Phylogenetic analysis of Ehrlichia species isolated from horses and dogs in Iran.

Overview

• This study investigated the presence and genetic relationships of Ehrlichia species, which are bacteria causing ehrlichiosis, in horses and dogs across various provinces in Iran.
• The research used PCR techniques to detect the bacteria and analyze their genetic makeup, revealing the types of Ehrlichia species prevalent in the country and their distribution among different animal hosts.

Objectives of the Study

• Determine the prevalence of Ehrlichia species in horses and dogs in Iran.
• Perform phylogenetic analysis to identify and categorize the Ehrlichia species found in these animals based on specific genetic markers.

Methodology

• Sample Collection: Blood samples were collected from a total of 400 animals including 200 horses and 200 dogs.
• Geographical Coverage: Samples were taken from five different provinces in Iran — Kerman, Khuzestan, West Azerbaijan, Golestan, and Mazandaran.
• Detection of Ehrlichia spp.: Polymerase chain reaction (PCR) was employed to amplify the 16S rRNA gene, a common genetic marker for bacterial identification.
• Gene Amplification for Phylogenetic Analysis: Semi-nested PCR was performed targeting three specific Ehrlichia genes:
  • dsb gene (disulfide bond formation protein gene)
  • TRP36 gene (tandem repeat protein 36 gene)
  • gltA gene (citrate synthase gene)

Key Findings

• Prevalence: 4.5% of total samples tested positive for Ehrlichia species.
  • Specifically, 3% of the horses and 6% of the dogs were infected.
• Regional Differences: Highest prevalence was observed in Kerman and Khuzestan provinces.
  • Lowest prevalence was found in West Azerbaijan, Golestan, and Mazandaran provinces.
• Host Consideration: The study highlights that dog and horse populations are important epidemiological factors in the spread of ehrlichiosis within Iran.

Phylogenetic Analysis Results

• Analysis based on the dsb and TRP36 gene sequences identified two main Ehrlichia species circulating in the sampled animals:
  • Ehrlichia canis: Typically associated with canine ehrlichiosis, this species was prevalent among dogs sampled in this study.
  • Ehrlichia ruminantium: Known to cause heartwater disease mainly in ruminants, also detected in the sampled populations, suggesting its presence in the region and potential cross-species spread.

Implications and Significance

• This study provides valuable data on the distribution and types of Ehrlichia species affecting horses and dogs in Iran.
• Understanding the phylogenetic relationships helps track the bacterial strains circulating in different regions, which can inform diagnostic, preventive, and treatment strategies.
• Since dogs and horses are identified as key reservoirs or hosts, controlling ehrlichiosis in these animals could be crucial for public and animal health in Iran.
• This research supports epidemiological surveillance efforts by pinpointing geographic hotspots for infection.