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Diseases of Aquatic Organisms

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DAO 147:127-140 (2021)  -  DOI: https://doi.org/10.3354/dao03638

Co-infection of Lactococcus garvieae and Tilapia lake virus (TiLV) in Nile tilapia Oreochromis niloticus cultured in India

Thangaraj Raja Swaminathan1,*, Sundar Raj Nithyanantham1, Lekshmi Narendrakumar1, Arathi Dharmaratnam1, Neeraj Sood2, Pravata Kumar Pradhan2, Krupesha Sharma Sulumane Ramachandra3, Kuldeep Kumar Lal2

1Peninsular and Marine Fish Genetic Resources Centre, ICAR National Bureau of Fish Genetic Resources, CMFRI Campus, Kochi, Kerala 682 018, India
2ICAR National Bureau of Fish Genetic Resources, Canal Ring Road, Lucknow, Uttar Pradesh 226 002, India
3ICAR Central Marine Fisheries Research Institute, Kochi, Kerala 682 018, India
*Corresponding author:

ABSTRACT: Tilapia lake virus (TiLV) and Lactococcus garvieae are 2 major pathogens of cultured Nile tilapia Oreochromis niloticus. In June-July 2018, a disease outbreak was reported in Nile tilapia cultured in brackish water floating cages in Kerala, India. Affected fish died gradually, and cumulative mortality reached ~75% within 1 mo. In the present study, TiLV and L. garvieae were isolated from the infected fish and confirmed. Nucleotide analysis of the partial sequence of segment 3 revealed that the present TiLV isolate showed 100% similarity with TiLV MF574205 and 97.65% similarity with TiLV KU552135 isolated in Israel. The partial 16S rDNA nucleotide sequence of L. garvieae shared 99% similarity with the 16S rDNA nucleotide sequence of L. garvieae isolated from Nile tilapia in Brazil. Eight virulence genes (hly1, hly2, hly3, NADH oxidase, adhPav, LPxTG-1, LPxTG-4, adhC1) were amplified in the present isolate. In the experimental challenge study, the onset of mortality started earlier in fish co-infected with TiLV and L. garvieae (3 d post-infection [dpi]) compared to other groups. Cumulative mortality (90% at 12 dpi) was significantly higher in the co-infected group than in fish infected with TiLV (60% at 12 dpi) and L. garvieae (40% at 12 dpi) alone. This study reveals that synergistic co-infection with TiLV and other bacteria may increase mortality in disease outbreaks. To the best of our knowledge, this is the first reported co-infection of L. garvieae with TiLV associated with mass mortality in Nile tilapia in India.


KEY WORDS: Tilapia lake virus · TiLV · Lactococcus garvieae · Co-infection · Nile tilapia · India


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Cite this article as: Swaminathan TR, Nithyanantham SR, Narendrakumar L, Dharmaratnam A and others (2021) Co-infection of Lactococcus garvieae and Tilapia lake virus (TiLV) in Nile tilapia Oreochromis niloticus cultured in India. Dis Aquat Org 147:127-140. https://doi.org/10.3354/dao03638

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