免疫增强剂在水产养殖中的应用

免疫增强剂作为一种有效控制鱼类疾病的物质，在水产养殖中已得到广泛地应用。目前较常用的免疫增强剂主要有合成化学剂类、微生物类衍生物、动植物提取物、维生素以及激素和乳铁蛋白等。国内外对多糖、几丁质、乳铁蛋白等在鱼虾中的抗病作用做了大量报道，对促生长作用的免疫增强剂(VB、VC、生长激素、促乳素等)也有过不少研究。在虾贝类非特异性免疫系统中，免疫增强剂主要是通过激活吞噬细胞、激活酚氧化酶活力等来提高机体的抗病能力；在鱼类免疫系统中则主要表现为激活抗菌溶菌活力、提高抗体免疫效应以及激活补体等。机体内的免疫活性与机体的抗病能力密切相关，免疫增强剂能有效增强免疫因子的活性，对控制细菌性病原(鳗弧菌、分支杆菌等)和病毒性病原(对虾白斑病毒、鲤痘疮病毒等)有重要意义。在给予免疫增强剂的途径中，注射法是最有效的方法，口服法和浸泡法因其使用便捷也有过不少报道，但这两种方法会随着时间的延长而使药效受到影响。过多、过量的服用免疫增强剂会导致机体的免疫抑制。然而，在实际养殖过程中，免疫增强剂造成的负面影响却没有引起人们的足够重视。从总体上来说，免疫增强剂能有效降低水产动物的患病几率，促进机体生长。但我们必须看到它不是对所有疾病都能起到积极的预防效果，因而在使用免疫增强剂的过程中，应在类型、剂量、方法及病理状况等多种因素的综合考虑下，来有效地应用它，为水产养殖业服务。

Applications of immunostimulants in aquaculture

Immunostimulants are valuable for the control of fish diseases and may be useful te fish culture. The immunostimulatory effects on gulcan, chitin, lactoferrin and levamisole of fish and shrimp have been reported. Nutritional factors such as VB, VC, growth hormone and prolactin have also been reported to be immunostimulants. These immunostimulants mainly facilitate the function of phagocytic cells and increase their bactericidal activities. Several immunostimulants also stimulate the natural killer cells, complement, lysozyme and antibody responses of fish. The activation of these immunological functions is associated with increasing the protection against infections disease. Resis-tances to bacterial pathogens such as Vibio anguillarun , V. salmonicida ,and streptococcus sp. and to parasitic infections such as WSSV and Herpesvirus cyprini can be increased by administration of immunostimulants. In jecting administration of immunostimulants is the most effective method in us-ing immunostimulants. Oral and immersion methods have aslo been reported, but the efficacies of these methods decreases with long-term administration. Overdoses of several immunostimulants have not been well-studied. In conclusion, immunostimulants can reduce the losss caused by diseases in aquaculture; however, they may not effectively resist all diseases. For the effective use of immunostimulants, the timing, dosages, method of administration and the physilogical condition of fish need to be taken into consideration.