3. Shrimp Iridescent Virus Disease

Shrimp iridovirus disease is an acute, contagious disease that infects crustaceans. At present, the disease is prevalent in major crustacean farming areas in my country.

【pathogen】

The pathogen is Iridovirus 1 of Decapodidae, belonging to the family Iridoviridae, genus Iridovirus of Decapodidae, with a size of 150-160 nanometers, and the nucleic acid type is DNA. The reported shrimp blood cell Iridovirus and Crayfish Iridovirus are the viruses of this virus. Both isolates can cause shrimp iridovirus disease.

【Popular Features】

Decapod iridescent virus 1 can infect shrimp from larvae to subadult stages. During aquaculture, prawns are susceptible to infection when the body length is 4-7 cm. The mortality rate of cultured Penaeus vannamei and Macrobrachium rosenbergii can reach more than 80 percent. Virus infection will occur when the breeding water temperature is between 16 and 32 °C, and the high epidemic period is concentrated from April to August.

Susceptible species include Penaeus vannamei, Macrobrachium rosenbergii, Macrobrachium japonicus, P. cruzi, Crayfish, White lobster and Port crab.

Decapod iridescent virus 1 can be transmitted horizontally through feces, cannibalism, etc. The circulation of virus-bearing seedlings is an important reason for the rapid spread of the disease.

【Clinical symptoms】

The diseased shrimp showed symptoms such as jejunum and stomach, hepatopancreas atrophy, light color, stop feeding, and decreased vitality. Dying individuals lose their ability to swim and sink to the bottom of the pool.

After infection of Macrobrachium rosenbergii, obvious white triangular lesions appear under the carapace at the base of the frontal sword, which is called "white head" or "white spot" in the industry. The diseased white shrimp also showed slight whitishness at the base of the frontal sword, but the white shrimp showed partial tolerance to infection with the virus. Some diseased Penaeus vannamei also have obvious red body symptoms.