Ticks and mites, itches and fevers

Ticks, ‘scrub itch’ and the illnesses that go with them are known hazards of life in North Queensland, especially for people who spend time in the bush as farmers or bushwalkers. I have wanted to write about them for years but the subject is complicated and I have only recently found time to sort it all out to my own satisfaction.

Here we go, then – but first a disclaimer: my information is the best I can offer but I’m not a health professional. If you’re sick and suspect ticks or mites, please see a doctor. Tell them where you have been, too, as it will probably help their diagnosis.

In brief:
  • Ticks and mites are arachnids. They are not insects but related to spiders.
  • All of them need a blood meal at some stage of their life cycle, and many of them will take human blood instead of their usual fare (i.e., the blood of marsupials, rats, cattle, dogs, etc).
  • Some of their bites provoke an allergic reaction.
  • Some of them inject poisons (toxins) in their saliva as they feed.
  • Some of them inject bacteria (Rickettsia family or others) which can make us very sick with typhus or other diseases. Antibiotics normally clear up these illnesses quite well, if we act quickly enough.
  • Ticks should be removed as quickly as possible when discovered but (importantly) without squeezing their bodies.

Each of these points will now become a longer section, in the same order. Scroll straight to the bottom if you simply want to remove a tick safely.    

Ticks and mites

Arthropods are animals with external skeletons and jointed appendages and they are divided into four main groups: insects (six legs), arachnids (eight legs), myriapods (‘many legs’, e.g. centipedes) and crustaceans (slaters, prawns, crabs and more).

In turn, Arachnids are divided into spiders (about half of the total), scorpions, ticks, mites, and several smaller groups. Ticks (Parasitiformes) and mites (Acariformes) are not particularly closely related but they have evolved similar body plans because of their similar lifestyles.

Eggs of both mites and ticks hatch into larvae, larvae moult into nymphs (juveniles), and nymphs moult into adults. In mites, only the larvae bite us (nymphs and adults live on plants). All three life-stages of ticks, however, live exclusively on blood. Mites are tiny, only around half a millimetre long as adults, but ticks can be several millimetres long.

The mites we are interested in are a group called the Trombiculidae, commonly known as chiggers, spider mites, berry bugs, harvest mites, bush-mites, red bugs or scrub-itch mites. There are photos of adults (larvae and nymphs are too small to photograph) here on iNaturalist. The ticks which concern us are the Ixodidae, the Hard Ticks. Visit this page on iNaturalist for photos of Australian Hard Ticks.

In general, each species of mite or tick has its preferred host species but they find their hosts by chance, often dropping or crawling from vegetation onto the first warm body that gets close enough, so they do bite other victims.

Kangaroo Tick Amblyomma triguttatum
Kangaroo Tick feeding on human host

Health risks of mite and tick bites

The best single-page reference on the health risks that I have located is this page from the Australasian Society of Clinical Immunology and Allergy (ASCIA). It is not too technical for the average reader but it is a longer read than what I have here.

(1) Irritation and Allergic reactions

Bites can trigger allergic reactions, just like the bites of sand-flies, ants or mosquitos, and even the smallest mite larvae can provoke the reaction. Mild swelling and irritation is common but extreme reactions (anaphylaxis) can occur. Treatment is basically the same as for other allergic reactions – antihistamines, soothing skin creams, steroid creams, and, if needed, epipen. “Scrub itch” is our response to bites of mite (and perhaps tick) larvae, in the form of red lumps with or without a rash.

(2) Toxins

Mites and ticks inject a complicated mixture of chemicals into their victims, including anti-coagulants to make the blood easier to extract and an anaesthetic so that the victim doesn’t notice their attack. These can be toxic, but the effect depends on how big the attacker is and how long it is attached. Mite and tick larvae are simply not big enough to inject much poison, but an adult tick can make us very ill.

The Queensland Museum Paralysis Tick fact sheet (pdf) says that, “In the humid coastal region of eastern Australia almost all tick bites on people are from the Australian Paralysis Tick, Ixodes holocyclus.

My own experience suggests their statement may underestimate bites from other species. Most ticks, of course, go unidentified and my own commonsense suspicion is that doctors only see the sickest people, so they only identify only the most dangerous species. All I can say for certain is that we have had a Kangaroo Tick (Amblyomma triguttatum) and a couple of Haemaphysalis but none of the ticks identified in my own family circle have been Paralysis Ticks.

This page is quite technical but very thorough in dealing with tick paralysis. Its key points are:

  • A salivary neurotoxin, only produced by an engorged female tick during feeding, induces paralysis.
  • Symptoms typically develop after the tick has been attached for 3 to 7 days and may vary depending on the species of tick.
  • Most patients with tick paralysis will fully recover with supportive care and removal of the tick.

(3) Bacterial illnesses

Mites and ticks carry bacteria in their guts, and these bacteria can be injected along with their saliva and make us ill. The most common bacteria are varieties of Rickettsia and they give us fevers which are known as Typhus or Rickettsial illnesses. Common symptoms include fever, headache, and a rash, typically beginning one to two weeks after exposure.

There are lots of these diseases worldwide, each caused by a different species of bacteria. They are spread to us by body lice and fleas as well as ticks and mites, from animal hosts including pets, livestock and wild animals. Treatment for all of them is the same so it doesn’t matter so much if tracking down the cause of a particular illness happens to be impossible. I will just mention four that seem particularly relevant:

  • Scrub typhus is caused by Orientia tsutsugamushi spread by mites. (Ref)
  • Queensland tick typhus, aka Australian tick typhus, is caused by the bacterium Rickettsia australis, transmitted by the ticks Ixodes holocyclus and Ixodes tasmani. (Ref 1 Ref 2)
  • Lyme Disease is also caused by bacteria transmitted in a tick bite. The species of tick that carry the bacteria are not native to Australia so it’s not likely you can catch Lyme disease here, in spite of persistent rumours. (Ref)
  • Q Fever is an illness caused by Coxiella burnetii, found in ticks and many animals. It can be transmitted to us by ticks but is most commonly picked up through direct contact with animals. (Ref)

Removing ticks (and mites)

I put “and mites” in brackets because we rarely have to remove them. They are very small and they drop off when they have had enough to eat, and we often don’t notice the bite until afterwards when it starts itching.

Ticks are different. Larvae may drop off after their meal, to moult somewhere else, and so may nymphs. Adult females, though, want a bigger meal and may hang on for hours or days if not noticed and removed. They are bigger and attached for longer, so they can inject more toxins and bacteria, making us sicker.

Fortunately, they are big enough to see. Recommended removal techniques are (1) to kill the tick with insecticide before trying to remove it or (2) using fine tweezers to grab it by the head and pull it out without squeezing the body. (Squeezing the body may inject more of the nasties.)

  • Expert advice from the federal health dept, ASCIA (and video), is that freezing the tick with an ether-containing spray is the best option.
  • If that is not possible, a pyrethrin-containing insecticide is next best – a couple of applications a minute apart, and leave the tick to drop out in its own time. (This is what the Qld Museum recommended a few years ago. They also note that many insecticides are not recommended for human skin contact and scabies cream is therefore the best choice.)
  • Tweezers are the last option, because they may cause the tick to inject more bacteria or toxin.
  • Insect repellent, metho and turps are all worse than useless because they may irritate the tick but won’t kill it.

All sources of expert advice do also say “urgently seek medical attention” as a first or second choice, but we know that’s not always realistic. Anyone camping at (e.g.) White Mountains or mustering at (e.g.) Rainsby is going to have to deal with it on the spot, because the nearest doctor is hours away.

The same expert advice also recommends prevention: hats, long-sleeved shirts, long pants tucked into socks, and insect repellent. Some people I know habitually spray their clothing with insecticide. Avoiding pushing through scrub is a good idea, too, when possible.

If all of the above sounds too worrying, relax. Most of us don’t see ticks very often, and we get over any bites without too much trouble.

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