日照沿海养殖三疣梭子蟹血卵涡鞭虫流行病发生过程研究

血卵涡鞭虫(Hematodinium spp.)是一类严重危害海洋甲壳类动物的新型寄生性病原,可引发养殖三疣梭子蟹“牛奶病”,导致梭子蟹大量死亡,造成巨大经济损失。目前,对于血卵涡鞭虫在日照养殖梭子蟹中的流行发生情况还未见报道,2020年8月和2021年5～11月期间在日照主要梭子蟹养殖区开展流行病学调查研究,通过形态学观察、组织病理检测和分子生物学鉴定发现了血卵涡鞭虫(Hematodinium perezi)在日照地区的流行分布,并发现其流行病发生在6～9月间,高发期为7～8月,感染率高达52.5%。感染宿主的血淋巴和心脏、肝胰腺、鳃、肌肉等组织中发现了丝状滋养体、类变形虫滋养体、蛛网状滋养体、团块状聚合体、孢子前细胞和孢子等血卵涡鞭虫的多个生活史阶段。在养殖池塘环境水体中检测到血卵涡鞭虫存在,水体中血卵涡鞭虫丰度与宿主感染率存在错峰现象,间隔3～4周。流行病的发生与水体温度和盐度变化密切相关,7～8月较高的水温(26.2～28.6°C)促进了血卵涡鞭虫在宿主体内快速增殖及流行病爆发,而较低的盐度(20.7～25.3)可能抑制了环境水体中血卵涡鞭虫的存活及其传播扩散。以上研究结果初步...

EPIDEMIC OUTBREAK OF HEMATODINIUM DISEASE IN CULTURED PORTUNUS TRITUBERCULATUS ALONG RIZHAO COAST

The parasitic dinoflagellate Hematodinium is an emerging infectious pathogen affecting a broad range of marine crustaceans, causing milk diseases in cultured Portunus trituberculatus, eventually resulting in massive mortality of crabs and consequent large economic losses. At present, the distribution of Hematodinium parasites in mariculture area of Rizhao, Shandong, has not yet been studied. An epidemiological survey was conducted in major P. trituberculatus culture areas in Rizhao in August 2020 and May-November 2021. The distribution of Hematodinium perezi in Rizhao was identified by morphological observation, histopathological examination, and molecular identification. The Hematodinium epidemics occurred between June and September, and peaked in July and August with the highest prevalence of 52.5%. Multiple typical life stages of H. perezi including filamentous trophonts, amoeboid trophonts, arachnoid trophonts, clump colonies, prespores, and dinospores were observed in tissues (e.g. haemolymph, hepatopancreas, heart, gills) of Hematodinium-infected crabs. The presence of H. perezi was detected in pond water, and there was about 3~4 weeks interval between the peak of H. perezi abundance in ambient water and the prevalence in cultured P. trituberculatus. The occurrence of Hematodinium epidemics was closely related to the changes in temperature and salinity. The higher temperature (26.2~28.6 °C) in July-August contributed to the rapid proliferation of Hematodinium in crustacean hosts, resulting in the outbreak of Hematodinium epidemics. The lower salinity (20.7~25.3) likely inhibited the survival and spread of Hematodinium in environmental water. The present study preliminarily revealed the Hematodinium prevalence in Rizhao area, and further elucidated the ecological course of the occurrence of Hematodinium epidemics, and provided an scientific reference for the control and prevention of Hematodinium epidemics in future.