For more than a century, it’s been a mysterious death sentence for horses which has left vets baffled and owners heartbroken.

First identified in Montrose in 1907, equine grass sickness seems to strike out of the blue, leaving affected horses fighting for the lives within hours of being struck down.

In some cases, shocked owners only realise their beloved horse or pony has been affected when they find them lying dead in their stables.

Now scientists trying to unravel the puzzle of what causes the disease are preparing to develop an app which it’s hoped may help owners spot when their animals might be most at risk.

The app would use a range of environmental data including weather trends, soil analysis and previous cases of the illness to help predict the ‘perfect storm’ of factors that may lead to horses being affected.

Scientists leading research into the condition envisage owners being able to share their location with the app, which would then provide a ‘grass sickness forecast’.

Although the app would not be able to predict with certainty which fields or horses might be at risk, the information would give owners the chance to make decisions over whether to place their horses in stables and feed them with hay instead of allowing them to graze outdoors.

Hopes of the distinctly modern weapon in a 115-year-old battle follow a recent brainstorming event, which brought together 30 scientists from a range of backgrounds not normally associated with the illness or equine health, in the hope of identifying a previously unspotted clue.

Organised by the Moredun Research Institute in Edinburgh, it involved experts in veterinary immunology, genetics, bacteriology, biology and pathology sharing thoughts on the condition and its possible causes with environmental specialists in soil, plant health and fungus.

The event – the first time that experts from such a wide variety of different backgrounds have gathered to discuss the condition - has been described as a “game changer”. It is said to have sparked a range of new ideas surrounding what might cause the mysterious illness.

First identified in Angus in 1907 following the deaths of a number of Army horses based near Montrose, equine grass sickness emerges between April and June, and claims at least 150 horses, ponies and donkeys across the UK every year.

It affects the animal’s nervous system, sending signals which paralyse the digestive system, leaving it unable to eat or drink.

Once in its grip, almost all affected animals die within a few hours. Those that do survive need intensive nursing and have shortened lives as a result.

Despite decades of research and a range of theories about what causes it, the disease remains a mystery, and has no cure.

There is also no clear pattern: some horses can have the condition for some time and go through a period of failing to eat before they become seriously ill, while others can succumb extremely quickly.

Often owners face the additional worry of whether other horses and ponies sharing the same field may also fall victim.

Although it can occur anywhere, the northeast of Scotland is regarded as an Equine Grass Sickness hotspot: five ponies from the Queen’s Highland Pony heard at Balmoral died between June 2017 and May 2018.

Last year it emerged the herd has played a key role in the Edinburgh research facility’s work, providing a range of environmental data and samples for a newly established nationwide biobank.

Set up by the Moredun Foundation, the Equine Grass Sickness Fund and supported by the British Horse Society and World Horse Welfare, it is building up a national picture of affected horses, weather and soil conditions, stress factors and other criteria which it’s hoped may help join the dots between cases.

Kate Thomson, administrator of the Equine Grass Sickness Foundation, said: “Information from the new biobank and an enhanced case questionnaire introduced last year are now providing vital data for scientists.

“So much of what we know, especially around management and environmental factors, is anecdotal, and the biobank and case database are crucial to help test what we think we know, and ultimately improve our advice.

“We can monitor factors like weather, local geology, and environmental factors and put these together with horse related data.

“It is like layering up a lasagne, whereas before our data was limited to a couple of layers, now we are getting many different types of information, which added together make a giant stack.”

A key area of research involves recreating a horse digestive system in a petri dish and introducing potential causal agents.

A predictive weather model is also being developed.

“If we are successful, the next step would be to develop an app, so that people could check the ‘grass sickness forecast’ in their location,” she added.

“The data we have so far is limited but is already starting to challenge our current thinking. If we can get people making timely case reports this will help us develop this tool.”

Horse owners who have been affected by the disease – even from previous years - are now being asked to share details including weather and ground conditions at the time, to help build up a picture.

Research fellow, Dr Kathy Geyer, of the Moredun Research Institute, said: “Vets and owners often say there are seven to ten days of dryish weather and intermittent frosts; temperature differentials seem to trigger cases.

“However, there’s not been much scientific research done on it, so we have been rooting through past data trying to feed that into the model.

“It's hard to get hold of good weather data and we need more case data.”

She called for owners and vets who have experienced cases, even historic ones, to share information.

“Unfortunately, there’s no quick fix,” she added.