A trial of a vaccine for the prevention of potentially deadly Equine Grass Sickness is being launched across Britain, following a successful pilot trial involving 95 horses and ponies in Scotland last year.
Horse owners are being invited by the the Animal Health Trust to take part in what it is describing as a ground-breaking trial.
Equine Grass Sickness is a debilitating and often fatal disease affecting horses, ponies and donkeys. It occurs predominantly in northern Europe, with Britain recording the highest incidence worldwide.
Almost all cases occur in horses with access to grazing and it is thought they are exposed to some form of noxious agent in the soil ingested as a contaminant of grass.
There is growing scientific evidence to suggest that the disease may be caused by the bacterium Clostridium botulinum (C. botulinum) type C, which is found commonly within soil.
The bacterium is capable of producing a range of toxins, including some that damage the nervous system, to which horses are particularly sensitive.
The current theory is that Equine Grass Sickness is a toxico-infectious form of botulism caused by C. botulinum type C, with the disease occurring when a combination of risk factors triggers the production of toxins within the horse’s intestinal tract.
As vaccinating horses protects against other similar diseases, such as tetanus and botulism, theoretically it is possible that it could be prevented by vaccination.
A field vaccine trial is the only way to evaluate whether a vaccine is effective in reducing the risk.
Following the successful pilot study in 2013, the trust is now in a position to start recruiting horses to be enrolled in the trial. It will be conducted by the trust in collaboration with the Universities of Edinburgh, Liverpool and Surrey.
The trial will follow 1100 horses and ponies for two years. Only healthy horses and ponies with a valid passport kept on premises with a history of Equine Grass Sickness cases in the previous two years will be eligible to be enrolled.
“Half of the horses and ponies on the trial will be vaccinated with a C. botulinum type C toxoid vaccine; the other half of the horses and ponies will receive an inactive placebo injection,” explained Dr Jo Ireland, the trust’s Equine Grass Sickness research co-ordinator.
“We will record, review and compare incidence of Equine Grass Sickness between the two groups to determine the efficacy of the vaccine.
“If we see reduced disease incidence in vaccinated horses, this would provide a major breakthrough in the prevention of Equine Grass Sickness.”
The project has received funding from several sources, including Neogen Corporation, Animal Welfare Foundation; Horserace Betting Levy Board; Racing Foundation; Moredun Foundation Equine Grass Sickness Fund; Hong Kong Jockey Club; Dodson and Horrell; South Essex Insurance Brokers; British Horse Society and the EB Moller Charitable Trust.