[The occurrence of Cryptosporidium spp. in synanthropic flies in urban and rural environments].

This study was carried out to determine the role of non-biting synanthropic flies as carriers of Cryptosporidium spp. oocysts in the vicinity of the city of Gdańsk (NE Poland). In 2001-2003, flies were collected from three breeding sites: cow sheds and meadows in the Bystra cattle farm and municipal landfill Szadółki using inhaustors (aspirators) and entomologic nets. A total of 2358 specimens of the families: Muscidae (n = 1598), Calliphoridae (n = 739) and Sarcophagidae (n =21) were collected and analysed in 249 pools consisted of 9.5 insects, in average. Microscopic examination was used to detect Cryptosporidium spp. oocysts in the fly faeces deposited on the glass microscope slides and stained by Zhiel-Nielsen method. The mean number of faecal droplets per one glass slide was 11.5. Ooocysts of Cryptosporidium spp., stained from light pink to bright red, were found in fly faeces deposited on 25 (27.5%) of 91 glass slides checked. The highest prevalence of the pathogen was observed in faecal droplets deposited by flies collected in municipal landfill (50% investigated slides). DNA of Cryptosporidium spp. was extracted from the surface eluants of flies and/or their gut homogenates and purified. Then extracts were examined by PCR using CPB-DIAGF and CPB-DIAGR primers amplifying a variable region SSU-rRNA of all Cryptosporidium species. Altogether 387 isolates, 228 from surfaces and 159 from gut homogenates, were obtained from 249 pools of flies and analyzed. A specific 435 bp fragment of DNA was obtained in 49 (12.7%) lysates tested. In 10.4% pools, DNA of the pathogen was detected only in the surface eluants while in 7.6% only in gut extracts. In the case of two pooled samples (0.8%) Cryptosporidium spp. was found in both types of lysates. In total, Cryptosporidium spp. was detected in 47/249 pools of flies (18.9%). Assumed that each positive pool contained just one infected fly, the percentage of specimens able to oocysts transmission were calculated at the minimal level 2.0% (n = 47/2358). The result confirm that synanthropic flies can harbour oocysts of Cryptosporidium spp. both externally and internally, and disseminate them mechanically in the environment. Therefore, under unsanitary conditions they could be involved in the transmission of human and animal cryptosporidiosis.