Profuse diarrhoea in an immunocompetent returning traveller

A middle-aged man who recently travelled to Brazil presented to our centre with a one-week history of profuse watery diarrhoea and mild gastrointestinal symptoms. Microbiological investigation of a faecal sample was negative for Salmonella, Shigella, Campylobacter and Escherichia coli O157. No parasites were seen in direct microscopic examination of a formalin-ethyl acetate concentrated sample. However, examination of a modified acid-fast stained smear showed several spherical oocysts of Cyclospora measuring 10-12 μm in diameter. Oocysts demonstrated variable degree of staining from intensely red (Fig.1a), partially stained (Fig. 1b) to not stained at all (Fig. 1b, black arrows). Oocysts of Cyclospora are morphologically similar to those of Cryptosporidium, however, the larger sizein Cyclospora, is a useful features to differentiate these two parasites. Oocysts of Cyclospora can also be visualised in an unstained wet preparation of faecal specimens. In addition, they will autofluoresce when examined under ultraviolet (UV) microscope. Recently, several commercial, FDA-approved molecular diagnostic panels became available for direct and specific detection of Cyclospora with high sensitivity.