Tick Poisoning in Native Australian Fauna

Bandicoots

Bandicoots are an important host for Ixodes holocyclus. The ticks Ixodes tasmani and Ixodes fecialis are the main ectoparasites of the Eastern Barred Bandicoot (Perameles gunnii) in Victoria. Bandicoots successfully carrying heavy Ixodes burdens at the time of capture may succumb to a single adult female tick after being free of ticks in captivity for several months.

Birds

Ixodes holocyclus: can cause paralysis. Ticks also act as intermediate or transport hosts for other parasites. Ixodes kohlsi in sea birds.

Echidnas

The echidna tick Aponomma concolor is commonly found on wild and captive echidnas. Other species of ticks have also been recorded including Ixodes holocyclus, I. tasmani, Haemaphysalis humerosa, Amblyomma australiense, Am. echidnae, Am. moyi, Am. papuanum, and Aponomma hydrosauri and Ap. undatum. When present in large numbers ticks may be associated with dermatitis or anaemia. They may also be associated with the transmission of haemo-protozoans and arboviruses. Ivermectin 1% injection may be used to treat tick infestations at a dose of 200 mcg/kg by subcutaneous injection. Subcutaneous injections can be given just anterior to the quills on the neck or on the underbelly.

Reference:

Booth, :Monotremes, Wombats and Bandicoots, in Proceedings No Australian Wildlife; University of Sydney Post Graduate Committee in Veterinary Science, 199

Many echidnas present with large numbers of ticks. They are mostly echidna specific ticks and cause no problem, similarly for the echidna flea. The animal should not be stressed in order to remove them- i.e. leave them alone unless the animal is under anaesthesia for some other purpose.

Reference:

Bellamy, T: Handrearing Native Animals, in Proceedings No Australian Wildlife; University of Sydney Post Graduate Committee in Veterinary Science, 199

Flying foxes

The Tolga Bat Hospital, on the Atherton Tablelands near Cairns in Queensland is a centre for the rehabilitation of local flying foxes, many of which suffer from tick paralysis. It is mainly Pteropus conspicillatus (spectacled flying fox) which is afflicted. It is still a mystery as to how they are picking up the ticks.

Kangaroos

Ticks are common and generally cause no problem, however the paralysis tick can cause signs in some joeys on first exposure. Removal of the tick is usually sufficient to allow recovery. Treatment with canine tick antiserum should be approached with caution.

Reference:

Bellamy, T: Hand rearing Native Animals, in Proceedings No Australian Wildlife; University of Sydney Post Graduate Committee in Veterinary Science, 199

Koalas

Ixodes holocyclus, Haemaphysalis spp. Native koalas with no previous exposure are reported to be susceptible to the paralysis tick Ixodes holocyclus. For this reason coastal areas of eastern Victoria within the range of this tick are usually avoided when koalas are translocated from other parts of that state.

Ticks concentrate their blood meal while feeding. A fully engorged adult female I. holocyclus may weigh 1 gram but each tick may have been responsible for for removal of around 5 mL of blood from the host. Exsanguination during heavy tick infestation can therefore be an important cause of morbidity or mortality.

The "tick season" on the North Coast of NSW August to March coincides with the time that juvenile koalas leave their mothers. Many cubs and occasionally adult koalas are found debilitated or dying as a result of heavy infestation with I. holocyclus and Haemaphysalis spp ticks. Changes to the natural habitat which force koalas to travel long distances between trees through dense scrubby undergrowth are though to predispose toward heavy infestations.

Clinical signs

Koalas may be bleeding freely at the site of tick attachment (which is often around the throat). Some animals flick their paws spasmodically as if agitated. Pale mucous membranes and oedema of the face, neck and abdomen may be apparent in severely anaemic koalas.

Diagnosis

Blood samples collected from free ranging koalas from Walkerville, on the southern coast of Victoria, showed mild anaemia and relative eosinophilia attributed to heavy infestations of the opossum tick Ixodes tasmani during Spring and Autumn. Significant reductions in erythrocyte count, packed cell volume, and haemoglobin concentration, as well as elevation in eosinophil count , were noted during comparison of samples from Walkerville koalas in Aug 1980 and Jan 1981, in association with increased tick numbers.

The regenerative response to haemorrhagic anaemia caused by ticks was studied by collecting serial blood samples at about weekly intervals from two adult and four juvenile or sub-adult, tick infested, free ranging koalas brought into care from the Port Macquarie area in northern NSW. All koalas initially had reduced erythrocyte counts, PCV and haemoglobin levels. Intense regenerative regenerative responses overcame this normocytic, normochromic anaemia within 2-3 weeks of removal of the ticks. Recovery was characterised by high levels of circulating reticulocytes (up to 40% uncorrected, normal 0-6%), nucleated red cells (up to 200 per 100 white cells, normal 0-10), marked polychromasia and anisocytosis, and prominent erythrocyte inclusions evident in Giemsa stained smears. Absolute eosinophilia was also common during recovery.

Transmission electron microscopy of the erythrocyte inclusions showed them to be primarily iron filled mitochondria. It is now thought possible that these inclusions may have been Haemobartonella sp. A frequent association between Haemobartonella infection and tick infestation has been previously noted.

Treatment

Physical removal of adult ticks, and bathing koalas in Ectodex (TM) (Schering) if many nymphs are present, has been recommended. An oral iron supplement is sometimes added to the supplementary feed (e.g. Incramin (TM) baby iron drops (Lederle Labs) 4-6 drops daily).

Reference: 

Blanchard, W H: Medicine and Husbandry- Koalas, in Proceedings No , Australian Wildlife; University of Sydney Post Graduate Committee in Veterinary Science, 199

Platypus

Ixodes ornithorhynchi is a host specific ticl found mainly around the base of the hind feet, forefeet and the base of the tail of the platypus. larvae, nymph and female ticks occur on the platypus, while males have never been found. It is presumed that the males live their life in the platypus burrows.

In wild Victorian platypus, burdens varied from 0-90 with burdens of 6-20 being the most common. As reported by Whittington and Spratt, 1989, higher burdens were not associated with lower packed cell volumes. Probably their greatest harm is as the likely vectors of the red cell parasite Theileria ornithorhynchi.

In captivity, ticks are readily controlled with an injection of ivermectin at a dose of 200 mcg/kg subcutaneously when platypus are first brought into the captive situation. Reinfestation has not occurred in captivity. Amblyomma triguttatum trigutattum has also been recorded from platypus.

Reference:

Booth, Monotremes, Wombats and Bandicoots, in Proceedings No Australian Wildlife; University of Sydney Post Graduate Committee in Veterinary Science, 199

Reptiles

Ticks are found on members of all reptile groups and are especially common in Australian pythons. Species of the genera Amblyomma, Aponomma, Hyalomma and Ornithodoros are most common. They rarely occur in such heavy burdens as mites but are potential pathogens, causing anaemia, ulcerative skin lesions and acting as vectors for protozoal blood parasites and filariae... see p503 for further info

Bluetongue lizards

Reptile ticks are commonly found on blue-tongues; they attach under the scales and in the ear canal. They do not normally attach to mammals, and are not known to cause paralysis (Glenn Shea, Australian Museum)

Reference: 

McCracken, H: Reptile Disease in Proceedings No Australian Wildlife; University of Sydney Post Graduate Committee in Veterinary Science, 199

Wombats

Aponomma auruginans- wombat specific, probably the most common; Ixodes cornuatus- recorded from Powelltown, Vic; Ixodes victoriensis- few specimens recorded; Ixodes tasmani- wide host range.

Reference:

Booth, :Monotremes, Wombats and Bandicoots, in Proceedings No Australian Wildlife; University of Sydney Post Graduate Committee in Veterinary Science, 199