Abstract:
In comparison to other arachnids, ticks are major vectors of disease, but less than 8% of
the known species are capable of inducing paralysis, as compared to the ~99–100% arachnids that
belong to venomous classes. When considering the potential monophyly of venomous Arachnida,
this review reflects on the implications regarding the classification of ticks as venomous animals
and the possible origin of toxins. The origin of tick toxins is compared with scorpion and spider
toxins and venoms based on their significance, functionality, and structure in the search to find
homologous venomous characters. Phenotypic evaluation of paralysis, as caused by different ticks,
demonstrated the need for expansion on existing molecular data of pure isolated tick toxins because
of differences and discrepancies in available data. The use of in-vivo, in-vitro, and in-silico assays for
the purification and characterization of paralysis toxins were critically considered, in view of what
may be considered to be a paralysis toxin. Purified toxins should exhibit physiologically relevant
activity to distinguish them from other tick-derived proteins. A reductionist approach to identify
defined tick proteins will remain as paramount in the search for defined anti-paralysis vaccines.