Viral-like particles associated with cuticular epithelium necrosis in cultured Litopenaeus vannamei (Decapoda: Crustacea) in Ecuador (original) (raw)
Related papers
2005
White spot syndrome virus (WSSV) causes disease and mortality in cultured and wild shrimp. A standardized WSSV oral inoculation procedure was used in specific pathogen-free (SPF) Litopenaeus vannamei (also called Penaeus vannamei) to determine the primary sites of replication (portal of entry), to analyze the viral spread and to propose the cause of death. Shrimp were inoculated orally with a low (10 1.5 shrimp infectious dose 50% endpoint [SID 50 ]) or a high (10 4 SID 50) dose. Per dose, 6 shrimp were collected at 0, 6, 12, 18, 24, 36, 48 and 60 h post inoculation (hpi). WSSVinfected cells were located in tissues by immunohistochemistry and in hemolymph by indirect immunofluorescence. Cell-free hemolymph was examined for WSSV DNA using 1-step PCR. Tissues and cell-free hemolymph were first positive at 18 hpi (low dose) or at 12 hpi (high dose). With the 2 doses, primary replication was found in cells of the foregut and gills. The antennal gland was an additional primary replication site at the high dose. WSSV-infected cells were found in the hemolymph starting from 36 hpi. At 60 hpi, the percentage of WSSV-infected cells was 36 for the epithelial cells of the foregut and 27 for the epithelial cells of the integument; the number of WSSV-infected cells per mm 2 was 98 for the gills, 26 for the antennal gland, 78 for the hematopoietic tissue and 49 for the lymphoid organ. Areas of necrosis were observed in infected tissues starting from 48 hpi (low dose) or 36 hpi (high dose). Since the foregut, gills, antennal gland and integument are essential for the maintenance of shrimp homeostasis, it is likely that WSSV infection leads to death due to their dysfunction
Virus-like particles in a monogenean (Platyhelminthes) parasitic in a marine fish
International journal for parasitology, 1993
JUSTINE J.-L. and B~N A M I J. -R. 1993. Virus-like particles in a monogenean (Platyhelminthes) parasitic in a marine fish. International Journal for Parasztology 23: 69-75. In Microcotyle sp., a gill parasite in the marlne fish Abudefdufatzalogus near Dakar, Senegal, various organs were studied by transmission electron microscopy. One of the six worms studied contained virus-like particles located only in the outer layer and in the cytoris (deep cell bodies) of the tegument. The tegument ultrastructure is described for both healthy and infected monogeneans. The outer layer of the tegument, 2-5 pm thick, does not havemicrovilli. The virus-like particles are cytoplasm~c, about 70 nm in diameter with a single-layered capsid-like structure 10-12 nm thick, and have an icosahedral symmetry. They originate from viroplasms and accumulate in paracrystalline arrays up to I pm in size. By their ultrastructural characteristics, these virus-like particles are related to the Reoviridae or, more probably, the Birnaviridae. This is the third report of viruses in monogeneans, and the first in a polyopisthocotylean monogenean. It is hypothesized that monogeneans could act as vectors of viral diseases among their host fishes.
Diseases of Aquatic Organisms, 2005
White spot syndrome virus (WSSV) is a devastating pathogen in shrimp aquaculture. Standardized challenge procedures using a known amount of infectious virus would assist in evaluating strategies to reduce its impact. In this study, the shrimp infectious dose 50% endpoint (SID 50 ml-1) of a Thai isolate of WSSV was determined by intramuscular inoculation (i.m.) in 60 and 135 d old specific pathogen-free (SPF) Litopenaeus vannamei using indirect immunofluorescence (IIF) and 1-step polymerase chain reaction (PCR). Also, the lethal dose 50% endpoint (LD 50 ml-1) was determined from the proportion of dead shrimp. The median virus infection titers in 60 and 135 d old juveniles were 10 6.8 and 10 6.5 SID 50 ml-1 , respectively. These titers were not significantly different (p ≥ 0.05). The titration of the WSSV stock by oral intubation in 80 d old juveniles resulted in approximately 10-fold reduction in virus titer compared to i.m. inoculation. This lower titer is probably the result of physical and chemical barriers in the digestive tract of shrimp that hinder WSSV infectivity. The titers determined by infection were identical to the titers determined by mortality in all experiments using both i.m. and oral routes at 120 h post inoculation (hpi), indicating that every infected shrimp died. The determination of WSSV titers for dilutions administered by i.m. and oral routes constitutes the first step towards the standardization of challenge procedures to evaluate strategies to reduce WSSV infection.
Environmental Microbiology, 2008
The concept of polymicrobial disease is well accepted in human and veterinary medicine but has received very little attention in the field of aquaculture. This study was conducted to investigate the synergistic effect of white spot syndrome virus (WSSV) and Vibrio campbellii on development of disease in specific pathogen-free (SPF) shrimp Litopenaeus vannamei. The juvenile shrimp were first injected with WSSV at a dose of 30 SID 50 shrimp -1 (SID50 = shrimp infectious dose with 50% endpoint) and 24 h later with 10 6 colony-forming units (cfu) of V. campbellii shrimp -1 . Controls receiving just one of the pathogens or negative inocula were included. In the treatment with WSSV only, shrimp started to die at 48-108 h post injection (hpi) and cumulative mortality reached 100% at 268-336 hpi. In the treatment with only V. campbellii injection (10 6 cfu shrimp -1 ), cumulative mortality reached 16.7%. Shrimp in the dual treatment died very quickly after V. campbellii injection and 100% cumulative mortality was obtained at 72-96 hpi. When WSSV-injected shrimp were given sonicated V. campbellii instead of live V. campbellii, no synergistic effect was observed. Density of V. campbellii in the haemolymph of co-infected moribund shrimp collected 10 h after V. campbellii injection was significantly higher than in shrimp injected with V. campbellii only (P < 0.01). However, there was no difference in WSSV replication between shrimp inoculated with WSSV only compared with dually inoculated ones. This study revealed that prior infection with WSSV enhances the multiplication and disease inducing capacity of V. campbellii in shrimp.
Histological demonstration of (WSSV) on L. vannamei by different staining techniques
Important mortalities in Mexican shrimp farms have been caused by a virus coming from cultured penaeid shrimps in Asia and America since the 1990´s. In many places in Asia, reported under different names but a similar histopathologic characteristics, in the Americas. This disease appeared in 1999 in the Pacific coasts under the name of White Spot Syndrome Virus (WSSV), the macroscopic symptoms include white spots on the surface of the exoskeleton, mainly in carapace region, and a reddish coloration of the whole body. Microscopic signs, observed by light microscopy, include a cellular degeneration and severe nuclear hypertrophy in tissues derived from the ectoderm and mesoderm layers. Litopenaeus vannamei were collected in farms in Sinaloa, Mexico, during the Summer of 2001 to identify by means of different staining methods, histological alterations and inclusion bodies on infected tissues. Organisms were fixed with Davidson´s solution for 48-60 h and preserved in OH 70°. Tissues of the cephalotorax region (gills, hepatopancreas, stomach and digestive tract) were included in paraffin and transversal and longitudinal sections (5-7 ¼m) were obtained. Samples were stained with Hematoxylin-Eosin, Hematoxylin-Eosin/Phloxine, Lendrum, Mallory and Bismarck brown techniques. Different infection levels of White Spot Syndrome Virus (WSSV) inclusion bodies were observed, mainly in the stomach and gill regions, similar to the one described for Penaeus japonicus, P. chinensis, P. monodon, P. indicus and P. merguiensis.
Diseases of Aquatic Organisms, 1992
Histological and ultrastructural studies of abnormal lymphoid organs from a populat~on of cultured Penaeus vannamei (Crustacea: Decapoda) revealed the presence of a previously unreported virus infecting this group of marine invertebrate animals. Named L O W (lymphoid organ vacuolization virus), the virus was found in the cytoplasm of lymphoid organ cells which had a highly vacuolated cytoplasm and intracytoplasmic eosinophilic to pale basophilic, Feulgen negative, inclusion bodies. Many affected cells also possessed pyknotic or karyorrhectic nuclei. In some foci, affected lymphoid cells formed large multicellular spherical structures, termed spheroids, which lacked a central vessel. Icosahedral nucleocapsids averaging 30 nm in diameter were present in dense cyto-plasn~ic aggregates, occasionally forming paracrystalline arrays, or a s single rows of particles thatwere closely associated with host cell membranes where they acquired their host-membrane-derived envelope. Purified enveloped virions had a buoyant density of 1.23 g ml-' and a diameter of 52 to 54 nm, while nucleocapsids were icosahedral in shape. 30 to 31 nm in diameter, and exhibited a buoyant density of 1.32 g ml-' Constitutive polypeptides had a molecular weight of 70. 60, 38 and 37 kDa. Based on its size, structure, and virogenesis, LOVV is considered to b e a member of the Togaviridae.
Aquaculture, 1999
. White spot syndrome virus WSSV is one of the most important pathogens of penaeid shrimp. It is widely distributed in most Asian countries where penaeid shrimp are cultured, as well as in the Gulf of Mexico and SE USA. The virulence of six geographic isolates of WSSV was compared using Litopenaeus Õannamei postlarvae and Farfantepenaeus duorarum juveniles. The six geographic isolates of WSSV originated from China, India, Thailand, Texas, South Carolina, as well as from crayfish maintained at the USA National Zoo. For challenge studies, virus infected tissues were given per os to L. Õannamei postlarvae and Fa. duorarum juveniles. Resultant WSSV infections were confirmed by histological examination. The cumulative mortality of L. Õannamei postlarvae reached 100% after challenge with each of the six geographic isolates of WSSV. However, the Texas isolate caused mortalities more rapidly than did the other shrimp isolates; the crayfish WSSV isolate was the slowest. In marked contrast, cumulative mortalities of juvenile Fa. duorarum reached only 35-60%, and varied among the geographic isolates of WSSV. Interestingly, in Fa. duorarum, the Texas WSSV isolate was also the most virulent, while the crayfish WSSV was the least virulent. The findings suggest that slight differences in virulence exist among geographic isolates of WSSV, and that susceptibility may vary with species and lifestages of the host. q 0044-8486r99r$ -see front matter q 1999 Elsevier Science B.V. All rights reserved.