ECHINOCOCCUS EQUINUS HYDATID CYST IN THE LIVER OF A PRZEWALSKI’S HORSE ( EQUUS PRZEWALSKII) IN A CANADIAN ZOO.

This research describes the discovery of cysts caused by a parasite, Echinococcus equinus, in the liver of a Przewalski’s horse in a Canadian zoo – a first in North America, and the first instance in a Przewalski’s horse.

Context and Discovery

• This study was prompted by the euthanasia of a 23-year-old captive-born Przewalski’s horse mare in a Canadian zoo for severe colic that arose from a ruptured jejunal pseudodiverticulum.
• In the process of investigating the horse’s health condition, the researchers discovered an encysted larval cestode, a type of parasite, in a granuloma in the horse’s liver. This was not the primary cause of the horse’s illness, hence it was described as an “incidental finding”.

Investigation and Diagnosis

• The investigators positively identified the larval cestode as Echinococcus granulosus using gel-based Polymerase Chain Reaction (PCR), a molecular biology technique that copies a DNA sequence to facilitate its examination.
• Further genetic sequencing of the copied DNA revealed an exact match with a particular species of parasite, Echinococcus equinus. This DNA sequencing ensures exact species identification, which is important in understanding the pathology and epidemiology of the disease observed.

Significance of the Finding

• The presence of Echinococcus equinus marks what is believed to be the first molecular confirmation of this particular species in North America. This means there had been no previously documented instances of this species being detected in this region using molecular techniques like PCR and DNA sequencing.
• Moreover, this is the first time Echinococcus equinus has been reported in a Przewalski’s horse. These horses are an endangered breed, native to central Asia. Found both in the wild and captivity, they are believed to be the direct ancestors of domesticated horses. This new finding may have implications for the species’ veterinary care and conservation strategy.