Bloody Ticks

WARNING: PICTURES OF TICKS MAY MAKE YOUR SKIN CRAWL

I’m gonna let you in on a secret. Growing up, I used to be obsessed with removing ticks from my dog in Ghana, and sometimes keeping them in detergent to see how long they would survive for. Would say sorry mum and dad but they already know this. I was a weird child. Oh whoops, I still am. Weird and proud.

It sounds disgusting but I was helping my poor dog. I can distinctively remember there being two types. The first type was small and reddish, it was never filled with much blood and was very difficult to remove. It was also difficult to kill so I had to use a part of the broom stick and a hard stone to squish it to death. The second type was grey, early in development they were tiny dot babies and later were large, engorged with blood so easy to kill. The engorged stage was always surrounded by the early stage ‘babies’ as well as what looked like a larger version of the reddish tick. These large engorged ticks were easy to remove, sometimes just falling off. They were disgusting little creatures but hilarious when flipped on their backs; they would just wriggle trying to flip over.

Ticks are arachnids just like spiders. There are two families of ticks, the Ixodidae (hard ticks), and Argasidae (soft ticks). Through reading now I know it wasn’t two different types of ticks on my dog, just different stages of the hard tick which have different morphologies through their life cycle.

Ticks go through four stages of life; egg, 6 legged larvae (or seed tick), 8 legged nymph, and adult. After hatching from the eggs, as obligate blood feeders all other stages of ticks must feed on blood to survive. Some ticks need different hosts for this development to complete their life cycle, however dog ticks feed on the same host throughout their life development. That is why I could find different tick morphologies on the same dog. They have a great easy source of blood so why venture elsewhere?

The engorged adult drops off and lay thousands of eggs which develop to larva. They possess a sensory apparatus called 'Haller's organ’ (basically front legs) which they use to find their hosts by detecting animal breath and body odors, or by sensing body heat, moisture, and vibrations. They then use their outstretched legs to attach to a potential host, later finding thin skin to insert their feeding tube and sometimes secreting anaesthesia and/or a cement-like substance that keeps them firmly attached during the duration of their blood meal. Through the blood meal both tick and host may transmit pathogens to and from each other.

Personally, the three interesting areas of ticks are their mouthparts, saliva and mating.

The mouthparts differ slightly between soft and hard ticks in terms of visibility, the hard ticks having more visible components compared to the soft ticks. Two outside highly mobile palps, two chelicerae and the protected central hypostoma (feeding tube). The palps stay outside not entering the skin, the chelicerae pierce the skin and move forward and backwards in a breaststroke-like motion creating a wound for the penetration of the hypostome. The hypostome has projections directed backwards for strengthened attachment when it plunges into the skin.

Ticks saliva is functional. They can produce a milky white material that hardens surrounding the hypostome. This secretion occurs for up to 72 hours adding layers, strengthening the attachment of tick to host during feeding. There is also an increase of saliva production which has active substances such as anticoagulants, vasodilators, anti-inflammatory agents etc playing a crucial role in modulating the inflammatory response in the host.

What I thought was a ‘red tick’ next to a ‘grey tick’ was actually a male and female tick mating! The male tick feeds briefly and does not feed to engorgement like the female. Whilst the female tick continues feeding, the smaller male remains on top of the female tick and mates.

What diseases do ticks transmit?

Ticks can transmit all sorts! Anaplasmosis, Ehrlichiosis, Lyme Disease, Rocky Mountain Spotted Fever, Tick Paralysis and more.

Ticks not only infect dogs but humans, cows, rabbits and more. This makes them very important pathogen carriers. Lyme disease for example is endemic in regions in England during summer due to disease carrying ticks found in woodland areas and even gardens, and the increase time we spend outdoors in good weather. Of course I think ticks are pretty cool creatures but next time I will stay away from ticks just in case a hypostome plunges into my skin.

Further reading:

How ticks get under your skin: insertion mechanics of the feeding apparatus of Ixodes ricinus ticks: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3826218/

Of ticks, mice and men: understanding the dual-host lifestyle of Lyme disease spirochaetes: https://www.ncbi.nlm.nih.gov/pubmed/22230951