Van Wyk J A, Van Rensburg L J
Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110 South Africa.
Onderstepoort J Vet Res. 2003 Jun;70(2):121-9.
Over a period of about 12 years, 30 abnormal Schistosoma mattheei cercariae were found among a total of approximately 2.8 million examined. Initially seven were recovered from about 1.02 million (0.0007%), which were examined individually while being counted with the aid of a stereoscopic microscope. Subsequently, on the strength of relatively high percentages of abnormal individuals recovered when counting cercariae that failed to penetrate into oxen, it appeared that the morphologically abnormal cercariae were unable to swim and would mostly sediment out of a suspension while most of the normal cercariae would remain swimming. This surmise is supported by recovery of 23 morphologically abnormal cercariae (0.001%) from about 1.8 million, by examining the sediment after the cercarial suspension had been left standing undisturbed in glass measuring cylinders. The abnormalities ranged from aberrant tails only (e.g. an underdeveloped tail, or different degrees of schism) or aberrant heads only, to abnormalities of both the heads and tails. A suggested schematic classification of abnormal cercariae is presented. A young, adult hamster was exposed to eight S. mattheei cercariae with complete schism of the shaft of the tail, by pipetting the cercariae onto the shaved abdominal skin of the anaesthetised animal. Two underdeveloped females were subsequently encountered in squash preparations of the liver when the hamster was killed for worm recovery 10 weeks after infection, thus showing that some of the abnormal cercariae were viable. A method is also described for killing and fixing cercariae while retaining some of the shining brilliance of live cercariae, without them becoming shrivelled, granular and semi-opaque, as occurs when cercariae die spontaneously or are killed with heat. This is apparently the first report of abnormal cercariae of S. mattheei. In addition, a method of concentrating abnormal cercariae after emergence from a snail, a schematic classification of abnormal cercariae and a method for killing and fixing cercariae while retaining much of the shiny brilliance of live cercariae are also reported for the first time as far as is known.
在大约12年的时间里，在总共约280万只接受检查的血吸虫中，发现了30只异常的马特血吸虫尾蚴。最初，在约102万只（0.0007%）中发现了7只，这些尾蚴是在借助体视显微镜计数时逐个检查的。随后，由于在对未能穿透牛体的尾蚴计数时发现异常个体的回收率相对较高，似乎形态异常的尾蚴无法游动，并且在悬浮液中大多会沉淀下来，而大多数正常尾蚴仍会保持游动状态。当尾蚴悬浮液在玻璃量筒中静置后检查沉淀物时，从约180万只中回收了23只形态异常的尾蚴（0.001%），这一推测得到了证实。异常情况从仅尾部异常（如尾部发育不全或不同程度的裂开）或仅头部异常，到头部和尾部均异常不等。本文给出了异常尾蚴的示意性分类。通过将尾蚴移液到麻醉动物剃毛的腹部皮肤上，使一只幼年成年仓鼠接触8只尾部轴完全裂开的马特血吸虫尾蚴。感染10周后，当仓鼠被处死以回收虫体时，在肝脏的压片标本中随后发现了2只发育不全的雌虫，从而表明一些异常尾蚴是有活力的。本文还描述了一种杀死并固定尾蚴的方法，同时保留活尾蚴的一些光泽，而不会像尾蚴自然死亡或受热杀死时那样变得皱缩、颗粒状和半透明。这显然是关于马特血吸虫异常尾蚴的首次报告。此外，据所知，本文还首次报告了一种从蜗牛中逸出后浓缩异常尾蚴的方法、异常尾蚴的示意性分类以及一种杀死并固定尾蚴同时保留活尾蚴大部分光泽的方法。
