Klossiella equi, an underreported parasite of equids in the Americas.

Overview

• This study reveals that the kidney parasite Klossiella equi is much more common in horses across different populations in the Americas than previously recognized, highlighting limitations in traditional detection methods.

Background

• Klossiella equi is a parasite belonging to the Apicomplexa phylum, specifically the Coccidia subclass, known to infect the kidneys of equids such as horses.
• It has a worldwide distribution but is generally considered uncommon and usually detected incidentally during microscopic examination of kidneys in routine necropsies.

Study Objective and Design

• The study aimed to better understand the prevalence of K. equi infections in horses by testing kidney samples from various equine populations in North America.
• Kidneys were opportunistically collected from three groups:
  • Routine necropsies at the Ontario Veterinary College (OVC) – 48 animals
  • Wild horses from Sable Island, natural mortalities – 25 animals
  • Horses from the University of Kentucky research herds, including mares (3) and foals (16)

Methods

• The researchers developed a Polymerase Chain Reaction (PCR) technique targeting a 575 base pair section of K. equi’s mitochondrial genome to detect infections from kidney tissue DNA.
• This molecular method offers more sensitive detection compared to traditional histological (microscopic) examination of kidney tissues.

Key Findings

• Overall infection prevalence was found to be 45% (41 out of 92 animals tested positive).
• No infections were identified in animals less than 10 months old, indicating age-related differences.
• Among animals aged one year or older, prevalence drastically increased to 58% (40/67).
• Prevalence by group was:
  • Ontario Veterinary College – 50% (24/48)
  • Sable Island wild horses – 56% (14/25)
  • University of Kentucky mares – 100% (3/3)
• Histological examinations often missed infections; in 20 PCR-positive OVC cases, routine pathology did not detect K. equi.
• A DNA sample from Argentinian horse’s urine confirmed the identity of the parasite via sequence matching with the K. equi reference genome at 100% over 957 base pairs.

Conclusions and Implications

• K. equi infections are common among equids in different geographic locations across the Americas but are likely vastly underreported.
• Traditional histological methods lack sensitivity for detecting these infections, and molecular diagnostics like PCR provide a more accurate detection tool.
• Findings suggest that veterinary diagnostic protocols may need to incorporate molecular testing to properly identify K. equi infections and better understand their clinical significance.