Koi are very hardy. With proper care, they resist many of the parasites that affect more sensitive tropical fish species, such as Trichodina, Epistylis, Ich and other ciliated protozoans. Two of the biggest health concerns among koi breeders are the koi herpes virus (KHV) and Rhabdovirus carpio, which causes spring viraemia of carp (SVC). No treatment exists for either disease. Only biosecurity measures such as prompt detection, isolation and disinfection of tanks and equipment can prevent the spread of the disease and limit the loss of fish stock. In 2002, spring viraemia struck an ornamental koi farm in Kernersville, North Carolina, and required complete depopulation of the ponds and a lengthy quarantine period. For a while after this, some koi farmers in neighbouring states stopped importing fish for fear of infecting their own stocks.