Dynamics of haemocytes from Pseudosuccinea columella circulating infected by Fasciola hepatica

Abstract The lymnaeids are important in the epidemiology of Fasciola hepatica, a neglected and endemic zoonosis. The interaction between the internal defense system of Pseudosuccinea columella and F. hepatica has been little studied. In the present study the effect of infection by F. hepatica on P. columella circulating haemocytes was investigated. Changes in the average number of total circulating haemocytes have been observed at 30 minutes post-infection and 1, 7, 10, 14, 21, 28 and 50 days post-infection (dpi). Miracidia were observed head-foot and mantle at 30 minutes post-infection. Miracidia/Sporocysts in the mantle skirt 1 dpi, and fully formed sporocysts were observed in the head-foot at 7 dpi. Rediae became evident at 10 dpi and were located between the haemocoel and the muscles from 14 dpi; 50 dpi, the rediae in the digestive gland contained cercariae. The statistical analysis of the total haemocytes of P. columella infected by F. hepatica showed significant differences on the 30 minutes post-infection and 1, 14, 21, and 28 dpi in comparison to uninfected molluscs (0 dpi). Therefore, the interference observed on the internal defence system of P. columella may have direct association with the development of F. hepatica.

摘要 椎实螺类（lymnaeids）在肝片形吸虫（Fasciola hepatica）的流行病学传播中发挥着关键作用，该寄生虫是一种被忽视的地方性人畜共患病。目前针对柱状拟琥珀螺（Pseudosuccinea columella）体内防御系统与肝片形吸虫之间的相互作用的研究尚少。本研究探究了肝片形吸虫感染对柱状拟琥珀螺循环血淋巴细胞（circulating haemocytes）的影响。我们分别在感染后30分钟、感染后1、7、10、14、21、28及50天（dpi，感染后天数），对循环血淋巴细胞的总数量均值变化进行了观测。感染后30分钟时，可在宿主头足区与外套膜中观测到毛蚴（miracidia）；感染后1天，外套膜褶中出现毛蚴/胞蚴（sporocysts）；感染后7天，头足区可见完全发育的胞蚴。雷蚴（rediae）于感染后10天开始显现，自感染后14天起，其定位于血腔（haemocoel）与肌肉组织之间；至感染后50天，消化腺内的雷蚴已携带尾蚴（cercariae）。对感染肝片形吸虫的柱状拟琥珀螺的总血淋巴细胞进行的统计分析显示，相较于未感染的软体动物（molluscs，感染后0天），感染后30分钟、1、14、21及28天的总血淋巴细胞数量存在显著差异。综上，本研究观测到的柱状拟琥珀螺体内防御系统受到的干扰，可能与肝片形吸虫的发育进程存在直接关联。