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APPROXIMATE DISTRIBUTION of Ixodes holocyclus

Overview on distribution
Older information on distribution
Newer information on distribution

Overview

Information about both the national and the international distribution of Ixodes holocyclus has been misleading. Some maps and references have suggested that it is found in such distant countries as Indonesia, Papua/New Guinea and even India. Its occurrence in Tasmania has been another source of contention.

Cases of paralysis attributed to I. holocyclus in India are probably caused by D. auratus or other ticks. It is unlikely that I. holocyclus is found in New Guinea or Indonesia as cases of paralysis have not yet been described from there.

Despite the claims in older references, it is likely that Ixodes holocylus is only truly established along the east coast of the Australian mainland. It is also likely that the cases of paralysis recorded in Tasmania are caused by a similar though separate species, that is neither Ixodes holocyclus nor Ixodes cornuatus. Ixodes cornuatus may be a subspecies of Ixodes holocyclus expressing a variable ability to cause paralysis, or it may, together with I holocyclus, combine to form a "species complex" in south east Victoria. The "Tasmanian paralysis tick" may represent a species still to be defined.

For comparative distributions maps of 4 of the most common ticks found on domestic animals in Australia- go to Distinguishing Common Ticks on the East Coast of Australia.

Older information on distribution

India, Indonesia and New Guinea?

According to Nuttall (1908) Ixodes holocyclus was found in New Guinea and India. This was concluded from a description of one male 1 male adult from New Guinea (collected by S. Schaedler (Leyden Mus Nat Hist) and from one nymph specimen (Berlin Museum) collected from E India [qualified with a (?)] and another nymph also from India (R Blanchard collection).

According to Kelly (1977), I. holocyclus was found in New Guinea, Indonesia and India. Kelly may have been referring to information in Nuttall et al (1908).
In another reference (Goddard, 1988) a diagram shows that New Guinea has Ixodes holocyclus but that India does not. This source indicates elswhere that in India the tick D. auratus is reported to cause paralysis. See the page "which ticks" cause paralysis around the world.

The best information on international distribution comes from Roberts (1960). According to Roberts: "ticks under the name of I. holocyclus Neumann, 1899, were recorded from India, Kei Island, Indonesia, and from New Guinea as well as from Australia. The record from India by Neumann (1899) was based on three nymphs, one mounted on a slide, the hosts being noted as Sciuris variabilis and "ecureuil rouge". Sharif (1928), in his revision of Indian Ixodidae, included this species in his key to the species of Ixodes, but made no other mention of it. Apparently its inclusion in his paper was based on Neumann's record. The Indonesian record by Krijgsman and Ponto (1932) also refers to a nymph. I. holocyclus, however, is not included by Anastos (1950) in his list of-the scutate ticks of this area. The New Guinea record comes from roneod reports (1953, 1954) issued by the Department of Agriculture, Stock, and Fisheries, Port Moresby. In view of the fact that there are several species all superficially similar to I. holocyclus, the nymphs of some of which have not been described, all the above records are regarded as doubtful. This is particularly so for New Guinea with its I. cordifer of Neumann (1908), I. cordifer cordifer and I. cordifer bibax of Schulze (1935), and I. confusus, and from where no case of tick paralysis, as might be expected were I. holocyclus to occur there, has been recorded"

Australia

According to Nuttall (1908) Ixodes holocyclus was found in Western Australia. This was concluded from 2 female adults from kangaroos and 2 nymphs from an unknown species (ex Rothschild collection). Ixodes holocyclus was not represented in the material from this State seen by the Roberts (1960) and there are no records of tick paralysis from this part of Australia.

Seddon (1951) gives the distribution of I. holocyclus in Australia as follows:

This tick is confined to the coastal areas along the northern and eastern coasts of Queensland and New South Wales, part of Victoria and Tasmania and is restricted to brush and scrub country. For the most part it occurs only within a few miles of the coast, but in southern Queensland and northern New South Wales it extends somewhat further inland. Thus in Queensland it is present in all coastal areas and also in the Burnott, as far west as the Bunya Mountains, in the whole of the Brisbane watershed, and also at Warwick.
In New South Wales likewise it is most prevalent along the coast, especially in the Macleay and Kernpsey districts and around Sydney, but on the far north coast extends inland as far as the valleys leading into the Dividing Range. Around Sydney it is especially common in the area between Port Jackson and the Hawkesbury River. Quite recently this tick has made its appearance on the Western side of the George's River, at Glenfield.
In eastern Victoria this tick is present along the coast as far as Lakes Entrance and in Tasmania it is confined to the east coast and Hobart . . In 1945, this tick was found in Melbourne, the infested dog dying from tick paralysis.

In the extensive material available to Roberts (1960) the most southern locality from which I. holocyclus was collected was Bairnsdale, near Lakes Entrance, on the east coast of Victoria. Several specimens seen from this locality were taken from dogs affected. with tick paralysis.

No specimens of this species were seen from Tasmania, but Roberts' enquiries confirmed Seddon's (1951) report of the occurrence of tick paralysis in this State. I. cornuatus is present in Tasmania, and as there is a single record of the association of this species with paralysis. The reference by Seddon (1951) to I. holocyclus in Tasmania could refer to I. cornuatus. I. hirsti also occurs in Tasmania and the role of this species in tick paralysis is unknown.

I. holocyclus has also been collected from Armidale, N.S.W., a locality not included in Seddon's distribution records (Roberts, 1960).

Ross (1924), in his studies on tick paralysis in the dog, attributed this condition to I. holocyclus Neumann and gave a detailed description of all the life cycle stages of this tick. His description and figures agree very closely with tile description published by Neumann (1899) and by Nuttall and Warburton (1911). Schulze (1935), however, considered that the species determined by Ross (1924) as I. holocyclus was not Neumann's I. holocyclus and based this opinion on an examination of a "cotype" of Neumann's in the Berlin Museum, which he figured as possessing a sternal plate. He also said that Neumann's I. holocyclus came from New Zealand. Schulze regarded Ross's I. holocyclus as a new species to which he gave the nane I. rossianus. It would seem that Neumann's cotype seen by Schulze could be a specimen of I. hirsti and had beenerroneously identified by Neumann as I. holocyclus. The locality mentioned by Schulze (1935), namely New Zealand, is also erroneous as no species of Sternalixodes occurs in that country (Dumbleton, 1953).

Of the five species of Australian Sternalixodes, I. holocyclus is closest to I. cornuatus. The females of neither species possesses a sternal plate, the absence of which readily separates them from the females of I. hirsti, I. trichosuri, and I. confusus. The female I. cornuatus may be readily separated from I. holocyclus by the larger dimensions of its capitulum and scutum, by the strong, blunt cornua, and by the hypostome dentition. The males appear almost identical morphologically, but I.cornuatus may be recognized by its greater size, the more abruptly terminating tarsi, and by the hypostome dentition (Roberts, 1960). That the distinction between I. cornuatus and I. holocyclus is always clear is now being contested (see below).

 

An occurrence has been reported in the ACT - this was of nymphs, probably I. holocyclus, found on birds that most likely migrated from endemic areas. [This does raise the general possibility of sporadic occurences in more distant but climatically favourable areas however.]

Newer information on distribution

Since the taxonomy and identification of ticks is still an evolving discipline these "distributions" may similarly change. For example I. myrmecobii (found in south-western Western Australia) and I. cornuatus (found in southeast coastal [see note] NSW, central Victoria, and which also may cause paralysis) are closely related to I. holocyclus. They may prove to be subspecies of I. holocyclus.

New South Wales

In general Ixodes holocyclus is found throughout coastal areas of Eastern Australia as far south as the Lakes Entrance-Bairnsdale region of Victoria. In the Sydney area it is most common between the Harbour and the Hawkesbury River and westward to Castle Hill. However it has been found in suburbs south of the Harbour and as far west as the Blue Mountains (Carter, 1985). According to Roberts (1960) it is found as far north as Normanton in North Queensland (although this may be an error according to Stephen Doggett, quoting BF Stone). In New South Wales most reports indicate a distribution within 15 km of the coast. However there are localised occurrences further inland- for example the lower Blue Mountains on the edge of the Sydney basin, the Armidale area (presumably New England NP) and in the lower regions of the Barrington Tops (George Dellar pers com). In Queensland they are found in rainforest country as far west as the towns of Warwick and Dalby (Bunya Mtns).

Stephen Doggett (pers com.) does not believe that Ixodes cornuatus occurs in southeast coastal NSW. He has done extensive collecting in the region and has never found any evidence for the species. Likewise he feels that most reports are mis-identifications of Ixodes holocyclus. The problem (in his opinion) is that Roberts never described the species adequately (his drawings of this species are not good).

Tasmania

Stephen Doggett has collected so called "Ixodes cornuatus" from Tasmania and these are extremely different from Ixodes holocyclus on the mainland. There are obvious differences in colour, colour patterns (especially on the legs) and size. Janey Jackson at the University of Melbourne, is looking into these species. So far, according to S. Doggett, she has apparently found evidence for only fairly small isolated populations of I. cornuatus near Melbourne (see current research) .

The most recent electrophoretic data from Janey Jackson (Jackson et al, 1998) suggests that mainland Ixodes holocyclus and Ixodes cornuatus represent variants of a single species (i.e. I. holocyclus). This information suggests that the risk of tick paralysis therefore extends into the range previously attributed to Ixodes cornuatus, namely Eastern Victoria including areas surrounding Melbourne, and as far West as the Maryborough region of western Victoria. This would explain sporadic reports of tick paralysis in dogs in these areas. The presence of a species complex on the mainland may account for the apparent differences in the ability of ticks to cause paralysis in domestic animals.

The possibility of differences between the ability of I. cornuatus on the mainland and in Tasmania to cause paralysis raises doubt as to whether they are the same species. This hypothesis has been supported by the fact that the electrophoretic profiles of Tasmanian and Mainland ticks morphologically described as I. cornuatus are in fact greater than the differences between mainland ticks described as I. holocyclus and I. cornuatus.

In the diagram on the right the Tasmanian paralysis ticks (resembling I. cornuatus) are located in the central highlands rather than the east coast, in variance with the other diagrams on this page. According to Jackson et al (1998) there is no evidence to suggest that Ixodes holocylus is found in Tasmania. Apparently cases of tick paralysis do occur in Tasmania however, and possibly with an increasing frequency (James Wallner, 1998, pers com).

For a brief description of the ticks in Tasmania see Roberts' article "The Tick Fauna Of Tasmania".

A question [NF]- Is it possible that the mainland paralysis tick might be able to develop as an introduced species in Tasmania?

 

 

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