The Role of Host Biology, Vector Biology, and Temperature in the Distribution of Trypanoplasma bullocki Infections in the Lower Chesapeake Bay

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Abstract
The hemoflagellate T. bullocki and its leech intermediate host, Calliobdella vivida, were studied concurrently over an 18-mo. period. C. vivida occurred throughout the lower Chesapeake Bay but was most abundant near the mouths of major rivers where salinity ranged between 15 and 22 ppt [parts per trillion]. C. vivida produced 1 generation/yr and aestivated in cocoons. Nine different fishes harbored C. vivida, and leeches fed on an additional 5 spp. in the laboratory T. bullocki infected 35% of 595 C. vivida examined, and infected 13 spp. of teleost fishes representing 10 families, although it was most prevalent in flatfishes. The hogchoker, Trinectes maculatus, was infected throughout the year, but infections in summer flounder, Paralichthys dentatus, were only observed during winter. Infections of T. bullocki in migratory fishes were rare and were restricted to periods of leech contact during early spring or late fall. Flagellates were rare in blood samples from hogchoker or absent in summer flounder for up to 9 wk after experimental inoculation by syringe or leech at 25.degree. C. Fishes subsequently cooled to 15.degree. C or less developed acute infections. This pattern was the result of host-mediated effects rather than of parasite temperature tolerance.