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The National Equine Headshaking Survey (NEHS)
The project was initiated by three scientists based at the School of Agriculture at De Montfort University; Sam Cook (an equine science student and owner of a headshaker herself), Richard Geering, MRCVS and Daniel Mills, PhD, MRCVS. In 1997 the National Equine Headshaking Survey (NEHS) was created. Its purpose was to establish an overview of the condition in the UK with a view to understanding its epidemiology and causes. Recruitment to the survey was a great success and created probably the largest collection of information on individual headshakers in the world. As a result, De Montfort University funded a PhD studentship to elaborate on this progress and Katy Taylor was recruited for this purpose. When the department moved to the University of Lincoln in 2001, the NEHS moved with it, under the continued supervision of Daniel Mills.
Current findings
The first survey in 1998 recorded over 250 completed questionnaires from owners of headshakers in the UK. Their reports of the condition as it appeared in their horses were presented in Mills et al (2002a) – see Literature. Their reports of the effectiveness of various therapies were presented in Mills et al (2002b) – see Literature. The nose net was reported to be the most useful management device and when Margaret Donnelly of Equilibrium Products approached the team with a new style, we helped her to evaluate it. Its efficacy matched that of the owner’s reports and was presented to the veterinary community in Mills and Taylor (2003) – see Literature.
A range of further studies were conducted as part of the PhD studentship. Firstly a case control survey compared the management of over 80 headshakers with a non-headshaking horse. No management practices appeared to be significant risk factors for the problem; however, it did appear that headshakers were more likely to be reported with other allergies. This was presented to the veterinary community in Taylor et al (2001) – see Literature. A second survey of over 200 headshakers was completed, with similar results to the first. This suggested a consistency to the problem and a similarity in presentation of the condition with other headshakers in other surveys.
The remainder of the studentship focused on ways of determining the efficacy of a range of treatments for headshakers. It was anticipated that success in some treatments and not others might provide a method for distinguishing between headshakers. However, for the reasons discussed below, this proved to be difficult. Owners from the NEHS database volunteered their horse for a number of trials summarised below:
Two simple field trials
A facemask that limits light to eyes - This was tested on over 20 horses but with minimal improvement. This suggests that although the symptoms are similar between British and American headshakers, light is a much stronger trigger for US (Californian) horses. This may be because they are suffering from irritation in a different location in the nerves or because sunlight is brighter / more intense / more prolonged in that region.
A bitless bridle - This was tested on nearly 30 horses. Many of the owners enjoyed riding their horse in this bridle and some small improvements in overall headshaking were reported in just 2 weeks.
Two placebo-controlled trials
[A placebo is a device that looks exactly like the treatment being evaluated but is without any specific effect, i.e. it is inactive. Placebos are used in a trial because they allow the researchers to work out how much improvement can be attributed to the specific action of the treatment as opposed to anything else. Improvement that can be attributed to ‘anything else‘ is that which is reported when the patient is using the placebo (the ‘placebo effect’) and can often be quite large, depending on the type of trial and the patient. It is important that the researchers directly involved and the patient do not know whether they are receiving a placebo since this can alter their perception of the treatment. The use of placebos is important otherwise we do not know whether the patient might have improved anyway and the treatment is actually without any specific action for the disease in question.]
A magnetic headcollar – This was tested on 20 horses with each trying a magnetic headcollar (a normal headcollar with small magnets inside the strap overlying the poll) and a placebo headcollar (looked the same but the magnets were demagnetised) for 2 weeks each. There was no evidence of greater improvement when the horses were wearing the magnetic headcollar compared to the placebo. This suggests that magnetic headcollars of this kind are no more effective than a placebo.
A herbal supplement – Based on Chinese herbal medicine for respiratory problems and allergies. This was tested on 30 horses with both trying the supplement and a placebo supplement for 5 weeks each. No evidence of efficacy greater than placebo was detected with the supplement.
In the last two (placebo-controlled) trials, significant improvements were reported under all treatments, placebo and product, but the efficacy of the product was no greater than the placebo. This raises an important question – can the apparent success of current alternative and conventional therapies for headshaking be attributed to the ‘placebo effect’ only? This is a possibility because NONE of the therapies (conventional or complementary) in current use have been shown in an independent scientific study to be more effective than a placebo. Based on our studies, even large improvements can be reported when the treatment is a placebo. It is therefore important that all products are tested against a placebo or suitable controls if owners are to be in a position to select the most effective therapy for their horse with a high level of confidence. Our understanding of headshaking based on the apparent efficacy of treatments is also limited since they may be having no actual specific effect on the headshaking.
NEHS Questionnaire
This site was created to inform owners about headshaking and to let them know about our ongoing research. If you believe that your horse has a headshaking problem as described in this site and would like to help, please print out the questionnaire below. Once completed, please return it to the address at the end of the form. Your details and those of your horse will be held by us in confidence and, with your permission we may contact you for further assistance in the future.
Please print out and complete the questionnaire below if you:
Currently own a horse with a headshaking problem which occurs when they are exercised (it may also, but not exclusively, occur when they are resting)
- Download and print NEHS Questionnaire.pdf
© Katy Taylor, De Montfort University, Leicester, UK