The patient has an infestation of mites. But what kind of mites?
Mites are a diverse group of arachnid arthropods that are relatively small and can easily be overlooked. Mites are less than 1mm in size and oval in shape with a semi-transparent color that is darker after feeding, especially mites that feed on blood which will develop a more reddish to brownish color.
While some mites can subsist on plants, there are others that will parasitize or even be predatory. Mites are very mobile with the adults having eight legs and the larval forms having six legs. Overwhelmingly they are generally harmless to humans with only a few being the source of allergic reactions and or be able to transmit disease to humans.
When we think of mites that cause the symptoms seen in this patient we generally suspect the human itch mite (Sarcoptes scabiei var. hominid) which is the cause of scabies.
Scabies infestations cause intense itching from the mites burrowing into the upper layers of the epidermis where they lay their eggs. The burrowing action along with the presence of the eggs that are released as they burrow will produce an intense reaction. The larvae that hatch from the eggs (in about 10 days) will also be a source of an allergic reaction. These larvae (which will have six legs) make their way on to the skin and search out hair follicles where they will feed and molt to the early eight leg adult stage. The burrowing action of the mites will produce tiny tracking marks on the skin. Reactions to the burrowing initially may take weeks to occur. Future infections, due to prior sensitization, may induce allergic reactions in less than 24 hours. The larval waste products also produce allergic reactions in the host. These allergic reactions manifest as intense pruritus. Adult mites can live in the skin for three to four weeks.
A signature symptom of scabies is that it will generally be found on humans where there are skin folds or areas of skin to skin contact. That being said, the organisms can be found most commonly in-between the fingers, the folds of the wrist, and abdominal folds. These areas are thus most likely to have the symptoms of redness, small pimple like rashes, and the signs of tracking and intense itching. Besides skin to skin contact, scabies can also be transmitted to others by the sharing of infected towels and or clothing. The organism is very transmissible.
Scabies between the fingers. Note the very small raised areas and redness. (Image from CDC – Lores)
Though Sarcoptes scabiei var. hominid is not known to transmit any diseases, the intense itching that it causes can result in secondary bacterial infections most commonly from Staphylococcus aureus or Streptococcus pyogenes.
But going back to this patient. This patient was found not to have scabies. This patient was found to be infested with bird mites, likely the Starling mite (Ornithonyssus bursa). These mites are most active in the early spring and early summer and tend to be nocturnal in their feeding. They are natural parasites of pigeons, starlings, sparrows and chickens feeding on their blood. Feeding on avian blood is necessary for the completion of their life cycle.
After the identification of the mites was made by the laboratory, a nurse epidemiologist was dispatched to the patient’s residence to investigate where the source of the bird mites might be. Noting that the patient had reported the sensation of bugs crawling on his skin was mainly while he was trying to sleep, the bedroom was decidedly the primary area of interest.
Upon entering the apartment it could be described as modestly small with a combination kitchen and sitting area, and a very small bedroom toward the rear. The bedroom contained enough room for a small dresser and a small bed which was placed against a wall that provided the only window in the room. An air conditioner was in the window. The patient stated that he located the bed by the window because he claimed the apartment was warm and the air conditioner provided both cooling as well as white noise that made him fall asleep sooner. That is until he started to feel the sensation of bugs crawling on him that prevented him from sleeping as well as the pruritus that followed.
An inspection of the window area revealed that there was plenty of space around the air conditioner and the window to allow for the entry of arthropods. But most importantly was the finding of a birds nest snuggly located between the air conditioner and the window sill. This would provide a perfect source for the bird mites as well as a perfect ease of entry for the mites to infest the unsuspecting patient while he slept. Indeed bird mites are found to be an infestation problem for poultry farmers, zoo keepers, pet store owners, pet owners, and persons living in close proximity to a birds nest.
The mites infestation would most likely subside as the human blood meal would not be able to provide the bird mites with the necessary nutrients needed to continue its cycle. They require feeding on avian blood. Even though this infestation would eventually subside, it was recommended that the bird nest be eliminated , the air conditioner be properly sealed, and measures taken to avoid the re-nesting of birds around the air conditioner. The application of an insect repellant containing diethyl meta-toluamide (DEET) or 3-methyl-n->diethylbenzamide was recommended until the mites were completely eliminated, as well as an anti-itch cream to reduce any itching. While antibiotics may be needed if a secondary infection due to the itching is suspected, in this case there was no evidence of a secondary infection.
Formication as an initial diagnosis was incorrect but not an unusual presentation in persons experiencing depression, anxiety disorder, bipolar disorder, schizophrenia, and delusional parasitosis. Therefore a thorough clinical history should be ascertained, as well as an investigation as to any probable infestation cause, before suspecting a case of formication. There was one case that comes to mind where I had literally 5 one-gallon plastic bags with material collected from a patient that described to her physician the feeling of bugs crawling all over her at all times of the day. The material consisted of hair from various parts of the body; skin from various parts of the body, and multiple pieces of clothing, etc… In the end there were no arthropods found. She was a patient that indeed had chronic depression and was eventually diagnosed as a case of formication.
I hope you enjoyed this discussion and as always I welcome any comments or added information/experiences to add to the discussion.