Delusional parasitosis: an entomological perspective after a 20-years-experience in two public medical and veterinary entomology laboratories.

Delusional parasitosis (DP) is psychiatric disorder characterized by the unshakeable belief of being infested by endo- or ectoparasites, without any evidence of infestations. Hence, DP sufferers often consult medical entomologists or dermatologists, rather than seeking help from a mental health practitioner. Here we present 39 cases of suspected DP occurred in twenty years in two Italian public medical entomology laboratories, to highlight their common features and peculiarities, based on the interviews and material brought to our laboratories. Our results confirmed that DP affects both sexes, but is more frequent in females over the age of 50 years. Cases of psychological contagion, mostly affecting elderly people, were reported within seven family units. Some rare or unique features of DP sufferers involved: the fixed belief to be infested by endoparasites, olfactory hallucinations of unpleasant smell, self-harm to get rid of the imaginary parasite and suicidal thoughts. We suggest the term "Digital pics sign" to describe a modern derivative of the "Matchbox sign", where the DP sufferers showed pictures and videos, in person or sent by email, as proofs of being infested. Medical entomologists, being the most frequently contacted professionals by DP sufferers, may be crucial to raise awareness about this psychological disorder and to encourage a multidisciplinary approach amongst medical professionals and pest control operators.