Veterinary Research Forum

Abstract The complete mitochondrial genome sequence of Dermacentor marginatus isolated from Hainan Island, a tropical island in China, has recently been elucidated. This ornate sheep tick is a three-host species, meaning it requires feeding on different hosts throughout its larval, nymph, and adult stages. This broad host range contributes significantly to its role in the transmission of various pathogens including spotted fever group rickettsia. The mitochondrial genome of D. marginatus was sequenced and found to be a circular, double-stranded DNA molecule with a total length of 15,005 bp. The genome exhibited a guanine and cytosine (GC) content of 21.23%, reflecting its unique genetic composition. Annotation of the genome revealed the presence of 37 genes, comprising 22 tRNA genes, 13 mRNA genes as protein-coding genes, (PCGs) and two rRNA genes. Phylogenetic analysis placed D. marginatus closest to D. silvarum from Heilongjiang province in China, clustering with D. sinicus from Hubei province in China. D. marginatus also exhibited proximity to D. species from China and other countries forming a distinct cluster. The availability of the complete mitochondrial genome sequence of D. marginatus marked a notable advancement in deciphering the genetic diversity and evolutionary path of this tick species. The study concentrated on the mitochondrial genome of D. marginatus from Hainan Island, examining its genetic and phylogenetic features, and assessing genomic variations that may influence mitochondrial function and tropical adaptation. The investigation into the genetic adaptations of D. marginatus to its tropical niche yielded vital information for forecasting how tick populations may react to changes in climate and diverse environmental conditions.

Abstract Rhipicephalus sanguineus, a repulsive obligate blood feeder, is a three-host tick inflicting tremendous damage. Blood-sucking initiates tick-pathogen-host interactions along with alterations in the expression levels of numerous bioactive ingredients. Key molecules regulating blood meals were identified using the transcriptomic approach. A total number of 744 transcripts showed statistically significantly differential expression including 309 significantly upregulated transcripts and 435 significantly downregulated transcripts in semiengorged female ticks compared to unfed ticks, all collected in 2021. The top 10 differentially upregulated transcripts with explicit functional annotations included turripeptide OL55-like protein, valine tRNA ligase-like protein and ice-structuring glycoprotein-like protein. The top 10 differentially down-regulated transcripts were uncharacterized proteins. Gene Ontology (GO) enrichment analysis revealed four associated terms in the cellular component category and 16 in the molecular function category among the top 20 terms. Differentially expressed genes (DEGs) were enriched in GO terms ID 0000323 (lytic vacuole) and ID 0005773 (vacuole).  The top 20 enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways included metabolism, cellular processes, organismal systems and human diseases. The DEGs were enriched in the KEGG term ID: ko-04142 (lysosome pathway) associated with intracellular digestion in the tick midgut epithelium. Molecular markers annotated via comparative transcriptomic profiling were expected to be candidate markers for the purpose of tick control.