Efficacy of inactive bivalent and trivalent Streptococcus agalactiae bacteria (biotype 1 & 2) vaccines on tilapia, Oreochromis niloticus

Abstract

Streptococcosis is a significant fish disease impacting tilapia culture in Indonesia, causing losses estimated up to IDR 15.0 billion annually. This study aims to assess the efficacy of bivalent and trivalent vaccines containing Streptococcus agalactiae bacteria on tilapia. The formula of the bivalent vaccine contains 75% of S01-196-16 and 25% of N14G isolates (v/v). Trivalent vaccine contains 30%, 35%, and 35% of N14G, NP1050, and SG01-16 isolates (v/v), respectively. A challenge test assessed the efficacy of the vaccines, and it was carried out at 30, 90, and 150 days post-vaccination by artificially infection at LD60. Selected bacteria isolate to be appointed in the challenge test are N14G (biotype 2) and S01-196-16 (biotype 1). Relative Percentage of Survival (RPS) was used as the main indicator of vaccine efficacy. The results revealed that the highest RPS of a bivalent vaccine against S. agalactiae (S01-196-16) was achieved at the first challenge (61.84%), and trivalent vaccine against S. agalactiae (N14G) and S. agalactiae (S01-196-16) was achieved at the first challenge (61.53% and 76.20%, respectively). Bivalent and trivalent S. agalactiae bacteria vaccines are promising “tools” to control streptococcosis on tilapia.

Streptococcosis on Nile tilapia (Oreochromis niloticus) in Indonesian freshwater aquaculture

“…The following summarizes the variety of clinical symptoms as indicators of abnormalities associated with visually observable streptococcosis: darker and/or paler body color (melanosis), bulging eyes (uni/bi-lateral exophthalmos), corneal opacity, accumulation of blood/hemorrhage in the abdominal cavity (dropsy/ascites), hemorrhages in the eyes, gills and the base of the fins (hemorrhages), body shape resembling the letter "C"/deformation of the spine (C-shape), flaccid swim bladder, black/brown liver, swelling of the spleen, kidneys and other internal organs. Symptoms thought to be "typical" of this disease are disorders of the brain and eyes, so is often termed "meningoencephalitis and panophthalmitis syndrome" (Taukhid & Purwaningsih, 2011;Hardi et al, 2011;Yanong & Francis-floyd, 2013;Kayansamruaj et al, 2014;Iregui et al, 2014;Taukhid et al, 2014;Suhermanto et al, 2019;Taukhid et al, 2021;Sarjito et al, 2021). Some of the clinical signs of tilapia infected by S. agalactiae are shown in Figure 1.…”

“…Observable indicators of fish health performance include a drop in appetite (anorexia), and unbalanced/erratic swimming movements as a result of brain and nerve dysfunction, although in some other cases of streptococcosis there are no obvious symptoms of illness, although persistent mortality occurred. Based on pathological-anatomical observations, it has been strongly suspected that septicemia infection mainly affects the brain and nervous system (Salvador et al, 2005;Taukhid & Purwaningsih, 2011;Yanong & Francis-floyd, 2013;Iregui et al, 2014;Suhermanto et al, 2019;Taukhid et al, 2021;Sarjito et al, 2021).…”

“…Tilapia (Oreochromis niloticus) is known as a fast-growing farmed fish species, relatively easy cultivation techniques, and able to adapt to a wide range of ecological zones. The fish species is also the belle of freshwater aquaculture, providing employment, improving welfare, contributing significantly to reducing stunting, and supplying animal protein for all levels of society (Caruso et al, 2013;Sukenda et al, 2014;Taukhid et al, 2014;Taukhid et al, 2021). Indonesia is the second largest tilapia producer in the world after China, with national production in 2019 reaching 1,506,156 tons with a value of 34.7 trillion rupiah (MMAF, 2021).…”

“…The main diseases during the production cycle of tilapia in Indonesia are due to infection with Streptococcus bacteria (Streptococcosis) and Aeromonas (Motile Aeromonas Septicemia/MAS) or co-infection by both genus of bacteria. Streptococcosis is host species specific to the fish species, while MAS is a cross-species disease of freshwater fish that is always involved and aggravates cases of infectious diseases initiated by other types of pathogens (Taukhid, 2018;Taukhid et al, 2021).…”

“…In intensive aquaculture, the governance paradigm of fish health management must be directed towards effective, environmentally friendly, and sustainable precautions. The strategy of fish health management does not fully rely on the use of chemicals/antibiotics which have a negative impact on the fish, the aquatic environment, and consumers (Taukhid et al, 2021). Alternative strategies based on preventive and future-relevant measures is ecologicalbiological approaches such as the implement-tation of biosecurity systems, the use of vaccines for potential endemic diseases, probiotics, essential herbs, and the development of more disease-resistant populations.…”