Isolation and molecular identification of the etiological agents of streptococcosis in Nile tilapia (Oreochromis niloticus) cultured in net cages in Lake Sentani, Papua, Indonesia.
Infections with Streptococcus spp. were observed in Nile tilapia cultured in net cages in Lake Sentani, Papua, Indonesia. Clinical signs included exophthalmia, erratic swimming, ascites in abdominal cavity, and external hemorrhages. Four types of bacterial colonies (SK, K10, P20, and M12) were isolated from the brain, kidney, and eyes. Based on phenotypic and genetic (16S rDNA sequencing) characteristics, the isolates were identified as Streptococcus iniae (SK), Streptococcus agalactiae (K10 and P20) and Lactococcus garvieae (M12). The latter species has not been previously isolated or reported from fish streptococcosis in Indonesia. Intraperitoneal injection of healthy tilapia with the bacterial species caused significant morbidity (70%) within 3 days and 100% mortality at 6 days post injection. Experimental infections and reisolation of the bacteria from morbid and dead fish suggest they are the causative agents of streptococcosis, which rendered high mortality among cage cultured Nile tilapia in Lake Sentani. Our results suggest the need for developing diagnostic tools for accurate identification of the agents of streptococcosis. As tilapia aquaculture continues to expand as a means of food production and livelihood in Indonesia, it becomes crucial to ensure that fish resources are monitored and protected from the adverse effects of infectious diseases.
Laboratory of Fish Parasites and Diseases, Department of Fisheries, Faculty of Marine Science and Fisheries, Hasanuddin University, Makassar, Indonesia.
Hilal
H
Anshary
Fish Quarantine and Inspection Agency Regional Jayapura, Ministry of Marine Affairs and Fisheries, Jakarta, Republic of Indonesia.
Rio A
RA
Kurniawan
Laboratory of Fish Parasites and Diseases, Department of Fisheries, Faculty of Marine Science and Fisheries, Hasanuddin University, Makassar, Indonesia.
Sriwulan
S
Sriwulan
Fish Quarantine and Inspection Agency Regional Jayapura, Ministry of Marine Affairs and Fisheries, Jakarta, Republic of Indonesia.
Ramli
R
Ramli
School of Veterinary Medicine, Department of Anatomy, Physiology, and Cell Biology, University of California, Davis, CA 95616 USA.
Dolores V
DV
Baxa
Cage; Lactococcus garvieae; Lake Sentani; Nile tilapia; Streptococcosis; Streptococcus