Bacteria from Fish and Other Aquatic Animals - Survival-training.info

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Aquatic Animal Species and Organism Relationship
1.1 Host Species, Bacteria and Disease
This chapter deals with the relationship between
the host species and the bacterial flora that
may be either part of the normal flora of that
host, or pathogenic for that host. This information
is presented in two formats. Table 1.1 lists
the aquatic animal hosts in alphabetical order
under their common name. The scientific name
is in parentheses. Some hosts are grouped
under their Family name, which is in capitals.
For example, trout and salmon are listed
under SALMONIDS; dolphin, porpoises, seals
and whales are listed under SEA MAMMALS;
aquarium fish are listed under ORNAMENTALS.
The adjacent columns in the table list the bacteria
that have been reported to be either pathogens
of the host or that are considered part of
the normal flora, the tissue site of infection,
or the pathology presented and the disease
state. Some organisms are considered to be
opportunistic pathogens and in a healthy host
may be part of the normal flora. In a stressed
animal, these same bacteria may overcome
host defence mechanisms and cause morbidity
or infection in the animal. There are some organisms
that have been identified and isolated from a
host, but the pathogenicity of the organism is
unknown, as virulence studies were not carried
out.
In the second format, in Table 1.2, the
information is presented by listing the bacteria
in alphabetical order, with adjacent columns
listing the name of the disease, the tissue
site where the organism may be found, the
aquatic animals where the organism has been
reported, and the geographical location of the
disease.
1.2 Bacterial Diseases
The following section provides more detail than
in the tables on some of the more commonly
recognized fish bacterial diseases. The diseases
are described in a brief form, as there are other
texts available that provide more comprehensive
detail on diseases of fish. See recommended
texts in Chapter 8, ‘Further Reading and Other
Information Sources’.
Bacillary necrosis of Pangasius
This is a recently reported disease found in
freshwater catfish (Pangasius hypophthalmus
Sauvage) in Thailand. The causative organism
has been identified as Edwardsiella ictaluri,
which in catfish in America causes the disease
known as enteric septicaemia of catfish. The
disease in Pangasius presents as multifocal, white
lesions, irregular in size and found in internal
organs, predominantly the kidney, liver and
spleen. In histology the lesions appear as areas
of necrosis and pyogranulomatous inflammation.
The causative bacterium was identified as E.
ictaluri biochemically; however, when examined
microscopically the bacterial cells showed a
greater pleomorphism in length and size than
normally seen with other strains of E. ictaluri
(Crumlish et al., 2002).
©N.B. Buller 2004. Bacteria from Fish and Other Aquatic Animals:
a Practical Identification Manual (N.B. Buller) 1