Infectious Hypodermal and Hematopoietic Necrosis
Encyclopedia
Infectious hypodermal and hematopoietic necrosis (IHHN) is a viral
disease of penaeid shrimp
that causes mass mortality (up to 90%) among the Western blue shrimp (Penaeus stylirostris) and severe deformations in the Pacific white shrimp (P. vannamei
). It occurs in Pacific farmed and wild shrimp, but not in wild shrimp on the Atlantic
coast of the Americas. The shrimp-farming
industry has developed several broodstocks of both P. stylirostris and P. vannamei that are resistant against IHHN infection.
The disease is caused by a single-stranded DNA
virus simply called "IHHN virus", the smallest of the known penaeid shrimp viruses (22 nm
).
The mutation rate in the genome has been estimated to be ~1.4 x 10-4 substitutions/site/year. This is considerably higher than the rate in the double stranded DNA viruses and similar to that found in RNA viruses. It is also similar to the rate found in other single stranded DNA viruses.
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
disease of penaeid shrimp
Penaeidae
Penaeidae is a family of prawns, although they are often referred to as penaeid shrimp. It contains many species of economic importance, such as the tiger prawn , whiteleg shrimp, Atlantic white shrimp and Indian prawn. Many prawns are the subject of commercial fishery, and farming, both in marine...
that causes mass mortality (up to 90%) among the Western blue shrimp (Penaeus stylirostris) and severe deformations in the Pacific white shrimp (P. vannamei
Whiteleg shrimp
Whiteleg shrimp , also known as Pacific white shrimp, is a variety of prawn of the eastern Pacific Ocean commonly caught or farmed for food.-Description:...
). It occurs in Pacific farmed and wild shrimp, but not in wild shrimp on the Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
coast of the Americas. The shrimp-farming
Shrimp farm
A shrimp farm is an aquaculture business for the cultivation of marine shrimp or prawns for human consumption. Commercial shrimp farming began in the 1970s, and production grew steeply, particularly to match the market demands of the United States, Japan and Western Europe...
industry has developed several broodstocks of both P. stylirostris and P. vannamei that are resistant against IHHN infection.
The disease is caused by a single-stranded DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
virus simply called "IHHN virus", the smallest of the known penaeid shrimp viruses (22 nm
Nanometre
A nanometre is a unit of length in the metric system, equal to one billionth of a metre. The name combines the SI prefix nano- with the parent unit name metre .The nanometre is often used to express dimensions on the atomic scale: the diameter...
).
Virology
This virus has been classified as Penaeus stylirostris densovirus. The genome is 4.1 kilobases in length. There are three open reading frames in its genome: a left non structural protein (NS1) of 2001 base pairs (bp), a mid non structural protein (NS2) of 1092 bp and a right capsid protein of 990 bp. NSI appears to be a DNA helicase with ATPase activity.The mutation rate in the genome has been estimated to be ~1.4 x 10-4 substitutions/site/year. This is considerably higher than the rate in the double stranded DNA viruses and similar to that found in RNA viruses. It is also similar to the rate found in other single stranded DNA viruses.