Thursday 4 June 2015

Clinical course of schizophrenia and Toxoplasma gondii infection

Regular readers of this blog probably know that I'm quite interested in the idea that the parasitic organism known as Toxoplasma gondii might have some rather interesting 'connections' to the presentation of [some] schizophrenia (see here). That the cat that might be sat in front of you as you read this post might have the ability to 'share' such a marvellous organism such as T. gondii as per the 'feline zoonosis theory of schizophrenia' (see here) is another aspect that has been also been discussed.

The paper by Tuncay Çelik and colleagues [1] (open-access available here) further adds to the growing peer-reviewed literature on this topic with their findings indicating that: "Toxoplasma-infected subjects had 15× higher probability of having continuous course of disease [schizophrenia] than Toxoplasma-free subject." I might add that before anyone gets the wrong idea about the labelling of schizophrenia as a 'disease', those are the authors words not mine.

A few pointers on the Çelik study might be useful:

  • A total of 94 participants diagnosed with schizophrenia (median age: 40 years) were included for study. Various details were garnered about participants including "illness status, clinical course, awareness of the illness, electroconvulsive therapy, compliance with medication and illness type" and used as 'indicators of prognosis' to "compare with the anti-Toxoplasma gondii serological status."
  • Blood samples were provided to screen for anti-Toxoplasma gondii IgG antibodies - a measure of recent or past exposure to T. gondii - and participants were grouped according to seropositivity or not. 
  • Results: approaching half of participants were positive for anti-Toxoplasma gondii IgG antibodies (46%). Based on reports of illness status - chronic, partial remission or remission to a great extent - the "T. gondii seropositivity rate among ‘chronic’ patients was found to be 72% whereas it was 22% in partial remission group and no case was positive in remission to a great extent group." This implies that those with an on-going presentation of schizophrenia (i.e. not remitting) were quite a bit more likely to be positive for immunological evidence of recent or past exposure to T. gondii.
  • Taking into account the clinical course of schizophrenia - ranging from a single episode of symptoms to continuous presentation - authors reported that "T. gondii infection was significantly more prevalent among the ‘continuous’ group than the others." I'm not an expert on the lifelong presentation of schizophrenia or rather symptoms associated with schizophrenia so will have to take the authors word for it on this occasion. 
  • On the basis of these and other results, the authors conclude that: "a negative correlation between the clinical picture of schizophrenia and the presence of anti-T. gondii IgG antibodies in patients with latent toxoplasmosis" is present. Further that: "T. gondii infections may be associated with worse prognosis among patients with schizophrenia."

Stepping back and realising that this was a 'snapshot' study where only one testing occasion was used for T.gondii exposure and schizophrenia symptom presentation on top of the "small size of the study group", these are interesting results. We are told that "none of the patients showed clinical evidence of immunodeficiency" which may yet be an important point when it comes to ascertaining the hows and whys of T.gondii infection and a condition as complicated as schizophrenia.

The idea that the clinical course of schizophrenia - some schizophrenia - may be to some degree 'affected' by the presence of antibodies to T. gondii is an intriguing one. Not only does it offer further evidence for the involvement of the immune system in cases (see here) but also the tantalising prospect that clearance of the pathogen might affect the symptom profile. We know, for example, that certain antipsychotics drugs used in the management of schizophrenia and psychosis may also possess certain 'anti-parasitic' actions [2] and could already be working by this mode of action. Whether this also means that more traditional anti-parasitic measures might also have a clinical place under certain circumstances is a question that remains unanswered (bearing in mind my caveat about not providing medical or clinical advice on this blog). It's not as if other 'medicines' haven't been looked at with schizophrenia in mind before (see here).

Oh, and I'll perhaps come to the paper by Mendy and colleagues [3] suggesting that: "Toxoplasma seropositivity may be associated with reading and memory impairments in school-aged children" at some point in the future and what it could mean for at least some schizophrenia with cognitive functions in mind...

Music: Longfellow - Kiss-Hug-Make Up.


[1] Çelik T. et al. Association between latent toxoplasmosis and clinical course of schizophrenia - continuous course of the disease is characteristic for Toxoplasma gondii-infected patients. Folia Parasitol (Praha). 2015 Jan 1;62. pii: 2015.015.

[2] Fond G. et al. Comparative analysis of anti-toxoplasmic activity of antipsychotic drugs and valproate. Eur Arch Psychiatry Clin Neurosci. 2014 Mar;264(2):179-83.

[3] Mendy A. et al. Toxoplasma gondii seropositivity and cognitive functions in school-aged children. Parasitology. 2015 May 20:1-7.

---------- Celik T, Kartalci S, Aytas O, Akarsu GA, Gozukara H, & Unal S (2015). Association between latent toxoplasmosis and clinical course of schizophrenia - continuous course of the disease is characteristic for Toxoplasma gondii-infected patients. Folia parasitologica, 62 PMID: 25960559

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