HISTORY AND EPIZOOTIOLOGY OF HAPLOSPORIDIUM-NELSONI (MSX), AN OYSTER PATHOGEN IN DELAWARE BAY, 1957-1980
HISTORY AND EPIZOOTIOLOGY OF HAPLOSPORIDIUM-NELSONI (MSX), AN OYSTER PATHOGEN IN DELAWARE BAY, 1957-1980
复制标题
DOI：
10.1016/0022-2011(82)90043-x
复制
发表时间：
1982-01-01
影响因子：
3.4
通讯作者：
HASKIN, HH
中科院分区：
文献类型：
--
作者：
FORD, SE;HASKIN, HH
1957至1959年间，一种以前不为人知的子孢子虫寄生虫，现在被命名为H.nelsoni(前身为Minchinia nelsoni)，或MSX，杀死了特拉华湾下部90%-95%的牡蛎。从那时起，对本地牡蛎进行了长达20年的研究，以确定这种宿主-寄生虫关联导致的长期疾病和死亡模式。本地牡蛎对MSX-KILE的抵抗力已经将疾病死亡率降低到原来的一半左右，尽管这种病原体在海湾仍然非常活跃。自最初的流行性动物流行以来，MSX水平呈周期性波动，每6-8年出现一次高峰。疾病压力低的时期紧随着非常寒冷的冬天，而平均或高于平均冬季温度与MSX活动高相关。在高峰期，下湾的每一只牡蛎都可能被感染。尽管这种寄生虫的盐度有限，但下湾的盐度几乎总是有利于MSX的，而河流流量的波动对该地区的MSX几乎没有影响。每年夏天，感染期都会复发。一些牡蛎在被感染后不久就会死亡；另一些在冬天存活，但在春季死亡，因为病原体复合了正常的越冬压力。当气温接近20度时，许多幸存者能够抑制或消除感染。C在晚春。本地牡蛎对MSX-KILE的抵抗力与预防感染的能力无关，而与寄生虫对局部非致命性病变的限制有关。在牡蛎稀少的地区持续存在感染热点，受感染的牡蛎中缺乏孢子，以及未能传播疾病，这在实验上导致了一种假设，即交替或储存宿主产生了MSX的感染期。
Between 1957 and 1959, a previously unknown sporozoan parasite, now designated as H. nelsoni (formerly Minchinia nelsoni), or MSX, killed 90-95% of the oysters in lower Delaware Bay. Native oysters were studied for > 20 yr since then to determine long-term disease and mortality patterns resulting from this host-parasite association. Development of resistance to MSX-kill in native oysters has reduced disease mortality to about half original level, even though the pathogen continues to be very active in the bay. Since the initial epizootic, MSX levels have fluctuated in a cyclic pattern with peaks every 6-8 yr. Periods of low disease pressure follow very cold winters, while average or above average winter temperatures correlated with high MSX activity. During peak years, every oyster in the lower bay may become infected. Although the parasite is salinity limited, salinities in the lower bay, the area from which oysters are marketed, are nearly always favorable for MSX, and fluctuations in river flow have almost no effect on MSX in this region. Infection periods recur each summer. Some oysters die soon after becoming infected; others survive through winter, but die in spring as the pathogen compounds normal overwinter stresses. Many survivors are able to suppress or rid themselves of infections when temperatures approach 20.degree. C in late spring. Resistance to MSX-kill in native oysters is not correlated with an ability to prevent infection, but with restriction of parasites to localized, nonlethal lesions. The persistence of hot spots for infection in areas where oysters are sparse, the lack of spores in infected oysters and failure to transmit the disease experimentally lead to the hypothesis that an alternate or reservoir host produces infective stages of MSX.