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.
Keywords: Amazon lowland; Amerindian communities; diagnosis; digital handheld microscope; resource-poor setting; scabies.