淡水养殖凡纳滨对虾IHHNV-WSSV共感染率调查分析及其对免疫相关酶活性的影响

对虾白斑综合征病毒(white spot syndrome virus,WSSV)和传染性皮下及造血器官坏死病毒(infectious hypodermal and hematopoietic necrosis virus,IHHNV)均为需向OIE报告的虾类病毒,本研究于2014年对上海地区部分淡水养殖凡纳滨对虾WSSV和IHHNV的感染及共感染情况进行了跟踪、检测和人工感染分析。检测结果显示,WSSV和IHHNV平均单感染率分别为42.6%和38.5%,双病毒共感染率为20.5%,其中,IHHNV-WSSV共感染率与WSSV感染率呈正相关。病理和累计死亡率分析显示,尽管IHHNV-WSSV组的对虾累计死亡率比同一时间点WSSV组低,但是这两组濒死对虾鳃丝细胞的病变都很严重,病变程度无明显差异。免疫相关酶——超氧化物歧化酶和酸性磷酸酶活性分析表明,IHHNV-WSSV共感染可以在一定程度上比单纯WSSV感染激起更高和更快些的免疫应答,但是,随着感染时间的延长,IHHNV-WSSV共感染表现出比WSSV单感染更长时间的免疫抑制。研究表明,虽然IHHNV-WSSV共感染可在一定时间范围和一定程度内降低对虾累计死亡率,但是共感染可造成病毒致病性的叠加和宿主更长时间的免疫保护低下,因此,IHHNV-WSSV共感染导致的损失可能比单病毒感染更大。

Investigation and analyses of IHHNV-WSSV co-infection in Penaeus vannamei cultured in freshwater and its effects on immune-related enzymes

As white spot syndrome virus(WSSV) and infectious hypodermal and hematopoietic necrosis virus(IHHNV) were both shrimp-infecting viruses and should be reported to the OIE.A follow-up investigation of prevalence of WSSV and IHHNV in P. vannamei cultured in freshwater in Shanghai was carried out in 2014. Results showed that the average single infection rate of WSSV and IHHNV was 42.6% and 38.5% respectively, while co-infection rate of the two viruses was about 20.5%. The prevalence of IHHNV-WSSV co-infection was positively correlated with that of WSSV. Analyses of histopathology and cumulative mortality indicated, although the cumulative mortality of shrimp in the IHHNV-WSSV group was always lower than that in the WSSV group at the same time point, gill tissues of moribund shrimp in the two groups were both damaged seriously, and no significant difference between them was found. The activities of immune-related enzymes(superoxide dismutase and acid phosphatase) demonstrated, compared to the single infection of WSSV, the dual infection of IHHNV and WSSV was able to activate the body's immune system faster and kept the immune response at a higher level during a short period; however, IHHNV-WSSV usually led to an higher and longer immune suppression post activation, which, together with the dual damages caused by IHHNV and WSSV,suggested that co-infection of IHHNV-WSSV would cause greater economic losses than a single infection.