PMI Determination in Horses

Published: May 24th, 2012

Category: News

Ribonucleic Acid (RNA) Decay Profile for Determination of the Postmortem Interval in Horses

Nanny Wenzlow, DVM, MRCVS

Horses are frequently abused, neglected, illegally killed or slaughtered for black market meat production. The illegal slaughter of horses has increased over the past years in the United States (US), especially in South Florida. Animals are either stolen and slaughtered, or slaughtered in place and their carcasses are left behind. The motivation for consuming horse meat is reinforced by the myth that horse meat can cure cancer and other diseases. Horse meat is less expensive than beef and is sometimes used in the US for mixing in with beef, or is sold for a premium for exportation on the black market.  Unfortunately, the penalties for horse theft are less stringent compared to cattle theft.

Horses that are suspected to be victims of a crime will be subject to investigation by law enforcement, animal welfare agencies, or other investigators including insurance companies. In fact, the horse industry has always been plagued by insurance fraud. In some of those situations, the investigation could be assisted by estimating the length of time the horse has been dead, establish a crime by association with the scene, support or refute alibis,  include or exclude potential suspects, natural diseases or other natural events that may have participated in the demise of the animal.

The ability to accurately estimate the time since death, also called time of death or postmortem interval, is paramount to successful prosecution of crimes against horses. As the crime rate against animals in general is increasing in the US and worldwide, field efficient and reliable methods for accurate estimation of the time since death in the early postmortem interval are needed.

Using modern scientific methods, a novel and accurate methodology will be established to estimate the time since death in horses.  The determination of the time since death is a challenge and no realistic or applicable methods are available to evaluate the time interval within the first five days after death. Contrary to what the public believes and unfortunately supported by crime based television shows, determining the time since death using the decreasing body temperature is only of moderate precision in the majority of circumstances. Only a few other methods have been tested in dogs for an interval of 24 to 48 hours but these also lack accuracy for field application, are limited by their field applicability, and have not been applied or tested in the horse.

No method is available to estimate the time since death in horses and therefore molecular methods which assess the decay profile of the ribonucleic acids (RNA) in various tissues of horses will be used. Owner surrendered horses that have already been put-to-sleep for other reasons will be dissected and the ribonucleic acids of these horses will be examined during the first five days after death. In addition a robust, rapid technique called polymerase chain reaction (PCR) will be used to examine the breakdown of genes specific to the horse.  This method will be tested in all of the major tissues of the horse and will examine the effect of environmental temperature on this decay profile.

This application melds researchers in equine internal medicine, molecular science, forensic science, and veterinary pathology to create foundational, state of the art techniques for equine forensics and these combined methods are expected to allow the development of a very repeatable profile that can be adapted to the field and to laboratory setting. The result of our studies will aid in legal investigations for successful prosecution of crimes committed against animals.

Dr. Nanny Wenzlow is a PhD candidate in the Department of Infectious Diseases and Pathology, College of Veterinary Medicine and her senior mentor is Dr. Maureen Long.