Necrotising hepatopancreatitis (NHP), is also known as Texas necrotizing hepatopancreatitis (TNHP), Texas pond mortality syndrome (TPMS) and Peru necrotizing hepatopancreatitis (PNHP),[1] is a lethalepizootic disease offarmed shrimp. It is not very well researched yet, but generally assumed to be caused by abacterial infection.
NHP mainly affects the farmed shrimp speciesLitopenaeus vannamei (Pacific white shrimp) andLitopenaeus stylirostris (western blue shrimp), but has also been reported in three other American species, namelyFarfantepenaeus aztecus,Farfantepenaeus californiensis, andLitopenaeus setiferus.[2] The highest mortality rates occur inL. 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 inTexas in 1985; the disease then spread to shrimpaquacultures inSouth America.[2]
NHP is associated with a small,gram-negative, and highlypleomorphicRickettsia-like bacterium that belongs to its own, newgenus in the classAlphaproteobacteria.[1]
The aetiological agent is the pathogenic agentCandidatusHepatobacter penaei, an obligate intracellular bacterium of the order α-Proteobacteria.[3]
Infected shrimps show gross signs including soft shells and flaccid bodies, black or darkenedgills, dark edges of thepleopods, anduropods, and anatrophiedhepatopancreas that is whitish instead of orange or tan as is usual.[4]
Thepathogen that causes NHP seems to prefer high water temperatures (above 29 °C or 84 °F) and elevated levels of salinity (more than 20–38 ppt). Avoiding such conditions in shrimp ponds is thus an important disease control measure.[5]
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