Thursday, 17 March 2011

Parasitic worms, bacteria and more

For those of a squeamish disposition, I would suggest that this is perhaps not the post for you. If the thought of parasitic infestation and other things related to our gut and nether regions fill you with that 'euch' feeling, best to stop here now.

For those brave souls who continue with me (hopefully not too shortly after a large meal), this is another one of my 'other musings' posts which might have some relevance to autism spectrum conditions at some points. Unlike other articles on this topic, I am not posting any graphic images showing tapeworm infection or anything like that; just my words and your imagination - now there's a psychology experiment.

Parasitic infestation. It conjours up some kind of Hollywood horror film like one of my favourites the 1978 'Invasion of the Body Snatchers' starring Donald Sutherland. Unfortunately like many things, parasitic infestation has been given a bad rap in recent years. The truth is that without such infestation, it is questionable whether any of us would be here at all.

My very limited knowledge of parasites and worms (not the earth-variety) has been growing in recent weeks. Partly as a result of an interest in how such parasitic infestations of the human gastrointestinal tract might actually be beneficial from an immune point of view at least in some cases, and partly because of the potential applications of such a 'therapeutic' tool to various autoimmune conditions.

Many authors who adhere to the 'hygiene' hypothesis as potentially explanatory of the rise of allergic diseases in modern society have talked about our increasing preoccupation with cleanliness and how various infestations that would once have been considered the 'norm' not so many hundreds of years ago are now seen as abnormal and perverse. Granted there are some infestations (such as head lice) which don't seem to serve any immediate benefit to their host (i.e. us). More and more it seems though that certain, specific infestations could carry a more symbiotic relationship potentially offering equal benefits to us and the worms wishing to reside inside our murky depths.

A recently published trial looking at the potential benefits of hookworm infestation on gluten challenge in coeliac disease caught my eye today. The paper suggested that such a therapy was well-tolerated but unfortunately showed little effect on symptoms following a gluten challenge. This however follows other trials using such helminthic therapy suggestive of a more positive effect for other gastrointestinal conditions such as Crohn's disease and other inflammatory bowel conditions.

Don't get me wrong: I know that many other studies have highlighted the potential negative effects of parasitic infestation on health, particularly in Africa and other developing nations. It strikes me that factors such as age, general health, environment (i.e. clean water) and specific pathology seem to be the major forces in balancing benefits against negatives of such infestations; also allowing for the fact that different organisms present with different effects to their host.

How does this tie into autism? Well it doesn't per se. Aside from a few posts about co-morbid parasitic infections in autism on the internet, things like giardia causing giardiasis (related to pica?), there is perhaps no immediate benefits to be seen. If one however explores the possibility that a co-morbid inflammatory bowel problem may be present alongside the autism, the potential perhaps seems more apparent [please note I am not recommending this as an intervention option merely as a potential area for further investigation].

Right moving from worms to bacteria. Many of my posts seem to end up talking about gut bacteria and its possible connection to all sorts of conditions including autism. I would not say that I am obsessed with gut bacteria but I can't help but feel that it is a much under-rated part of our physical being.

OK formalities out of the way, how would you feel about a fecal transplantation? Yes you heard me; taking the stuff-that-nobody-likes-to-talk-about and transplanting it to another person. Mmm, you are probably thinking is he serious? Well, yes I am.

Fecal transplantation (under various names) is something under investigation and being used for quite a few different things including pseudomembranous colitis (caused by clostridium difficile infection). The theory goes that our stools contain our gut bacterial fingerprint, and in cases where not-so-nice bacterial species take hold, a donor provides a 'sample' which supposedly helps to recolonise the gut with the much-better bacteria.

I could see quite a bit of consumer resistance to such a therapy. It is perhaps not surprising that it tends to be the last line of treatment when it is used. The theory however does not seem as outlandish as first thoughts suggest; indeed if one were able to overcome the palatability of the intervention (i.e. being given an enema and being fed through a nasogastric tube, made up from another person's stool) one might suggest it could be of interest. There is also some development in PR in this area in terms of formulating the stool into an oral dosage form to further help its image.

There are lots of questions still to answer about this form of therapy. The first issue I thought about was all the other 'stuff' in our stools and whether we yet know enough about the gut microflora to be able to 'transplant' it without creating new problems (remember HIV transmission and hemophilia). I know that the transplantations are normally from family members and are screened for known agents (emphasis on 'known') but there is still lots and lots of questions to answer. Some of these questions are hopefully being answered through studies such as this one.

Again back to autism - how does this fit in? Well there is some evidence accumulating to suggest some cases of autism are associated with unusual gut bacterial profiles and in particular the role of specific clostridia species. Likewise, selective decontamination of the gut with drugs like vancomycin have been shown to potentially affect autistic symptoms (at least in the short-term - homeostasis?). The question is whether the area of fecal transplantation represents a next step or a step too far?

I hope that readers have not been too grossed out by all this talk of worms and poo. I promise my next post will be something altogether more pleasant. Over to you Donald Sutherland..