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Diseases of Aquatic Organisms

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DAO 79:9-17 (2008)  -  DOI:

Lactococcus lactis subspecies lactis also causes white muscle disease in farmed giant freshwater prawns Macrobrachium rosenbergii

Pei-Chi Wang1, Yu-De Lin2, Li-Ling Liaw3, Red-Shiung Chern2,*, Shih-Chu Chen2,4,**

1Department of Tropical Agriculture and International Cooperation, 2Department of Veterinary Medicine, and
4Graduate Institute of Animal Vaccine Technology, National Pingtung University of Science and Technology, Pingtung 912, Taiwan, ROC
3Bioresource Collections and Research Center, Food Industry Research and Development Institute, Hsinchu 300, Taiwan, ROC
*Corresponding author. Email:
**Corresponding author. Email:

ABSTRACT: From May to August 2001 in Taiwan, 27 farms for the giant freshwater prawn Macrobrachium rosenbergii experienced white tail disease outbreaks in animals approximately 3 to 5 mo old, with total lengths from 6 to 8 cm. Examination of the infected prawns revealed not only previously reported Lactococcus garvieae (16 farms) but also the novel L. lactis subsp. lactis (10 farms). One farm had shrimp infected with both bacteria. In the farms with L. lactis infections, the cumulative mortality was approximately 25 to 60%. Gross signs of disease were opaque and whitish muscles, while histopathology included marked edema and necrotic lesions, with inflammation in the muscles and hepatopancreas. Bacteria isolated using brain/heart infusion medium or tryptic soy agar were Gram-positive and ovoid. Eleven isolates from different farms were identified as L. lactis subsp. lactis using API 20 Strep and Rapid ID32 Strep tests and using PCR assays specific for the L. lactis subsp. lactis 16S rDNA gene (650 bp amplicon) and for the 16S to 23S rDNA interspacer region (380 bp amplicon). In addition, sequencing of the full 16S rDNA genes of 2 of the isolates (MR17 and MR26; GenBank Accession Numbers AF493058 and AF493057, respectively) revealed 99.9% identity between the isolates and 98.7% identity to several complete 16S rRNA sequences of L. lactis subsp. lactis at GenBank. Experimental infections with our isolates gave gross signs and histopathological changes similar to those seen in naturally infected prawns. The mean lethal dose of 4 isolates and the reference strain L. lactis subsp. lactis BCRC 10791 ranged from 4.2 × 106 to 2.5 × 107 colony-forming units prawn–1, indicating virulence similar to that previously reported for L. garvieae. This is the first report confirming L. lactis subsp. lactis as a pathogen in juvenile and adult prawns from aquaculture.

KEY WORDS: Lactococcus lactis subsp. lactis · Giant freshwater prawn · Macrobrachium rosenbergii · PCR · 16S rDNA sequencing · 16S to 23S rDNA interspacer regions gene

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Cite this article as: Wang P, Lin Y, Liaw L, Chern R, Chen S (2008) Lactococcus lactis subspecies lactis also causes white muscle disease in farmed giant freshwater prawns Macrobrachium rosenbergii. Dis Aquat Org 79:9-17.

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