Cyclospora spp. in herbs and water samples collected from markets and farms in Hanoi, Vietnam

To determine the prevalence of Cyclospora spp. oocysts in herb and water samples as well as in fecal specimens of clinical cases of diarrhoea in Hanoi, Vietnam. From November 2004 to October 2005, water and herb samples collected from markets and farms in Hanoi were examined for the presence of Cyclospora spp. oocysts in concentrated sediments and washings using UV epifluorescence examination of a wet mount. In addition, hospital based surveillance studies were carried out using a structured questionnaire which focused on potential risk factors for cyclosporiasis. Stool specimens were collected from individuals with diarrhoea attending primary healthcare facilities and examined for Cyclospora spp. oocysts by modified acid fast smear and wet mount examination using both light and UV epifluorescence microscopy. Cyclospora spp. were found in 34/288 (11.8%) market water and herb samples, and in 24/287 (8.4%) farm samples. All varieties of herbs sold at the market and grown in farms were contaminated with Cyclospora spp. oocysts. A marked seasonal increase in Cyclospora spp. contamination was observed before the rainy season (39/288) from November to April compared to the rainy season (19/268) from May to October (chi(2) = 7.593, P = 0.006). However, Cyclospora spp. was not found in any stool samples collected in hospital-based surveillance studies. These results confirm the presence of Cyclospora spp. which varies seasonally in environmental samples (water and herbs collected from farms and markets) within the Hanoi metropolitan area.