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Title: | 淡水長臂大蝦(Macrobrachium rosenbergii de Man )後期幼苗病毒性疾病之初步研究 A preliminary study on virial diseases in postlarva of freshwater prawns(Macrobrachium rosenbergii de Man ) |
Authors: | 董哲煌 |
Publication Year : | 1997 |
Degree: | 碩士 |
Abstract: | 本研究之目的,在於探討淡水長臂大蝦(Macrobrachium rosenbergii)後期幼苗(PLl-PL30 )罹患尾部肌肉白化症之致病原因。於疫情調查方面,發現此病發生的時間可能全年皆有,但於七月到十二月發生機率較高,一般於放養後十天內發生病變,而罹病之後期幼苗腹部肌肉白化呈不透明狀,一般病變發生於二至六腹節,病蝦行動緩慢無力,喜攀附於池壁或水草,死亡率達百分之五十以上。 對於池水水質,蝦體病原菌分離方面,池水之三項測定(氨、亞硝酸、化學需氧量)於病蝦池與健康池並無太大差別。而罹病蝦池池水總生菌數與健康蝦池沒有顯著差異,罹病蝦體內生菌數與健康蝦亦無太大差別。於病變部份甚少或分離不出細菌,而於頭胸部亦無法分離出有意義之菌株,而鏡檢蝦體亦不曾發現外寄生物。 於組織切片中發現,於 H & E 染色下肌肉病變部份發現大量粉紅色之玻璃變性產物,血球浸潤,肌肉細胞核不正常大量增殖與聚集,肌纖維空泡碎裂。此病變之肌纖維呈現略嗜鹼性,可被染上Giemsa , 於Pyronin Methylgreen 染色中染成藍紫色,於 Gram 染色中染成鮮紅色,微弱之 PAS 正反應,於 Acridine orange 染色中發出紅色螢光,而於各種染色下皆沒有發現任何細菌、黴菌、原生動物存在病變組織中,而部份病變肌肉組織中可發現病毒之包含體,此包含體為嗜鹼性, Giemsa 濃染, Feulgen 正反應,於Pryonin Methylgeen 染色中染成明亮之綠色,於Gram染色中染成鮮紅色, PAS 負反應。而被病毒感染之細胞呈現腫大之細胞核,外移之染色質,並於 Pyronin Methylgeen 染色可被染成淡綠色,可以被區分出來,而除了肌肉外並沒有發現其他組織被感染。 於電子顯微鏡下,發現於病變肌肉細胞之細胞質中有大量病毒存在,此病毒大小約 22.9士3.6nm ,為正二十面體形狀,無包覆,能於核外產生大形不規則形之包含體,其中病毒顆粒排列有時整齊,有時散亂,並於病毒包含體內可發現電子束集中之病毒質( Virogenic storma ) ,且於17個不同池病蝦檢體中有10池可由電子顯微鏡下檢出病毒。以六種魚類細胞株感染,皆沒有感受性。 此病毒相較於已發表之甲殼類病毒之特性皆有許多不同之處 ,因此暫時命名為 Macrobrachium muscle virus(MMV)以便稱呼。 Freshwater prawns (Macrobrachiurn rosenbergii) in southern Taiwan exhibited idiopathic muscle necrosis in abdominal segments. It was found that this symdrome likely occurred throughtout all the year and in most cases took place within ten days after moving post-larvae into outdoor ponds during July to December. Non-transparent muscle opacity was a commonly observed feature of the muscle in abdominal segment 2-6. The common phenomena were the progressively weakening of their swimming ability and inclining to stay on grasses or the walls of ponds. Their mass larval mortalities were probably more than 50%. The quantity of the four water factors (ammonia, nitrate, COD, gross bacteria) in the infective ponds was not more than that of the non-infective ponds. Furthermore, we never found epibiotic organisms during microscopic observation in both healthy and muscle necrosis prawns. In paraffin sections, we found that muscle fibres had displayed progressive segmental myofibre degeneration and necrobiotic myopathy, including eosinophilia or hyalinization, fragmentation, flocculation, granulation and haemocyte infiltration.The prominent shrinkage of the myofibres caused by progressive loss of myofibre parenchyma (myofibrils and saroplasm) led to diffuse areas of myofibre disorganization, associated with numerous single, rows, aggregations and sheets of hyperchromatic myonuclei, often centrally or eccentrically placed (nuclear internalization) and pyknotic nuclei. Yet, no bacteria, fungi or internal parasites were discovered in any necrosis muscle. Our electron microscope examination showed that there were mass parvovirus-like particles existing in infected muscle cytoplasm. Their sizes were about 18-20 nm, without any envelop. This virus was able to form large , icosahedral , basophilic, feulgen positive, intranucliar inclusion body. By means of pyronin methylgreen stain, we could clearly distinguish these light-green inclusion bodies from purple muscle nuclei. In final analysis, we conclude that this virus is different form any crustacean virus that has ever been published. For this very reason, we temporally call it Macrobranchium Muscle Virus (MMV)- the first pathogenic virus found in the freshwater prawns (Macrobrachium rosenbergii). |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/76327 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 漁業科學研究所 |
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