Francisella noatunensis subsp. orientalis pathogenesis analyzed by experimental immersion challenge in Nile tilapia, Oreochromis niloticus (L.)

Francisella noatunensis subsp. orientalis infects striped catfish (Pangasianodon hypophthalmus) and common carp (Cyprinus carpio) but does not kill the hosts

“…orientalis (Fno) has been reported as a devastating pathogen due to its high transmissibility and virulence, particularly in the naturally susceptible fish species (Colquhoun and Duodu, 2011). The result obtained in the current study was consistent with previous publications that Nile tilapia and red tilapia were gravely vulnerable to Fno infection (Nguyen et al, 2015;Soto et al, 2013). Apart from tilapia, other fish species such as three-lined grunt (Kamaishi et al, 2005), hybrid striped bass (Ostland et al, 2006), 11 species of ornamental cichlids (Hsieh et al, 2007), Chinese catfish and barramundi (Soto et al, 2012) have also been reported as naturally infected hosts of Fno.…”

“…By contrast, Fno has a negative effect on warm water fish species such as three line grunt (Parapristipoma trilineatum) (Kamaishi et al, 2005), tilapia (Oreochromis spp.) (Hsieh et al, 2006), hybrid striped bass (Morone chrysops x M. saxatilis) (Ostland et al, 2006;Soto et al, 2009), and ornamental cichlids (Camus et al, 2013). Typical histopathological lesions for piscine francisellosis are characterized by multiple visceral granulomas, noticeably in the spleen and kidney, but also found in the liver, gut and gills (Nguyen et al, 2015;Olsen et al, 2006;Soto et al, 2009).…”

Immune Responses and Protective Efficacy of a Formalin-Killed Francisella Noatunensis Subsp. Orientalis Vaccine Evaluated through Intraperitoneal and Immersion Challenge Methods in Oreochromis Niloticus

“…However, this direct injection method does not accurately mimic natural infection [16] even though it guarantees an equal challenge dose in all fish [24]. The immersion challenge method mimics waterborne natural infection by cohabitation; however, the challenge dose per fish is unequal [47]. Therefore, our results include some variability in disease severity, as expected.…”

Effect of size and temperature at vaccination on immunization and protection conferred by a live attenuated Francisella noatunensis immersion vaccine in red hybrid tilapia

“…Granulomas and fields of necrosis occupied up to 80% of parenchymal area in some sections. Unlike early lesions, vacuolated macrophages containing small coccoid bacteria typical of Fno were not observed [14]. Vacuolated macrophages were uncommon and when present often contained granular cytoplasmic debris.…”