Coendangered hard-ticks: threatened or threatening?

Abstract

The overwhelming majority of animal conservation projects are focused on vertebrates, despite most of the species on Earth being invertebrates. Estimates state that about half of all named species of invertebrates are parasitic in at least one stage of their development. The dilemma of viewing parasites as biodiversity or pest has been discussed by several authors. However, ticks were omitted. The latest taxonomic synopses of non-fossil Ixodidae consider valid 700 species. Though, how many of them are still extant is almost impossible to tell, as many of them are known only from type specimens in museums and were never collected since their original description. Moreover, many hosts are endangered and as part of conservation efforts of threatened vertebrates, a common practice is the removal of, and treatment for external parasites, with devastating impact on tick populations. There are several known cases when the host became extinct with subsequent coextinction of their ectoparasites. For our synoptic approach we have used the IUCN status of the host in order to evaluate the status of specifically associated hard-ticks. As a result, we propose a number of 63 coendangered and one extinct hard-tick species. On the other side of the coin, the most important issue regarding tick-host associations is vectorial transmission of microbial pathogens (i.e. viruses, bacteria, protozoans). Tick-borne diseases of threatened vertebrates are sometimes fatal to their hosts. Mortality associated with pathogens acquired from ticks has been documented in several cases, mostly after translocations. Are ticks a real threat to their coendangered host and should they be eliminated? Up to date, there are no reliable proofs that ticks listed by us as coendangered are competent vectors for pathogens of endangered animals.

Zoonotic pathogens associated with Hyalomma aegyptium in endangered tortoises: evidence for host-switching behaviour in ticks?

“…Major drivers for this trend include land use, climate changes and globalization [31,32]. On the other hand, for certain tick species which are co-distributed with their endangered hosts, like the case of H. aegyptium , the trend is a decreasing geographical range [2]. However, in general, a decrease in the availability of natural host populations could lead to host-switching behaviour [33].…”

“…The main hosts for adults are Palearctic tortoises of the genus Testudo [2]. Hence, the distribution of this tick is restricted to the distribution of the principal hosts: Mediterranean bioregion from the Atlantic coastland of Morocco through Northern Africa, Balkan countries, Middle East, and Caucasus and steppic regions in Central Asia, Afghanistan, and Pakistan [3-5].…”

Complete Mitochondrial Genome Sequence Data Provides Genetic Evidence That the Brown Dog Tick Rhipicephalus sanguineus (Acari: Ixodidae) Represents a Species Complex

“…There are three tick families: the Ixodidae (hard ticks), the Argasidae (soft ticks), and the Nuttalliellidae (restricted to southern Africa) 2,3. The Ixodidae is the most important tick family of medical and veterinary importance, which consists of the prostriate and metastriate ticks 4.…”

An annotated list of fish parasites (Isopoda, Copepoda, Monogenea, Digenea, Cestoda, Nematoda) collected from Snappers and Bream (Lutjanidae, Nemipteridae, Caesionidae) in New Caledonia confirms high parasite biodiversity on coral reef fish

“…This is hard to defend to the general public, because “parasites tend to lack charisma” [129] and many blood-sucking parasites transmit diseases [134]. However, parasites play a major role in the balance of populations and the evolution of their hosts [114,129,130,135], and, as such, are an important and irreplaceable part of biodiversity and ecosystems.…”