Molecular Detection of Canine Ehrlichiosis in Baghdad, Iraq

Abstract

Ehrlichiosis is a widespread disease transmitted from dog to dog by ticks and caused by specific rickettsial bacterial disease in dogs by three main species, including Ehrlichia canis, Ehrlichia chaffeensis, and Ehrlichia ewingii. Aim: Molecular investigation of canine ehrlichiosis (Ehrlichia canis, E. ewingii, and E. chaffeensis) in Baghdad province.  Methods: The study was conducted in Baghdad, between October 2023 and March 2024 on 155 dogs. All samples were examined by nested PCR, and cases were positive when producing product fragment about 396 bp for each species in the second round of PCR of each Ehrlichia species. Results: The results revealed that the infection rate per dog was 7.74% as follows: 12 dogs had an overall infection rate, 12 dogs had E. canis infection, 7 dogs had E. chaffeensis infection, and 3 dogs had E. ewingii infection. The study documented instances of mixed infections caused by multiple Ehrlichia species among the 7 cases. However, this study showed no association between canine ehrlichiosis infection and age, as well as the sex of dogs while significant in huskies. The analysis of the 16S rRNA gene of E. canis revealed that the Iraqi isolates exhibited the highest homology with isolates from countries, such as Turkey, Japan, India, and China. The sequences of the 16S rRNA gene of E. chaffeensis were grouped within clades; the first clade was very similar to isolates from Mexico, South Korea, and Argentina, while the second clade clustered with isolates from China, Egypt, South Korea, and other parts of the world. Phylogenetic analysis for E. ewingii obtained in the present study revealed the high homogeneity of the Iraqi isolate to clade 1 of E. ewingii with Mexico, Grenada, and China, while clade 2 included another Iraqi isolate of E. ewingii with the isolates from India and the USA. Conclusion: The study concluded that this study detected the infection rate of Ehrlichia species in dogs in Baghdad, and concluded from phylogenetic trees that presented a significant multiple hosts of these pathogens, including dogs, cats, ticks and humans, indicated that had the zoonotic potential of Ehrlichia species. This study contributed in the study epidemiological factors, and genetic diversity of Ehrlichia species in dogs.