Ticks are blood-sucking arthropods that can act as vectors for various diseases in both animals and humans. A recent article published in Frontiers in Zoology summarizes findings that suggest ticks may also be considered venomous ectoparasites. For example, Ixodes holocyclus is a species of Australian tick whose saliva can induce paralysis in humans and animals. According to the new article, about 8% of known tick species can induce paralysis. Ornithodoros savignyi ticks even secrete a lethal salivary toxin (for mice at least). Several proteins from venomous families have been identified in tick saliva such as:
- Kunitz peptides: target ion channels and inhibition of enzymes that degrade proteins, aka proteases
- Cystatins: another protease inhibitor
- Defensins: small proteins that in ticks act as antimicrobial proteins and in some species can break down red blood cells
- Lipocalins: cardiovascular effects and blood clot inhibition
- Phospholipase A2: function in ticks unclear, may help with prolonged feeding
- Lectins: tick lectin shown to suppress the immune system of mice
Based on these components of tick saliva, the study authors argue that ticks should be considered venomous ectoparasites.
Cabezas-Cruz A and Valdés JJ. Are ticks venomous animals? Frontiers in Zoology. 11:47, 2014. doi:10.1186/1742-9994-11-47
In the spring of 2010, while lying in the grass of a California Blue Oak grove, a Spinose Ear Tick (Otobius megnini) crawled into my left ear and began sucking. It stayed in my ear for 80 days. Although I felt a strange rumbling shortly after attachment, and went to a doctor to check my ear out (he didn't see the tick, but saw lots of wax) I didn't think much of it. Gradually I noticed my arms and legs "falling asleep". As time progressed my thinking began to get foggy, the world outside seemed hard and harder to connect with. I visited a doctor, and while at his office I heard a loud rumbling in my ear and out popped this round "Volkswagon Bug" shaped tick.
Over the past 4 1/2 years I have been mostly disabled as a result of the tick's venom. It seemed that once the tick left, the process of building up venom switched to releasing the venom. Soon my body swelled up with fluid and I gained around 25 pounds. I developed acute bronchitis that lasted three years and, in the early stages, a great sensitivity to anything that could be the least bit toxic. I remember picking up an old garden hose and immediately my whole arm turned a flaming red which caused great pain for about fifteen minutes.
In November 2012 the ringing in my ears reached a very loud volume, the next day or so it appeared to me that the acidic venom began to pour out of my ear and down my throat. Inside my throat was covered in blisters, my tongue, lips, chin and exterior throat were bloody in color. I felt like I had swallowed slate! It was as if I had ingested a powerful acid. I could not eat for several weeks, living on yogurt and chocolate soy milk. I spit out pints of phlegm. I think the acid burns penetrated from my mouth and throat all the way out to my skin. My skin today is still misshapen.
The process of elimination comes in waves. November 2012 was the biggest wave. In February this year another wave erupted. It was still quite strong and disabling, but I was able to function. Right now, I am going through another wave. This one it seems the toxin isn't flowing out in bursts, but rather a slow steady drain. Also the neurotoxin has accumulated in my toes and my head (first it was my legs, then my feet, now my toes). My sinuses are burning, but compared to 11-2012, it is mild. I haven't found much at all about this condition, doctors are perplexed by my disorder, but go along with trying to help me. I haven't heard of anyone else has had an experience like mine. If my story could be of help in understanding more about tick venom, I am willing to communicate with anyone doing research on this matter.
Amazing story - thanks for sharing
You can imagine how *I* felt at around 2am after a lively New Year's celebration in the bush when I discovered a tick attached to my scrotum....