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

Abstract

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.

Diversity and geographic distribution of haplotypes of Dirofilaria immitis across European endemic countries

“…Most sequences (75%) formed the Di1 haplotype, which is in agreement with a previous study using mt sequences of COI and 12S rDNA derived from the GenBank, which showed that 272 out of the 277 D. immitis sequences (98%) formed a dominant haplotype [ 47 ]. In total, only five haplotypes were delineated based on these two mt markers from sequences from 26 countries [ 47 ], which is much lower than in the current study.…”

“…Most sequences (75%) formed the Di1 haplotype, which is in agreement with a previous study using mt sequences of COI and 12S rDNA derived from the GenBank, which showed that 272 out of the 277 D. immitis sequences (98%) formed a dominant haplotype [ 47 ]. In total, only five haplotypes were delineated based on these two mt markers from sequences from 26 countries [ 47 ], which is much lower than in the current study. One of the reasons could be that the haplotypes in the current study were based on the entirety of the combined COI and NADH genes, which offers a broader insight into the genetic diversity of each isolate and better delineation of haplotypes while the sequences used in previous study [ 47 ] covered a fragment of the COI gene.…”

“…As mentioned previously, a study based on the D. immitis sequences available in the GenBank successfully identified five haplotypes of D. immitis and 12 haplotypes of D. repens by targeting the COI and 12S rDNA genes which supports our main finding that D. immitis has lower genetic diversity than D. repens [ 47 ].…”

“…In total, only five haplotypes were delineated based on these two mt markers from sequences from 26 countries [ 47 ], which is much lower than in the current study. One of the reasons could be that the haplotypes in the current study were based on the entirety of the combined COI and NADH genes, which offers a broader insight into the genetic diversity of each isolate and better delineation of haplotypes while the sequences used in previous study [ 47 ] covered a fragment of the COI gene. However, it is also evident from our repeated analysis that a long enough COI fragment may be used solely for haplotype delineation in D. immitis, because of no diversity in NADH gene.…”

Dirofilaria immitis: Genotyping Randomly Selected European Clinical Samples and USA Laboratory Isolates with Molecular Markers Associated with Macrocyclic Lactone Susceptibility and Resistance

“…Given the geographical expansion of dirofilariosis it will be important to monitor the effectiveness of MLs in Europe and the possible emergence of resistance. To date, there is minimal published information on the genetic makeup and diversity of European isolates, with Laidoudi et al [24] finding a single common haplotype present in European samples analyzed. In the current study, we analyze the prevalence of the validated North American SNP markers associated with susceptibility and resistance to MLs in European clinical samples.…”