Isolation and molecular identification of the etiological agents of streptococcosis in Nile tilapia (Oreochromis niloticus) cultured in net cages in Lake Sentani, Papua, Indonesia

Abstract

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.

Aeromonas jandaei and Aeromonas veronii caused disease and mortality in Nile tilapia, Oreochromis niloticus (L.)

“…; Anshary et al . ; Kayansamruaj et al . ); francisellosis caused by Francisella noatunensis subsp .…”

Aeromonas shuberti as a cause of multi‐organ necrosis in internal organs of Nile tilapia, Oreochromis niloticus

“…However, with the rapid development of the tilapia culture industry, various bacterial diseases frequently outbreak due to intensified culture and high stocking density conditions of intensive farming. Pathogens, such as streptococcosis (Anshary, Kurniawan, Sriwulan, Ramli, & Baxa, ; Verner‐Jeffreys et al., ), edwardsiellosis (Kwon, Nam, Kim, & Kim, ; Park & Jeong, ; Soto, Illanes, Revan, Griffin, & Riofrio, ; Soto et al., ), columnaris disease (Dong, Lafrentz, Pirarat, & Rodkhum, ; Sebastiao, Nomura, Sakabe, & Pilarski, ), francisellosis (Assis, Tavares, Pereira, Figueiredo, & Leal, ; Ortega et al., ; Sebastiao, Pilarski, Kearney, & Soto, ) and motile aeromonas septicaemia (Dong et al., ; Li & Cai, ; Soto‐Rodriguez, Cabanillas‐Ramos, Alcaraz, Gomez‐Gil, & Romalde, ), have resulted in substantial economic losses to the local aquaculture industries.…”

Development of Streptococcus agalactiae vaccines for tilapia

“…(Shoemaker et al 2011), Aeromonas hy dro phila (Ibrahem et al 2008), Flavobacterium spp. (Shoemaker & LaFrentz 2015), Lactococcus garvieae (Anshary et al 2014), Francisella asiatica (Hsieh et al 2006), and Edwardsiella tarda (Thune et al 1993). Currently, infections caused by Streptococcus spp., especially S. agalactiae and S. iniae, are the most common and cause huge economic losses to the tilapia industry.…”