The study, published in the British Journal of Dermatology, looked at 148 cases of delusional infestation.  This is a surprisingly common and debilitating condition where the patient believes that parts of their body or their environment are infested either by parasites, insects, worms or bacteria and now, increasingly, things such as atypical viruses, fungi, inanimate materials such as fibres, nanoprobes, and ‘things new to science’.  This wider range of infesting objects led to the name of the condition being changed from delusional parasitosis to delusional infestation. This term had been introduced in 2009.

The study was carried out by a multi-disciplinary team at hospitals, universities and research units with the objective of determining the number of true infestations, assessing the types of pathogen each patient believed themselves to be infested with and gathering details about the type of specimen(s) provided and how it was presented (ie type of container etc) to the clinician treating them.  The presentation of alleged proofs of infestation is commonly referred to as the ‘matchbox sign’ but the present study further backed their proposal to change this to ‘specimen sign’.

None of the patients in the sample had a true infestation – even those who brought specimens that were infesting parasites (eg a snake mite and a flea) proved on examination not to be infested or to show signs of current infestation.  There were wide variations in the types of alleged infestations reported and some interesting differences in the different European Centres – for example in pre-Alpine Italy there were no ‘inanimate’ pathogens reported, whereas in France these accounted for 63 per cent of the cases seen.  Overall only 35 per cent of patients believed they were infected with an actual parasite.

Just under 50 per cent of the patients in the study presented a specimen as proof of the infestation.  These might be a single object or up to 20 specimens from a single patient.  Most frequently these proved to be skin particles or hair.  Insects were also represented but of these only two were human parasite species and in both cases the patient showed no sign of being infested.  The specimens were most frequently seen in plastic bags, envelopes, in small glasses or boxes or stuck to adhesive tape – matchboxes rarely featured.  The researchers suggested that in future these ‘specimens’ might be brought as photographs, videos and on other virtual media.  This is important as patients are accessing increasingly sophisticated equipment to research their own condition.  Some patients have spent vast time and money resources to prove their infestation.

All the researchers stressed that it was vital that true infestation is ruled out prior to making a diagnosis of Delusional Infestation, and that all researchers continue to search for a true infestation if the patient continues to have symptoms.

Antony Bewley one of the research team says:

“The symptoms presented by these patients could be due to actual infestation, or indeed to other skin disorders, or disorders of the nervous system, therefore it is tremendously important to ensure that all physical causes are ruled out before moving to a diagnosis of delusional infestation.  If a patient feels they are not being taken seriously it can be very difficult to begin upon any kind of meaningful therapy to address the psychological issues. I and my colleagues always analyse carefully the material with which my patients present”

Peter Lepping from Glyndŵr University Wrexham says: “Other research has shown that treatment can be very successful.”

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