Perkinsus spp. displays a remarkably broad spectrum of host organisms, and all stages after settlement are susceptible (even if infection intensity increases with the age of the host.) . Documented hosts encompass various clam species such as Sydney cockle Anadara trapezia, little− neck cockles Austrovenus stutchburyi , grooved carpet shell Ruditapes decussatus , Japanese carpet shell R. philippinarum , etc. Additionally, oysters (e.g., Jinjiang Oyster Crassostrea ariakensis, black− lipped pearl oyster Pinctada margaritifera, etc.) are confirmed hosts. Within the known geographic range, other bivalve and gastropod species may potentially fall prey to this parasite. Notably, members of the Arcidae, Malleidae , Isognomonidae , Chamidae , and Veneridae families exhibit particular susceptibility.
This has substantial implications for both the fisheries and aquaculture sectors, resulting in substantial economic losses. Prevalence is highly variable depending on host and environmental conditions, but it is often 100% . Infections in clam hosts can be lethal depending on environmental conditions, and death may occur 1 or 2 years after infection.
Histology remains a pivotal and conventional diagnostic method for detecting Perkinsus spp., although polymerase chain reaction (PCR) , in situ Hybridization (ISH) , and t ransmission electron microscopy (TEM) are recommended to provide a species−specific diagnosis. This study investigates Perkinsus spp. infections in wild Grooved carpet shell R. decussatus collected from three distinct brackish environments in Sardinia, Italy ( i.e., Calich, Porto Pozzo, and Santa Gilla) dedicated to extensive aquaculture.
Histological analysis of tissue sections from each clam (n=300) was performed to identify the presence of Perkinsus spp., determine its prevalence, and assess the immune response in t arget organs and infected tissue (i.e., connective tissue of all organs, and haemocytes). Perkinsus spp. were retrieved in all sites, with varying infection percentages and a substantial host immune response. The highest prevalence was recorded in clams from Calich lagoon, particularly in the digestive gland (37%) and gills (68%). Porto Pozzo and Santa Gilla lagoons displayed a gill prevalence of 23%. Anyway , the prevalence of Perkinsus spp. in the kidney was less frequent across all sampling sites, with parasite presence ranging from 7% (Porto Pozzo lagoon) to 22% (Calich lagoon). The presence of haemocytes infiltration, observed across all sites and organs, was significantly correlated with the protozoan Perkinsus spp. (p<0.001). R. decussatus were found to be suitable as biological indicators sensitive to environmental stressors, such as perkinsosis. However, further monitoring plans in these areas are essential.