Seasonal and water quality significance of gregarine protozoan parasites occurrence in Wild Bivalve, Anadara cornea (Reeve, 1844) from Terengganu, Malaysia

Malaysia is known as a country that experience two main seasonal patterns, i.e., monsoon and non-monsoon season. Three different categories of seasons based on the quantity of rainfall were divided by previous studies started from January to December 2018, which are dry season, moderate season and rainy season. Wild bivalve, Anadara cornea populations at Setiu Lagoon in Terengganu, Malaysia was examined for gregarine parasites for a year. The objective of this study was to associate the incidence of gregarine in common wild bivalves, A. cornea (Reeve, 1844) concerning seasons and water quality parameters. From the study, the total number of phagocytes found was n = 33,239, with a total of 480 host samples. The total prevalence of the parasites was 97.5%, with a 95% confidence interval value which was CI=96.1% to 98.9%. The prevalence of the parasites was significantly higher during the rainy season as compared to dry and moderate seasons. The findings also proved that the intensity of the parasites decreased at every transition of season. In-depth, the correlation between the prevalence of the parasites vice versa, season, and water quality might be contributed to the intensity of the parasite infestation needs to be clarified.