Another take on ticks: ’tis the season

Mary Gardner

Without my friend noticing, a creature smaller than a little fingernail was perched on a stem of grass and leapt to the safety of his sock.

A brave act on the part of a blind and deaf animal, following the whiff of butyric acid in the sweat of mammals.

Although starving, the little one then climbed right up to the base of my friend’s neck and dug in. Literally.

That, for you, is a tick.

Using sharp jagged mouth-parts, the tick pierced the skin and burrowed, reaching safety as well as a supply of fresh blood. He settled in for a ten-day leisurely feed. But my friend noticed some irritation and spotted him. I sprayed the animal with an ether, freezing it to death.

All that advice to cover ticks with cremes or simply remove with tweezers? These are overseas tips, all wrong for the Australian paralysis tick Ixodes holocyclus. This is the most common tick found on people in our eastern seaboard. The Australasian Society of Clinical Immunology and Allergy (ASCIA) finds that this tick has different mouth-parts and feeding habits unlike overseas ticks.

Paralysis ticks have toxins in their saliva

The paralysis tick has toxins in its saliva. Different people’s reactions are unpredictable but can be life-threatening. Given this unique situation, the Australasian Society of Clinical Immunology and Allergy (ASCIA) says ‘freeze it, don’t squeeze it’.

Use FIVE squirts of a dimethyl ether spray. This will kill the tick in place, minimising its fright response. A scared tick injects more toxins. Once dead, the tick will fall out, or can be removed with tweezers.

Human reactions to the tick toxins can range from mild itching to respiratory shock, paralysis and death. Another side effect is a subsequent allergy to red meat and gelatin products. Repeated tick bites may start an allergic reaction or increase its severity.

In February 2019, research began into what afflicts people here who have Debilitating Symptoms Complex Attributed To Ticks (DSCATT). Overseas, Lyme’s disease is caused by a bacterium which, to date, has not been found in wild Australian ticks. But as ticks worldwide are renowned for carrying pathogens, researchers suspect that there will be some sort of bacteria or virus living in Australian ones too.

Seventeen species bite people

Of the seventy species of Australian ticks, only seventeen bite people. The paralysis tick belongs to one group of fifty-six species called hard ticks (family Ixodidae). Their mouth-parts stick out from their heads. They live in low vegetation, sniffing for mammals.

Soft ticks (fourteen species, family Argasidae) have mouth-parts which are held under the body. They travel into the burrows of animals upon which they feed.

All ticks are Arachnids, members of the spider family. As they grow from egg to juvenile to adult, they start with six legs but finally they have eight. They must have a blood feed at each life-stage.

Some species live their whole life eating the blood of one host. Other species find a host, grow, drop off and then find a new host species. Still others, the paralysis tick included, drop off a host at each life stage, working through three different host species over their lifetime.

Some ticks are known for carrying harmful bacteria. In Australia, the ornate kangaroo tick carries Queensland tick typhus, and a reptilian tick carries Q fever.

Ticks better researched overseas

Overseas, ticks have been better researched and are well known for also carrying one of six groups of viruses. Only mosquitoes outdo ticks for transmitting viruses.

The precise match between tick, virus and host is critical. The tick needs blood for nutrition. The virus needs the host’s cells particular DNA or RNA processing systems. The virus subverts the system to make more copies of itself. Often this harms, but does not necessarily kill the host.

The study of ticks and viruses expands our philosophy and cosmology. Biologist Jakob Johann von Uexküll (1864-1944) explained that ticks and every other creature experienced life according to their umwelt: the world revealed to them by their own unique senses and particular needs. This species-specific perspective became a main concept in neurophilosophy. 

Another biologist J.B.S. Haldane (1892–1966) first proposed that viruses played a vital role in the origin of life on earth. In 2009, the idea was expanded by Eugene Koonin. His scenario about a primordial virus world and early evolution suggests viruses are integral to life.

Studies also reveal that viruses are ancient and sometimes very useful. One startling example is about ancient viral infections of early mammalian cells. Viral genes were shared and exist today in modern mammalian cells. They code for protective layers around an embryo. This ‘hides’ the stranger from the mother’s immune system, allowing growth in utero. Otherwise the mother would create antibodies against the embryo.

A final thought. All ticks may well have evolved in the Australian sector of Gondwana in the Devonian era, 398 million years ago. They lived with amphibious labyrinthodonts, swamp predators. Such teams were ancestors of all of us terrestrial animals and our many ticks.