Etiological factors driving white feces syndrome in farmed Pacific whiteleg shrimp, Penaeus vannamei in Tamil Nadu, India

White feces syndrome (WFS) in Penaeus vannamei has a dynamic etiology in shrimp culture. The etiological factors associated with WFS, namely Enterocytozoon hepatopenaei (EHP), aggregated transformed microvilli (ATM), midgut parasites, and environmental factors (temperature, pH, salinity, ammonia, nitrate, and nitrite) were investigated within shrimp farms in the coastal districts of Tamil Nadu. The investigation encompassed 62 WFS-affected shrimp farms, along with a subset of three WFS-negative farms to ensure a comprehensive analysis. Severity scores (0, 1, and 2) were assigned for each factor and their interrelationship was investigated using principal component analysis (PCA). The PCA analysis highlights the endemic presence of EHP (52 farms), along with elevated nitrate, ammonia, and water salinity, as key driving factors of WFS in shrimp farms among the coastal districts of Tamil Nadu. Histological evidence unveils the high prevalence of ATM structures (54 farms) in the hepatopancreas of WFS-affected shrimps. Micro eukaryotes, including gregarines, cestodes, and digeneans, were commonly observed parasites in the white midgut of WFS-affected shrimps. The occurrence of WFS appears to be more frequent during rainy days and is particularly prevalent between 40 and 50 days of culture (DOC). The insights on the interrelationship between the etiological factors associated with WFS can contribute to a better understanding of management strategies and aid in the development of preventive measures to mitigate the occurrence of WFS in shrimp farms across Tamil Nadu, India.