Abstract
The Marine cage-culture of Taiwan has begun from Penghu
county and the Penghu sea. Cage-culture farming of
fishes is the major direction of fishery in the future.
But the fish disease and epidemiology of this type
of farming are urgent need to investigate for the
monitoring and preventing the problem of the disease.
This study investigated and analysed the aetiology
and the pathology of the infectious disease of this
type of farm fish in the Penghu sea area. In the meantime,
it also studied the connection between the environment
and the disease occurring. Results of the investigation
from 1997 till 2002, had shown that the most significant
pathogenic disease of marine cage-culture fish was
found to be bacteria disease with the frequency of
63.3%(195/308). Then it followed the parasitic disease
with frequence of 28.5%(88/308), more over, the viral
disease which represented 7.5% (23/308). Among all
of the disease cases, there were only 2 cases found
to be induces by fungi, Which were accidental infections.
One hundred seventy four bacterial strains were Gram’s
negative from total of 195 isolated strains (89.2%),
Which were including pathogenic Vibrio spp. 33.3%(65/195),
Photobacterium damselae subsp. piscicida, 26.2%(51/195),
and Aeromonas spp. 5.6%(11/195). While 21 bacterial
strains isolated were belonged to Gram’s positive
from total 195 isolated strains(10.8%). Streptococcus
iniae in this part was 61.9%(13/21), It showed that
Strep. iniae represented the major pathogen of Gram’s
positive group of bacteria in the Penghu sea area.
The less important disease was parasitic infestation.
In these cases the infestation of protozoa had 70.5%(62/88),
Trichodina sp. was the most serious one, 45.5%(40/88).
As to viral diseases, the Iridovirus disease and Lymphocystis
were found on red sea bream and grouper, and were
34.8%(8/23) and 65.3%(15/23) respectively. Because
cobia is the major species of this particular type
of farm culture, it was found that pseudotuberculosis
and lymphocystis were the most frequent diseases to
occur. Thus those rate are much higher. Majority of
fish diseases always happen in the first year of cultivation,
especially the first early 6-months, but when they
survived over the winter it would no problem afterward.
Therefore, it is important that the pathogens in the
sea, the ambient temperature and the host healthy
status are interacting each other, to show up the
epidemic. Furthermore, many pathogens are actually
carried from the hatchery, and during the transporting,
the fish are injury and stress at this early stage
of cultivation could come across the serious loss.
It is especially true on Trichodina infestation with
a secondary bacterial outbreaks after transferring
young fingerlings to cage-culture. For this reason,
the young fish should get primary quarantine and disinfection
before transfer to the cage. The hatchery and subsequent
grower should eliminant the abnormality and the pathogen
is detected and properly treated as soon as possible.
In this way, it can control the disease of fry and
fingerling, including iridovirus infection, and simultaneously
it should reduce the stress factor, to control fish
diseases of the marine cage-culture.
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海鱺假性結核病之病性與流行分析 海鱺假性結核病又稱巴氏桿菌症(Pasteurellosis)在本縣的養殖海鱺魚群中，本病是重要而經常發生的疾病，其病原為Ph.
damselae subsp. piscicida。得病魚之解剖肉眼病變，在體表、鰭基部及肛門周圍有皮膚出血，實質臟器病變，可見脾臟腫大2~4倍，表面及實質密發0.5~2mm大小之白色壞死結節，腎臟腫大可見密發1~2
mm大小白色壞死結節，胃粘膜潮紅潰瘍，腸管出血。臨床微生物檢驗以病魚的脾臟和腎臟直接在玻片上作臟器塗抹，Diff-Quik快速染色鏡檢，可見許多兩端濃染短桿菌散佈於血球和細胞間。自得病魚之脾及腎臟病灶部位釣菌做細菌分離，以BAP、3
% NaCl之BHIA、3% NaCl MacConkey agar及TCBS等培養基畫線培養，置於25℃，48小時後，可見細菌菌落發育，其中在BAP及3%
BHIA上為細小菌落，MacConkey agar 則於三至五日後發育為淡粉紅色細小菌落，TCBS上不發育。
組織病理檢查可見肝臟充血，輕微的空泡變性。脾臟多發性的凝固樣壞死及肉芽腫病變。腎臟有間質性腎炎與單核炎症細胞浸潤，並可見多發性壞死及肉芽腫的病變，腸管黏膜亦見出血。快速診斷時可以臨床解剖病變及臟器塗抹細菌為參考。確診時依細菌生化特性，並以單株抗體凝集試驗BIONORR
kit二次確定。
自1999.1~2002.12魚病中心檢診病例統計，有35%的海鱺疾病屬於Ph.d.p或本菌的混合(繼發)感染，發病狀況以圖表列示如圖。發病在放苗階段者大約是每年四月到六月，仔魚體重100g以下。秋冬的低溫發病季節為九月到隔年的二月，病魚已屬500g以上，大則已達2
Kg。現場的疫情追蹤所得，海鱺假性結核病發病率約60 %，致死率約50 %，魚苗進入污染海域，潛伏期約4~7天，在第七天開始魚群食慾減退及少數死亡，每日約1/2000，死亡率逐日上昇，在發病後的5~7天即達到高峰，每日5~10%的死亡。藥物治療有效時，死亡率維持1~3天可見下降趨勢，箱網內發病後病程約持續10~20天，平均約14天；若未投藥或有抗藥性則第七天的死亡數仍會上昇，致死率會達80%，或者更高。一般狀況，死亡停止並停藥後，2~3週會有第二次Ph.d.p的病原侵襲而再發病，而發病率及致死率卻仍高，僅會少許的下降0.5~2%。有些箱網魚群會一直重覆感染3~4次才停止。就實驗室結果而論，藥物敏感性試驗以四環素類、奎嚀類及氯黴素等有效，其中氯黴素的效果最好。
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