Researchers in France and Spain have diagnosed a number of men who have sex with other men with dermatophilosis, a skin disease that normally infects livestock, even though the cases had no known exposure to affected animals. Cases have also been detected in Germany, one of the researchers told STAT.
The clusters of infections are in some ways reminiscent of the emergence of mpox in 2022 in networks of gay men and other men who have sex with men. But people who have diagnosed some of these dermatophilosis cases describe a disease that is much milder in presentation.
The infection is triggered by the bacterium Dermatophilus congolensis.
In articles published ahead of print in the Centers of Disease Control and Prevention’s Emerging Infectious Diseases journal, doctors reported small clusters of infections in Barcelona and Lyon, with the latter group having some ties to Paris and several other French cities.
The first author of the paper about the Spanish cluster, Vicente Descalzo, told STAT that after the articles were posted on the journal’s website, a doctor in Berlin contacted him to report that cases were being seen there as well. Descalzo is an internal medicine specialist who works in the STI/HIV unit of Barcelona’s Drassanes-Hospital Vall d’Hebron.
The primary symptom of the disease is a rash. The pimples or pustules mostly appeared in areas of the body exposed during sexual contact, the authors of the paper about the French cluster reported.
To date, all diagnosed cases have been mild, and either cleared up on their own or were treated successfully with antibiotics. The bacterium appears to be susceptible to multiple antibiotics.
Both groups of researchers reported that most of the infected men described having attended saunas before developing the rash. Though Descalzo cautioned that the possible role of saunas in transmission is still just a hypothesis, the bacterium is known to spread more efficiently in humid settings.
“Humidity is a very important factor of development of Dermatophilus congolensis,” Didier Pin, a veterinarian at VetAgro Sup, a veterinary university in Lyon, told STAT in an email.
The group from Lyon reported on nine cases, one of whom recounted having had multiple sexual partners at saunas in Paris. Bacterial samples from eight of the cases underwent genetic sequencing and showed close similarity.
“The combination of close genomic relatedness between the 8 sequenced isolates and shared sexual exposures suggest interhuman transmission within sexual networks,” wrote the authors, who work at the University Hospital of Lyon.
The Barcelona team likewise reported on nine cases, all of whom disclosed they had visited venues for sexual encounters in the week before their symptoms began. Eight of the nine attended saunas. Four of the men reported recent travel elsewhere in Europe where they’d had sexual encounters. None of the men reported having had contact with livestock.
Like the Lyon cluster, genetic sequencing of bacteria from the Barcelona cases showed they were all closely related to one another, suggesting there had been a single introduction of Dermatophilus congolensis into this community, the authors said.
At the time of the interviews, neither group had compared its sequences to those generated by the other group.
Since its article was submitted for publication, the Lyon team has confirmed more cases — 25 in total — in Lyon, Paris, Bordeaux, Saint-Étienne, and Annecy, said Matthieu Degreze, first author of that study and a junior scientist at the hospital. One of the cases had recently been in Turkey; another had been in Italy, where he had a sexual encounter. He did not have symptoms at that time.
Degreze said the Lyon researchers suspect those two men may have been infected during their travels. But neither they nor the researchers in Barcelona know whether men who have been infected but who don’t yet have lesions can transmit dermatophilus.
The Barcelona group has only confirmed one additional case, but Descalzo said that after posting about the paper on social media he has heard from other Barcelona-area physicians who have said they too had seen a case or two.
Both Descalzo and Degreze believe the condition is underdiagnosed. Given the mildness of the symptoms, Descalzo said he would anticipate that doctors might just prescribe an antibiotic, which in most cases would likely hasten the end of the infection.
Demetre Daskalakis, a former director of the division of HIV prevention at the Centers for Disease Control and Prevention, agreed that the more health care providers and researchers look, the more cases they’ll likely see. But how significant this pathogen is in people is still uncertain. “The question’s going to be: What does that mean in the real, clinical world?” he said.
In animals, the bacterium causes pustules and lesions, predominantly in cattle, sheep, and horses. Depending on the species and the part of the animals’ bodies that are affected, the disease is sometimes known as rain scald or rain rot, grease heal, and strawberry foot rot. The condition is largely mild, though it can occasionally progress to more severe disease.
It is not clear if that might also be true in people. But there is some concern about how the infection might manifest if contracted by someone with uncontrolled HIV or another condition that compromises the immune system. None of the infected individuals in the Lyon or Barcelona clusters were immunocompromised.
Daskalakis, who quit the CDC last summer in protest of the firing of its director at the time, Susan Monarez, raised some concern about the prospects of such infections.
“It seemingly presents like a pretty benign folliculitis,” said Daskalakis, referring to a common skin condition where hair follicles become inflamed and small pimples form.
“Which is good, except that I’m not sure what that would do if you have an immunocompromised population, which I think is probably the thing to be the most concerned about,” said Daskalakis, who is now chief medical officer at the Callen-Lorde Community Health Center in New York City. He was director of the National Center for Immunization and Respiratory Diseases when he left the CDC.
Pin agreed this will be something to watch for, if the bacterium continues to spread.
“Comorbidities could worsen dermatophilosis in animals. I suppose that it is the same in humans, even if it is much more rare,” Pin said in an email.
Daskalakis also worried that if the bacterium continues to spread in networks of men who have sex with men, it might complicate confirmation of mpox cases when patients with that disease seek a diagnosis. But Descalzo said he didn’t think that would be a problem for physicians trained to detect sexually transmitted infections.
“If you are working in STI clinics, you really know how mpox presents. And for me, the [dermatophilosis] cases I personally saw at the clinic didn’t really have this problem,” he said.
Human infections of dermatophilosis have been reported previously, but only rarely and only in people who work with animals or have had close contact with infected animals. One such report described an infection in a 15-year-old girl who had been to a horseback riding camp. Two others detailed infections in tourists who had ridden elephants in Thailand.
The World Health Organization told STAT that it was aware of the reports. In an emailed statement, the agency said it believes the potential of dermatophilosis to rise to the level of an epidemic to be low at this time, noting that “clusters of novel or previously rare skin infections have been documented intermittently in recent years within close contact and sexual networks and venues.”
But the agency said the reports highlight the importance of clinicians being made aware of unusual or emerging infections in sexual health care services, and the need for appropriate testing when the cause of skin lesions is unknown.
Daskalakis said it would be prudent for the owners of saunas frequented by men who have sex with men and for the men themselves to ensure they are practicing good hygiene.
“It’s a good time for these saunas to make sure that they’re doing a lot of cleaning,” he said. “But I think it also speaks to men who are attending these venues. You can try to say, ‘Don’t attend the venues,’ but it’s not going to work. We know that historically. I think it’s [about] making sure that they’re doing all the stuff that they need for hygiene and making sure they shower after encounters, etc.”