yellowhead disease

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Aquatic Animal Diseases Signifcant to Australia:Identifcation Field Guide 4th Edition

Yellowhead disease(Also known as infection with yellowhead virus)

EXOTIC DISEASE

Yellowhead disease in giant black tiger prawn (Penaeus monodon); note yellow heads of infected prawns on the

left. Prawns on the right are normal.

Source !" #ightner

Signs o disease

Im!ortant Animals with disease may show one or more of the signs below$ but the pathogen

may still be present in the absence of any signs.

!isease signs at the farm$ tank or pond level are

aggregation of moribund prawns near the surface at pond edges abnormally high feeding rate of infected %&'%gram prawns for several days and then

cessation of feeding

mass mortality (up to '*) +&, days after cessation of feeding.

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A-uatic Animal !iseases Signicant to Australia:/dentication 0ield 1uide$ ,th edition

1ross pathological signs are

yellowing of the cephalothora2 and general bleaching of the body

white$ yellow or brown gills

e2ceptionally soft digestive gland compared with normal

yellow$ swollen digestive gland$ making the head appear yellow.

3icroscopic pathological signs are

moderate to large numbers of deeply basophilic$ evenly stained$ spherical$ cytoplasmic

inclusions within tissues of ectodermal and mesodermal origin.

Disease agent

4he causative agent of yellowhead disease is yellowhead virus$ a coronalike 56A virus in the

genus Okavirus$ family Roniviridaeand order 6idovirales. Yellowhead virus (genotype ') is

one of si2 known genotypes in the yellowhead comple2 of viruses and is the only known agent

of yellowhead disease. 1illassociated virus is designated as genotype + (covered separately

within the eld guide). 0our other known genotypes in the comple2 (genotypes 7&8) occurcommonly in black tiger prawn (Penaeus monodon) in 9ast Africa$ Asia and Australia$ and are

rarely or never associated with disease.

"ost range

Yellowhead disease is highly infectious for most known species of cultivated penaeid prawns.

6atural and:or e2perimental infections have been reported to occur in the following species of

penaeid and palaemonid shrimps$ prawns and krill.

Common name Scientifc name

arred estuarine shrimp Palaemon serrifer

lack tiger prawna Penaeus monodon

rown tiger prawn Penaeus esculentus

1reentail prawn Metapenaeus bennettae

erent species to disease. #aboratory trials have

shown that yellowhead virus can cause high mortality in black tiger prawns$ Pacic white

shrimp$ Pacic blue shrimp$ northern brown shrimp$ northern pink shrimp$ Sunda river prawns$

mysid shrimp and barred estuarine shrimp. ?ntil proven otherwise$ it should be assumed thatmost penaeid prawns worldwide are susceptible to infection with yellowhead virus.

#resence in Australia2


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EXOTIC DISEASE$not !resent in Australia%

E!idemiolog&

4he tiger prawn su>ers acute epidemics$ with mortality reaching '* within 7&% days

of the rst appearance of the gross signs.

Yellowhead virus can be transmitted hori@ontally by inection$ ingestion of infectedtissue$ immersion in membraneltered tissue e2tracts or cohabitation with infected

shrimp. 4ransmission has also been demonstrated by inection of e2tracts of paste

prawns (Ascetessp.) collected from infected ponds.

"ertical transmission occurs from both male and female parents$ possibly via surface

infection or contamination of tissue surrounding fertilised eggs.

4iger prawns younger than '% days postlarvae are resistant to yellowhead virus in

comparison with those from postlarval days +&+% to subadult$ which are highly

susceptible.

3ortalities usually occur during the early to late uvenile stages in rearing ponds.

4here appear to be at least four genotypes of virus in the yellowhead virus group.

1enotype ' is the causative agent of yellowhead disease.

Di'erential diagnosis

4he list of similar diseases below refers only to the diseases covered by this eld guide. 1ross

pathological signs may be representative of a number of diseases not included in this guide$

which therefore should not be used to provide a denitive diagnosis$ but rather as a tool to

help identify the listed diseases that most closely account for the gross signs.

Similar diseases

6ecrotising hepatopancreatitis$ 4aura syndrome$ white spot disease

Sam!le collection

!ue to the uncertainty associated with di>erentiating diseases using only gross pathological

signs$ and because some a-uatic animal disease agents might pose a risk to humans$ only

trained personnel should collect samples. You should phone your state or territory hotline

number and report your observations if you are not appropriately trained. /f samples have to

be collected$ the state or territory agency taking your call will provide advice on the

appropriate course of action. #ocal or district sheries or veterinary authorities may also

provide advice regarding sampling.

Emergenc& disease hotline

4he national disease hotline number is 'B 8C% BBB. 4his number will put you in contact with

the appropriate state or territory agency.

Further reading

4he accepted procedures for a conclusive diagnosis of yellowhead disease are summarised in

the =orld Drganisation for Animal Eealth Manual of diagnostic tests for auatic animals !"##$

available at www.oie.int:en:internationalstandardsetting:a-uaticmanual:accessonline.

4his hyperlink was correct and functioning at the time of publication.

Further images

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http://www.oie.int/en/international-standard-setting/aquatic-manual/access-onlinehttp://www.oie.int/en/international-standard-setting/aquatic-manual/access-online


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(' F +) Eistological section of the lymphoid organ (#D) of a uvenile giant black tiger prawn (Penaeus monodon)

with severe acute yellowhead disease at low (%+%G$ 0igure ') and high ('CG$ 0igure +) magnication. A

generalised$ di>use necrosis of #D cells is shown. A>ected cells display pyknotic and karyorrhectic nuclei. Single or

multiple perinuclear inclusion bodies$ ranging from pale to darkly basophilic$ are apparent in some a>ected cells

(arrows). 4his marked necrosis in acute yellowhead disease distinguishes it from infection due to 4aura syndrome

virus$ which produces similar cytopathology in other target tissues$ but not in the #D.

Source !" #ightner

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(7) Eistological section ('G) of the gills from a uvenile black tiger prawn (Penaeus monodon) with yellowhead

disease. A generalised$ di>use necrosis of cells in the gill lamellae is shown$ and a>ected cells display pyknotic and

karyorrhectic nuclei (arrows). A few large$ conspicuous$ generally spherical cells with basophilic cytoplasm are

present in the section. 4hese cells may be immature haemocytes$ released prematurely in response to a

yellowhead virus&induced haemocytopaenia.

Source !" #ightner

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(, F %) Eistological sections of the lymphoid organ (#D) of uvenile Pacic white shrimp ( Litopenaeus vannamei)

(0igure ,$ 'G) and northern brown shrimp (Farfantepenaeus aztecus) (0igure %$ %+%G) e2perimentally infected

with yellowhead virus. Severe (grade 7&,) di>use to multifocal necrosis$ characterised by cells with increased

eosinophilic cytoplasm$ pyknotic or karyorrhectic nuclei (arrows) and pale to densely basophilic perinuclearinclusions$ is present.

Source !" #ightner

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(8 F C) Eistological sections ('G) of the gills of a uvenile northern pink shrimp (Farfantepenaeus duorarum)

(0igure 8) and the oesophagus of a Pacic white shrimp (Litopenaeus vannamei) (0igure C) e2perimentally infected

with yellowhead virus. Severe (grade ,) di>use to multifocal necrosis$ characterised by cells with increased

eosinophilic cytoplasm$ pyknotic or karyorrhectic nuclei$ and pale to densely basophilic perinuclear inclusions$ is

present.

Commonwealth of Australia 2012This work is copyriht! "t may #e repro$uce$ in whole or in part su#%ect to the inclusion of an acknowle$ement of the source an$ no commercial usae or sale!

H+ + 8+C+ 7I77

AAEJda>.gov.au

da>.gov.au


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Source !" #ightner

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