Population model for Amyloodinium ocellatum infecting the spotted seatrout Cynoscion nebulosus and the red snapper Lutjanus campechanus

Abstract

The dinoflagellate Amyloodinium ocellatum, a major pathogen in warm water mariculture, has a trophont, a tomont and a dinospore life history stage. This paper presents a population model for A. ocellatum infecting spotted seatrout Cynoscion nebulosus and red snapper Lutjanus campechanus and evaluates the relative effect of each vital rate on the A. ocellatum population growth rate. The vital rates were estimated by incubating trophonts in vitro and tracking their development through the successive life history stages at 25°C and 33 ppt. The A. ocellatum population growth rate was 1.90 d-1 for spotted seatrout and 1.92 d-1 for red snapper. Highest elasticity values (0.24 and 0.23 in spotted seatrout and red snapper, respectively) corresponded to transitions from the dinospore to the trophont stage, the trophont stage to the tomont stage and the tomont stage back to the dinospore stage in both host species (self-loops not included). A 50% change in vital rates showed that the mean number of dinospores produced by a tomont had the largest effect on the A. ocellatum population growth rate (15%), followed by the dinospore infection rate (14%), the tomont sporulation rate (12%) and the dinospore mortality rate (10%) in both host species. A comparison of modeled and experimental vital rate threshold values revealed a 2.5- (spotted seatrout) or a 2.6-fold (red snapper) difference in the values for dinospore mortality, which is the smallest difference among all the modeled and experimental vital rates. Therefore, measures that increase dinospore mortality have a greater likelihood of influencing the outcome of an epidemic.

An epidemiological model for proliferative kidney disease in salmonid populations

“…Successful application of epidemiological models for these diseases fundamentally relies on the incorporation of the ecological dynamics of the different host populations. In the context of fish diseases, epidemiological models have been exploited to address various issues, such as sea lice infection on salmon farms [22]; Koi herpes virus of the common carp ( Cyprinus carpio ) [23]; amyloodinosis, a disease of warm water mariculture [24]; fish-borne zoonotic trematodes in agriculture-aquaculture farms [25]; Ceratomyxa shasta , a myxozoan parasite endemic to river systems throughout the Pacific northwest region of North America [26]; and whirling disease, a myxozoan disease of farmed and wild salmonids [27]. As for PKD, the only modeling attempt used a Bayesian probability network to assess the decline of brown trout, citing PKD as a driver of increased mortality [28].…”

Amyloodiniosis in aquaculture: A review

“…We can also produce parasites via an uncontrolled methodology to produce tomonts, dinospores, and trophonts, 44,153,161 which produces good but very variable quantities of parasites. This is due to the difficulties in maintaining a stable and controlled number of A. ocellatum in the tanks that gives time to the fish to be infested and shed tomonts to the system that will allow the maintenance of the dinospore population.…”

Establishment of a gill cell line from yellowfin seabream (Acanthopagrus latus) for studying Amyloodinium ocellatum infection of fish

“…The dinospores are the infectious stage of the parasite, which lives freely in the water in search of a new host. The gills are the primary infection site for the dinospores (Dequito et al., 2015; Landsberg et al., 1994; Levy et al., 2007; Li et al., 2023; Masson, 2009). In addition, A. ocellatum has a low host specificity, allowing it to infect a taxonomically diverse host range and reproduce at temperatures ranging from 18 to 30°C (Paperna, 1984).…”