Very low intraspecific sequence variation in selected nuclear and mitochondrial Parascaris univalens genes.

The study explores the genetic sequences of the Parascaris univalens, a species of worm prevalent in equines. By using various gene sequences and comparing these with archived data, it suggests that previous assumptions about equine worm species may be incorrect.

Background of the Research

• The research focuses on parasites in equines, specifically two species that are morphologically similar, Parascaris univalens and Parascaris equorum.
• The differences between these two species can only be reliably identified using specialized testing methods, which are rarely used due to their complexity.
• Because these tests aren’t often used, it’s generally assumed that either species could be present in most studies.
• However, more recent studies have used karyotyping to identify these species, and those have consistently found only Parascaris univalens — the last time Parascaris equorum was identified was more than 30 years ago.

Objective of the Research

• The researchers aim to improve species-specific detection through molecular markers — sequences that can reveal the presence of specific species.
• They used sequences from 12S rRNA, cytochrome oxidase I (COI), and the complete internal transcribed spacer (ITS)-1 and -2, and compared these sequences with those from the GenBank archive.

Research Findings

• All karyotyped specimens were identified as Parascaris univalens, which formed homogenous clusters. This suggests that the species hasn’t seen much evolution or variation.
• However, they found a small number of sequences that were similar but not identical, originating from donkeys in China. It’s suggested that these might represent a different genotype or species of Parascaris.
• When they compared these samples to the GenBank, their sample also lined up with most of the sequences that had been assigned to either Parascaris univalens or Parascaris equorum, implying the majority of these actually belong to Parascaris univalens.

Implications and Future Research

• The findings challenge prevailing assumptions about the presence and prevalence of different species in the Parascaris genus.
• The consistent identification of Parascaris univalens suggests that PCR-based species diagnosis may be possible once molecular markers have been identified for Parascaris equorum from karyotyped specimens, simplifying the process of species identification for future researchers.