In Situ Diagnosis of Scabies Using a Handheld Digital Microscope in Resource-Poor Settings-A Proof-of-Principle Study in the Amazon Lowland of Colombia.

Hollman Miller,Julian Trujillo-Trujillo,Hermann Feldmeier

doi:10.3390/tropicalmed3040116

Abstract

Scabies is a neglected tropical disease associated with important morbidity. The disease occurs worldwide and is particularly common in resource-poor communities in the Global South. A validated technique for the diagnosis of scabies in resource-poor settings does not exist. The objective of the study was to determine the practicability and accuracy of handheld digital microscopy in three indigenous communities in the Amazon lowland of Colombia, where scabies is the most common parasitic skin disease. One-hundred-and-eleven children and adults from three indigenous communities with a presumptive diagnosis of scabies were examined clinically by using a handheld digital microscope placed directly on the skin. The microscopical identification of a mite was verified by an “experienced mother”, a woman who had acquired the skills to diagnose scabies as part of traditional Amerindian medicine. The “experienced mother” removed the parasite with a fine needle and placed it on a flat surface in order to enable its direct examination with the digital microscope. Using digital microscopy, scabies was diagnosed in 24 out of 111 participants and confirmed by the extraction of a Sarcoptes mites from the acarine eminence. A characteristic tunnel (burrow) with or without mite could be clearly identified irrespective of the degree of pigmentation of the skin. Besides, digital microscopy revealed pathological characteristics of scabies hitherto unknown and impossible to be seen in dermoscopy, such as partially or totally obliterated tunnels, tunnels with multiple entry or exit points, circumscribed hyperpigmentation around obliterated tunnels and mites secluded in a nodule. This proof-of-principle study demonstrated the accurate diagnosis of scabies by handheld digital microscopy in patients with pigmented skin and the feasibility of this technique in resource-poor settings.

Highlights

A parasitic skin disease caused by the mite Sarcoptes scabiei var. hominis, causes considerable morbidity through both direct effects and secondary bacterial infection [1,2,3,4]
As scabies can mimic a spectrum of skin diseases of infectious and non-infectious etiology, its clinical diagnosis requires experience
We show that (i) Sarcoptes mites can be reliably detected inside the tunnel they have created; (ii) tunnels vary considerably in shape, length and structure; and (iii) if a mite is present, it is almost always located in the acarine eminence at the end of the tunnel

Summary

Introduction

A parasitic skin disease caused by the mite Sarcoptes scabiei var. hominis, causes considerable morbidity through both direct effects and secondary bacterial infection [1,2,3,4]. The disease occurs worldwide and is common in resource-poor communities in the countries of the Global South [7,8]. As scabies can mimic a spectrum of skin diseases of infectious and non-infectious etiology, its clinical diagnosis requires experience. Clinical manifestations may differ between babies, children and adults [12,13], and may vary between settings [14,15] and in the tropics, bacterial superinfection can further complicate the diagnosis [4,8,16]. To enable effective case management in the countries of the Global South, a diagnostic method is needed which is accurate and appropriate in people with moderately to intensely pigmented skin

Objectives

Methods

Results