Bushek David, Ford Susan E, Chintala Marnita M
Baruch Marine Field Laboratory, Belle W. Baruch Institute for Marine Biology and Coastal Research, University of South Carolina, PO Box 1630, Georgetown, South Carolina 29442, USA.
Dis Aquat Organ. 2002 Oct 4;51(3):217-25. doi: 10.3354/dao051217.
Perkinsus marinus, a pathogen of the eastern oyster Crassostrea virginica, is transmitted directly among oysters. Previous studies found viable P. marinus parasites in the feces and pseudofeces of oysters within hours of injection with parasites, suggesting that the parasite may be voided from live oysters and subsequently dispersed in the water column. The experiments described here were designed to quantify P. marinus shed in the feces and pseudofeces of experimentally infected oysters. The results indicated that parasites were shed in 2 phases. A 'decreasing' phase occurred within 2 wk of challenge and before net parasite proliferation began in the host. An 'increasing' phase occurred after P. marinus had begun replicating. The quantity of P. marinus recovered in the feces and pseudofeces of exposed oysters was only about 5 % of the dose administered. In vitro-cultured P. marinus were eliminated at a greater rate than wild-type P. marinus and the fraction discharged was not associated with culture phase. Oysters that were continuously dosed with P. marinus in their food gradually lost the ability to discard the parasite in pseudofeces. The quantity of P. marinus shed in feces of infected oysters was correlated with both the P. marinus body burden and subsequent survival time, suggesting that noninvasive fecal counts could predict infection intensity and survival. The results indicate that in an epizootic, shedding of P. marinus via feces is relatively small compared to the potential number released by cadavers of heavily infected oysters, but that fecal discharge may be important in transmission before infections become lethal.
马里努斯派金虫（Perkinsus marinus）是美国东海岸牡蛎（Crassostrea virginica）的一种病原体，可在牡蛎之间直接传播。先前的研究发现，在向牡蛎注射寄生虫后的数小时内，其粪便和假粪便中存在存活的马里努斯派金虫寄生虫，这表明该寄生虫可能从活牡蛎中排出，随后散布在水柱中。此处描述的实验旨在量化实验感染牡蛎的粪便和假粪便中排出的马里努斯派金虫。结果表明，寄生虫分两个阶段排出。“减少”阶段发生在攻击后的2周内，且在宿主中寄生虫开始净增殖之前。“增加”阶段发生在马里努斯派金虫开始复制之后。暴露牡蛎的粪便和假粪便中回收的马里努斯派金虫数量仅约为给药剂量的5%。体外培养的马里努斯派金虫比野生型马里努斯派金虫的清除速度更快，且排出的比例与培养阶段无关。在食物中持续接种马里努斯派金虫的牡蛎逐渐失去了通过假粪便排出寄生虫的能力。感染牡蛎粪便中排出的马里努斯派金虫数量与马里努斯派金虫的体内负荷和随后的存活时间均相关，这表明非侵入性粪便计数可以预测感染强度和存活情况。结果表明，在一次流行病中，与重度感染牡蛎尸体释放的潜在数量相比，通过粪便排出的马里努斯派金虫相对较少，但在感染变得致命之前，粪便排出在传播中可能很重要。
