Comparison of in vitro-cultured and wild-type Perkinsus marinus. II. Dosing methods andhost response

[摘要] ABSTRACT: Endoparasites must breach host barriers to establish infection and then must survive host internal defenses to cause disease. Such barriers may frustrate attempts to experimentally transmit parasites by Œnatural¹ methods. In addition, the host¹scondition may affect a study¹s outcome. The experiments reported here examined the effect of dosing method and host metabolic condition on measures of virulence for the oyster parasite Perkinsus marinus. Oysters, Crassostreavirginica, were challenged with wild-type and cultured forms of P. marinus via feeding, shell-cavity injection, gut intubation and adductor-muscle injection. For both parasite types, adductor-muscle injections produced the heaviest infectionsfollowed by shell-cavity injection, gut intubation, and feeding. There was no difference in parasite burdens between oysters fed cultured cells by acute vs chronic dosing, and parasite loads stabilized over time, suggesting a dynamic equilibrium betweeninvasion and elimination. P. marinus distribution among tissues of challenged oysters indicated that parasites invaded the mantle and gill, as well as the gut, which has been considered the primary portal of entry. Frequency distributions of P.marinus in oysters challenged with 3 different culture phases indicated an aggregated distribution among hosts and suggested that stationary-phase parasites were easiest for the oyster to control or eliminate and log-phase parasites were the mostdifficult. Host metabolic condition also affected experimental outcomes, as indicated by increased infection levels in oysters undergoing spawning and/or exposed to low oxygen stress.

[学科分类] 生物科学（综合）

[关键词] Disease;Parasite;Oyster;Crassostrea virginica;Portal of entry;Metabolic condition