Friday, 16 December 2011

Autism and gastroenteritis

Somethin' fishy @ Paul Whiteley 2010
We've all suffered from it at one point or another. That uncontrollable feeling of having to get to the toilet and, pardon my language, squirting from one or both ends for hours or even days at a time, in a manner quite unbefitting our usual habits. This scenario often follows either a very badly prepared meal - 'I knew I shouldn't have had the prawns', contact with a fellow squirter (and some viral/bacterial currency exchange) or after a visit to some exotic part of the world. I am sure that many people might raise a smirk at this description; that is until they are the ones taking up residence next to the toilet in order to get there in time. I am of course referring to gastroenteritis and from here on in, be prepared for bacteria, viruses and poo.

Gastroenteritis is another quite nebulous diagnosis in terms of what exactly it is and indeed how it is managed. The medical terminology refers to inflammation of the gastrointestinal tract caused by either a virus or bacteria. Having said that, its a little like saying you have a cold, in terms of what a cold covers and the numerous causes of it. One of the more recent studies on infectious intestinal illness here in the UK by Tam and colleagues* (open-access) estimated that case numbers are high and contribute quite substantially to the overall healthcare burden.

Gastroenteritis is not normally a serious condition. I say not normally but don't be under any disillusion that many thousands, hundreds of thousands of people around the world contract gastroenteritis and, particularly in developing countries, it ends their days especially young children. Even in our 'developed' societies, gastroenteritis for very young children or for the very elderly can be dangerous as a result of things like the dehydration it can bring. The causes of gastroenteritis as I said are numerous; ranging from various bacteria to various viruses.

NHS Choices lists a separate entry for gastroenteritis in children. It talks about the near certainty that children will come into contact with the pathogens which can cause viral gastroenteritis, particularly the Norovirus and rotavirus and sapoviruses, as a function of children being children, mixing with one another and not always having ideal handwashing practices. Perhaps one of the only redeeming features is that generally speaking, immunity is built up to the viruses after multiple childhood contacts and subsequent reinfections often tend to be fairly minor.

OK, descriptions finished, how does this relate to autism spectrum conditions?

I should perhaps make a distinction here when I talk about gastroenteritis and autism, in that I am not talking about chronic gastroenteritis as detailed in one of my previous posts, but rather the more transient type present particularly in early childhood. Having said that see a little later in the post. Gastroenteritis has been mentioned in the case histories of quite a few people with autism involved in research. This paper for example (which was discussed in this post), discusses hospitalisation of one child for dehydration following gastroenteritis. Indeed, Kanner is his description of autism in 1943 noted bouts of gastroenteritis in the early histories of some of his cohort. OK, I hear you say, individual cases do not a relationship make. That is true.

There is some evidence that episodes of gastroenteritis, viral gastroenteritis, 'might' be slightly more common in autism than other populations. This paper reported a non-significant increase in reported viral gastroenteritis in autism cases in the first 2 years of life using a case-control study design. The prevalence was non-significant but the authors saw fit to discuss it, perhaps because of some increase in frequency when looking at the children in their cohort who were more severely affected with autism.

Without trying to make too many connections that might not be there, this recent paper on prolonged viral gastroenteritis potentially being related to inflammatory enteropathy in immuno-deficient hosts makes me wonder about any possible link between episodic gastroenteritis and more long term issues. This in light of previous research talking about immune system issues in some cases of autism.

The case has not yet been made to suggest that episodic gastroenteritis is anything but a coincidence in cases of autism, caused by the same risk factors as that noted in everyone else. Having said that, the various other research examining a more chronic inflammatory bowel condition associated with some cases of autism, does perhaps incline us to start looking more closely at episodic gastroenteritis in cases of autism and whether there is any more direct connection to be had.

* Tam CC. et al. Longitudinal study of infectious intestinal disease in the UK (IID2 study): incidence in the community and presenting to general practice. BMJ. June 2011