Thursday, 30 June 2011

Tick, tick, tick...boom

Despite the very dramatic title of this post, I am not going to be discussing explosives nor even the Will Smith (not forgetting Jazzy Jeff) song which carried such lyrical swagger, but rather a few things related to the small but mighty tick (and no, not that tick either). For those of a squeamish disposition who prefer not to see creepy-crawlies and their various effects on body parts, I would perhaps suggest not clicking on this link (or even worse this link) which describes, in quite some detail, how the tick and its bite is potentially linked to a condition called Lyme disease.

For those who didn't click on the link but are still curious, Lyme disease is an inflammatory disease which occurs when a tick harbouring the bacteria Borrelia burgdorferi bites and transmits said bacteria to humans. The name Lyme comes from the place Lyme, USA where an outbreak of the disease leading to a cluster of cases of juvenile arthritis led to the first comprehensive description. The symptoms can include things like lethargy, fever, headaches, muscle pain and in more serious cases, joint inflammation and changes to behaviour. This last symptom relating to behaviour is a little non-descript although some people have speculated that this could include autistic-like behaviours. Bacteria affecting behaviour also conjours up some interesting links with the many and varied posts made on this blog relating to how external organisms might be able to affect our presented behaviour; but I digress.

Looking on the web, there is quite a lot of interest in a possible connection between Lyme disease and lots of different conditions. Chronic, persistent Lyme disease has found some overlap with conditions such as Chronic Fatigue Syndrome / Myalgic Encephalomyelitis (CFS/ME) and fibromyalgia (FM) given the described similarities in symptoms. Indeed, there is some evidence that Lyme disease may co-exist alongside conditions such as FM, although a universally causative relationship has not yet been established. As mentioned, a particular form of arthritis is one of the more serious symptoms associated with Lyme disease but there are a variety of other effects linked to the nervous system for example.

Autism has also been speculatively linked to Lyme disease, although I would perhaps emphasise the 'speculatively' side of things. The evidence for an association is sparse to say the least, and currently non-existent (at least in PubMed listed journals) in terms of data on things like serological co-morbidity and any potential effects on autistic symptoms following infection or treatment for Lyme disease. That being said, the prescribed treatment schedule for Lyme disease utilising antibiotics such as the tetracyclines has found some initial favour in the management of symptoms in autism-linked conditions such as Fragile X syndrome albeit tied into potential effects outside of antimicrobial activity.

Although the data is sparse, there is some common sense reason for looking at the potential involvement of Lyme disease in some cases of autism. As per my comments in previous posts, autism is not protective of developing other conditions/diseases/infections, so one could perhaps see that a child with autism walking in woodland with their parents would be at equal risk of being bitten by a tick as everyone else. Whether or not there would be some increased likelihood of being bitten is not known. Gestational Lyme disease, diagnosed on the presence of anti-Borrelia burgdorferi antibodies, can be associated with adverse neonatal and post-natal outcomes for the infant. This, despite the fact, that pregnancy might actually provide some protective immunological effects. Some of the adverse outcomes described by Nadal and colleagues show some possible connection to autism (hyperbilirubinaemia, hypotonia, macrocephaly) but it is altogether a different thing to say that such outcomes related to autism might be caused by secondary Lyme disease. Further research would perhaps be required.

I appreciate that for some people thinking about ticks and what they could do is spine-tingling stuff. Suffice to say that the risk of getting a tick bite is pretty low assuming that a few precautions are taken, not least keeping away from tick hotspots (long grass off the beaten track where deer may roam).