Vibrio vulnificus The source of infection would seem to be water with gills as

Vibrio vulnificus the source of infection would seem

This preview shows page 354 - 357 out of 594 pages.

Vibrio vulnificus The source of infection would seem to be water, with gills as a principal portal of entry into the eel (Marco-Noales et aL, 2001). In other work, intramuscular injection of eels with large numbers of bacterial cells, i.e. 4.85 x 10^, resulted in 80% mortality in the population within 7 days, at a water temperature of 25°C. This confirms the pathogenicity, albeit weak, of V. vulnificus. The pathogenicity mechanisms contained in ECP which are lethal to fish (Lee et aL, 1997) included haemolysins, lipases, phospholipases and proteases (Amaro et aL, 1992). Evidence has been presented which attributed virulence to the LPS O side chain (Amaro et aL, 1997). Interestingly, cultures from diseased European eel produced opaque, translucent colonies, and the cells possessed a capsule, which was not essential for the development of disease (Biosca et aL, 1993). MISCELLANEOUS PATHOGENS "Candidatus Arthromitus" It was considered that an unspecified toxin may be involved in the pathogenic process (Michel et aL, 2002a).
Image of page 354
Pathogenicity 335 UNKNOWN GRAM-NEGATIVE ROD According to Palmer et al. (1994) infectivity was achieved by injecting cells into Atlantic salmon, which became moribund after 6-10 days, and died within 30 days. Moribund fish displayed haemorrhagic areas in the jaw, cranium and at the base of the fins. The organism considered to be the cause of Varracalbmi was challenged i.p. into groups of Atlantic salmon smolts (average weight = ~37 g) with the outcome that total mortalitiy resulted with a dose of 4 x 10^ cells (51% mortality with a dose of 4 X 10"^ cells) (Valheim et al, 2000).
Image of page 355
10 Control It is worth remembering the age-old adage that "prevention is better than cure", and certainly it is possible to devote more attention to preventing the occurrence of disease in fish. This is especially true for farmed fish, which tend to be at the mercy of all the extremes which their owners are capable of devising. Principally, in the industrialised nations farmed fish are subjected to questionable water quality and high stocking regimes. These are among the known prerequisites for the onset of disease cycles. Yet, the owners are among the first to seek help if anything adverse happens to the valuable stock. Fish may be reared under ideal conditions, in which case, the stock are inevitably in excellent condition without signs of disease. Such sites, for example located in Venezuela and the former Yugoslavia, are usually supplied by fast-flowing, clear river water. Careful feeding regimes are adopted, and the stocking levels are comparatively low. The latter point would make the enterprise unacceptable in the more industrialised nations of Western Europe. Therefore, much attention has been devoted to control measures. These have been categorised in Table 10.1. Although most emphasis has been placed on aquaculture, some effort has gone towards considering disease in wild fish stocks.
Image of page 356
Image of page 357

You've reached the end of your free preview.

Want to read all 594 pages?

  • Spring '20
  • Bacteria, representative, gram-negative bacteria

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors