Hepatopancreatic parvovirus (HPV)

Shrimp get sick too. Hepatopancreatic parvovirus disease is an infectious shrimp disease caused by the virus HPV (Hepatopancreatic parvovirus). HPV infects tissues of digestive tract including hepatopancreas, anterior midgut caeca and midgut epithelium. Hepatopancreatic parvovirus disease was first reported in marine farmed shrimp from Singapore in1984. There were also reports a similar disease in P. chinensis (China), P. monodon (Philippines), P. semisulcatus (Kuwait) and P. merguiensis (Singapore).

HPV consists of a small virion (22 nm) with a negative single-stranded DNA that replicates in the nucleus of the target cells. It is suspected that HPV could produce more often health problems in densely populated aquatic animal production environments. Hepatopancreatic parvovirus disease is known to occur as co-infection with other pathogens such as Laem-Singh virus (LSNV).

Importantly, in spite that HPV may not cause evident massive mortalities in grow out ponds, it may produce slow growth and reduced production in farmed P. monodon. HPV can be spread between shrimp populations through horizontal contamination both by contaminated water or cannibalism. In spite that vertical transmission is unlikely, eggs can be contaminated into spawning tanks coming into contact with infected female feces. HPV infection can be detected by PCR analysis in almost all shrimp life stages as post-larvae, juveniles and adults. HPV detection in eggs or larvae, may be possible when egg have suffered contamination during spawning.

Causative agents of Hepatopancreatic parvovirus disease. The pathogenic agent HPV also known as Penaeus monodon densovirus (PmDNV), being a putative parvovirus (Brevidensovirus). Currently HPV disease has been reported in Asia, Africa, Australia and the Americas.

Clinical signs of HPV. There is no one specific sign for HPV infection. With the pathogen generally causing atrophy of the hepatopancreas, anorexia, slow growth, reduced activity and gill fouling. It is suspected that HPV infected shrimp are also infected by other viral pathogens which frequently mask HPV infection effect. Heavy hepatopancreas infections cause no evidence of inflammatory response with haemocyte migration.

Chronic mortalities have been associated to HPV infection in farmed shrimp in early larval or postlarval populations. Hepatopancreatic parvovirus disease may produce slow growth in juvenile stages. HPV infection effect on adults is not clear. However, it may ensue mortality when severe infections are present simultaneously with high metabolic demands for example due to gonad maturation. Epizootics due to HPV infection have not been reported in shrimp farming facilities. Considerable losses to farmers can be incurred due to stunted growth as a result of HPV.

Early detection using Shrimp MultiPath^TM  (SMP). Early testing and detection with SMP can give hatchery and farm managers valuable time to notice the presence of pathogens before clinical signs appear and prior to mass mortalities. In commercial hatcheries, nursery ponds and growout ponds, HPV infection can be detected early, and farmers advised as soon as postlarvae become positive or juveniles are recently stocked in ponds. In maturation scenarios broodstock infected with HPV can be removed from the spawning cohort to minimize chance of transmission to progeny due to infected feces. This information is an early warning system preparing farmers for a critical period where slowing the spread of the disease and maximizing production outputs is still possible.

Reference: https://genics.com.au/wp-content/uploads/2022/02/HPV-Disease-Guide-2022-.pdf?x60024

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