Changes

==Introduction==

==Introduction==

'''''Edwardsiella ictaluri''''' belongs to the '''''Enterobacteriaceae''''' family and is a '''Gram negative''', short, pleomorphic '''rod''', measuring 0.75 × 1.5-2.5 µm, which is '''weakly motile''' at 25-30°C, but not at higher temperatures.  It has peritrichous flagella and occasionally pili that can be seen with a scanning electron micrographs and can have between one to three '''plasmids''' depending on their molecular mass.  It is generally considered an '''obligate pathogen''', although it can survive in steralised pond bottom mud for over 90days but does not compete well with other microbes.  The organism is lactose negative, catalase-positive, cytochrome oxidase-negative, glucose fermentative and reduces nitrate to nitrite <ref name="Shotts and Teska, 1989">Shotts, E.B., Teska, J.D., (1989)  '''Bacterial pathogens of aquatic vertebrates'''. In: Austin B, Austin DA, eds. ''Methods for the Microbiological Examination of Fish and Shellfish'''. Chichester, UK: Ellis Horwood, 164-186.</ref>.

'''''Edwardsiella ictaluri''''' belongs to the '''''Enterobacteriaceae''''' family and is a '''Gram negative''', short, pleomorphic '''rod''', measuring 0.75 × 1.5-2.5 µm, which is '''weakly motile''' at 25-30°C, but not at higher temperatures.  It has peritrichous flagella and occasionally pili that can be seen with a scanning electron micrographs and can have between one to three '''plasmids''' depending on their molecular mass.  It is generally considered an '''obligate pathogen''', although it can survive in steralised pond bottom mud for over 90days but does not compete well with other microbes.  The organism is '''lactose negative, catalase-positive, cytochrome oxidase-negative, glucose fermentative and reduces nitrate to nitrite'''.<ref name="Shotts and Teska, 1989">Shotts, E.B., Teska, J.D., (1989)  '''Bacterial pathogens of aquatic vertebrates'''. In: Austin B, Austin DA, eds. ''Methods for the Microbiological Examination of Fish and Shellfish'''. Chichester, UK: Ellis Horwood, 164-186.</ref>.

''E. ictaluri'' '''affects fish species only''' and '''causes enteric septicaemia of catfish (ESC)''' and various other species of fish.  ESC is considered one of the '''most important infectious disease''' problems in the '''commercial catfish industry''' in the '''USA'''.  '''''E..tarda''''' causes '''Edwardsiella septicemia (ES)''' which is also known as '''fish gangrene, emphysematous putrefactive disease of catfish''' or '''red disease in eels''' and it '''can affect other animals'''.  Whereas '''''E. hoshinae''' infects birds and reptiles'''.  

''E. ictaluri'' '''affects fish species only''' and '''causes enteric septicaemia of catfish (ESC)''' and various other species of fish.  ESC is considered one of the '''most important infectious disease''' problems in the '''commercial catfish industry''' in the '''USA'''.  '''''E..tarda''''' causes '''Edwardsiella septicemia (ES)''' which is also known as '''fish gangrene, emphysematous putrefactive disease of catfish''' or '''red disease in eels''' and it '''can affect other animals'''.  Whereas '''''E. hoshinae''' infects birds and reptiles'''.  

==Clinical Signs==

==Clinical Signs==

With the '''chronic form of ESC''' clinical signs include, '''altered mentation, listlessness''' and '''chaotic swimming with ‘head-up, tail-down’ posture, circling''' and '''mortality'''.  In later stages the '''dorsum of the head swells''' and '''ulcerates revealing areas of the brain''' (hence the name ‘hole in the head disease’).  With '''acute forms of ESC''' you can see '''petechial haemorrhages around the buccal area, throat, abdomen and the fin base, that progress to depigmented ulcers'''.  Fish generally suffer from ''moderate pale inflamed gills, exophthalmia, anaemia, haemorrhagic enteritis, systemic oedema, dropsy, ascites and splenomegaly'''. General '''behavioural changes''' include '''loss of balance, swimming near the surface, lethargy and cessation of feeding'''.   

With the '''chronic form of ESC''' clinical signs include, '''altered mentation, listlessness''' and '''chaotic swimming with ‘head-up, tail-down’ posture, circling''' and '''mortality'''.  In later stages the '''dorsum of the head swells''' and '''ulcerates revealing areas of the brain''' (hence the name ‘hole in the head disease’).  With '''acute forms of ESC''' you can see '''petechial haemorrhages around the buccal area, throat, abdomen and the fin base, that progress to depigmented ulcers'''.  Fish generally suffer from '''moderate pale inflamed gills, exophthalmia, anaemia, haemorrhagic enteritis, systemic oedema, dropsy, ascites and splenomegaly'''. General '''behavioural changes''' include '''loss of balance, swimming near the surface, lethargy and cessation of feeding'''.   

==Epidemiology==

==Epidemiology==

The  bacteria can survive in pond sediment and once a population of fish have recovered from an infection of ECS, they can become '''carriers'''. It can be found in the kidneys of fishes and is thought to be shed in the faeces of fish.  

The  bacteria can survive in pond sediment and once a population of fish have recovered from an infection of ECS, they can become '''carriers'''. It can be found in the kidneys of fishes and is thought to be shed in the faeces of fish.  

'''Outbreaks''' are mainly '''seasonal''' and '''occur within a set temperature range of  18-28°C''', primarily in spring and autumn.  This temperature limitation precludes the bacterium from being a pathogen for humans or other warm-blooded animals <ref name="Janda et al., 1991">Janda, J., Abbott, S.L., Kroske-Bystrom, S., Cheung, W.K., Powers, C., Koka, R.P., Tamura, K., (1991)  '''Pathogenic properties of Edwardsiella species'''. ''Journal of Clinical Microbiology'', 29:1997-2001.</ref> and is not therefore zoonotic. Other '''environmental factors''' have been '''linked to outbreaks''' and include '''poor water quality, high stocking density and other stressors'''.   

'''Outbreaks''' are mainly '''seasonal''' and '''occur within a set temperature range of  18-28°C''', primarily in spring and autumn.  This temperature limitation precludes the bacterium from being a pathogen for humans or other warm-blooded animals <ref name="Janda et al., 1991">Janda, J., Abbott, S.L., Kroske-Bystrom, S., Cheung, W.K., Powers, C., Koka, R.P., Tamura, K., (1991)  '''Pathogenic properties of Edwardsiella species'''. ''Journal of Clinical Microbiology'', 29:1997-2001.</ref> and is not therefore zoonotic. Other '''environmental factors''' have been '''linked to outbreaks''' and include '''poor water quality, high stocking density and other stressors'''.   

''E.ictaluri''  can '''invade the, gill mucosa, olfactory organ and nasal epithelium and nerve, brain meninges, skull and capillaries in the dermis of the skin'''.  

''E.ictaluri''  can '''invade the, gill mucosa, olfactory organ and nasal epithelium and nerve, brain meninges, skull and capillaries in the dermis of the skin'''.