Study on Giant Intestinal Cystic Disease of Common carp Caused by Thelohanellus kitauei in Northern Vietnam

Haiduong province is far from Hanoi center for 40 km in east, a large area for freshwater production in Northern Vietnam, Common carp is major cultural species. However, disease is a serious problem for fish farmers. Major disease is giant intestinal cystic caused by Myxobolus sp with low growth rate, high FCR, and high mortality. This paper provides information based on the survey from 212 fish farms in four districts, following with diseased fish were sampled for diagnosis. The results showed that major fish culture system in Haiduong is polyculture (99.61%) with ratio of Common carp was from 15.63-32.10% of total fish stocking. There are 31.91% of diseased fish ponds. Non disinfected ponds could be infected with 4.28 times higher compared to that of disinfected ponds. Infected fish often black colour, swollen abdomen and intestine contains liquid and white cystics (92 cystics) with size of cystic is up to 5.3x3.7 cm. Myxobolus sp. was identified as Thelohanellus kitauei.