Putative spawner-isolated mortality virus associated with mid-crop mortality syndrome in farmed Penaeus monodon from northern Australia

The redclaw freshwater crayfish Cherax quadricarinatus has a reputation for being hardy and resistant to handling stress. However, in recent years, possibly since 1996, C. quadricarinatus farmers in northern Queensland have noted a decrease in stress resistance in their stock. A presumptive reovirus in the hepatopancreas, and a putative p a~o v i r u s in the gills, were associated with chronic mortalities in C. quadncarinatus at one northern Queensland farm. Hypertrophic nuclei with marginated chromatin were observed in gill epithelium in moribund crayfish which had recently been relocated to a laboratory from the holding tank fachty on the farm. Affected nuclei appeared to be vacant or contained a faint granular basophilia in H&E stained sections. However, toluidine blue staining revealed a homogenously granular appearance of the nuclei. Transmission electron microscopy revealed approximately 20 nm diameter virus-like particles within the nucleus. Eosinophilic, Feulgennegative, cytoplasmic inclusions were observed in distal hepatopancreatocytes in 1 moribund C. quadricarinatus collected from the same on-farm holding tank approximately 6 mo later. This crayfish did not display the gill lesions. Transmission electron microscopy showed that the inclusions contained icosahedral virus particles 35 to 4 0 nm in diameter. The histopathology and preliminary virus morphology of the presumptive hepatopancreatic reovirus, and the histopathology, ultrastructural pathology and preliminary virus morphology of the putative gill pawovirus, are reported herein.

Section: Two Moribund Crayfish Collected In June 1998mentioning

confidence: 99%

Description of a presumptive hepatopancreatic reovirus, and a putative gill parvovirus, in the freshwater crayfish Cherax quadricarinatus

Edgerton

Webb²,

Anderson³

et al. 2000

“…In northern Queensland farms, 3 of 4 initially affected farms received postlarvae from a single hatchery in January 1994. Once SMV becomes systemic in prawns by breaking through the lamina propria of the gut into the haemocoel, one of the main tissues that become probe-positive are the gonads (Owens et al 1998). This suggests a possible mechanism for vertical transmission from broodstock to postlarvae through infected reproductive tissues.…”

Section: Discussionmentioning

confidence: 99%

“…In situ hybridisation of Penaeus monodon using a gene probe developed for SMV had shown that the major trophic tissue, and usually the first tissue infected, was the gastrointestinal tract (Owens et al 1998). Target organs included the hepatopancreas, midgut caecae, midgut and to a lesser extent, the hindgut caecae.…”

Section: Introductionmentioning

confidence: 99%

Prevalence and effect of spawner-isolated mortality virus on the hatchery phases of Penaeus monodon and P. merguiensis in Australia

Owens¹,

McElnea²,

Snape³

et al. 2003

Self Cite

Spawner-isolated mortality virus (SMV) has been associated with mortalities in broodstock of Penaeus monodon and with mid-crop mortality syndrome on grow-out farms. Epidemiological evidence suggested an association between the SMV status of broodstock and subsequent survival of their progeny, and this paper describes investigations into that association. The faeces of 909 broodstock in 9 different groups were tested by a polymerase chain reaction (PCR) for SMV and positive results were confirmed by an internal dot-blot. Seventy-seven spawners (8.5%) were positive for SMV with prevalence ranging from 0 to 24% among groups. The prevalence in spawners of P. monodon was higher (24%) than in P. merguiensis (4%). Three longitudinal studies were undertaken to compare the survival of progeny from broodstock that were positive to SMV with those that were not. Survival in hatchery tanks of progeny from SMV-positive spawners was lower than those from SMV-negative spawners with reductions of 23% (p = 0.01), 7.3% (p = 0.214) and 18.9% (p = 0.129) in the 3 studies. The conclusions were less consistent when examined during each of the later stages of growth in hatchery pools, nursery and grow-out ponds, with progeny from SMV-postive spawners sometimes having better survival rates. However, survival was better overall in progeny from SMV-negative spawners. Simple linear regression showed survival was negatively related to the proportion of postlarvae from SMV-positive spawners, with a decrease in survival of 5.6% for each 10% increase in the proportion of postlarvae coming from SMV-positive spawners (p = 0.006). Data from 38 ponds showed 6.71% of losses were due to SMV. If these losses were consistent across the entire industry, the annual loss due to SMV would have been approximately AUD 3 million in 1999/2000.

“…In situ hybridisation (ISH) using gene probes to SMV (Owens et al 1998), YHV (Tang & Lightner 1999, Tang et al 2002 and GAV (Spann et al 2003) has associated these viruses with histopathology and helped determine their tissue distribution in chronically and acutely infected prawns. In this paper, we have used a sensitive RT-nested PCR test targeted to a region of the MoV M RNA segment with significant homology to the cognate RNA segment of Uukuniemi virus (Cowley et al 2005) to assess its prevalence in Penaeus monodon from eastern Australia.…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…Due to its commercial importance to these regions, viral diseases of this prawn species have been the focus of intense investigation. Viruses identified in P. monodon from eastern Australia include monodon baculovirus (MBV) (Doubrovsky et al 1988, Belcher & Young 1998, Vickers et al 2000, a lymphoidal parvo-like virus (LPV) (Owens et al 1991), gill-associated virus (GAV) (Spann et al 1995, Cowley et al 1999, 2000a, Smith 2000) and spawner-isolated mortality virus (SMV) (Fraser & Owens 1996, Owens et al 1998. A virus with spherical enveloped particles (74 nm average diameter) has also been detected in eye tissues of moribund farmed prawns (Smith 2000) and although they were slightly larger, some morphological similarity was noted to a reo-like virus detected in Malaysian P. monodon (Nash et al 1988).…”

Section: Introductionmentioning

confidence: 99%

RT-nested PCR detection of Mourilyan virus in Australian Penaeus monodon and its tissue distribution in healthy and moribund prawns

Cowley¹,

McCulloch²,

Rajendran³

et al. 2005

Mourilyan virus (MoV) is a newly identified virus ofPenaeus monodon prawns that is genetically related to the Uukuniemi virus and other phleboviruses of the Bunyaviridae. This paper describes an RT-nested PCR test that can reliably detect between 2 and 6 copies of a synthetic MoV RNA. Total RNA isolated from the lymphoid organ, gills and haemocytes of P. monodon with moderate infections gave comparable amplicon yields in the RT-PCR step of the test. However, in prawns with extremely low-level infections, haemocytes and gill tissue proved slightly more reliable in detecting MoV RNA following nested PCR. The distribution of MoV in tissues of healthy and moribund P. monodon was examined by in situ hybridisation (ISH) using a digoxigenin-labelled DNA probe to a ~0.8 kb M RNA segment cDNA insert in clone pMoV4.1. The DNA probe targeted a region in the MoV M RNA segment containing a coding sequence with homology to the C-terminus of the G2 glycoprotein of phleboviruses. In healthy prawns harbouring an unapparent MoV infection, ISH signal primarily occurred in the lymphoid organ, where it was more prominent in hypertrophied cells of 'spheroids' than within cells of normal tubules. ISH signal was also sometimes detected in cells of cuticular epithelium, segmental nerve ganglion and the antennal and tegmental glands. MoV was distributed widely throughout these and other cephalothoracic tissues of mesodermal and ectodermal origin in moribund P. monodon following experimental infection or collected from farm pond edges during disease episodes. Transmission electron microscopy of gill of moribund, captive-reared P. monodon identified spherical (~85 nm diameter) to ovoid MoV particles (~85 × 100 nm) in and around highly necrotic cells in which the nucleus and other organelles had disintegrated. MoV virions co-existed with rod-shaped virions of gill-associated virus and were often seen clustered within cytoplasmic vacuoles or associated with the outer rim of concentric ring-shaped structures comprised of endoplasmic membranes likely to represent degenerated Golgi. KEY WORDS: Mourilyan virus · Uukuniemi virus · Phlebovirus · Bunyavirus · Penaeus monodon · Penaeid shrimp · Prawn · In situ hybridisation · PCR Resale or republication not permitted without written consent of the publisherDis Aquat Org 66: [91][92][93][94][95][96][97][98][99][100][101][102][103][104] 2005 eye tissues of moribund farmed prawns (Smith 2000) and although they were slightly larger, some morphological similarity was noted to a reo-like virus detected in Malaysian P. monodon (Nash et al. 1988). Moreover, a small virus causing infectious hypodermal and haematopoietic necrosis virus (IHHNV)-like pathology (Owens et al. 1992) and a haemocytic rod-shaped virus (Owens 1993) were among 4 virion types found in diseased experimental hybrids of P. monodon and P. esculentus generated at a research facility in north Queensland in the early 1990s. More recently, a virus genetically related to bunyaviruses named Mourilyan virus (MoV) (Cowley et al. 2005)...