Thursday, August 25, 2011

Identifying the cause of Foal Immunodeficiency Syndrome

Researchers in the UK have now published details of their work which resulted in the development of a genetic test for Foal Immunodeficiency Syndrome (FIS, otherwise known as Fell Pony Syndrome).

By comparing the genetic material from affected foals, known carriers with no clinical signs, and normal animals, the research team were able to track down the mutation responsible to a particular portion of chromosome 26. Further studies showed that the genetic defect affected the sodium/myo-inositol cotransporter gene (SLC5A3).

In the report of their work published in PLoS Genetics, they explain: "This gene plays a crucial role in the regulatory response to osmotic stress that is essential in many tissues including lymphoid tissues and during early embryonic development. We propose that the amino acid substitution we identify here alters the function of SLC5A3, leading to erythropoiesis failure and compromise of the immune system. FIS is of significant biological interest as it is unique and is caused by a gene not previously associated with a mammalian disease. "

"Having identified the associated gene, we are now able to eradicate FIS from equine populations by informed selective breeding."


Effect of blinkers


How do horses respond to partial loss of vision?

In a study at Texas A & M University, eight driving horses were assessed to see if they responded differently to stimuli when wearing blinkers or not. A racing hood with half cup blinkers was used to restrict the field of view behind the horse. A similar racing hood without blinkers was used as a control.

One experimenter administered one of four stimuli while standing about nine strides behind the horse:

  • a length of steel chain was dropped onto an aluminium sheet
  • a children's toy gun was fired
  • an aluminium can containing coins was shaken
  • an umbrella was rapidly opened

The horse's heart rate was recorded after each stimulus.

They found that wearing blinkers was significantly associated with an increase in heart rate when worn by horses experiencing a noise for the first time. On the other hand, blinkers were significantly associated with a decrease in heart rate when worn by horses exposed to a primarily visual stimulus (the umbrella opening).

"It would seem logical that wearing blinkers would be advantageous when a visual distraction is hidden by the blinkers. Because the horses cannot see the object, he has no reaction to this object which is potentially frightening" they comment.

However, sounds are different. "This paper shows that horses wearing blinkers react more when they are exposed to unexpected noises." They point out that this reaction is not necessarily seen by an observer - most of the horses in the study showed little visible reaction to the noise stimuli. There was, however, a dramatic increase in heart rate.

The researchers suggest that this model of restricted vision could be used to investigate how horses react to other visual deficits such as total blindness, or the changes that occur after cataract surgery.

More details at

Catching things from horses

Two unusual cases of horse to human transmission of bacterial infections remind us of the importance of good hygiene practices when handling horses.

One report from the Netherlands concerns the suspected transmission of Methicillin-resistant Staphylococcus aureus (MRSA) type ST 398, from a foal to a 16 year old girl. The girl, who was confined to a wheelchair, developed an infected wound from which a strain of MRSA, identified as belonging to type ST398, was isolated.

Investigations into the source of the infection showed that the girl had had intensive contact with a Friesian foal. She had not been admitted to hospital in other countries, nor had she been in contact either pigs or calves - the common source of human infection with this type of MRSA.

Swabs from other members of the girl's immediate family and other animals in the household were negative for MRSA

The type of MRSA involved,  ST398, is one which is associated with livestock and has been spreading in Europe and North America. It is the most common type of MRSA identified in horses in the Netherlands.
The authors suggest that the foal was the most likely source of the infection. In fact, the foal itself had been hospitalised in an equine clinic two months earlier for treatment of a wound infection.

Another report describes a surgical operation that became infected with Streptococcus equi.

S. equi, the cause of strangles in horses, is a cause of great concern to many horses' owners, but is rarely a danger to humans or other domestic species.

The patient, a professional racehorse trainer, underwent treatment for an aortic aneurysm - a condition in which the walls of the main artery leaving the heart are weakened and balloon outwards. If untreated there is a risk of sudden rupture leading to sudden death.

A specialised endovascular technique was used, in which a stent, a tubular framework,  was inserted into the femoral artery in the groin, and passed up the artery until it came to lie within the affected vessel.

The stent became infected and the causative organism was identified as Streptococcus equi.


Faecal egg counts after tapeworm treatment

It may be more useful to look for tapeworm eggs the day after treatment rather than before. Research carried out by Johanne Elsener of Wyeth Animal Health and Alain Villeneuve of the Faculté de Médecine Vétérinaire, Université de Montréal looked at whether treating for tapeworms one day before carrying out a faecal examination improved the chance of identifying infected animals

The study involved horses of differing ages on a single stud farm - from weanlings to adult breeding mares and stallions.

All horses were presumed to be naturally infected with Anoplocephala perfoliata - as tapeworm-infected animals had been identified previously on the farm.

The horses were weighed and dosed according to weight.

The researchers examined faecal samples before and 24-48 hours after treatment with a paste containing praziquantel (and moxidectin). Faecal samples were examined using a modified Wisconsin sugar centrifugation technique - performed by a technician who was unaware of the treatment given to each .horse.

Overall, the researchers found that they were twice as likely to detect tapeworm eggs in the faeces of horses 24 - 48 hours after treatment with praziquantel than they were before treatment.

In adult horses (mares and stallions) the difference was statistically significant. Young horses (weanlings, yearlings and two year olds) showed a numerical increase in positive horses after treatment, but the difference was not statistically significant.

The two-year old horse group had the highest proportion of positive faeces, (66% horses were positive before treatment)

The researchers conclude that sampling after treatment may give a better idea of the true prevalence of tapeworm infection.

More details at