Mourilyan virus pathogenicity in kuruma shrimp (Penaeus japonicus)

Abstract

The bunyavirus Mourilyan virus (MoV) occurs commonly in Black tiger (Penaeus monodon) and kuruma shrimp (Penaeus japonicus) farmed in eastern Australia. There is circumstantial evidence of MoV causing mortalities among P. japonicus moved from farm ponds to tanks for rearing as broodstock. To directly assess its pathogenic potential, independent cohorts of pond‐ (n = 24) or tank‐reared juvenile (n = 21) P. japonicus were challenged intramuscularly with a cephalothorax tissue homogenate of P. monodon containing high loads of MoV (1.48 ± 0.28 × 108 MoV RNA copies/µg total RNA). In each trial, mortalities accumulated gradually among the saline‐injected controls. Mortality onset occurred 12–14 days earlier in the pond‐reared shrimp, possibly due to them possessing low‐level pre‐existing MoV infections. Despite the time to onset of mortality differing, Kaplan–Meier survival analyses confirmed mortality rates to be significantly higher in both the pond‐ (p = .017) and tank‐reared shrimp (p = .031) challenged with MoV. RT‐qPCR data on shrimp sampled progressively over each trial showed high loads of MoV to establish following challenge and discounted GAV and other endemic viruses from contributing to mortality. Together, the data show that acute MoV infection can adversely compromise the survival of juvenile P. japonicus.

A Novel Bunyavirus Discovered in Oriental Shrimp (Penaeus chinensis)

“… Rajendran et al (2006) reported the detection of up to > 10 4 copies/ng-RNA (> 10 7 copies/μg-RNA in the paper) of MoV in lymphoid organs of challenged P. japonicus associated with an increase of lymphoid spheroids. It has been experimentally confirmed that MoV infection can cause gradually accumulating mortality in P. japonicus ( Cowley, 2020 ). However, Oanh et al (2011) confirmed that P. monodon can tolerate a high-level MoV infection up to > 10 6 copies/ng-RNA (>10 9 copies/μg-RNA in the paper) in gills and that mortalities of the mid-crop mortality syndrome (MCMS) outbreaks are associated with the co-infection with gill-associated virus (GAV) rather than MoV.…”

“…In P. japonicus, elevated MoV infection loads were associated with gradually increased mortality in shrimps reared in tanks following their grow-out in farm ponds (Sellars et al, 2006). Its pathogenic potential has been confirmed recently in experimental challenge trials (Cowley, 2020).…”

“…Historically, arthropod-vectored bunyaviruses were discovered due to the diseases that they caused in vertebrates and plants. Similarly, bunya-like viruses from crabs and shrimps cause diseases associated with the inhibition of hemolymph clotting and elevated mortality during culture ( Bang, 1971 ; Corbel et al, 2003 ; Cowley et al, 2005a , b ; Sellars et al, 2006 ; Oanh et al, 2011 ; Cowley, 2020 ). However, information on the genome makeup and sequences of crustacean bunyaviruses only started to emerge in recent years ( Cowley et al, 2005b ; Li et al, 2015 ; Cowley, 2016 ; Sakuna et al, 2018 ; Bojko et al, 2019 ; Grandjean et al, 2019 ).…”