Invisible invaders: a decade of delusional infestation cases in Connecticut (2013–2023)

Abstract Delusional infestation (DI) is a psychiatric condition characterized by the fixed, false belief of being infested by parasites despite contrary evidence. Although DI patients frequently consult non-medical professionals including entomologists, existing literature derives almost exclusively from medical settings. This retrospective case series describes 264 individuals presenting with suspected DI to The Connecticut Agricultural Experiment Station Insect Information Office between 2013 and 2023, constituting the largest single-center case series reported in the United States. Cases were predominantly female (74.6%) with a mean age of 60.8 yr. Reported symptom onset showed a strong seasonal association with monthly mean air temperature. The median estimated symptom duration was 6 mo. Nearly half of individuals submitted physical specimens for examination, none containing arthropods capable of causing reported symptoms. Antiparasitic medications were nearly four times more prevalent than antipsychotics among this cohort. Delusional beliefs extended beyond the primary individual (inducer) in 29.5% of cases. Dermatology was the most frequently consulted medical specialty, while professional pest management was the most common prior intervention. Psychosocial impacts including social isolation, housing instability, and suicidal ideation were documented among affected individuals. The demographic and clinical profile closely mirrors that of medically based studies, while the shorter symptom duration in this series suggests entomology may encounter affected individuals earlier in the illness trajectory. These findings support the integration of entomological professionals into multidisciplinary DI management frameworks and the development of referral pathways to psychiatric care.