Research Advances on Tilapia Streptococcosis

Abstract

Streptococcus agalactiae, often referred to as group B streptococci (GBS), is a severe pathogen that can infect humans as well as other animals, including tilapia, which is extremely popular in commercial aquaculture. This pathogen causes enormous pecuniary loss, and typical symptoms of streptococcosis—the disease caused by S. agalactiae—include abnormal behavior, exophthalmos, and meningitis, among others. Multiple studies have examined virulence factors associated with S. agalactiae infection, and vaccines were explored, including studies of subunit vaccines. Known virulence factors include capsular polysaccharide (CPS), hemolysin, Christie-Atkins-Munch-Peterson (CAMP) factor, hyaluronidase (HAase), superoxide dismutase (SOD), and serine-threonine protein kinase (STPK), and effective vaccine antigens reported to date include GapA, Sip, OCT, PGK, FbsA, and EF-Tu. In this review, I summarize findings from several studies about the etiology, pathology, virulence factors, and vaccine prospects for S. agalactiae. I end by considering which research areas are likely to yield success in the prevention and treatment of tilapia streptococcosis.

Relationships between pond water and tilapia skin microbiomes in aquaculture ponds in Malawi

“…Several of the bacterial genera we found to be differentially abundant in fish skin contained species pathogenic to tilapia, including Aeromonas (hydrophila) (Dong et al, 2017), Streptococcus (agalactiae) (Zhang, 2021) and Pseudomonas (fluorescens) (Hal and El-Barbary, 2020). In addition to these fish skin enriched genera, further potentially pathogenic taxa were detected in pond water and fish skin.…”

Immunogenic Proteins of Group B Streptococcus—Potential Antigens in Immunodiagnostic Assay for GBS Detection

“…Other studies showed RPS (relative percentage survival) value after tilapia vaccination consisting of GBS FsbA protein reached 40.63% [67]. It allows to define FsbA as a multifunctional immunogenic protein, including immunoprotection as well as activation of the innate immune responses in the host and relevant antibody responses [68].…”

A Novel Efficient Piscine Oral Nano-Vaccine Delivery System: Modified Halloysite Nanotubes (HNTs) Preventing Streptococcosis Disease in Tilapia (Oreochromis sp.)

“…However, recently, the development of oral feed-based vaccines has been focused upon for them to become an ideal approach for preventing and controlling fish infectious diseases. Up to now, oral vaccines based on live attenuated S. agalactiae , E. coli , Bacillus subtilis and Lactococcus lactis expressing the S. agalactiae immunogenic proteins have been studied against streptococcosis disease in tilapia hosts [ 31 , 38 , 39 , 40 ]. Nevertheless, their relative percentage survival results still fluctuated, and some formulations also depended on oil adjuvants [ 27 , 31 ].…”

“…Up to now, oral vaccines based on live attenuated S. agalactiae , E. coli , Bacillus subtilis and Lactococcus lactis expressing the S. agalactiae immunogenic proteins have been studied against streptococcosis disease in tilapia hosts [ 31 , 38 , 39 , 40 ]. Nevertheless, their relative percentage survival results still fluctuated, and some formulations also depended on oil adjuvants [ 27 , 31 ]. Consequently, the development of fish oral vaccines based on encapsulation and entrapment strategies should receive more concern.…”

“…S. agalactiae , causing the infectious streptococcosis disease in mostly marine and freshwater fish, is one of the harmful pathogens spreading throughout the world, particularly in Southeast Asia, including Thailand [ 25 ]. Various forms of S. agalactiae vaccines utilized in tilapia have been drastically developed, including attenuated vaccines [ 26 , 27 ], inactivated vaccines [ 28 , 29 ], subunit vaccines [ 30 , 31 ] and DNA vaccines [ 32 , 33 ]. However, most of them were generated for injection administration and may not be practical for large-scale fish farming.…”