Is Demodex really non-pathogenic?

Although usually considered a non-pathogenic parasite in parasitological textbooks, Demodex folliculorum has been implicated as a causative agent for some dermatological conditions, such as rosacea-like eruptions and some types of blepharitis. Several anecdotal reports have demonstrated unequivocal tissue damage directly related to the presence of the parasite. However, this seems to be exceedingly rare, in contrast with the marked prevalence of this infestation. We have had the opportunity to observe one of such cases. A 38-year-old woman presented with rosacea-like papular lesions in her right cheek. Histopathological examination revealed granulomatous dermal inflammation with a well-preserved mite phagocytized by a multinucleated giant cell. This finding may be taken as an evidence for the pathogenicity of the parasite, inasmuch as it does not explain how such a common parasite is able to produce such a rare disease.

Schistosoma japonicum-like ova in liver and rectal biopsies of three cases in Sabah, Malaysia.

Three cases of schistosomiasis in 2 Filipinos and one Chinese in Sabah are reported. Diagnosis was based on incidental histological findings of Schistosoma japonicum-like ova in the liver and rectal biopsies. As these 3 patients are immigrants to Sabah, it is assumed that they are imported cases, and that Sabah has been free of the disease from 1970 to 1977.