Venomous ticks??

Image of a tick from: www2.outdoorchannel.com

Image of a tick stealing a meal from: www2.outdoorchannel.com

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.

Source:

Cabezas-Cruz A and Valdés JJ. Are ticks venomous animals? Frontiers in Zoology. 11:47, 2014. doi:10.1186/1742-9994-11-47