Illnesses & Diseases From Tick Bites

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The Arachnida family; scorpions, spiders, mites and ticks

Ticks belong to the arachnida family, along with spiders, scorpions and mites. Their life cycle consists of four stages: egg; larvae; nymph and adult. There are over 890 species of tick worldwide. Ticks are parasites and live solely on animal blood. They will feed on human blood just as happily as any other source which is a big problem as some ticks are vectors for some very unpleasant diseases which can be passed on to people whilst the ticks are feeding. During the tick’s feeding, bacteria, protozoa and viruses, that infest the tick, may be passed to the victim.

Ticks do not fly, but they can climb vegetation and hitch a ride on an animal whilst they cling on to it and feed. One of the most common ways for ticks to get into the home is on the bodies of cats and dogs. Once they have finished feeding, they will drop off the host and wait for the next meal to pass by. When a tick has engorged itself on a blood meal, it may nearly quadruple its size (from ~3mm to 11mm); at this stage, you may well see them on your domestic animals.

Tick bite illnesses

There is a wide range of illnesses that stem from tick bites. They can be encountered in most parts of the world. Of these illnesses, the two best known are Lyme Disease and Tick Born Encephalitis.

Please note that not all tick bites will result in an illness – the tick must be host to the pathogens that cause the diseases in the first place to become a disease vector.

Lyme Disease

Probably the best known tick borne disease that affects humans is Lyme Disease, which is a bacterial infection passed on by the tick bite. The symptoms resemble many other illnesses (for instance, flu) and so can be difficult to identify. The cardinal symptom (which will manifest in 70% of victims) is a red circular or oval rash which expands over time. The illness can be successfully treated with antibiotics in its early stages, but if untreated can go on to cause arthritis, heart and neurological problems.

There is some evidence to suggest that a tick bite from an uninfected creature may provide protection against Lyme disease through an acquired hypersensitivity against other bites (this is similar to an allergic response).

Tick Borne Encephalitis

In central Europe, tick bites carry with them the risk of Tick Borne Encephalitis (TBE). This illness can be fatal, causing meningitis, so in many areas, such as in Austria, immunisation campaigns are carried out. The initial phase of TBE takes place 1-2 weeks after the bite and consists of fever, myalgia and headache. Somewhere between 5-15% of victims progress to phase 2 which involves the central nervous system (meningitis, meningo-encephalitis or meningo-encephalomylitis) – this group is considered to suffer from TBE and a small percentage of these victims will die.

Other illnesses

In the USA, other tick born illnesses include: Rocky Mountain Spotted Fever; Ehrlichiosis; Anaplasmosis and Rickettsia Paekeri infection.

If a tick is still attached to you, remove the creature with a pair of tweezers by applying a steady rearwards pull. It is then a sensible precaution to seek medical advice – but remember the majority of these bites are innocuous.

References & Further Reading