New Research

This study presents the first report of multiple human bites by larvae of Haemaphysalis longicornis Neumann in the U.S. An adult male working on a public park in Hackensack City (New Jersey) removed eight attached larvae from the arm, armpit, and back. The worker developed small erythematous pruritic lesions that self resolved in two weeks. No other symptoms were associated with the bite. The Asian longhorned tick is not considered an anthropophilic tick species. Still, the parthenogenetic population present in the eastern U.S can reach high numbers in small areas increasing the risk of tick bites to non-specific hosts, including humans. Public health practitioners should become familiar with the Asian longhorned tick, and vectorial competence studies should be carried out to determine the risk of tick-borne disease transmission to humans.

Tick saliva contains a complex mixture of peptides and non-peptides that counteract their hosts’ hemostasis, immunity, and tissue-repair reactions. Recent transcriptomic studies have revealed over one thousand different transcripts coding for secreted polypeptides in a single tick species. Not only do these gene products belong to many expanded families, such as the lipocalins, metalloproteases, Antigen-5, cystatins, and apyrases, but also families that are found exclusively in ticks, such as the evasins, Isac, DAP36, and many others. Phylogenetic analysis of the deduced protein sequences indicate that the salivary genes exhibit an increased rate of evolution due to a lower evolutionary constraint and/or positive selection, allowing for a large diversity of tick salivary proteins. Thus, for each new tick species that has its salivary transcriptome sequenced and assembled, a formidable task of annotation of these transcripts awaits. Currently, as of November 2019, there are over 287 thousand coding sequences deposited at the National Center for Biotechnology Information (NCBI) that are derived from tick salivary gland mRNA. Here, from these 287 thousand sequences we identified 45,264 potential secretory proteins which possess a signal peptide and no transmembrane domains on the mature peptide. By using the psiblast tools, position-specific matrices were constructed and assembled into the TickSialoFam (TSF) database. The TSF is a rpsblastable database that can help with the annotation of tick sialotranscriptomes. The TSA database identified 136 tick salivary secreted protein families, as well as 80 families of endosomal-related products, mostly having a protein modification function. As the number of sequences increases, and new annotation details become available, new releases of the TSF database may become available.