Infectious hypodermal and hematopoietic necrosis (IHHN) is a parvoviral disease of penaeid shrimp that causes mass mortality among the Western blue shrimp and severe deformations in the Pacific white shrimp. 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.