Tuesday, 30 April 2013

Lyme and soda: hold the autism risk?

I've talked about the mighty tick previously on this blog and some speculation on how a tick harbouring the bacteria Borrelia burgdorferi (or a close relation) bites and transmits said bacteria to humans which can lead to Lyme disease and whether this might be implicated in some cases of autism.

 Tickety boo @ Wikipedia  
The suggestion from that post was that whilst the data was speculative and relatively sparse at that time on whether Lyme disease is common in cases of autism or indeed could 'cause' autism, there might be some room to test one or two hypotheses regarding a possible link between the two conditions.

Two years on, I'm happy to report that someone has finally looked at the possibility of a connection in the form of a letter by Mary Ajamian and colleagues* published in the journal JAMA. The results: no link between Lyme disease and autism in a sizeable cohort of children/young adults with autism or indeed Lyme disease and control participants.

The ins-and-outs of the study have been quite widely reported, for example with headlines like: 'Autism-Lyme Correlation Debunked' and 'Autism And Lyme Disease Link Is Bunk, Study Says'. Using a two-tiered assay based on initial screening for antibodies to B.burgdorferi (IgG and IgM) and Western blotting for antibodies in suspect cases, the authors were systematically able to test for signs of infection and found pretty much nothing.

Interestingly, the authors are quoted as saying that their study, whilst well-powered and based on the US CDC advice for screening for Lyme disease, might not necessarily spell the end of any association between Lyme disease and autism. To quote from this news source: "The researchers also pointed out that their analysis did not address the question of whether Lyme disease might cause autism-like behavioral deficits". That for example earlier infection during infancy or even in-utero might be linked to cases of autism was not part and parcel of the Ajamian study. Certainly with all the recent speculation turning to the earliest time of life being linked to autism risk - think folate and valproate for example - I don't think we are in a position to yet discount such possibilities. That and the renewed focus on the tetracyclines with autism in mind (used to treat Lyme disease).

But....

The Ajamian study must be seen as compelling evidence that no current infection pertinent to Lyme disease exists in cases of autism or controls, or at least the cases that were under investigation. I know infection is still quite a hot potato when it comes to autism risk (remembering this study by Hornig and colleagues** and all that XMRV overspill into autism spectrum disorders) bearing in mind the continued speculation on all those possible in-utero exposures whether viral or bacterial. I would bring you back to that most classical of autism risk factors - congenital rubella as per the study by Chess and colleagues*** - as evidence that external agents might be associated with autism onset and how the wider search for potentially linked pathogens should not be tarnished by the latest findings.

Update (10/05/13) And just a few days later... Lack of serum antibodies against Borrelia burgdorferi in children with autism by Burbelo and colleagues****.

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* Ajamian M. et al. Serologic markers of Lyme Disease in children with autism. JAMA. 2013; 309: 1771-1773.

** Hornig M. et al. Lack of association between measles virus vaccine and autism with enteropathy: a case-control study. PLoS ONE. 2008; 3: e3140.

*** Chess S. et al. Behavioral consequences of congenital rubella. J Pediatr. 1978; 93: 699-703.

**** Burbelo PD. et al. Lack of serum antibodies against Borrelia burgdorferi in children with autism. Clin Vaccine Immunol. May 2013.

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ResearchBlogging.org Mary Ajamian, Barry E. Kosofsky, Gary P. Wormser, Anjali M. Rajadhyaksha, & Armin Alaedini (2013). Serologic Markers of Lyme Disease in Children With Autism JAMA, 309 (17), 1771-1773