Transmission Routes and a New Freshwater Crustacean Host for Infectious Precocity Virus (IPV)

Macrobrachium rosenbergii holds significant importance in aquaculture within tropical and subtropical regions globally. An infection called infectious precocity virus disease (IPVD), caused by infectious precocity virus (IPV), has emerged in M. rosenbergii in China and causes significant economic losses. The diseased M. rosenbergii presents with the characteristics of sexual precocity and slow growth. Elaborating the route of transmission and host range of IPV is necessary to prevent the disease. Transmission of IPV to healthy M. rosenbergii can occur through the ingestion of IPV-infected tissue, immersion of viral filtrate, cohabitation with infected M. rosenbergii, or water-borne transmission in contaminated environment. Results showed that fertilized eggs and different growth and development stages (larvae Ⅰ-Ⅵ, postlarvae, juveniles, and adult prawns) from infected M. rosenbergii were negative for IPV, indicating that vertical transmissions did not occur. The results of artificial infection experiments showed that M. nipponense tested positive for the presence of IPV, but not in fishes Carassius auratus, Pangasius bocourti, Micropterus salmoides, and Oreochromis mossambicus, and crabs Scylla paramamosain and Eriocheir sinensis. IPV could cause slow growth in M. nipponense and mainly infected the second pereiopod, brain, eyes, and gills of M. nipponense. M. nipponense was found to be a new freshwater crustacean host for IPV. From December 2019 to March 2022, 260 M. nipponense samples in four regions were collected, including 230 M. nipponense IPV-positive samples according to nested PCR and 40 M. nipponense IPV-negative samples according to nested PCR. These findings could aid in preventing and managing IPV infections in crustaceans.