Necrotising hepatopancreatitis (NHP), is also known as Texas necrotizing hepatopancreatitis (TNHP), Texas Pond Mortality Syndrome (TPMS) and Peru necrotizing hepatopancreatitis (PNHP), is a lethal

epizootic In epizoology, an epizootic (from Greek: ''epi-'' upon + ''zoon'' animal) is a disease event in a nonhuman animal population analogous to an epidemic in humans. An epizootic may be restricted to a specific locale (an "outbreak"), general (an "epi ...

disease of farmed shrimp. It is not very well researched yet, but generally assumed to be caused by a

bacterial Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria were amon ...

infection. NHP mainly affects the farmed shrimp species ''

Litopenaeus vannamei Whiteleg shrimp (''Litopenaeus vannamei'', synonym ''Penaeus vannamei''), also known as Pacific white shrimp or King prawn, is a species of prawn of the eastern Pacific Ocean commonly caught or farmed for food. Description ''L. vannamei'' grow ...

'' (Pacific white shrimp) and ''

Litopenaeus stylirostris ''Litopenaeus'' is a genus of prawns, formerly included in the genus ''Penaeus''. It contains five species: *''Litopenaeus occidentalis'' (Streets, 1871) *'' Litopenaeus schmitti'' (Burkenroad, 1936) *''Litopenaeus setiferus'' (Linnaeus, 1767) * ...

'' (Western blue shrimp), but has also been reported in three other American species, namely ''

Farfantepenaeus aztecus ''Farfantepenaeus aztecus'' is a species of marine penaeid shrimps found around the east coast of the US and Mexico. They are an important commercial species in the US. The FAO refers to them as the northern brown shrimp; other common names, us ...

'', '' Farfantepenaeus californiensis'', and ''

Litopenaeus setiferus ''Litopenaeus setiferus'' (also accepted: ''Penaeus setiferus'', and known by various common names including Atlantic white shrimp, '' white shrimp'', ''gray shrimp'', ''lake shrimp'', ''green shrimp'', ''green-tailed shrimp'', ''blue-tailed ...

''. The highest mortality rates occur in ''L. vannamei'', which is one of the two most frequently farmed species of shrimp. Untreated, the disease causes mortality rates of up to 90 percent within 30 days. A first outbreak of NHP had been reported in

Texas Texas (, ; Spanish: ''Texas'', ''Tejas'') is a state in the South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2020, it is the second-largest U.S. state by ...

in 1985; the disease then spread to shrimp aquacultures in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sout ...

. NHP is associated with a small,

gram-negative Gram-negative bacteria are bacteria that do not retain the crystal violet stain used in the Gram staining method of bacterial differentiation. They are characterized by their cell envelopes, which are composed of a thin peptidoglycan cell wa ...

, and highly pleomorphic ''

Rickettsia ''Rickettsia'' is a genus of nonmotile, gram-negative, nonspore-forming, highly pleomorphic bacteria that may occur in the forms of cocci (0.1 μm in diameter), bacilli (1–4 μm long), or threads (up to about 10 μm long). The term "ricke ...

''-like bacterium that belongs to its own, new

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

in the class

Alphaproteobacteria Alphaproteobacteria is a class of bacteria in the phylum Pseudomonadota (formerly Proteobacteria). The Magnetococcales and Mariprofundales are considered basal or sister to the Alphaproteobacteria. The Alphaproteobacteria are highly diverse and ...

. The aetiological agent is the pathogenic agent Candidatus ''Hepatobacter penaei'', an obligate intracellular bacterium of the Order α-Proteobacteria. Infected shrimps show gross signs including soft shells and flaccid bodies, black or darkened

gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...

s, dark edges of the pleopods, and

uropod Uropods are posterior appendages found on a wide variety of crustaceans. They typically have functions in locomotion. Definition Uropods are often defined as the appendages of the last body segment of a crustacean. An alternative definition sugge ...

s, and an atrophied

hepatopancreas The hepatopancreas, digestive gland or midgut gland is an organ of the digestive tract of arthropods and molluscs. It provides the functions which in mammals are provided separately by the liver and pancreas, including the production of digestive ...

that is whitish instead of orange or tan as is usual. The

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ ...

that causes NHP seems to prefer high water temperatures (above ) and elevated levels of salinity (more than 20–38 ppt). Avoiding such conditions in shrimp ponds is thus an important disease control measure.

References

Penaeidae Diseases and parasites of crustaceans {{veterinary-med-stub