Scabies, the eternal return of the immortal disease (and the imminent danger of fungal infections such as ringworm)

There are diseases that have been with us since the beginning of time, they go up and down, but they are still with us. This is the case of scabies, known since time immemorial, of which there are biblical and even earlier references: the word scabies in Chinese was inscribed on turtle shells that were used for divination during the Shang dynasty (1600-1045.C. .), the first Chinese dynasty for which we have written sources.

“Currently, erroneously, scabies is considered to be something typical of antiquity, which no longer exists, or is associated with misery, dirt and poor hygiene. Nothing could be further from the truth,” says Cristina Galván, vice president of the International Association for the Control of Scabies (IACS) and member of the Fundación Lucha Contra las Infecciones.

The expert gave a presentation at the symposium Epidemiological challenges in current dermatology: diseases with increasing incidence and prevention strategies, which took place within the 50th congress of the Spanish Academy of Dermatology and Venereology (AEDV), held from May 10 to 13 in Santiago de Compostela. And scabies is one of those diseases with increasing incidence, although many associate it with other times.

Could we say that scabies is a kind of 'zombie disease' because it revives? “Zombies are already dead. If we look for an analogy, scabies would rather be something immortal”, says Galván. Said like that they give chills. But the truth is that the subject gives food for thought.. Scabies is an infestation or infection caused by a mite called Sarcoptes scabiei hominis variety, which only knows how to live on human skin, “what we call an obligate parasite. This has an important implication because at the moment there is no means to cultivate it and to test treatments.. The only culture medium it has is the warm skin of a living human”, explains Galván. The dermatologist indicates that there are no animal models either. “There are, but based on 'cousin' Sarcoptes, like the rabbit or pig variety.”

In addition to this difficulty for research, it has an important social implication: “Contagion is usually human to human, skin to skin. If no one was affected, no one would get it.”. If scabies has resisted millennia passing from skin to skin, we are not doing something right.

Scabies or scabies occurs because the mite digs tunnels in the human skin and deposits its eggs and droppings there.. The parasite, its eggs and droppings are what cause our body's immune reaction, which manifests itself with dermatitis and enormous itching that leads to scratching.. It is difficult to get infected simply by shaking hands, close and lasting contact is needed, “as in close coexistence in the case of communities or overcrowding related to the lack of access to decent housing, not the lack of hygiene “.

Microscopic view of scabies mites. SHUTTERSTOCK

“In Malawi we would go school by school, class by class, we would see all the children. And then we would go house to house and see where the child with scabies lived to treat the whole family.. As soon as we saw a young man with scabies on the penis, we didn't stop until we found the girlfriend because the scabies were clearly brought into the homes by young people through sexual contact and by school children,” Galván explains about the DerMalawi project, which she founded a few years ago. years.

That close and lasting skin-to-skin contact that occurs when having sexual relations is what also led to the outbreak of mpox (previously called monkeypox or monkeypox), which was controlled by surveillance programs, contact tracing and vaccination, in which the awareness and collaboration of the people was fundamental, something that does not happen with scabies. In fact, after the confinement there has been a rebound in scabies in Spain and in other countries.

“Actually, since 2011 we have been suspecting that there are more cases of scabies. It is not quantified, it is indirect data. There are publications that point to this increase during confinement, which is logical because we have lived more at home with our relatives and also we could not go to the doctor or we were afraid, so there was no way to treat. Scabies does not come out alone, it is because someone in the family is infected and has passed it on to others and if it is not treated it spreads exponentially. Not everyone did the confinement the same way either…”, underlines Galván.

But the specialist stresses that the number of cases in the world goes up and down, “the incidence of scabies goes by curves”, and this increase began before the pandemic. Among the reasons to highlight for these ups and downs and the fact that scabies continues among us millennia later is that scabies “is not a notifiable disease anywhere in the world, only when professional outbreaks occur, such as workers in a hospital, or institutional outbreaks, such as in a prison or a nursing home” -we must trust that it will be declared even in these cases in which it is possible that, in order not to sink its image, a residence, for example, hides it-.

In addition, “the germ is very silent, it takes between three and six weeks to get itchy and know that you have the disease, during which time you can be infecting more people. If someone has had a sporadic sexual relationship, it is possible that they will not contact that person later to tell them that they have scabies and they could have caught it. Even when it is said, the person to whom it is communicated may think 'but if nothing stings me', it doesn't matter, if you have had contagion it will sting you “. Therefore, says Galván, we have no idea of the real cases of scabies in the world.

Variable incidence in the world: between 0.2 and 70%

“When you look at the world map there are places where it seems that there is no scabies, but what is not there are data. The sites with high incidence are places where there has been interest or they have put a lot of money to do field work and see those figures.. This is the case in Australia and the Polynesian Islands, with a 71% incidence, compared to 0.2% in many countries.. It is very easy for these low figures to respond to the fact that they do not measure it. For example, in Malawi, where there were no figures, I did an incidence study in a rural area and 18% of people had scabies.. There are Bayesian models that calculate that at a given time on a given day there are 200 million people affected by scabies in the world and that the worldwide incidence per year is 455 million people”, Galván develops.

Another important aspect that explains this invisible permanence of scabies is that it is not considered a serious disease, it does not kill. It affects the quality of life, itches more at night and not being able to sleep, he does not perform well the next day at work. However, be careful with scabies: it is the leading cause of kidney and heart disease in countries without resources because scratching favors infections.

“People with scabies who do not have access to treatment always have bacterial infections, for two reasons: firstly because they scratch and secondly because it has been shown that the scabies mite paralyzes the complement system, which is essential in the immune response because we used to fight bacteria. In other words, you have a scratching wound, scabies favors infection and this sustained infection favors kidney and heart disease. Our great-grandparents and great-grandparents died of heart disease because there was no penicillin.. Now if you have angina and they give you penicillin, those diseases of the heart valves no longer exist. Well, in countries without resources, they happen not because of angina but because of uncured scabies.. In other words, scabies is important,” says Galván.

There are no figures, it is not communicated and it is not considered serious, but science does not devote much space to scabies either.. The dermatologist gives the example of The Lancet's Global Burden, published in 2019, which shows the burden of a disease in the world. “Of all the diseases that affect the skin, the ones that occupy the most space are acne and scabies, both accounting for 0.19% of the total number of DALYs [the number of years lost due to disability] globally.. Psoriasis is 0.14%, alopecia areata is barely 0.024%, and the highest is dermatitis (0.39%) because dermatitis encompasses everything, it simply means that the skin is inflamed.”

Despite this importance compared to other conditions, Galván emphasizes, “if you search PubMed for how many serious studies there are on scabies in the last five years, 40 appear, compared to much higher figures for the other skin diseases we have discussed.. Scabies is something that worries dermatologists and hospitals a lot, but at the moment of truth there is no interest. There are some studies, such as one of Carlos III, retrospective and based on analysis of records, whose conclusions can only be indicative.

Others measure the sales of permethrin, one of the treatments, but do not analyze whether the sales are to treat scabies or because the affected person repeats the treatment over and over again because the skin continues to itch a lot.. The scientific community has to be a little more formal and take more interest in scabies even if it does not entail great economic benefits”. In this sense, the dermatologist celebrates as an important step the study that, although very simple, the AEDV has launched, CLINI-AEDV, to see the current situation of scabies in our country.

Positive factors that “do very badly” for scabies

In the absence of data, it is not known exactly what amplitude the curves have over time, but Galván believes that what they have been noticing for some time is explained by various factors, “some of which are very positive but which are very bad for the spread of the scabies”. “First, the change in sexual behavior and group sex: if before I could have three sexual contacts in a month, now in a week I can have it with 30, as many people told us in the interviews we did through the mpox (before called monkeypox or monkeypox).

Another factor is the increase in life expectancy.. “The elderly population is increasing and the number of elderly people who live institutionalized has grown exponentially since 2010 and it is in those places where there are many people and there is rotation (an assistant washes one and goes to wash another and another, and rotates ) where it is easier to spread scabies. In addition, there are many diseases that used to kill us and are now chronic because there are treatments, but they lower the defenses.. This is a very important point, although infrequent: there is a special scabies that is that of people with low defenses, which can be older people who have immunosenescence, that is, their defenses have aged, or immunodeficiency caused by medications and this type of scabies is much more contagious than common scabies.

Galván explains that when the mite lays its eggs and the protonymphs are born, our defenses kill 99% of them, but if we don't have defenses that doesn't happen.. “Science is of the opinion that when there is a patient very affected by scabies, full of wounds and scabs and who has not slept for a month, they actually have between six and 10 live mites. People with immune problems can have thousands of mites on their skin.. If we add to this that the manifestations of scabies are due to the immune reaction to the mite, but your body does not react, the clinical picture does not have the typical signs of usual scabies, such as itching, and it is very difficult to diagnose.. When these cases occur, the possibility of contagion to others is much greater, even with the sheets in the laundry of a residence.

At this point, the specialist mentions the so-called fomites: the clothes, the chair, the towel…. “The culture medium is warm skin. The mite has been seen to survive for some time in excellent conditions of humidity and temperature.. Thus, the guidelines say that you have to treat the person, the environment and the fomites, except for the Japanese guide that says that you only have to do it in the case of Norwegian or hyperkeratotic scabies (that of people with impaired immunity).. My personal experience in Malawi is different: we did a massive treatment and I selected a population of 30,000 inhabitants, we started with 18% of people affected and we did not treat the fomites (it is difficult in a place without a washing machine, without bags to store, without enough access to water and without spare clothes) and after our intervention there were 2% of those affected, despite being in the ideal conditions of humidity and temperature of the Tropics”.

We must also remember the study in humans carried out by the zoologist Kenneth Mellanby in World War II (which no current medical ethics committee would have approved) exchanging the fomites of the patients and whose conclusion was that these were not the main method of transmission. However, until proven otherwise, it is important to follow clinical guidelines and treat fomites as they recommend, washing clothes at 50 degrees for at least 10 minutes, keeping them in the freezer for at least five hours at -10 degrees, or storing them contact with humans for a week, stresses the specialist.

The last factor for the dermatologist is the possible resistance of the mite to the treatments, “some studies say that there is and others say that it is not, that what is done wrong is the treatment of the contacts”. 5% permethrin is used as the base treatment (topical use) and ivermectin, which is more comfortable when oral. They are equally effective and in both cases they need to repeat the dose because neither kills the eggs well, says Galván. “There are other topical preparations and studies with other macrolactones, different from ivermectin, which have a very long half-life on the skin and we are looking forward to them because, after a single dose, as the eggs hatch, it would kill them”. All in all, Galván stresses that scabies is much easier to cure than ringworm, “especially if it affects the head, and the WHO has already referred to resistance to antifungals as the great pandemic that awaits us.”

Ringworm outbreak in Spanish hairdressers

Precisely we all remember the outbreak of ringworm that was detected in hairdressers throughout Spain at the beginning of this year, something striking because it sounds like an old thing to us, from other times. Ringworms or dermatophytosis are caused by dermatophytes, a type of fungus specialized in feeding on keratin (the protein in hair, skin, and nails).. Depending on their habitat, they can be anthropophilic (inhabiting humans), zoophilic (in animals) or geophilic (in the soil) and can be transmitted from human to human, from animal to human or from object to human (by contact with surfaces touched by an infected human or animal).

Microsporum canis under microscope. SHUTTERSTOCK

Ringworm of the head or tinea capitis is highly contagious (less prolonged contact is enough than in scabies) and affects mainly children from six months to 12 years, with a slight predominance in males.. The curious thing is that the outbreak that was detected at the beginning of the year was among adolescents (with an average age of 19), in this case associated with the weekly shaving and degrading that young people perform in the occipital and temporal areas in the hairdressers and most certainly caused by sharing electric razors and infected material that had not been properly disinfected.

“The fungi that inhabit humans usually give non-inflammatory ringworms, they produce some redness, scaling, but usually not great inflammation. Zoophiles, when they pass from an animal to a human, are more likely to get inflammatory ringworm, with fever, suppuration, adenopathies in the lymph nodes, that is, more 'scandalous', and if it is not treated promptly it can give a scarring alopecia. And geophiles are a mixture, it is neither as inflammatory as that of zoophiles nor as little inflammatory as that of anthropophiles”, explains Leonardo Bascón, dermatologist at the General Hospital of Granollers (Barcelona) and lead author of the study Outbreak of dermatophytosis in head and neck region associated with shaving in hairdressers: multicenter descriptive study of a series of cases, showing the findings that gave rise to the alarm.

“One of the conclusions that we did see in the study is that despite the fact that the majority fungus is one that inhabits humans, Trichophyton tonsurans, and which should have produced almost exclusively non-inflammatory ringworms, we found a higher percentage than usual of ringworms. inflammatory and one of the hypotheses that we handle is that behind it may be that with the very trauma of the razor when shaving, the fungus, which by itself should not produce so much inflammation, penetrated the deepest layers of the skin and produced it” , Bascón tells about this study, a collaborative work with 107 cases collected by Spanish specialists (there was a previous study done in Germany in 2021 on ringworm associated with hairdressing, but with a very small cohort: only 18 cases).

The authors have followed up on what Bascón presented in a presentation at the 50th Congress of the AEDV. “We surveyed the dermatologists who participated in the study and almost half, 47%, have perceived a decrease in the number of cases received in the four months since the article was published.. Therefore, we believe that the alert has worked, we do not know if due to greater awareness among adolescents because it had a great impact, for example, on TikTok with eight million views, or due to greater awareness of disinfection and sterilization measures in hairdressers. And the other half of dermatologists have hardly noticed any changes. Only 5% have noticed an increase in tinea capitis.”

The survey also asked dermatologists if they perceived that the Public Health authorities in their community had taken any action regarding this outbreak.. “The vast majority, 70%, were not aware that the Public Health of their autonomous community had done anything and we believe that Public Health should take more action on the matter.. Although it is not a notifiable disease, we would like to ask for more regulation at the level of hygiene measures in hairdressers to prevent it from happening again,” adds Bascón.

The danger of asymptomatic carriers

Those 107 cases were treated with oral terbinafine for an average of seven weeks, indicates Bascón, which is the treatment used for tinea capitis (between six and eight weeks minimum).. “In the body, topical treatments are generally used, but in the head, and I want to emphasize this, the topical treatment does not reach the follicle, so the treatment has to be oral, which can be combined with the topic, but never alone. topic. In some cases of tinea capitis that are only treated with topicals, the patient becomes what we call an asymptomatic carrier: he continues to have the fungus, but does not give him symptoms and the person does not perceive it as a problem, he continues to go to the hairdresser and have it treated. keep broadcasting because it was not treated well. That is why it is very important to have an influence, also for primary care physicians who are often the first filter, in oral treatment to prevent things from escalating.”

The dermatologist at the Hospital de Granollers says that for the moment they have not perceived resistance to the treatments, but the truth is that ringworm has always been present. “In some historical moments it was more prevalent, 18th-19th centuries; in others it decreased due to hygienic measures, greater control in veterinary matters, fewer stray animals that we see now, for example, but it has always been there.. Dermatophytes are a highly adaptable species. The one found in the study, T. tonsurans, is originally endemic to Southeast Asia and Australia, then spread to Central and South America during colonial times, and from there to Europe and the US, where it is currently responsible for more than 90% of tinea cases. capitis, with a predilection for people of African descent, and Microsporum canis is the second most common etiology. En tinea capitis, M. canis (zoophilic) is predominant in some European countries and in others T. tonsurans”, concludes Bascón.

For Vicente García-Patos, head of the Dermatology Service of the Vall d'Hebron Hospital in Barcelona, “these ringworms, and the majority of fungal infections in our environment, fortunately are superficial, affecting the skin and mucosa. The most common is athlete's foot or tinea pedis (ringworm of the foot).. From time to time there is an upturn in these superficial fungal infections, causing more or less extensive epidemics, as has happened with ringworm of the scalp related to the fashion of shaving hair.. But today we have very effective topical and oral antifungal treatments with a fantastic safety profile.”

In addition to ringworm on the scalp from shaving, there are other emerging mycoses, according to García-Patos. “Thanks to the improvement of molecular diagnostic techniques, we began to see specific cases, but that we had not seen before, of a species of unusual fungus. It was described less than 15 years ago, especially in Asia, and with globalization they are beginning to be described all over the world.. It is called Arthroderma or Trichophyton benhamiae and is mainly transmitted by guinea pigs, dogs and cats, causing superficial ringworm.. Fungal infections of the nails (onychomycosis) are also becoming more frequent: their incidence increases with age and we have an increasing life expectancy. On the other hand, the yeast Candida, a saprophyte of the digestive tract and the female genital mucosa, although it is part of the microbiome, can cause mucosal candidiasis, which is very annoying, when taking broad-spectrum antibiotics or oral or inhaled corticosteroids.”

Microscopic view of candidiasis. SHUTTERSTOCK

But García-Patos insists that this type is superficial, except when this candida can pass from the digestive tract or from vascular catheters into the blood and produce really serious infections.. “It occurs in immunosuppressed patients, for example, in extremely premature infants, in transplant recipients and in cancer patients. Although candidiasis continues to be the most common invasive fungal infection, the increase in immunosuppressed patients is also causing an increase in other angioinvasive fungal infections, such as aspergillosis, fusariosis, and mucormycosis.”

Immunocompromised patients, what worries the most

“There are two profiles of immunosuppressed patients especially susceptible to opportunistic fungal infections: those with very intense and generally acute immunosuppression, for example caused by chemotherapy, leukemia or a recent hematological or solid organ transplant, with profound neutropenia [ decreased white blood cells], where candidiasis and invasive aspergillosis predominate; and other chronic, long-term immunocompromised patients, such as solid organ transplant recipients who receive lifelong medications to prevent rejection, in whom some opportunistic fungi such as Alternaria and other phaeohyphomycoses (pigmented fungi that produce melanin) cause deep localized infections from trauma, which can sometimes even become systemic,” explains the dermatologist.

The specialist indicates that also many chronic treatments to treat immune-mediated, autoimmune or autoinflammatory diseases “encourage the innate and acquired defenses against fungi such as neutrophils and Th17 lymphocytes, which are essential for their control, to stop working and favor the development of these superficial, deep and systemic infections. Fortunately we have an arsenal of antifungal drugs, both topical and oral and intravenous, very broad and effective, but like all antibiotics and antimicrobials, rational use must be made to avoid generating resistance.. Most continue to work perfectly, but it is an important issue, as it happens with bacteria, since certain species of fungi that are no longer so sensitive to some antifungals are becoming more frequent, recommending the practice of in vitro sensitivity studies (antifungogram). ) especially in invasive mycoses”, emphasizes García-Patos.

This type of invasive opportunistic mycosis with systemic compromise is very serious in immunosuppressed patients and can cause a mortality of more than 50%.. In this context, the role of the dermatologist is very important, underlines García-Patos. “Many manifest with very subtle skin lesions, especially with purpura, vesicles, scabs, skin necrosis…. Multidisciplinary care of these patients, including the dermatologist, is essential for early recognition of these lesions, suspecting the diagnosis of invasive mycosis, taking the appropriate samples (skin biopsy and rapid techniques to identify fungi) and starting antifungal treatment as soon as possible. systemic, it's essential for the patient to get ahead.

García-Patos comments that in certain areas of the world there are so-called endemic deep mycoses. “For example, in South America there are a series of diseases, especially by direct inoculation or by inhalation of these spores, which cause endemic diseases, such as mycetoma, coccidioidomycosis and paracoccidioidomycosis.. They affect immunosuppressed people, but also immunocompetent people. The response to antifungals is less and some deep mycoses, which even affect the bone, may require amputations.. At the symposium on emerging mycoses [within the congress held by the AEDV] we have experts from Mexico and Paraguay, with extensive experience in these processes.”

The dermatologist warns: “Some mycoses typical of tropical or desert climates have not yet reached us, but migratory movements and climate change may justify their appearance in our environment, especially those related to the inhalation of spores.”