Study on Intestinal Giant Cystic Disease of Common carp caused by Thelohanellus kitauei in Hai Duong province

Abstract

Hai Duong is one of the Northern provinces, Vietnam, having a largest area of freshwater
aquaculture development. Of which, common carp is major cultural species. However, in the recent
years epidemic occurred frequently in this culture fish species, causing heavy loss for the fish farmers.
The typical disease is ulcer in the intestine caused by Myxobolus sp. This paper provided information
about the biological characteristics of this disease through surveying 212 fish farm households with
257 fish ponds in four districts in Hai Duong province. The diseased fish samples were collected
for determining the disease symptoms, characteristics, histological and gross lesions. The studied
results showed that integrated fish culture system in Hai Duong province accounted for 99.61%. Of
which common carp species shared 15.63 - 32.10% of the fish stocking density. The rate of common
carp culture pond suffering with giant cystic disease was 31.91%. The risk of disease infection in the
un-disinfected ponds was higher 4.28 times in comparison with the disinfected ponds. The infected
fish presented the typical signs, such as: slow growth, black color body, swollen abdomen and
intestine contained liquid and white spores (up to 92 spores/fish) with size of 2.65 x 2.04 cm (Max.
5.3 x 3.7 cm). Myxobolus sp. was identified as Thelohanellus kitauei. This disease caused a big loss
for the fish farms due to slow growth of fish, high FCR and mortality, reduction of marketable fish