Sirs, Parija and Srinivasa's plea for structured application of high-quality stool microscopy in patients suffering from frank or suspect parasitoses ( Parija & Srinivasa 1999) merits warm support ( Berlin et al. 1999 ). We would like to add to the authors' considerations the usefulness of microscopy in outbreaks of diarrhoea of bacterial or viral aetiology that could have been triggered by contaminated food or drinking water ( Mossel & Struijk 1999). This may show preponderance of particular bacterial types and/or intact or lysed blood corpuscula. Microscopic monitoring may even point to a viral causative agent, if none of the typical characteristics of the most prevalent enterobacterioses or parasitoses can be detected. Microscopy may provide guidance to and substantially accelerate diagnosis, therapeutic intervention and sometimes even containment of further morbidity from the same source.
Control of outbreaks is, in addition, particularly facilitated by microscopic inspection of food ( Breed 1911; Brekenfeld 1932; Pantaléon & Baudeau 1958; Mossel & Zwart 1959; Mossel & Visser 1960) or water ( Zuckerman et al. 1999 ) specimens that could constitute the putative vectors of disease ( Mossel et al. 1995 ). We have successfully used the key in Table 1 for decades. It is submitted for trial to the readership, particularly in regions with limited resources. Even in privileged areas of the world, it is often most difficult to identify and microbiologically examine food specimens without delay in the condition in which they were ingested. An appropriately stained smear of a food macerate according to the procedure in Table 1 will provide tentative information for fast diagnosis and intervention.