Tilapia Lake Virus

Tilapia are species of fish that has become an important global food source due to their omnivorous diet, tolerance for high-density aquaculture, and relative disease resistance. Naturally, the ever present danger is that 'farming' of a single species of fish can lead to increased susceptibility of viruses.

Since 2009, tilapia aquaculture has been threatened by mysterious mass die-offs in farmed fish in Israel and Ecuador[1]. Scientists have now found the reason: a novel orthomyxovirus[2].
Tentatively called the Tilapia Lake Virus (TiLV), it has a 10-segment, negative-sense RNA genome. The largest segment, segment 1, contains an open reading frame with weak sequence homology to the influenza C virus PB1 subunit (Translated: with the exception of a small genetic segment, that only remotely resembled a virus associated with the reproduction of influenza C). The other nine segments showed no homology to other viruses but have conserved, complementary sequences at their 5′ and 3′ termini, consistent with the genome organization found in other orthomyxoviruses.

Tilapia with disease show swollen brains (in Israel) and liver disease (in Ecuador). In the coming weeks, the researchers will publish on the link between the Tilapia Lake Virus and an outbreak of disease among tilapia in Colombia[3].

[1]Aygnor et al: Identification of a novel RNA virus lethal to tilapia in Journal of Clinical Biology - 2014
[2]Bacharach et al: Characterization of a Novel Orthomyxo-like Virus Causing Mass Die-Offs of Tilapia in mBio – 2016. See here.
[3] Kembou Tsofack et al: Detection of Tilapia Lake Virus (TiLV) in Clinical Samples by Culturing and Nested RT-PCR in Journal of Clinical Microbiology - 2016

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