PRV

Piscine reovirus (PRV) is a novel reovirus that can infect Atlantic and Pacific salmonids, leading to further vulnerability to infections and/or syndromes. It occurs in the flesh of the fish.

A farm salmon with Piscine reovirus from a supermarket weighed 1.6 kg gutted. Normal harvest-size is 4.6 – 6 kg. The cause of the sores is unidentified.

There are plausible associations between infections of PRV and Heart and Skeletal Muscle Inflammation (HSMI) and/or cardiomyopathy syndrome (CMS) in Atlantic salmon. HSMI is characterized by anorexic fish that display erratic and abnormal swimming behaviour. Autopsies of diseased fish will include a pale heart, yellow liver, ascites, swollen spleen and petechiae in the perivisceral fat. Wild fish infected with PRV, and associated infections that impact the function of the heart muscle, may experience mortality in-river prior to spawning.

Palacious et al. (2010) have found that tissue distribution and load of PRV are correlated with disease in naturally and experimentally HSMI-infected salmon. PRV has been identified through processing samples (high-throughput pyrosequencing) of serum and heart tissue of experimentally HSMI-infected fish. Lovoll et al. (2010) identified the complete genomic sequence of PRV. Formal implication of the relationship between PRV and HSMI will involve isolation of PRV in cell culture, which has not been attempted thus far.

Transmission: Transmission can occur horizontally through the water column.

Prevention: Measures should be taken to control PRV due to its plausible relationship to HSMI and potential threats to transmission to wild salmon populations along with domestic salmon production.

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References:
1. Palacios G, Lovoll M, Tengs T, Hornig M, Hutchison S, et al. (2010) Heart and Skeletal Muscle Inflammation of Farmed Salmon Is Associated with Infection with a Novel Reovirus. PLoS ONE 5(7): e11487. doi:10.1371/journal.pone.0011487

2. Lovoll M, Wiik-Nielsen J, Grove S, Wiik-Nielsen C et al. (2010). Virology Journal 7:309.

3. Watanabe K, Karlsen M, Devold M, Isdal E, Litlabo A, et al. (2006) Virus-like particles associated with heart and skeletal muscle inflammation (HSMI). Dis Aquat Organ 70: 183–192.