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ticks

ticks in Australia

introduction

  • ticks are blood sucking, external parasites which belong to the order Acarina (which also contains mites)
  • Australia has ~75 species of ticks which are divided into 2 families - soft ticks (family Argasidae of which there are only a few species), and hard ticks (family Ixodidae).
  • the main tick of medical concern is the Paralysis Tick (Ixodes holocyclus).
  • tick bites may cause hypersensitivity reactions and rarely, anaphylaxis
  • other diseases potentially spread by ticks in Australia include:
    • Tick typhus is an infection with a rickettsia transmitted from native animals by ixodid ticks and is confined to the eastern coast line of Australia and Bass Strait Islands. Clinical symptoms include headaches, multiple rashes, swollen glands, fever and flu like symptoms. The disease is rarely fatal and is commonly treated with antibiotics.
  • diseases spread by ticks in USA but not currently recorded in Australia include:
    • Lyme disease - although first global description was in the Hunter Valley in Australia, there are no confirmed cases in Australia since the 1980's.
    • Rocky Mountain spotted fever - Rickettsia rickettsii spread to humans by Dermacentor ticks. Widespread throughout most of USA and including southern Canada, Central America and parts of South America.
    • Colorado Tick Fever - viral infection usually in March-September with peak in June. Mainly found in the high regions of western USA and Canada.
    • Babesiosis - Babesia microti is endemic in the Northeast of USA.
    • Ehrlichiosis - Ehrlichia chaffeensis is a gram negative coccobacillus causing an illness like Rocky Mounted spotted fever but without the rash. Most commonly foud in the south central states of Missouri, Oklahoma, Tennessee and Arkansas.
    • Anaplasmosis - Anaplasma phagocytophilum is a gram negative coccobacillus and the cause of human granulocytotropic anaplasmosis, formerly known as human granulocytic ehrlichiosis. Human infection first described in the late 1990's. Most commonly transmitted in May-June by the deer tick and other ixodes species.

the Paralysis Tick

habitat

  • main host is the bandicoot.
  • mainly confined to a 20km wide area along the eastern coast of Australia and are especially common in wet sclerophyll forests and temperate rainforests.
  • the 6-legged larval tick sits at tips of vegetation awaiting a host to brush past then they attach to the host feed on blood for 4- 6 days then drop off so they can moult to the 8 legged nymphal stage.
  • nymphs require a further blood meal for 4-8 days before moulting to the adult stage.
  • the 8 legged adult female Paralysis tick will feed for up to around 10 days, drop off the host and lay eggs over several weeks.
  • adults are more abundant in the spring and the early summer months, larvae in mid to late-summer, and nymphs during winter.
  • ticks may wander on the body for 2 hours or so before attaching, and often prefer to migrate to behind the ears or the scalp.
  • very susceptible to dry conditions as eggs need to be deposited in moist leaf litter.

clinical features

  • mainly children affected (ticks take a high toll on pets every summer)
  • initial symptoms of tick paralysis may include unsteady gait, increased weakness of the limbs, multiple rashes, headache, fever, flu like symptoms, tenderness of lymph nodes, and partial facial paralysis. Tick paralysis develops slowly as the tick engorges, which will take several days.
  • Despite the removal of the tick, the patient's condition typically will continue to deteriorate for a time and recovery is often slow.
  • Undetected ticks are another possible reason for any prolonged debilitation.
  • antitoxin is available from CSL.

tick removal

  • If a tick is detected that is attached, never attempt to place any chemical such as methylated spirits onto the tick, nor should it be touched or disturbed, as the tick will inject saliva into the skin, which could make the situation worse.
  • a tick’s mouthpiece is barbed, not spiralled, so twisting the tick to pull it out doesn’t help.
  • the tick should be sprayed with an aerosol insect repellent preferably containing pyrethrin or a pyrethroid (if a repellent cannot be found which contains a pyrethroid, then Lyclear, a scabies cream containing permethrin will work fine).
  • The combination of hydrocarbons and the pyrethrin acts as a narcotic and a toxicant, and prevents the tick from injecting its saliva. The tick should be sprayed again one minute later (or dabbed with the Lyclear) and left.
  • After 24 hours it should drop off naturally or be gently removed with fine-tipped forceps placed as close to the skin as possible.
  • It is normal for a tick bite to remain slightly itchy for several weeks.

prevention

  • if walking in tick infested areas:
    • wear long trousers and tuck into socks, and tuck shirts into pants
    • wear light coloured clothing so you can see ticks on clothing easier
    • An insect repellent containing DEET or Picaridin should be applied, with a cream repellent applied to the skin and a spray repellent to footwear and clothing
    • reapply repellant every few hours
    • on returning home, remove all clothing and place in hot dryer for 20 minutes which will kill all remaining ticks
    • examine children and pets for ticks on returning from bushland areas.
ticks.txt · Last modified: 2011/04/15 18:39 by gary