Suspended animation

DISTRESSING images and footage of horses affected by the recent outbreak of EHV-1 in Europe illustrate the neurological effects of this highly contagious disease. The paralytic form, termed equine herpes myeloencephalopathy (EHM), can cause progressive ataxia with marked incoordination of the hind- and occasionally forelimbs, weakness of the bladder and tail, and recumbency.

The virus enters the bloodstream in the immune cells – white blood cells called lymphocytes and monocytes – and is carried around the body. This disseminates the infection to secondary sites, where the virus can replicate in the endothelial cells lining the small blood vessels, which results in infection, inflammation and blood clots. This compromises the spinal blood supply and causes the neurons (nerve cells) to swell and bleed. The extent and location of the neurological lesions determines the nature and severity of the clinical signs.

Modern treatments are available but can be very expensive when dosed for an average-sized 500kg horse. While medications can help, many horses with EHM will die or be euthanased due to complications – often within 48 hours of showing the first clinical signs.

Horses cope poorly with extended time lying down, mainly due to their size, so those that are recumbent are prone to problems including bacterial pneumonia, bacterial cystitis and myopathy (muscle disease). Suspending a horse in a sling during recovery (pictured, above), where possible, can lessen the chance of these complications.