Meningoencephalitis in farmed monosex Nile tilapia (Oreochromis niloticus L.) caused by Streptococcus agalactiae

Isolation and Identification of GBS Bacteria From Mastitis by Camp Test and Lancefield’s Serological Grouping

“…The carbohydrate fermentation test results gave positive results because the changed from red to yellow colour due to phenol red indicator that changed the colour in the acidic pH, this is in agreement with Belhadj et al (2014). β hemolytic Streptococcus could ferment several sugars and gave positive results for Glucose, Maltose, Sucrose, Lactose, Arabinose, Galactose, Sorbitol, D-Mannose while could not fermentation (negative results) of Mannitol, Inositol, this result was an agreement with Bwalya et al (2020), Lucia et al (2017, Adikesavalu et al (2017), Hardi et al (2011), Pourgholam et al (2011.…”

PATHOGENICITY AND PATHOLOGY OF Streptococcus agalactiae IN CHALLENGED MOZAMBIQUE TILAPIA Oreochromis mossambicus (PETERS 1852) JUVENILES

“…The observations on the extensive haemorrhages and haemocyte infiltration in the meninges suggested meningoencephalitis. Conspicuously, S. agalactiae strains, isolated from O. niloticus with severe meningoencephalitis (Adikesavalu et al, 2017), were able to elicit similar disease manifestations in a relatively hardy species like O. mossambicus. Alterations such as dilated and ruptured blood capillary, disintegration of the liver as well as intrahepatic exocrine pancreatic tissues and melanin reaction were noted in the liver (Figure 4a-b).…”

“…Also, S. agalactiae has a predilection for the brain as it is the primary organ for infection (Hernández et al, 2009;Iregui et al, 2014;Iregui et al, 2016). The histological sections of experimentally in-fected O. mossambicus brain revealed extensive haemorrhages, lymphocyte infiltration in the meninges, increase in intercellular space possibly due to oedema, neurons with marginated nuclei and marginated haemocytes (Figure 1a-d), all of which are indicators of S. agalactiae infection (Zamri-Saad et al, 2010;Alsaid et al, 2013;Adikesavalu et al, 2017). The observations on the extensive haemorrhages and haemocyte infiltration in the meninges suggested meningoencephalitis.…”

“…Before the challenge, the acclimatized fish were checked visually for the gross and external signs of diseases including the parasites on the body and gills. The bacterial infection in the tilapia kidney (n=2), if any, was tested on BHIA (Adikesavalu et al, 2017). The absence of gross and external signs of diseases and the bacterial growth on BHIA confirmed that the stocks were healthy and devoid of obvious diseases.…”

“…There are several reports and reviews of diseases of aquacultured tilapias (El-Sayed, 2006;Amal and Zamri-Saad, 2011;Iregui et al, 2014;Zamri-Saad et al, 2014;Mishra et al, 2018) and all pointed at streptococcosis as the major problem. Prevalence of streptococcal infection with meningoencephalitis in tilapia is rare in India until the observations in Nile tilapia, O. niloticus during the summer season (Adikesavalu et al, 2017). As tilapia aquaculture continues to expand as a means of food production in India, it becomes crucial to ensure that fish resources are protected from the adverse effects of diseases.…”