Scabies

Melanie Thompson is a paediatrician working in the Kimberley, WA. She is interested in indigenous health and dares you to listen to her talk without itching. Scabies is one of the world’s top 50 infectious diseases, and we thought it deserved the chance to shine. Say hello to our little friend…

The Global and Local Impact of Scabies

Scabies affects around 100 million people globally at any given time, placing it in the top 50 infectious diseases in terms of disability-adjusted life years. Its impact exceeds that of diseases like dengue fever.

In Australia, especially among children, scabies prevalence is alarmingly high, with rates even higher in tropical, under-resourced regions. – Prevalence of scabies worldwide—An updated systematic literature review in 2022 – Schneider – 2023 – Journal of the European Academy of Dermatology and Venereology – Wiley Online Library

If you think it has gone away, read this recent article in the Lancet.

Chosidow O, Fuller LC. Scratching the itch: is scabies a truly neglected disease?. The Lancet Infectious Diseases. 2017 Sep 20.

The Biology of Scabies

Scabies is primarily caused by the mite Sarcoptes scabiei var. hominis. This microscopic arthropod has a complex lifecycle involving egg-laying, larval, and adult stages, predominantly occurring on the human host. Understanding the lifecycle is crucial for effective treatment strategies.

The female mite burrows into the epidermis, laying eggs as it progresses into the stratum corneum. These eggs hatch into larvae, which then mature into adult mites.

Pathophysiology of Scabies

Immune Response and Inflammation: The burrowing of mites and their eggs, faeces, and saliva triggers an immune response in the human host. This response leads to inflammation, characterized by intense itching and a rash, typically developing several weeks after the initial infestation.

Delayed Hypersensitivity Reaction: The itching associated with scabies is primarily due to a delayed hypersensitivity reaction to the mites. The delay in symptom onset during initial infestation is due to the time the body’s immune system takes to develop this reaction.

Types of Scabies Infestation

Simple Scabies: Also known as ordinary scabies, this form is characterized by a limited number of mites on the body, usually less than 15. Symptoms include itching and a pimple-like rash, with burrows visible upon close examination.

Crusted Scabies: This more severe form of scabies, also known as Norwegian scabies, occurs primarily in individuals with weakened immune systems, such as those with HIV/AIDS, cancer, or those on immunosuppressive drugs. It is characterized by thick crusts of skin containing thousands of mites and eggs. Crusted scabies is highly contagious and more challenging to treat.

How is scabies spread?

Scabies is predominantly transmitted through prolonged skin-to-skin contact. This makes certain populations, such as children in schools, patients in healthcare facilities, and individuals living in crowded conditions, particularly vulnerable.

While scabies mites cannot survive long without a human host, transmission can occasionally occur through contaminated bedding, clothing, or furniture. This indirect transmission is more common with crusted scabies due to the higher number of mites.

Impact on Infants and Young Children:

Infants and young children are particularly susceptible to severe forms of scabies. Unlike adults, who typically develop the classic symptoms of itching and rash primarily between the fingers, wrists, and other body folds, infants may present with more widespread and severe symptoms. They often develop pustules and may exhibit rash on the palms of their hands and soles of their feet, areas less commonly affected in adults. This widespread distribution can lead to increased discomfort and risk of secondary infections due to the more delicate nature of their skin.

Diagnostic Challenges in Younger Age Groups:

Diagnosing scabies in infants and toddlers poses unique challenges. The symptoms in this age group can mimic other common pediatric skin conditions like eczema or diaper rash, leading to potential misdiagnosis.

Accurate diagnosis of scabies can be challenging, especially in its early stages or in atypical presentations. Skin scraping and microscopic examination are commonly used to confirm the presence of mites, eggs, or faecal matter (scybala).

Digital Imaging in Scabies

Digital imaging is a promising tool in diagnosing scabies. High-resolution digital cameras and specialized software can capture detailed images of the skin, allowing for a closer examination of the signs of scabies infestation. These images can then be analyzed for characteristics typical of scabies, such as burrows and the presence of mites.

Integrating digital imaging with telemedicine platforms can improve access to dermatological expertise, particularly in remote or underserved areas. Patients can have their skin condition assessed remotely by specialists, expediting diagnosis and treatment.

Machine Learning Algorithms in Scabies Detection

Machine learning algorithms are being explored for their potential to diagnose scabies. These algorithms can be trained on large datasets to recognize patterns and features indicative of scabies. A key benefit of using AI is the potential for increased accuracy and consistency.

While research in this area is still in its infancy, preliminary studies have shown promising results. The continuous development of AI models and the accumulation of more comprehensive image datasets will enhance the effectiveness of these tools.

How do we treat scabies?

The treatment options for scabies in young children and infants are more limited compared to adults. For example, permethrin cream, a common treatment for scabies, is typically advised only for children over two months of age. Similarly, oral treatments like ivermectin are not recommended for children weighing less than 15 kilograms. This demographic needs a carefully tailored approach.

The safety profile of scabies treatments is a crucial consideration in younger patients. Since their skin is more permeable, there is a higher risk of systemic absorption of topical medications.

The Social Implications of Scabies

Scabies, often perceived as a disease of poor hygiene or poverty, carries a significant stigma. This can lead to feelings of shame and embarrassment among affected individuals, particularly in children who may face bullying from their peers. Understanding this stigma is crucial, as it often leads to reluctance in seeking timely medical advice, thus exacerbating the spread of the disease.

In many communities, there’s a lack of understanding about scabies, its causes, and its transmission. This ignorance can lead to misconceptions and unwarranted fear, further isolating affected individuals and families. In close-knit communities, this could mean that affected children are kept out of school, and adults may face social ostracism or discrimination at work.

Healthcare providers play a critical role in educating patients and communities about scabies. Providing accurate information and dispelling myths can help reduce the stigma associated with the condition. This involves explaining that scabies is not necessarily a result of poor hygiene and can affect anyone, regardless of their living conditions or socioeconomic status.

Educational initiatives, particularly in schools and community centres, can change perceptions about scabies. These initiatives focus on how scabies is transmitted, its symptoms, the importance of seeking treatment, and ways to prevent its spread. This education helps destigmatise the condition and empowers communities to manage and prevent scabies outbreaks proactively.

Engaging with community leaders and influencers can be a powerful way to change perceptions at the grassroots level. These leaders can help disseminate accurate information, address cultural beliefs and practices that contribute to stigma, and advocate for the needs of affected individuals and families.

Empowering Patients and Families:

Empowering patients and their families through education and support is key. This includes teaching them about effective home management strategies, preventing re-infection, and the importance of completing treatment regimens. Support groups, either in person or online, can provide a platform for sharing experiences and coping strategies, reducing the sense of isolation.

By addressing the social implications of scabies through education, community engagement, and supportive care, we can create an environment where individuals are encouraged to seek treatment early. This improves outcomes for the individual and helps control the disease’s spread at the community level.

You can listen to this talk as you walk to work on any device that supports podcasts.

References

Psychological impact and social stigma: International Journal of Dermatology

Role of healthcare providers in scabies education: British Journal of General Practice

Public health campaigns and scabies: Health Promotion International

Community leadership in health education: Journal of Community Health

Scabies in infants and young children: Pediatric Dermatology

Challenges in diagnosing scabies in young children: Clinical Pediatric Dermatology

Safety and efficacy of scabies treatments in pediatrics: Journal of the American Academy of Pediatrics

Role of caregivers in scabies management: Family Practice

Emotional and psychological aspects of pediatric scabies: Child Psychiatry & Human Development

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