Buscopan is used for treating the painful contractions of spasmodic colic and is a scheduled veterinary drug in South Africa. However, riders who compete at national level in equestrian sports fall under Fédération Équestre Internationale (FEI) regulations, and these ban the use of this drug during competitions unless it is administered by a vet. This is because the drug contains the prohibited substance scopolamine, also found in the weed Datura.
Over the past few years, riders whose horses have tested positive for scopolamine in their urine have been suspended and fined the equivalent of R8 000, despite the fact that the scopolamine could be present due to Datura seeds or stems in the feed.
The dangers of poisoning by Datura stramonium or D. ferox (both declared noxious weeds in South Africa) have been previously described in Farmer’s Weekly. Usually, horses do not eat the green plants as they smell and taste unpleasant. However, they grow readily in tef and eragrostis fields and can be baled in hay.
Wide range of symptoms
Research has shown that the dried stems and leaves, as well as the small black seeds, can contain high levels of scopolamine. Poisoning can lead to impaction colic and mortalities.
However, symptoms may not be so dramatic and a horse that has eaten Datura may show only widened pupils (midriasis) and dry gums. The heart-rate may be lower or higher than normal, depending on the time that has passed since the plant was consumed.
In experiments where Buscopan was injected into a horse, scopolamine was detectable in urine for 24 hours. It was also found in the urine of horses that consumed Datura. But the results of the FEI sample taken during a competition will become available only weeks or months later, when it is impossible to test the feed for scopolamine.
The FEI is aware of this, of course. Yet in 2015, it decided that the fine and suspension of the rider would still be imposed, despite the possibility that the scopolamine could have originated in the feed. The ruling can only be contested if the feed was found to be contaminated with Datura – but as noted, this is unlikely to be available by the time the ruling is made.
A suspension can have devastating effects on a rider. Few FEI-level competitions are held every year and the subsequent six-month suspension could destroy a rider’s career on the international stage.
The lesson to be learnt is that any rider competing at national level (SA Championships) should make absolutely sure that his or her horses feed on uncontaminated hay.
This can be done by spreading out the hay and searching it by hand, before putting it into a hay net. The organisers of show venues can also do their bit by removing all small Datura plants.
Dr Mac is an academic, a practising equine veterinarian and a stud owner.