, Diagnosis an-&& of Shrimp Diseases - Central Institute of ...

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VIRAL DISEASES WITH SPECIAL REFERENCE TO INDIAN SHRIMP FARMINGT.C.Santiago, K.K. Vijayan, S.V. Alavandi and N. KalaimaniViruses are ~~ltramicroscopic, infective agents capable of multiplying in the host livingcells causing improper cell function or cell destruction leading to the death of the host. Viraldiseases constitute the most serious problems of shrimp culture due to the high infectivity,pathogenicity and total lack of curative measures. Worldwide, shrimp aquaculture hassuffered substantial economic losses due to pathogenic viruses, and the Indian shrimp farmingis no exception. So far, 15 viruses infecting cultured shrimps have been recorded across theshrimp farming countries of the world (Table). Till today, only five viruses have beenrecorded from Indian farms.Monodon baculovirus (MBV)Nrrture of infection:Monodon baculovirus (MBV) is the first viral pathogen to be recorded from thecultured penaeids of India. Presently the virus is enzootic in Indian hatcheries and farms,infecting both P. monodon and P. indicus. MBV infections have been observed in thehepatopancreatic cells of all life stages of the prawn except egg, nauplius and protzoea 1 and2 stages. Postlarvae and farmed shrimps of all sizes with severe MBV infections appearnormal and healthy. The virus, widely distributed in the cultured populations is well toleratedby the shrimps, as long as rearing conditions are optimal. Hence, under good culture practicesthe impact of the MBV infection can be minimal. However, under adverse environn~entalconditions, MBV may predispose infected shrimp to infection by other pathogens, causingpoor growth, secondary infections and mortality.Pathogenisis and diagnosis:MBV is a single-enveloped, rod shaped, occluded double stranded DNA virusbelonging to the group baculovirus. The virus occurs freely or within proteinaceouspolyhedral occlusion bodies in the nucleus, with virions measuring 75-300nm. The presenceof MBV in the prawn can be detected by direct microscopic examination of iinpressionsmears of infected hepatopancreas (HP) or midgut tissue, stained with 0.05 to 0.1% ofmalachite green by demonstrating the usually multiple spherical intranuclear incl~~sion bodies.Histoiogical preparations of the infected HP can be used for further confirmation due to the
presence of prominent eosinophiiic single to multiple spherical bodies within thehypertrophied nuclei of the hepatopancreatic tubule or midgut epithelial cells. Transmissionelectron microscopy (TEM) can also used to show the presence of MBV virions. DNA basedrapid diagnostic tools? polymerase chain reaction (PCR) and DIG-labelled DNA probes arealso available for the early diagnosis of MBV.Prevention nnd control:MBV infection may be prevented only through avoidance by quarantine methods,destruction of contaminated stocks, and disinfection of contaminated faciiities. There is notreatment for MBV, however good farm management can minimize this disease.Infectious Hepatopancreatic and Lymphoid organ Necrosis Disease (IHLN)Nature of infection:The first ever shrimp epizootic reported from India is the IHLN disease, from shrimpfarms located along the Kandaleru Creek, Nellore, Andhra Pradesh during July 1994. Thiswas a localized epizootic confined to the watershed areas of the Kandaleru Creek. The IHLNaffected the crops of culture duration ranging from 60 to 100 days weighing 3-28 g. The onsetof the disease was sudden and within 3-5 days post infection, more than 90 % of the stock inthe farms was lost. The disease prevailed in a virulent form for about three months. Grosssigns of the diseased shrimp were: light yellow or pinkish cephalothorax, reddishdiscoloration of the body and-appendages, empty gut, lethargy, poor escape reflex, secondarybacterial infection and mortality. Dead shrimps were found scattered all over the pondbottom. Only P. rnonodon was affected, P.indicus was found refractory to the disease.Prttlzogenisis and diagnosis:The most prominent feature of the disease was the highly melanized and shrunken HP.Acute damages were observed in the HP, manifested by multi-focal necrosis of the tubuleepithelium marked by hemocytic infiltration and encapsulation resulting in melanization.Densely stained, globular, basophilic bodies were observed in the HP cells and lymphoidorgan (LO). The mortality pattern and external signs of infection (yellow cephalothorax) ofthe disease suggested resemblance to yellow head virus (YHD) in the P. monodon. However,the prominent necrotic changes in the HP and LO and absence of pathological changes in thegills, indicated that the disease clearly differed from YHD, however, the etiology of thedisease was of viral nature. The peculiar host specificity to P. rnonodon, presence of
Page 5 and 6: OVERVIEW OF STRATEGIES FOR PREVENTI
Page 7 and 8: in harmonizing aquatic animal healt
Page 9 and 10: SI-IRXMP DISEASES: GENEIL4L ASPECTS
Page 11: quantitative level of pathogen is i
Page 15 and 16: Disease affected the shrimps of all
Page 19 and 20: BACTERIAL AND FUNGAL DISEASES OF SH
Page 21 and 22: Cause: The epibiotic bacteria stich
Page 23 and 24: PARASiTIC AND NON-INFECTIOUS IIISEA
Page 25 and 26: XOS-INFECTIOUS DISEASESNon-infectio
Page 27 and 28: INVESTIGATING SHRIMP DISEASES: OBSE
Page 29 and 30: lnay be a predisposing factor for b
Page 31 and 32: BACTERIOLOGICAL METHODSS.V. Alavand
Page 34 and 35: In place of ZMA, nutrient agar prep
Page 36 and 37: Interpretation: Positive reaction i
Page 38 and 39: Incubate at 37°C for 1-2 h.Examine
Page 40 and 41: Alkaligens: etc. are resistant. The
Page 42 and 43: Culture Media, Reagents and StainsC
Page 45 and 46: Differential characteristics of Vib
Page 47 and 48: Davidson's Alcohol Formatin Acetic
Page 49 and 50: Paraffin cold impregnationXylene an
Page 51 and 52: ProcedureDe-paraffinise the slid'c
Page 53 and 54: Biochemistry of Nucleic Acids with
Page 55 and 56: DNA e.rl1i6it.v base equivuleizcc!E
Page 57 and 58: hydrolyzed by dilute alkali. The su
Page 59 and 60: Polymerase Chain Reaction (PCR) is
Page 61 and 62: a number of viral, bacterial and pa
Page 63 and 64:
from 15-30 bases. Negative controls
Page 65 and 66:
PCR Primers for Indian WSVTwo sets
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ANTIOXIDANTS IN MANAGEMENT OF OXIDA
Page 69 and 70:
Many potent chemical carcinogens ar
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cells. It has been shown that possi
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AFB, induced ~nutagenesis in Salmon
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FIGURE 2. An overview of oxygen rad
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were responsible for production los
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for Asiatic region. The participati
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charge of the DNA fragment. The neg
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European countries have in place th
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irth to a new concept to treatment
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