Ragone Calvo L M, Walker J G, Burreson E M
School of Marine Science, Virginia Institute of Marine Science, College of William and Mary, Gloucester Point, Virginia 23062, USA.
Dis Aquat Organ. 1998 Jul 30;33(3):209-19. doi: 10.3354/dao033209.
In July 1996, the Virginia Institute of Marine Science initiated a sampling program to examine wild and cultured hard clams Mercenaria mercenaria for QPX, Quahog Parasite Unknown, a protistan parasite associated with severe mortalities of hard clams in localized areas in maritime Canada and Massachusetts, USA. The sampling program set out to seasonally monitor wild clams from one site, James River, Virginia, and cultured clams from 2 sites, Chincoteague Bay and Mattawoman Creek, Virginia. Histological examination of initial samples revealed 8% prevalence of the parasite in 1-2 yr old cultured clams in Chincoteague Bay. This is the first documentation of QPX in Virginia. To ascertain the distribution of the parasite in Virginia, the survey was expanded between August 1996 and July 1997 to include 16 additional sites. A total of 1305 wild and cultured clams was sampled from Chesapeake Bay tributaries and coastal areas where harvest and culture occur. QPX was not found in Chesapeake Bay, but was present in cultured clams from 3 coastal embayments--the original Chincoteague Bay site, Burton Bay and Quinby Inlet. The parasite was found in Chincoteague Bay at each sample period at prevalences ranging from 8 to 48%. Infections were generally light to moderate intensity and were most often observed in mantle and gill tissues. The maximum prevalence was observed in May 1997 and coincided with notable clam mortalities. QPX prevalences at the other sites were low, ranging from 4 to 15%. To date QPX has not had a significant impact on Virginia's hard clam fishery and aquaculture industry; however, the presence of the pathogen in 3 of the state's most productive hard clam growout areas warrants continued monitoring and research.
1996年7月，弗吉尼亚海洋科学研究所启动了一项采样计划，对野生和养殖的硬壳蛤（Mercenaria mercenaria）进行检测，以查找“蛤类寄生虫X（QPX，Quahog Parasite Unknown）”。QPX是一种原生生物寄生虫，与加拿大沿海地区和美国马萨诸塞州局部地区硬壳蛤的严重死亡事件有关。该采样计划旨在对弗吉尼亚州詹姆斯河一个地点的野生蛤以及弗吉尼亚州钦科蒂格湾和马塔沃曼溪两个地点的养殖蛤进行季节性监测。对初始样本的组织学检查显示，钦科蒂格湾1至2岁的养殖蛤中该寄生虫的感染率为8%。这是QPX在弗吉尼亚州的首次记录。为确定该寄生虫在弗吉尼亚州的分布情况，1996年8月至1997年7月期间，调查范围扩大至另外16个地点。共从切萨皮克湾支流以及有收获和养殖活动的沿海地区采集了1305只野生和养殖蛤。在切萨皮克湾未发现QPX，但在3个沿海港湾——钦科蒂格湾的原始地点、伯顿湾和昆比湾的养殖蛤中发现了该寄生虫。在钦科蒂格湾的每个采样期都发现了这种寄生虫，感染率在8%至48%之间。感染强度一般为轻度至中度，最常出现在外套膜和鳃组织中。1997年5月观察到最高感染率，同时出现了明显的蛤类死亡现象。其他地点的QPX感染率较低，在4%至15%之间。迄今为止，QPX尚未对弗吉尼亚州的硬壳蛤渔业和水产养殖业造成重大影响；然而，该病原体在该州3个最主要的硬壳蛤养殖区的存在，仍需要持续监测和研究。
