Sakuna, Kitikarn, Elliman, Jennifer, and Owens, Leigh (2017) Discovery of a novel Picornavirales, Chequa iflavirus, from stressed redclaw crayfish (Cherax quadricarinatus) from farms in northern Queensland, Australia. Virus Research, 238. pp. 148-155.

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Abstract

In 2014, northern Queensland crayfish from farms affected by particularly transportation and translocation stress, started to die with mortality reaching 20–40% after about three weeks and then mortalities subsided. Crayfish from 1 farm had 65% mortalities within 11 weeks. With histological examination of broodstock and juveniles, the muscle fibres were fractured with haemocytic infiltration reminiscent of viral infection or vitamin E/selenium deficiencies. Sequence dependent and independent PCRs failed to identify a viral aetiology. However, the whole transcriptomes of a case crayfish and an unaffected crayfish from a different population were assembled producing over 500,000 contigs. The complete sequence of a positive sense, single stranded RNA virus (+ve ssRNA virus; 9933 bp) and the large and medium segments of a bunya-like virus were detected. Transcript back-mapping and newly developed PCRs indicated that the viruses were in the case crayfish but not the control crayfish. The +ve ssRNA virus is clearly in the order Picornavirales, marginally in the genus Iflavirus in a clade of Chinese and Northern American terrestrial arthropod viruses. The internal Picornavirales motifs; RNA-dependent RNA polymerase, helicase (P-loop) and 2 viral capsids genes were easily identified. This is the first iflavirus identified from crustacea and is named Chequa iflavirus. Whether these viruses are responsible for the stress-related mortalities is unproven but the Chequa virus’ role seems limited as it appears it has been present in crayfish from at least the early 1990s; unless low-grade, chronic mortalities have been largely unnoticed.

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