Gulf States Marine Fisheries Commission

Yellow-Head Virus (YHV)

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Interest to Fisheries
Current Status


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Yellow-Head Virus (YHV)
Photo by Dr. Jeffrey Lotz

Scientific Name:

Other scientific names appearing in the literature of this species:

Yellow-head Disease (YHD), YH disease or YHD of Penaeus monodon. In Thailand the disease is called Hua leung (Chantanachookin et al. 1993, Lightner, 1996).

Common Name: Yellow-head Virus (YHV)

Distinguishing Features:

Yellow-head virus or YHV is a pleomorphic, enveloped virus with single stranded RNA of positive polarity, primarily localized in the cytoplasm of infected cells (personal communication, Dr. ECB Nadala, Jr., June, 1999). Observations by Chantanachookin et al. (1993) of viral development in the shrimp, Penaeus monodon, indicated there is a long filamentous form of the virus prior to capsid and envelope formation.

Similar Species:

Gill-associated virus (GAV) is a yellow head-like virus. It has been observed in Penaeus monodon in Queensland since 1996 (Spann et al., 1999).


While not fully characterized, YHV has been suggested by Dr. DV Lightner (1996) to belong in the family Rhabdoviridae or with a filamentous group within the family Paramyxoviridae. More recently Dr. ECB Nadala, Jr. (personal communication, June, 1999) has found morphological data which suggests that the virus may be more pleomorphic than rod-shaped. Cowley et al. (1999) have presented data on the amino acid sequence of Gill-associated virus (GAV), which is a yellow head-like virus, that suggests that the genome is positive sense, single stranded RNA. Together, the data from Dr. Nadala and Dr. Cowley indicate that YHV may be a member of the order Nidovirales, the family Coronoviridae and possibly the genus Torovirus (personal communication Dr. Nadala, June, 1999; Cowley et al., 1999). Cowley et al. (1999) emphasize that more information about the replication strategy of these viruses is needed to definitively place the virus in the appropriate genus and family within the order Nidovirales.

Viral replication seems to occur only in the cytoplasm without any sign of replication in the intact nuclei of infected cells. A long filamentous form of the virus (some over 800 nm in length), perhaps a precursor to the enveloped, rod-shape form is present in the cytoplasm of many cells. Viral envelopes appear to be acquired by passage of these provirions through the endoplasmic reticulum of the host cells. Enveloped virions then cluster in cytoplasmic vesicles, sometimes densely packed, resembling paracrystalline arrays, where they appear to divide into the smaller rod-shaped units (Chantanachookin et al., 1993).

Rod-shaped virions and filamentous precursors were found in normal, healthy, captured (wild) broodstock by Flegel et al. (1992). YHV may occur as latent, asymptomatic infections in broodstock shrimp and may possibly transfer from these shrimp to their offspring in larval rearing facilities (Chantanachookin et al., 1993).

Experimentally infected shrimp develop identical clinical signs (see below) to naturally infected prawns. Indications of disease are observed within 2 days post infection and generally 100% mortality occurs by 3-9 days post infection (Lu et al., 1995).

Clinical Signs and Disease Progression: Yellow-head principally infects pond-reared black tiger prawn Penaeus monodon. It was first reported in Thailand (1990) but is known to infect and cause mass mortality in shrimp farming operations throughout southeastern Asian countries. This syndrome occurs in the juvenile to sub-adult stages of shrimp 5 to 15 grams in size, especially at 50-70 days of grow-out (Lightner, 1996). At the onset of YHD shrimp have been observed consuming feed at an abnormally high rate for several days. Feeding abrubtly ceases and within 1 day, a few moribund shrimp appear swimming slowly near the surface at the pond edges. Affected shrimp exhibit light yellow coloration of the cephalothorax area and a generally pale or bleached appearance; they die within a few hours. By the following day, the number of similarly affected shrimp increases dramatically, and by the third day after the first appearance of moribund shrimp, the entire crop is typically lost (Lightner, 1996, Chantanachookin et al., 1993). Moribund shrimp with YHD generally appear pallid in color, with a yellowish, often swollen cephalothorax. Infected shrimp frequently exhibit whitish or pale yellowish to brown gills, and often a pale yellow hepatopancreas (Lightner, 1996).

Maximum Size:


YHV is known to occur in wild shrimp populations but the extent of its distribution in wild populations is not known. YHD seems to be widespread wherever Penaeus monodon are cultured and may be the same disease syndrome that has plagued the intensive culture of P. monodon for more than a decade in Asia--Taiwan (1986-87), Indonesia, Malaysia, China, and the Philippines (Chantanachookin et al., 1993). Wordwide spread of the virus is possible given the global exportation and re-processing of cultured shrimp products.

At least one incidence of infection occured in stocks of pond-reared shrimp in Texas (1995). The presumed source of virus was from nearby shrimp processing plants, known importers of exotic cultured shrimp (Lightner, 1996).

Interest to Fisheries:

While YHV primarily infects and causes disease in pond-reared black tiger prawns Penaeus monodon, species of Penaeid shrimp commonly cultured in the western hemisphere have been experimentally infected and diseased by YHV--Litopenaeus vannamei, L. stylirostris, L. setiferus, Farfantepenaeus aztecus, and F. duorarum (Lightner, 1996). Spread of YHV to western hemisphere fisheries is a possibility.

A plateau in production of cultured shrimp in the past few years can be attributed to mass mortalities due to shrimp viruses in spite of an ever increasing number of hectares used for shrimp farming worldwide. Development of strategies for control and eradication of pathogens is needed if the shrimp farming industry is to regain the growth it saw in the 1980's and early 1990's (Lotz, 1997).

Current Status of this Species in the Gulf of Mexico Ecosystem:

At least one incident of YHV infection in pond reared, juvenile Litopenaeus setiferus in south Texas was reported in 1995. Nearby shrimp packing plants that imported and re-processed raw, frozen shrimp were the presumed source of the virus (Lightner, 1996). Such incidents indicate that virus can be transported to local stocks of shrimp not known to be natural hosts for YHV.

Potential Impacts:

Since YHV has been shown to experimentally infect and cause serious disease in juvenile stages of the American penaeids Litopenaeus vannamei, L. stylirostris, L. setiferus, Farfantepenaeus aztecus, and F. duorarum, and because of experiences like the Texas shrimp pond infection of 1995, the potential exists for YHV to become a disease to contend with for shrimp farmers in the western hemisphere.

Assessment of Risks: Given unregulated movement of live seed, broodstock and frozen and raw products, it is likely that one or more shrimp viruses will become cosmopolitan in the future (Lotz, 1997).


Advice to farmers faced with an outbreak of YHD has been to harvest ponds at the first signs of disease. Early harvest may reduce, but not eliminate, economic loss (Chantanachookin et al., 1993). This advise presents a problem, since there is a possibility that exported, infected shrimp, fresh or frozen, can result in spread of viral infection to wild and/or cultured shrimp populations (Lotz, 1997).

An overall plan for the detection and control of dangerous pathogens that includes the co-operative efforts of farmers, aquatic health care specialists, scientists, and government agencies needs to be developed (Lotz, 1997).


Chantanachookin, C., S. Boonyaratpalin, J. Kasornchandra, S. Direkbusarakom, U. Ekpanithanpong, K. Supamataya, S. Sriurairatana, and T.W.Flegel. 1993. Histology And Ultrastructure Erveal A New Granulosis-like Virus In Penaeus Monodon Affected By Yellow-head Disease. Diseases Of Aquatic Organisms 17:145-157.

Cowley, J.A., C.M. Dimmock, K.M. Spann, and P.J. Walker. 1999. Genomic Characterization Of Gill-associated Virus, A Yellow Head-like Virus Infecting Penaeus Monodon In Australia [Abstract]. In: Book Of Abstracts. World Aquaculture '99. The Annual International Conference And Exposition Of The World Aquaculture Society, 26 April - 2 May, Sydney, Australia.

Flegel, T.W., D.F. Fegan, S. Kongsom, S. Vuthikornudomkit, S. Sriurairatana, S. Boonyaratpalin, C. Chantanachookhlin, J.E. Vickers, and O.D. Macdonald. 1992. Occurrence, Diagnosis And Treatment Of Shrimp Diseases In Thailand. In: W. Fulks And K.L. Main (eds.), Diseases Of Cultured Penaeid Shrimp In Asia And The United States. Oceanic Institute, Honolulu, Hawaii, USA P. 57-112.

Jackson, A.O., R.I. Francki, and D. Zuidema. 1987. Biology, Structure And Replication Of Plant Rhabdoviruses. In: Wagner R.R. (ed) The Rhabdoviruses. Plenum Press, New York P. 427-508.

Lightner, D.V. 1996. A Handbook Of Shrimp Pathology And Diagnostic Procedures For Disease Of Cultured Penaeid Shrimp. World Aquaculture Society, Baton Rouge, Lousisana, USA.

Limsuwan, C. 1991. Handbook For Cultivation Of Black Tiger Prawns. Tansetakit Co. Ltd, Bangkok (in Thai).

Lotz, J.M. 1997. Sepcial topic review: Viruses, biosecurity and specific pathogen-free stocks in shrimp aquaculture World Journal of Microbiology & Biotechnology 13, 311-9

Lu, Y., L.M. Tapay, P.C. Loh, J.A. Brock, and R.B. Gose. 1995. Distribution Of Yellow-head Virus In Selected Tissues And Organs Of Penaeid Shrimp Penaeus Vannamei. Diseases Of Aquatic Oraganisms 23:67-70.

Menasveta, P. 1990. The Present Status Of Aquaculture In Thailand And The Potential Use Of Biotechnology To Increase Coastal Aquaculture Production. In: Flegel, T.W., G. Tharun, Y. Yuthavong. (eds.) Biotechnology For Small Industries In Developing Countries. National Center For Genetic Engineering And Biotechnology, Ministry Of Science, Technology And Environment, Bangkok P. 55-63.

Nadala, E.,Jr., L. Tapay and P. Loh. 1997. Yellow-head virus: a rhabdovirus-like pathogen of penaeid shrimp. Diseases of Aquatic Organisms. Vol. 31:141-146.

Payment P., and M. Trudel. 1993. Methods And Techniques In Virology. Marcel Dekker, Inc., New York.

Rosenberry, B. 1991. World Shrimp Farming 1991 Aquaculture Digest, San Diego, CA P. 13.

Spann, K.M., J.A. Cowley, I.J. East, A. Donaldson, and P.J. Walker. 1999. Gill-associated Virus (GAV), A Yellow Head-like Virus Of Penaeus Monodon Cultured In Australia [Abstract]. In: Book Of Abstracts. World Aquaculture '99. The Annual International Conference And Exposition Of The World Aquaculture Society, 26 April - 2 May, Sydney, Australia.

Yudin A.I., and W.H. Clark, Jr. 1979. A Description Of Rhabdovirus-like Particles In The Mandibular Gland Of The Blue Crab, Callinectes Sapidus. Journal Of Invertebrate Pathology 33:133.

Other on-line references:

Date Created: 08/15/1998
Last Modified: 08/03/2005

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