Goldsmid J.1, S. Bettiol1 and R. Bradbury2,3 Psocids and Delusional Parasitosis Goldsmid J.1, S. Bettiol1 and R. Bradbury2,3 1. Discipline of Pathology, School of Medicine, University of Tasmania 2. Microbiology department, Royal Hobart Hospital, Tasmania 3. Menzies Research institute, Hobart, Tasmania Introduction Formication is a condition where a patient has sensations of crawling over the skin. This is often associated with delusional parasitosis (defined as a feeling of itching or crawling where no parasites can be found), in which patients imagine they are parasitised by worms or insects. This poster presents three cases of formication and/or delusional parasitosis Case 3 (cont.): The patient relocated to Tasmania, and was again diagnosed as formication. The condition had spread to other family members, with itching and crawling felt on the head and body. Claiming they “could not see these creatures only feel them and could feel eggs popping on their head”. No parasite was identified by the diagnostic lab from scalp scrapings. The patients self-treated with permethrin and shaved their heads. The index patient developed a rash on her body (Fig 3) and was diagnosed as scabies on clinical grounds, treatment with pyrethrin and ivermectin followed. Symptoms persisted and again self-treatment with pyrethrin followed. The patient consulted University of Tasmania and was asked to produce specimens of the “creatures”. No specimens were submitted, but drawings of the creatures, made using a magnifying glass, were provided (Fig 4,5). Discussion Case 1: The insect submitted in case 1 was undoubtedly a Psocid Case 2: The specimen submitted from Case 2, was identified as a damaged insect, of which only wings were identifiable. The wing morphology conformed to that of a winged Psocid Case 3: The drawings submitted in case 3, look remarkably like parts of the head and mouthparts of a Psocid The evidence from these three cases suggests psocids had been misidentified as headlice or mites by the patients (a delusional parasitosis), and had perhaps been the basis of the “formication” felt by the patients. In case 3, this delusion spread amongst family members to become what has been described as “mass delusional parasitosis”n Psocids are small ( 2 –3 mm) insects belonging to the Order Psocoptera. They can exist in both a winged and a wingless form1 (Fig 9) Psocids are ubiquitous throughout the environment, where they scavenge for food, being known as booklice or barklice. They are common in human habitations, often living in thatched roofs. According to Smit, “ the tiny insects fall on to the occupants and on everything in the house, causing much consternation. They do not bite human beings but cause some irritation when crawling over the skin”. Psocids are known to produce a characteristic “tapping” (note case 3; “could feel eggs popping on their head”). It should be noted, however, that while psocids can be erroneously mistaken for ectoparasites, they may be of medical significance in some instances, acting as allergens and being reported as a cause of allergic reactions in some cases (XXX) Fig. 9: Winged and wingless forms of psocids (Essig 1954) Fig. 6: Wingless psocid (Essig 1954) Case Histories: Case 1: The patient here found small insects in the house and bed and brought them for identification, fearing they were parasitic mites Case 2: This patient found insects in his bed and in his hair. He complained of itching of the scalp which had been damaged by scratching. He submitted a specimen of these “headlice” for identification through his GP Case 3: This patient had a long history of a crawling sensation on the skin. Diagnosed as “formication”, but convinced that headlice were involved, the patient self-treated with pyrethrin, malathion, derris and “dog soap”. Symptoms abated, but then returned. Fig. 1: The insect submitted as ?mite Fig. 7: Psocid wings (Smithers 1973) Fig. 3: Rash on body of patient in case 3 Conclusion It is probable that these three cases represent examples of delusional parasitosis, presenting in 2 cases as formication. Allergic reaction to the presence of Psocids crawling over the skin could not be excluded. Fig. 4: Drawing submitted by patient Fig. 8: Psocid mouth part (Essig 1954 Fig. 2: Specimen submitted as ?headlice References 1. Goldsmid, J.M. Unusual arthropod ectoparasitic infestations of man. Aust. Fam. Phys. 1985; 14: 386-388. 2.Essig, E.O. College Entomology.1954. NY MacMillan 3. Smithers, C.N. Psocoptera. In: The Insects of Australia. Canberra. 1973. Melbourne University Press. pp 367-375. 4. Smit, B. Insects in Southern Africa: How to Control Them. 1964. Oxford University Press. Cape Town Fig. 5: Drawing submitted by patient