Abstract
In order to know the infection source of BMN in mass production of kuruma shrimp larvae, epizootiological investigations were undertaken on several incidents of the disease at hatcheries. Histological examination was made on the mid-gut glands of both wild mature female kuruma shrimp (18 cm in mean body length) used as spawners and cultured kuruma shrimp (5.6 cm in mean body length) which were the survivors of the larvae infected with the disease. The culturing water of the latter had been introduced into rearing tanks of larvae in which BMN epizootics occurred later.
Epizootiological investigations suggested that latently infected spawners and cultured animals could become the vertical and the horizontal sources of infection, respectively.
Histological examination demonstrated the nuclear hypertrophy (most characteristic cytopathological change of BMN) of the mid-gut gland epithelial cells in both latently infected females and cultured shrimp. Fluorescent antibody technique rapidly revealed the presence of BMN specific virus antigen in the hypertrophied nuclei of latently infected females.
