Ecoepidemiology of Zoothamnium sp. as a gill ectoparasite in Penaeus vannamei and its relationship with water parameters

Ecoepidemiología de Zoothamnium sp. como ectoparásito branquial en Penaeus vannamei y su relación con los parámetros del agua

Resumen

The ciliate protozoan Zoothamnium sp. acts as an epibiont on the gills and carapace of shrimp and, at high densities, can cause respiratory impairment, molting disorders, reduced growth, and mortality. This study examines the ecoepidemiological relationship between Zoothamnium sp. infestation on the gills of Penaeus vannamei (mean weight 12.5 ± 2.3 g) and environmental water conditions, to evaluate the influence of aquatic parameters on infection prevalence. The research was conducted on a shrimp farm in the Gulf of Venezuela, near Casigua, in Falcón state. Adult P. vannamei shrimp were captured, and their gills were extracted for pathological analysis and identification of Zoothamnium. The prevalence of the ciliate was calculated using the standard prevalence formula (P = N/Nt × 100) and correlated with physicochemical water parameters pH, salinity, temperature, and transparency using Pearson's linear correlation test. The results showed that decreasing pH and salinity, along with reduced water transparency, favored the proliferation of the protozoan on the shrimp gills. The strongest correlation was observed between water transparency and prevalence (r² = 0.891). Water parameters significantly influenced the prevalence of Zoothamnium, and a proper control of water quality is essential to mitigate the negative impacts of this protozoan in shrimp cultures, thereby improving health and productivity in aquaculture systems.