Uptick in Rare Bugs and Mites

Emily Willingham

November 05, 2019

Thomas Herzinger, MD, remembers his one and only encounter with a case of body lice infestation all too well. A "visibly drunk" young man entered the examination room and began to disrobe. Herzinger — a dermatology resident at the time — immediately noted the textbook-perfect marks on the man's upper body that suggested the presence of body lice. A lot of body lice.

Alarmed, Herzinger, now a professor at Queens University in Kingston, Ontario, Canada, asked the man to hand over his t-shirt. Knowing that body lice feed on human blood but lay their eggs in clothing fibers, he told the young man not to shake his shirt. The inebriated patient misunderstood, however, and, to Herzinger's dismay, shook the t-shirt out.

"Suddenly, hundreds of little animals were crawling on the floor of my examination room," said the dermatologist. "I was terribly disgusted and itched for days," he added, although none of the bugs actually took up residence on him.

I was terribly disgusted and itched for days.

Although body lice infestations are uncommon and can typically be traced to poor hygiene, some formerly rare skin parasites appear to be making a comeback. Herzinger highlighted some of the culprits that clinicians might find themselves encountering more frequently at the 28th European Academy of Dermatology and Venereology Congress in Madrid.

With the trend in backyard chickens on the rise, the chicken mites (Dermanyssus gallinae) that infest these birds are along for the journey. And, occasionally, bird mites will take a detour into human habitations and onto humans, said Herzinger.

That's what happened to one 30-year-old woman who presented with a feeling of "bugs on the skin" and itchiness that worsened when she went outside, as described in a letter published in Cutis. The culprit host turned out to be a nest of starlings just above the porch where she sat in the evenings, and her symptoms resolved once the nest was removed.

These bird mites, including Ornithonyssus sylviarum, don't thrive long on humans, Herzinger reported. But bird-mite-related dermatitis might be a candidate on the differential list for patients presenting in the spring and summer with itchy, bloody, and crusted lesions that worsen at night.

Although the human is a "faulty host" for these mites, they are something to consider for patients presenting with recurring itchy lesions that have no other apparent insect-based cause.

Pediatricians have postulated that selfies are helping to spread head lice, ostensibly because young people touch heads to fit into the camera frame. A British team followed up on that idea and presented data showing that children with smartphones seem to have head lice more frequently than those without.

The research team, from the Oxford University Hospitals NHS Foundation Trust, stopped short of blaming selfies for the association, however, because their results did not reach significance. Smartphones might encourage children to congregate, and bugs will likely spread as a result, team member Tess McPherson, MD, acknowledged in a statement at the time, but selfies aren't specifically to blame.

Herzinger backed up that assertion. First, he explained, people taking selfies usually don't make contact long enough to transfer the insects. And second, the increase in head lice infestations started 30 to 40 years ago, long before the advent of smartphones.

In reality, the likely explanation for rising rates is the increase in global mobility, with parasites spreading as people go from place to place. "We know that there is an exponential increase in prescriptions for head lice medications when kids return to school after summer vacation," Herzinger said, which "could have something to do with all the traveling."

Scabies are also on the rise. Consults for scabies in Norway tripled from 2012 to 2018, with a parallel rise in sales of scabies-related therapies, he reported. Germany has seen similar increases.

"I think that we will probably see more scabies in the future," he said. Although he's seen other conditions misdiagnosed as scabies, the reverse is also true. He described the case of a patient who came to him for a suspected allergy to implant material, but the patient turned out to have "just plain scabies."

In a study conducted during World War II to determine how the mites (Sarcoptes scabiei) that cause scabies pass from person to person, volunteers offered to sleep in a bed where an affected person had just slept.

"Nobody could do these experiments today because no board would approve it," said Herzinger, "but they saw hardly any transmission." Even when people donned the underpants or other clothing worn by an affected person, they usually would not get scabies themselves.

The implication, he explained, is that scabies mites are "quite happy on their hosts" and are in no hurry to make a transfer out of their burrows in the skin, where the female mites lay eggs. "That's why it usually takes the same route as many venereal diseases, with really prolonged body-to-body contact in a warm cozy environment, to make the mite consider switching hosts."

Scabies mites prefer spaces between the digits and around the genitalia. That distinguishes them somewhat from bedbugs, which avoid "crawling deeply into your clothes and would rather bite your ankles and your wrists." Bedbugs "like to attack and run," he said.

In 2015, 80% of hotels in the United States had to treat for bedbug infestations, according to one report. In addition to bites on exposed areas, the parasites can elicit a systemic allergic response, which will look like a "generalized dermatitis with itchy little bumps all over," said Herzinger.

Unfortunately, bedbugs can go for almost a year without eating, so they're a parasite on the rise whose fall may not come any time soon. They are also showing resistance to common pesticides.

But fortunately, they "hate high temperatures and dry air," said Herzinger. Dry air over 40 °Celsius will "kill them within an hour."

28th European Academy of Dermatology and Venereology (EADV) Congress. October 11, 2019.

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