Delusional infestation (also called delusional parasitosis) is a very rare mental disorder that makes the patient have false belief or delusion that they are infected by worms, bacteria, fungi, mites or other living organisms. It becomes difficult for others to change the delusion of an affected person by reasoning, logical argument or persuasion. Usually, many affected individuals remain quite functional, however, in very fewer cases delusions of parasitic infection can interfere with their daily activities. This disorder is of somatic type, which is a subgroup of delusional disorders in which nonexistent disease forms the basis of the disorder.
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Signs and symptoms
One common symptom of delusional parasitosis is a crawling and pin-pricking sensation, as which is perceived as parasites are crawling on the body or burrowing into the skin. Suffers can even injure themselves in this delusion while trying to get rid of the parasites.
Delusional parasitosis is more commonly observed in women, and the frequency of the disorder is higher at the age of 40.
Delusional parasitosis diagnosis is divided into primary, secondary functional, and secondary organic groups.
Primary: In this, diagnosis is done of the entire disease entity and there is no additional deterioration of regular mental functioning or idiosyncratic thought processes. The parasitic delusions consist of a single delusional belief about some health issue. It is also termed as "monosymptomatic hypochondriacal psychosis", or "true" delusional parasitosis.
Secondary functional: Secondary functional delusional parasitosis is associated with some psychiatric condition like schizophrenia, clinical depression or obsessive-compulsive disorder.
Secondary organic: Secondary organic delusional parasitosis is when the state of the patient is caused by a medical illness or substance use. In the DSM-IV this condition corresponds with "psychotic disorder due to general medical condition". Some physical ailments that can underlie secondary organic delusional parasitosis are hypothyroidism, tuberculosis, cancer, cerebrovascular disease, vitamin B12 deficiency, neurological disorders, and diabetes mellitus. Any prior illness or medication causing formication or any side effect can trigger this type of delusional parasitosis.
Besides all that, other physiological factors that can cause formication are certain allergies, drug abuse, menopause, etc. Along with these physiological factors, certain environmental factors such as pollutants, airborne irritants, and other climatic conditions are also able to induce such "crawling" sensation in the skin of otherwise healthy individuals. Some people become so fixated on these sort of sensations and determining its possible cause that their attempt to fixation may lead to delusional parasitosis.
In the past few years, there has been an increase both psychiatric and dermatologic approaches to treat delusions of parasitosis. The disorder is being treated by using a multidisciplinary approach with dermatologists working hand-in-hand psychiatrists and others mental health specialists. One clinic in Singapore has already used this approach and observed that delusions of parasitosis were the most common psychophysiological disorder among some people. According to the study, around 20% of patients had psychiatric disorders underlying their skin problems. Apart from that, trichotillomania and dermatitis artefacta were also observed in the same individuals.
Treatment of secondary forms of delusional parasitosis is followed after treating the primary associated psychological or physical condition. Firstly, the primary cause or the main disease is treated as it can further cause other delusional disorders and schizophrenia. Earlier, pimozide was the preferred drug of choice for treating the typical antipsychotics. But now for treating atypical antipsychotics, medicines like olanzapine or risperidone are being used as first-line treatment.
However, it is also possible that some sufferers are going to reject the diagnosis of delusional parasitosis by medical professionals. Very few are willing to be treated, despite the demonstrable efficacy of treatment. So, to convince them is another huge task.