disease 4 bacterial diseases

8/10/2019 Disease 4 Bacterial Diseases

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Bacterial Diseases


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ESC and Columnaris

These two bacterial diseases are the most

common and most devastating bacterial

problems in the commercial catfish industry.

Estimated economic losses resulting from

these diseases is millions of dollars


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Enteric Septicemia of Catfish

(ESC Causative agent ! Edwardsiella "ctaluri

#ram $egative% rod shaped% wea&ly motile

Thought to be obligate but can survive in mud for

' days.

Similar to Edwardsiella Tarda


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)hich fish can get ESC*

Channel catfish most susceptible

)hite catfish% brown bullhead% wal&ing

catfish are also susceptible

Blue catfish can get it but are generally

resistant


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)hich fish can get ESC*

Esc has been isolated from some diseased

tropical fish.

Trout% salmon and tilapia have been

e+perimentally infected but natural

outbrea&s have not been reported.


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Clinical Signs

Behavior

Tail chasing or spiraling

Star ga,ing (head up tail down

Stop eating


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Clinical Signs

External Signs

Red and white ulcers

-petecial hemorrhages (pin point size)

-Raised pimples (buckshot appearance)

Hole or lightened area on head Exopthalmia

Swollen belly


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E+ternal Signs


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Deteriorating S&ull Cartilage


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Clinical Signs

nternal Signs

!lear " straw colored or bloody #luid in

body cavity

$ottled liver

%etechial hemorrhages in muscle

ntestine o#ten #illed with bloody #luid


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Diagnosing ESC

2oo& at behavioral and e+ternal signs

$ecropsy for internal signs

"solate bacteria from internal organs

-run diagnostic tests

-determine antibiotic sensitivity


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Causes of ESC

Combination

-athogen ! virulent Edwardsiella ictaluri

-Stress

-Environment ! that favors rapid proliferation of

the bacteria

#enerally in the 0ESC )indow1 34 ! 45

degrees 6


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/ow Does ESC Spread

Enters through

-#ut

-$ares-#ills

Transmitted through water

Transmitted by cannibalism Transmitted by carrier fish% e7uipment and

birds


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Treatment and revention

revention by reducing stress

-not always possible

$utritional supplements

)inter 6eeding

#enetic improvement

8accination

Treatment with medicated feeds


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9edicated 6eed Treatment of

ESC :omet ; and :omet B

-sulfadinetho+ine and ormetoprim

-6ed at recommended rate for < days

-; day withdrawal period

Terramycin-6ed at recommended rate for =!=> days

-5= day withdrawal period


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Economic Evaluation

$eed to ma&e sure that treating the fish

does not cost more than the fish are worth


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?ther 9ethods of Control

)ithhold 6eed

)ait for temperature change

8accines


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Causes of Columnaris

Causative agent ! 6le+ibacter columnaris

-#ram negative% rod shaped and motile

-$on ?bligate ! present in the naturalenvironment

Stress ! particularly in warm weather-Especially long term e+posure to low levels of

to+ic ammonia


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Characteristics of the Disease

:arely occurs unless fish are stressed

9ost fre7uently occurs between 9arch and

?ctober when water temperatures are above


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Characteristics of the Disease

Chronic at lower temperatures and more

acute at higher temperatures.

2i&ely to reoccur if original stress is not

removed

All ages% si,es and species can be effected


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Clinical Signs of Columnaris

External

-increase in thic&ness of mucous on s&in

-saddlebac& appearance

-areas of gray or colorless s&in leading to ulcers

and open lesions

-greybrown areas on the gills esp. at the tips-yellow colonies inside the mouth

-frayed fins


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Columnaris on #ills


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Columnaris (6rayed fins% tail rot


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Columnaris

S&in 2esions 2eading to ?pen lcers


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Diagnosis

E+ternal ! 9icroscopic e+amination of s&in

and gill wet mounts

"nternal ! "solation of bacteria and

identification proceedurs


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Treatment

Depends on whether the infection is internal

or e+ternal

E+ternal only ! 5 to > ppm 9n?>

"nternal only ! Terramycin

Both ! Terramycin

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