Morphological comparison of the adult and larval stages of the Australian ticks Ixodes holocyclus Neumann, 1899 and I. cornuatus Roberts, 1960 (Acari: Ixodoidea)

Dermatoses caused by infestations of immature Ixodes spp. on dogs and cats in Sydney, Australia

“…With correct reference material and light microscopy, general veterinary practitioners may confidently identify tick larvae or nymph to the level of the genus ( Ixodes ) 8 . The differentiation of species of ixodid ticks, particularly larvae, is more difficult 18 and there are numerous limitations to correct identification, even with parasitological expertise. Several species of the larval and nymphal stages of Ixodes within the subgenus Sternalixodes (which includes I. holocyclus and I. trichosuri ) are yet to be taxonomically described.…”

“…Four species of ticks were putatively identified: I. holocyclus (25%) (Figure 3), I. trichosuri (57%) (Figure 4), I. tasmani (two ticks, 1.5%), and Haemaphysalis longicornis (one tick, 0.7%). Identification was determined using the taxonomic keys of Roberts 8,17 and Jackson et al 18 (Table 1). Twenty ticks (15%) could not be clearly identified because of damage or absence of mouthparts; however, at least one tick could be clearly identified from each animal.…”

Tick paralysis of dogs in Victoria due to Ixodes cornuatus

“…The tick was identified as I cornuatus using recently established morphological criteria. 7 The cases reported above suggest that mainland populations of I cornuatus occurring outside the zone of sympatry with I holocyclus are capable of causing paralysis in dogs. It should be noted however that while the clinical signs observed in the cases reported were consistent with tick paralysis, it is rarely possible to provide conclusive evidence that the signs are specifically due to the ticks found on paralysed anaimals.…”

“…Ixodes holocyclus does not occur in Tasmania. 3,7,8 As is the case in Tasmania, instances of paralysis in domestic animals are relatively uncommon in Victoria, suggesting that this species of tick does not necessarily cause paralysis in its hosts. By contrast, hosts infested with adult I holocyclus frequently display signs of paralysis.…”

“…8 The current state of uncertainty may be due in part to difficulties associated with identifying these two species of ticks based on morphological characteristics, 7 since some of the features previously used to distinguish the species have been shown to be unreliable. 7 Recent genetic studies of I cornuatus have demonstrated differences between Tasmanian and mainland populations of the species, raising the possibility that only Tasmanian populations can cause paralysis. 8 These case reports describe two presumed instances of tick paralysis due to I cornuatus in Victoria.…”