Prevalence of Sarcoptes scabiei in Patients with Suspected scabies

Objective: Scabies is caused by an ectoparasite called Sarcoptes scabiei (S. scabiei), which penetrates the epidermis through skin folds and burrows in the stratum corneum, following the development of tunnels (sillion). The disease is specifically characterised by keratosis, allergy and itching that increases at night-time. This study aimed to investigate the frequency of S. scabiei in patients with a pro-diagnosis of scabies. Objective: Between January 2012 and December 2019, a total of 746 [n=388 (52%), female; n=358 (48%) male] patients aged 0-80 years were admitted to Firat University Hospital Parasitology-mycology Laboratory. Skin scrapings were taken from suspected lesions on anatomic regions such as the hands (wrist, interdigital skin, fingertip and palm), abdomen, penis and legs (thigh and bottom foot). They were examined under a light microscope after adding 15% potassium hydroxide solution. Results: S. scabiei was positive in 139 (18.63%) of 746 patients including a mother and her daughter and a married couple, where 68 (9.11%) were female and 71 (9.52%) were male. Conclusion: To our best knowledge, this is the first comprehensive study of scabies in Elazig. Despite the recent socio-economic and cultural developments observed in our country, scabies and all other parasitic infestations still remain to be important problems. We believe that improvement of the public vigilance together with early diagnosis will improve sanitation and provide protection against scabies and parasitic infestations.

Ribosomal and mitochondrial DNA sequence variation in Sarcoptes mites from different hosts and geographical regions.

In order to investigate the extent of the genetic variation in the DNA sequences of Sarcoptes scabiei, mite populations collected on Alpine chamois ( Rupicapra rupicapra), Pyrenean chamois ( Rupicapra pyrenaica) and red fox ( Vulpes vulpes) from different localities of Italy and Spain were studied. Sequence analyses were carried out on the second internal transcribed spacer of the nuclear ribosomal DNA and on the 16S mitochondrial rRNA gene. ITS-2 sequences showed a higher degree of genetic polymorphism, mostly randomly distributed in the isolates from different hosts and localities, although both genomic regions are characterised by fixed nucleotide substitutions which were able to discriminate the mites collected on Pyrenean chamois from north-western Spain and on foxes from north-eastern Spain and from north-western Italy with respect to the other isolates. These results suggest the existence of a limitation to free gene exchange between the studied populations, probably related to the genetic structuring of local populations rather than to a differential adaptation to host species.

Findings in vivo of Sarcoptes scabiei with incident light microscopy.

Parasites, especially Sarcoptes scabiei, may represent a difficult diagnostic problem. In many cases, the results of the usual methods for the diagnosis of scabies, such as microscopic identification, can be negative owing to the small number of parasites present in the cornified layer. Moreover, tape stripping or removal of mites with a needle is difficult and sometimes painful, and therefore, not well accepted. We have evaluated the applicability and usefulness of epiluminescence microscopy, a new technique frequently used for the study of pigmented lesions of the skin. Thirty seven patients with the presumptive clinical and/or anamnestic diagnosis of scabies were enrolled in our study. With this method many suspicious sites may be examined within a few minutes without causing any harm or discomfort to the patient.

The behaviour of Sarcoptes scabiei var. hominis in human skin: an ultrastructural study.

The biology of Sarcoptes scabiei var. hominis is poorly understood because of the lack of an in vivo or in vitro propagation system. To obtain more information on the mite behaviour in its natural habitat we conducted an ultrastructural study of burrows in a number of patients with common scabies. Scanning electron microscopy furnished attractive images of the tunnel, parasite body and eggs architecture and demonstrated the presence of holes in the tunnel roof probably representing aeration structures. Transmission electron microscopy showed a marked keratinocyte damage around burrowing mites, well evident ahead of the mite capitulum also. Faecal pellets containing keratinocyte micro-organelles (melanosomes and mitochondria) were documented in posterior midgut. For the first time we disclosed the adhesion mechanism of eggs to the burrow floor. We showed that the typical finger-like projections of the outer layer of the egg shell gradually disappear where the eggs are in contact with the tunnel floor. This allows the inner layer of the egg shell to fuse and stick with the damaged keratinocytes lining the tunnel floor. Our observation substantiates that Sarcoptes scabiei produces a proteolytic substance (salivary secretions?) that has a key role in its life cycle allowing burrowing, feeding and eggs-burrow adhesion.