Monodon Baculovirus Research Articles

A histopathological disease survey of cultured shrimp in North East Sumatera, Indonesia

Abstract. A disease survey was conducted in North East Sumatera, Indonesia, during June and July 1991. The objeet was to obtain information regarding the diseases present in shrimp culture faeilities. Shrimp were sampled for histopathological examination and details of the farm management and environment were recorded. The stocks sampled included some reported to be suffering from disease problems and some reported to be in good health. Samples were taken from 24 pond farms, five hatcheries and a broodstock fisherman. All farms and hatcheries cultured Penaeus monodon Fabricius, one farm also cultured Penaeus merguiensis de Mann, and two cultured Metapenaeus spp. Several wild caught P. monodon female broodstoek and some wild rice shrimp (Acetes spp.) were also sampled. The disease conditions detected in P. monodon were monodon baculovirus (MBV), hepatopancreatic parvo‐likc virus (HPV), septic hcpatopancreatic necrosis (SHN), bacterial septicaemia (BS), haernocytie enteritis (HE), lymphoid organ pathology (LOP), external fouling organisms (EFO), and a single unconfirmed case of infectious hypodcrmal and haemopoietic necrosis (IHHN). The Acetes spp. from one site had a microsporidean infection in the striated muscle of the abdomen. EFO was the most common disease condition, and was identified in 16 farms and three hatcheries. MBV was detected in 14 farms, three hatcheries and in one broodstoek. SHN was found in 13 farms with one case of concurrent BS and LOP was found in eight farms. HE was found in four farms and HPV was identified in shrimp with MBV on two farms and as the only disease in one broodstoek. The significance and implications of these findings for the developing industry in Indonesia arc discussed.

Efficiency of Chlorine as a Disinfectant Against Monodon Baculovirus (MBV)

The effect of chlorine in the form of calcium hypochlorite solution on the infec­tivity of Monodon Baculovirus (MBV) for Penaeus monodon postlarvae in a bioassay was investigated using several concentrations and exposure times. MBV was inacti­vated by a 24-hour exposure to 1,000 mg·I·1 chlorine. Lower concentrations for more time or higher concentrations for less time reduced the prevalence of infections but did noteliminate them. The presence of small amounts of host tissue did not reduce the effectiveness of the chlorine.

Preliminary characterization and partial cloning of the genome of a baculovirus from: Penaeus monodon (PmSMPV = MBV)

Monodon baculovirus (MBV), an occluded virus related to the Baculoviridae, which is enzootic in Southeast Asia in both wild and farmed Penaeus rnonodon populations, was isolated and purified. Virions were rod-shaped. enveloped, 265 to 282 nm in length and 68 to 77 nm in diameter. with unique appendages at each extremity. Singly enveloped nucleocapsids were 250 to 269 nm in length and 62 to 68 nm in diameter, showed a 'cross-hatched' surface appearance, and a doublelayered 'cap' structure closing its ends. Subunits of the occlusion body were 22 to 23 nm in diameter and had an icosahedral-like shape. These subunits (polyhedrins) exhibited at least 1 major polypeptide of 58 kDa by SDS-PAGE. The extracted nucleic acid was a very large supercoiled molecule, as shown by electron microscopy, and was demonstrated to be DNA by restriction enzyme digestion. BamHI restriction fragments obtained after agarose gel electrophoresis were separately cloned in the system plJC18-DH5a. Subsequently, restriction maps were establ~shed for the inserts, which ranged from 8.5 to 2.8 kbp (kilo base pairs) corresponding to the cloned BamHI restriction fragments. By its characteristics, we propose to include this virus in the subgroup A, subtype SNPV of the Baculoviridae family, and to name it PmSNPV according to the guidelines set forth by the International Committee on Taxonomy of Viruses.

Transformation of anterior midgut and hepatopancreas cells by monodon baculovirus (MBV) in Penaeus monodon postlarvae

The transformation of anterior midgut and hepatopancreas cells of the shrimp Penaeus monodon by monodon baculovirus (MBV) was investigated by means of light and electron microscopy with particular emphasis on the cytoplasmic organelles. The three types of MBV-infected hepatopancreas cells and the anterior midgut cells exhibit similarities in nuclear alterations such as nuclear hypertrophy, chromatin margination, virion assembly and formation of occlusion bodies. Similarities are also found in some changes of the cell organelles, e.g. reduction of rough endoplasmic reticulum, enhancement of ribosomes or occurrence of microfilament patches. In contrast, further alterations are largely cell specific and depend on the organelle ultrastructure prior to the virus infection. Specific changes are, for instance, proliferation of smooth endoplasmic reticulum around lipid droplets, and elongation and proliferation of dictyosomc cisternae in R-cells, or formation of huge dictyosomes with heavily dilated cisternae and membrane labyrinths at the nuclear envelope in F-cells. The cytoplasmic compartments of the B-cells and the anterior midgut cells change only moderately compared to R- and F-cells. The observed cytological alterations are discussed with respect to the function of the cell type.

The occurrence, development and histopathology of monodon baculovirus in Penaeus monodon in southern Thailand

The occurrence, development and histopathology of monodon baculovirus (MBV) in larvae, postlarvae (PL) and broodstock of Penaeus monodon was studied over a period of 1 year in southern Thailand. In histological samples of captured male and female broodstock obtained from the Andaman Sea, the incidence of individuals with MBV occlusion bodies (OB's) was approximately 5.7% during the period. Absence of MBV virions in electron micrographs of oocytes of MBV-infected females, mature eggs and nauplii indicated that the virus may not be transmitted transovarially. Together, these facts suggest that elimination of MBV from hatcheries by screening of quarantined wild broodstock would be feasible. In the hatchery, baculovirus OB's began to be clearly identifiable in the hepatopancreas of larvae at the third zoeal stage. During all subsequent larval and PL developmental stages, there was a high incidence of infected individuals, some with extremely large numbers of OB's. The average incidence of PL positive for OB's in histological specimens approached 100% during the period of the study in a survey that included eight commercial PL producers on both the Gulf of Thailand and the Andaman Sea. However, the incidence of OB-positive animals gradually fell as the shrimp grew older and OB's were often undetectable in healthy juveniles derived from infected PL within approximately 2 weeks of stocking in grow-out ponds. In some instances, it was possible to follow groups of PL from the nursery stage through to harvest of market-size shrimp. Average survival data for such shrimp followed in a large number of ponds over a period of 1 year indicated that MBV was well tolerated by Penaeus monodon if other rearing conditions were optimal. However, in the event of environmental or other stress, the incidence of animals showing large numbers of MBV particles increased dramatically.

Lymphoidal parvovirus-like particles in Australian penaeid prawns

Prawns in northern Queensland exhib~ted mult~nucleated g ~ a n t cell formation in hypertrophied lymphoid organs. Mostly farmed Penaeus monodon, P, merguiensls and P esculentus were involved The transformation involved mild nuclear hypertrophy, marglnated chromatin and basophilic da rken~ng of increased cytoplasm In a multinucleate giant cell. Areas of transformation were d~scre te , often bounded by elongated f~brocytes and sometimes fully encapsulated Basophilic inclusions occurred con~monly and eos~nophlhc lntranuclear inclus~ons rarely. These inclus~ons talned for DNA with acndlne orange fluorescence. Associated \nth lympho~dal changes was the presence of rounded F l~ke cells with basophilic, pyknolc nucleoli. Under the electron microscope, transformed lympho~dal cells d~splayed virus-hke parlcles of 18 to 20 nm diameter associated with inclusion b o d ~ e s in the nucleus These particles were similar to a parvovlrus and named lymphoidal parvovirus-like (LP\/). Their similarities and relationship to hepatopancreatic parvovirus and infectious hypodermal and haematopoletic necrosis virus are discussed. INTRODUCTION MATERIALS AND METHODS The lymphoid organ (or Oka organ) is a relatively newly discovered organ in penaeid prawns (Oka 1969) and is becoming increasingly important in disease studies. Lightner et al. (1987) described Oka organ hyperplastic spheroids and metastatic foci in ectopic localities in both Penaeus monodon Fabricus and P. penicillatus from Taiwan. Prlmary cell cultures from the lymphoid organ of P. n~onodon were capable of supporting in vitro replication of Monodon baculovirus when inoculated into the cultures (Chen & Kou 1989). Lymphoid t~ssue necrosis and haenlocytic infiltration lead to encapsulation, nodule formation and melanization and are often the earliest changes associated with bacterial infections (Nash 1990). In Australia, the lymphoidal spheroids in Penaeus nlerguiensis de Man have been associated with moribund wild spawners (Owens & Hall-Mendelin 1990). Suggestions were made that there were similarities between tissues showing lymphoid metastasis with the lymphoidal spheroids and tissues attacked by infectious haematopoietic and hypodermal necrosis virus (IHHNV). This paper reports on further investigations of lymphoidal changes in prawns and the probable causahve agent. Banana prawns Penaeus merguiensis were collected by a cast net in the Burdekin Rver , northern Queensland. Tiger prawns (P. monodon and P. esculentus Haswell) were collected from prawn farms in the local area. Prawns were split longitudinally, and fixed in Davidson's fixative. Histological sections were cut and stained using standard techniques (Culling et al. 1985). For electron microscopy, the diced lymphoid organ was fixed in 2 .5 % glutaldehyde/2 O/O paraforn~aldehyde in cacodylate buffer and postfixed in 1 O/O osmium tetroxide. The tissue was dehydrated and mounted in Spurr (Tm) resin. Sections were cut on a LKB Ultratome at 50 nm stained with uranyl acetate/ 70 O/O methanol and lead citrate and viewed at 80 kV on a Joel 2000FX transmission electron microscope

Detection of a baculovirus in the tiger prawn Penaeus monodon.

In postlarval Penaeus monodon from a hatchery in Asia a baculovirus was detected in the epithelial cells of the hepatopancreas by electron microscopy. The baculovirus was identified as the Monodon baculovirus (MBV).

Observation on pathogenicity and epizootiology of Penaeus monodon baculovirus(MBV) in cultured shrimp in Taiwan.

Studies on the epizootiology of MBV infection in P. monodon showed that the incidence of MBV in postlarval and juvenile P. monodon cultured in Taiwan increased from 15-17% in 1984-1986 to 80-85% in 1988. The infection rate of MBV in P. monodon broodstock populations investigated in 1988 was approximately 50%. A survey on cultured P. penicillatus in 1987 revealed 20-25% MBV infection rate.Studies of hatchery-reared postlarval P. monodon showed that MBV infection initiated mortality. Results from these pathogenic studies showed that environmental stressors significantly affect the survival of MBV-infected postlarvae, juvenile (s) and adult P. monodon and P. penicillatus. Histopathological observations performed in the present study revealed that mortality of P. monodon broodstocks may be caused by secondary infection of pathogenic bacteria.

日本国内におけるＭｏｎｏｄｏｎ Ｂａｃｕｌｏｖｉｒｕｓ検出例

In December of 1983, giant tiger shrimp Penaeus monodon (10-35mm in BL) having acidophilic spherical inclusion bodies in hypertrophied nuclei of mid-gut gland epithelium, was found in Yamaguchi Prefecture, Japan. These shrimp had been reproduced from the broodstock of the shrimp imported from Taiwan to Yamaguchi Prefecture and cultured by a shrimp culturist. By electron microscopy, it was found that the epithelial cells having inclusion bodies were infected with a baculovirus (76 × 325nm), and the inclusion body had a lattice array structure. From these observations, the virus was identified as Monodon Baculovirus (MBV). This is the first record of the detection of MBV in Japan. Since the population of the natural inhabitant of P. monodon is very small in the sea water area around Japan, the virus seems to be introduced from Taiwan accompanied with the broodstock importation. The infectivity trials with MBV did not reveal any formation of inclusion body or abnormal mortality in post larval kuruma shrimp, P. japonicus.

Mortalities of Juvenile Shrimp, Penaeus monodon, Associated with Penaeus monodon Baculovirus, Cytoplasmic Reo-Like Virus, and Rickettsial and Bacterial Infections, from Malaysian Brackishwater Ponds

A disease syndrome from Malaysia in extensively reared Penaeus monodon, in which P. monodon baculovirus (MBV), a cytoplasmic reo-like virus, rickettsia and bacteria were identified pathologically, is described. Typical MBV lesions were apparent in hepatopancreas; the reo-like virus did not produce any light microscope-visible lesions. Rickettsial microcolonies, present in hypertrophied connective tissue cells throughout all shrimp tissues, were associated with hemocyte infiltrations, aggregations and granulomas with melanization and fibrocytes. The organs with the highest prevalence of rickettsia-associated lesions were the heart, hepatopancreas, Y-organ, gills and parietal hemocoele linings. The Gram-negative, rod-shaped bacteria were associated with tissue changes and had a tissue distribution typical of a penaeid bacterial septicemia. Histologically, the rickettsia appeared primarily responsible for the disease with the secondary bacterial infections contributing to the mortalities seen. MBV and the reo-like virus may have facilitated the rickettsial infection or may have become patent in the weakened shrimp.

Observations on the geographic distribution, pathogenesis and morphology of the baculovirus from Penaeus monodon Fabricius

A baculovirus disease of Penaeus monodon Fabricius named monodon baculovirus (MBV) was found in populations of postlarval P. monodon that originated from three separate sources in the Southwestern Pacific region. The pathogenesis, lesion development and morphology of the virus was the same regardless of the origin of the P. monodon population. The apparent target organs and tissues for MBV are the hepatopancreatic tubule and duct epithelium of postlarvae, juveniles and adults, and the anterior midgut epithelium of very young postlarvae. It was not determined if MBV produces patent disease in the larval stages of P. monodon, nor how it is transferred from brood stock to their offspring. MBV disease may cause serious losses in compromised populations (especially in postlarvae and young juveniles), but under conditions favorable to the host, fewer mortalities occurred and only low-grade infections of the hepatopancreas were detected. Three stages in the pathogenesis of MBV disease were noted in the hepatopancreas. Stage 1 hepatopancreatocytes had slightly hypertrophied nuclei, but contained no occlusion bodies (a highly specialized type of inclusion body) and few completed virions; stage 2 cell nuclei also had hypertrophied nuclei, but contained developing occlusion bodies and completed virions; stage 3 cell nuclei contained mature occulusion bodies and abundant numbers of completed free and occluded virions. Cell necrosis and cytolysis or sloughing (releasing virus and occlusion bodies into the gut lumen) followed stage 3 development in living hosts. The morphology of MBV is consistent with members of the genus Baculovirus subgroup A. The MBV particles are rod-shaped, singly enveloped, and replicate in the nucleus, occur free or within proteinaceous polyhedral occlusion bodies, and are assumed to contain DNA as the nucleic acid type. The nucleocapsid of MBV measured 42 ± 3 nm by 246 ± 15 nm, while the enveloped virions measured 75 ± 4 nm by 324 ± 33 nm.