New insight into transmission dynamics of the crustacean pathogen Hematodinium perezi (Dinoflagellata) using a novel sentinel methodology Marine Ecology Progress Series

Hematodinium perezi causes disease and mortality in several decapod crustaceans along the eastern seaboard and Gulf coast of the USA. The route of transmission of the parasite is unknown, but infections exhibit a sharp seasonal cycle in its primary host, the blue crab Callinectes sapidus, that indicates the possibility of a short transmission period in its life cycle. We developed a sentinel methodology based on the use of naïve, uninfected, early benthic juvenile crabs (instars C1 to C10) to investigate the transmission of H. perezi. Crabs were collected from a non-endemic site, held for a short period for evaluation, and then deployed in a highly endemic site for 14 d. Transmission of the pathogen was successful; 12.7 to 25.7% of the crabs deployed at the endemic site became infected over this period. Infections developed rapidly, with 25% of new infections developing into heavy infections during the deployment. The large number of infections that developed using the sentinel methodology allowed for the first estimates of incidence (the proportion of new infections in a population over time) in this system. Incidence varied from 0.9 to 1.8% of the resident crab population per day and accounts for the high prevalence levels observed in the endemic coastal bays of the Delmarva Peninsula. The development of this sentinel methodology has broad application for studying disease ecology in this system and in other pathogens that infect decapods. Grant no. NA15NMF4270300