anne Murphy, head of equine science within University College Dublin’s School of Agriculture and Food Science, in close collaboration with Adams at the Gluck Centre.

Murphy said she was excited by the study, especially given the recent results from the University of Kentucky suggesting that blue light could help reduce some symptoms of PPID.

The Dublin team is seeking interest from owners of horses and ponies with PPID that meet a specific set of criteria to investigate if blue light treatment, using an Equilume brand mask, can influence the symptoms. The study will include both medicated (that is, receiving pergolide) and unmedicated horses and ponies.

“We are hoping for a big response from owners of PPID horses and ponies so that we get the numbers we need for a thorough investigation,” Murphy said.

Adams said one of the goals of her research programme at the Gluck Center is to help owners of horses with PPID.

“I reached out to Dr Murphy a few years ago with the novel idea of using the blue light mask as a way to extend day length and potentially modulate the biological response in PPID horses, both as a means to help us understand more about PPID and help manage the clinical symptoms.

“Our recent study results are promising, we just need to conduct this study on a larger scale and that’s exactly what this collaboration is aiming to do.”

The study will help researchers and veterinarians to better understand PPID as a disorder of older horses, and evaluate the impact of blue light at alleviating some symptoms of the disease.

Owners or managers of horses or ponies diagnosed with PPID which display a long curly hair coat can complete a short questionnaire to see if they are eligible to participate.

All selected participants will receive an Equilume Cashel blue light mask at the beginning (treatment group) or at the end (control group) of the study. The study requires the monthly collection of hair samples from participating horses and ponies, the submission of photographs and the completion of bi-monthly online questionnaires. Participant applications will be accepted until October 22, 2021.

Horses and ponies with PPID struggle with dental disease, chronic sinus and skin infections, intestinal parasites, and general ill thrift.
Horses and ponies with PPID struggle with dental disease, chronic sinus and skin infections, intestinal parasites, and general ill thrift. © University College Dublin

Suitable participants will be randomly assigned to either the treatment group, who will use the light mask, or the control group, members of which will not. The control group is as important as the treatment group and will allow the collection of valuable data related to the seasonal changes in symptoms of PPID horses.

The data collected will contribute significantly to knowledge of how PPID horses’ coat condition is affected throughout the year, and the results will help with the future management of this important condition.

How does PPID affect equines?

The pituitary gland, located at the base of the brain, plays a key role in regulating the body’s hormones. Many metabolic and reproductive functions, as well as blood pressure and electrolyte balance, are affected. Horses develop enlargement and benign tumors in a section of the pituitary gland known as the pars intermedia. While these tumors do not spread and rarely become large enough to cause neurological disease, they overproduce hormones that create an abnormal metabolic state.

One of the main hormones that increases is adrenocorticotropic hormone (ACTH). This can cause many problems, including delayed shedding (ranging from a few long hairs to a distinctly long and wavy coat), muscle wasting (especially over the topline), weight loss, increased thirst and urination, either sweating or an abnormally dry coat, behavior changes, reproductive abnormalities, and frequent infections due to immune system suppression.

While symptomatic treatment can address some signs (for example, a long hair coat can be managed by body clipping), the combined problems often lead to debilitation and reduce an older horse’s quality of life. Affected animals struggle with dental disease, chronic sinus and skin infections, intestinal parasites, and general ill thrift. More severe metabolic problems may occur if they develop other disorders (such as colic, diarrhea, or pneumonia), complicating their treatment.

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