Aboard the private yacht, the crew and passengers delighted in the sights of the open water. It was relaxing onboard: a welcomed break from the pressures of daily life. The crew slept at night on comfortable (albeit sometimes a bit scratchy) straw mattresses. Then the itching began. The crew’s skin erupted with large, comet-shaped welts. 

What we now know is that the crew, who sailed in 1909, experienced the first supposed Pyemotes ventricosus (P. ventricosus) outbreak leading to Pyemotes dermatitis. Also known as the straw itch mite, P. ventricosus is an ectoparasite; it lives on the outside of its host, which is often the Anobium punctatum, a beetle that eats wood. It often feeds on the beetles, but also feeds on humans if they come into contact. P. ventricosus may also exist in infested materials such as wood dust, straw, or grain. 

A Recent Infestation

Over the years, Pyemotes dermatitis has become increasingly uncommon. There have only been around 20 outbreaks, and 40 individual cases, over the last 114 years. For example, more recent outbreaks occurred in France (2006) and Poland (2017). 

According to reporting by Ars Technica, a French couple recently discovered how annoying these mites can be. The couple had been valiantly fighting wood-eating beetles from their wooden furniture. Seemingly without warning, an extremely itchy abdominal rash broke out. 

The couple waited for a few days to see if the rash would go away. Instead, the itching intensified. The woman’s welts even developed pink trails (which is why the welts are often described as comet-like). Worried that they had contracted something dangerous, the couple visited an infectious disease clinic. They were diagnosed with Pyemotes dermatitis soon after.

Luckily, this condition is relatively easy-to-treat. First and foremost, it involves getting rid of the infested furniture. Symptoms related to Pyemotes dermatitis typically clear up in a few weeks, though glucocorticoids and antihistamine treatments may also help. In this case, with medication, it took just over one week for the couple to feel better. 

Learn more about the couple and their experience, which was shared in the New England Journal of Medicine. 

About Pyemotes Dermatitis

Pyemotes dermatitis is an uncommon skin condition caused by P. ventricosus. According to information found in available medical literature, the P. ventricosus mites are most active in May to November, meaning that most cases will appear in this time period. P. ventricosus needs hosts to survive. Without hosts, the ectoparasite can only survive for around 48 hours.

Because these mites are incredibly small, they are nearly invisible to the human eye. This makes identifying them, or their bites, difficult. Typically, after being bitten, people will develop severely itchy red or pink welts. While many people present with the comet sign/tail, not everyone does. Absence of the tail does not signify absence of Pyemotes dermatitis. 

Other signs of this condition may include a central red puncture wound on the welts, brown skin pigmentation after the welts disappear, fever, chills, nausea and vomiting, joint pain, and headaches.