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Florida Medical Entomology Laboratory

Florida Medical Entomology Laboratory

Mosquito Control and the Challenge of Delusory Parasitosis

Mosquito control programs often receive urgent pleas from individuals who believe that they are suffering from insects that are biting, crawling, or burrowing under their skin despite an inability of these individuals to see or collect any arthropods. The sufferer may repeatedly visit mosquito control with a plea for professional assistance or for information to reduce or terminate the symptoms of the affliction. What is the best response to assist someone with this very real problem?

I had not encountered this problem before moving to Florida. However, as Director of the Florida Medical Entomology Laboratory I have met several individuals suffering from these symptoms over the past 10 years. I am sure this is not an uncommon experience in Mosquito Control Districts throughout Florida. Each of the individuals suffering from these unseen insect bites hopes, pleads, and demands a solution for their plight. This is a real challenge for the entomologist because in these instances there is no evidence of any kind that the symptoms are due to a biting arthropod. Indeed, in many cases the sufferer may freely admit seeking other professional advice, from a physician, professional pest control company, or other entomologists, all of whom were unable to ever see the suspected pest arthropod. Anyone who has ever tried to assist someone in this predicament is aware of the absolutely deep unshakable conviction such that, no matter what the evidence presented, the sufferer cannot be dissuaded that a small unseen arthropod is the cause of the problem.

The medical profession has a name for this form of behavior, a behavior so strong that it becomes a “fixed belief” that cannot be changed despite all evidence to the contrary. It is a “delusion” and this particular unswayable delusion is called “delusory parasitosis” (see Hinkle, N.C. 2000. Delusory parasitosis. Amer. Entomol. 46: 17-25) or DP.

My own personal experience with sufferers of DP supports the experiences of other scientists presented in the scientific literature. Sufferers make it known quickly that the symptoms have caused extreme and lengthy hardship. I have met people who cannot work, have destroyed their furniture, have moved multiple times, and have continually cleaned and scrubbed everything they own. Relationships with other family members, wives, and children can be strained or savaged. Many tried repeated pesticide applications, and several placed themselves in extreme danger through their use of home remedies. One poor unfortunate fellow told me he was drenching his skin daily with salad oil to reduce the insect biting. He then showed me rashes on his arm that he was certain were the result of invisible insects. I could not dissuade him from self medicating and could not convince him that the cause of his rash was likely the liberal home remedy dosing he was subjecting himself to. To a person, each of my experiences was with someone who had sought medical and other professional assistance, all to no avail. The symptoms persisted and the individual was clearly at wits end. All of these individuals wanted someone to make the symptoms go away.

Each DP sufferer is convinced that their symptoms are the result of unseen insects. I have gone through the same set of experiences with each of the individuals I have tried to help. It is important to be compassionate and understanding. Often individuals bring samples collected on clear tape that they believe to be clear proof of an arthropod cause of their distress. If they have not made a collection, I always request that they attempt to do so. Each time I look at these collections with the expectation that perhaps there might indeed be a small arthropod, evidence of a mite, or some biological cause for the problem. I have looked at a lot of dust, lint, fur, animal hair, all meticulously vacuumed from the home. Despite my lingering curiosity that sometime there might actually be something to support the belief of an arthropod as the cause; I have never seen an arthropod-positive collection. So I was just another skeptic, and the sufferer was again disappointed and left without the sought after cure. One has to feel sorry for their plight. It is very real.

Where does this leave the mosquito control professional in trying to assist people with these symptoms? Many sufferers have already seen a physician, they may even have been helped for a while, but the symptoms have returned. The most important advice I can offer: be compassionate! There may be other causes of the symptoms, not an arthropod, but other environmental and biological causes. Be compassionate and advise that although you could not find an insect as the cause, the symptoms they are experiencing are real and they should see a physician to determine the cause.

You have to feel sorry for these poor unfortunates, suffering from a condition that no one is able to alleviate. By the way, although my scientific side knows that the DP sufferer I have advised is not being attacked by insects, when they leave my office, as many other entomologists have already admitted, I do take notice if I should experience any itching after they leave. This is one powerful delusion.

Walter J. Tabachnick - Retired
Florida Medical Entomology Laboratory
University of Florida –IFAS
Vero Beach, Florida


Below is a list of resources that should provide some insight and hopefully be of use to mosquito control employees who encounter clients with mystery itches:

Delusory Parasitosis (Hinkle 2000)
Delusory Parasitosis: Bugged by “Bugs” (Kelly 2004):
Invisible Itches: Insect and Non-insect Causes (Potter and Koehler):