Intraspecific genetic variation and phylogenetic analysis of Dirofilaria immitis samples from Western China using complete ND1 and 16S rDNA gene sequences

Genetic and geographical delineation of zoonotic vector-borne helminths of canids

Several zoonotic vector-borne helminths (VBHs) infesting canids cause serious veterinary and medical diseases worldwide. Increasing the knowledge about their genetic structures is pivotal to identify them and therefore to settle effective surveillance and control measures. To overcome the limitation due to the heterogeneity of large DNA sequence-datasets used for their genetic characterization, available cytochrome c oxidase subunit 1 (cox1) (n = 546) and the 12S rRNA (n = 280) sequences were examined using combined bioinformatic approach (i.e., distance-clustering, maximum likelihood phylogeny and phylogenetic evolutionary placement). Out of the 826 DNA available sequences from GenBank, 94.7% were characterized at the haplotype level regardless sequence size, completeness and/or their position. A total of 89 different haplotypes were delineated either by cox1 (n = 35), 12S rRNA (n = 21) or by both genes (n = 33), for 14 VBHs (e.g., Acanthocheilonema reconditum, Brugia spp., Dirofilaria immitis, Dirofilaria repens, Onchocerca lupi and Thelazia spp.). Overall, the present approach could be useful for studying global genetic diversity and phylogeography of VBHs. However, as barcoding sequences were restricted to two mitochondrial loci (cox1 and 12S rRNA), the haplotype delineation proposed herein should be confirmed by the characterization of other nuclear loci also to overcome potential limitations caused by the heteroplasmy phenomenon within the mitogenome of VBHs.

Age and sex distribution of Dirofilaria immitis among dogs in Meshkin-Shahr, northwest Iran and molecular analysis of the isolates based on COX1 gene

Dirofilaria immitis is an important filarial nematode in dogs. In this study, age and sex distribution of this zoonotic nematode among dogs were investigated in northwest of Iran in Meshkin-Shahr city. Molecular characteristics of the isolates, based on cytochrome oxidase subunit 1 (COX1) gene were compared to the isolates from other areas of the world.Blood samples were collected from 91 dogs which were selected by simple classified accidental sampling. Thin and thick blood smear examinations were used to find out infectivity with D. immitis. DNA extraction was performed from adult D. immitis recovered from heart of infected dogs. The COX1 gene was amplified and sequenced. Phylogenetic analysis was carried out using sequences obtained in this study along with relevant sequences deposited in the GenBank. Phylogenetic analysis and sequence variation was performed using MEGA software in comparison with those COX1 sequences deposited in GenBank. Out of 91 dogs, 19 (20.87%) were found positive for infection with D. immitis. There was no statistically significant difference between males and females of dogs in terms of D. immitis infection. However, the rate of infection in dogs more than 2 years old was significantly higher than those with lower age. Both sequences analyzed in this study showed 100% homology to each other. Intra-species variation of these isolates with those from other areas of the world amounted to 0 to 0.50%. Phylogenetic analysis of the COX1 gene suggested that it is conserved, and can be used for study on genetic diversity and classification of filarial nematodes.