Environmental conditions in a lagoon and their possible effects on shellfish contamination by Giardia and Cryptosporidium

Abstract

Over a 1-year period, we carried out an analysis for the presence of Giardia and Cryptosporidium (oo)cysts in 934 specimens taken from four species of shellfish farmed in the Varano Lagoon. We also studied the chemical, physical and meteo-climatic parameters in the same environment, to evaluate the possible effects of environmental conditions on protozoan contamination in farmed shellfish. Using both IF and molecular tests, all 38 pools of shellfish gave negative values for Giardia and Cryptosporidium oo/cysts, thus confirming previous investigations. The environmental factors considered having a negative influence on the survival of Giardia and Cryptosporidium are high water temperatures (8–29°C) and high salinity levels (23–32 ppt). However, the small amount of freshwater discharged into the lagoon (up to 0.0091 m3 s−1), the long-lasting solar irradiation (mean of 896 W m−2) and the shallowness of the lagoon (mean 2.5 m) may also have a synergic effect in limiting the presence of Giardia and Cryptosporidium in the lagoon.