lecture 9a shrimp bacterial diseases

8/13/2019 Lecture 9a Shrimp Bacterial Diseases

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Shrimp Bacter ial Diseases


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Shrimp Bacterial Diseases

Covered

Vibriosis

necrotizing hepatopancreatitis

epicommensal fouling disease


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Shrimp Vibriosis

Known in Latin America as the Sea Gull

Syndrome due to shrimp swimming at surface of

pond (seagulls eat them)

numerous etiological agents: V. harveyi, V.vulnificus, V. parahaemolyticus, V. alginolyticus

Wide variety of gram negative motile rods

most frequently found in hatcheries, but a bigproblem for young PLs in ponds

all shrimp reared under stressful conditions are

susecptible


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Shrimp Vibriosis

Clinical Signs: high mortalities, in PLs, young

juveniles; moribund shrimp appear hypoxic and

often come to the pond surface or edge; sea birds

preying on shrimp; presence of luminescence intanks

Presumptive Diagnosis: clinical signs, large

amounts of bacteria in hemolymph, slow clotting,melanosis of shell

Confirmatory Diagnosis: isolation/purification

with appropriate media (TCBS), API RAPID-NFT

strips


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Shrimp Vibriosis: commonly

affected organs

Cuticle

hepatopancreas (midgut gland)

lymphoid organ

antennal gland

heart and hemolymph striated muscle


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Shrimp Vibriosis:

hepatopancreas

Most farms in Central America evaluate

shrimp on a weekly basis for vibriosis

grosssigns: black spots on cuticle internal signs: evaluation of hepatopancreas

using wet squash and evaluate blind tubules

for constrictions, presence of G- rods rate HP on a scale of 0-3, 3 being worse

medicated feed at 4g/kg oxytet,

nitrofurizolidone, sarafloxathin (Sarafin)


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Shrimp Vibriosis

Hatchery Control: improve husbandry,

especially in the areas of sanitation, feed

quality, water source purity, use ofprobiotics, vaccination (Serafin), antibiotics

Grow-out Control: improve stocking

handling to reduce stress, have feed in pondin advance of stocking, use of molasses and

nitrates as fertilizers


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Shrimp Vibriosis


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Necrotizing Hepatopancreatitis

Also known as NHP or Texas Pond MortalitySyndrome, for obvious reasons

this is a disease of the midgut gland, not, as with a

vibriosis, the blood

bacterium prefers high salinities (>10 ppt)

Agent: believed to be a new genus of theProtobacteria (alpha) group

found from Peru to Texas

small, G-, exists in two morphological forms(rod-shaped rickettsial-like and flagellated helix


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Host range: P. vannamei, P. aztecus, P.

setiferus, P. stylirostris, P. californiensis

Diagnostic methods: presence of massive

numbers of G- bacteria in HP tubuleepithelial cells, atrophy of HP, pallid HP

color; DIG-labeled DNA probe using in situ

or dot blot hybridization, TEM of HP cellsshowing granulatomous lesions

Clnical signs: reduced feed intake, empty

gut, anorexia, poor l:w ratios, pallid HP


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Simple diagnosis: most farmers use wet

mounts of HP and look for reduced lipid

droplets, melanization of tubules

Control strategy: frequent histopathological

examinations, use of oxytet at 4 g/kg (4,000

ppm), avoidance of high salinity conditions


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Zoea II Syndrome

Problem facing hatcheries throughout the western

hemisphere

condition results in heavy mortalities, mainlyconcentrated in the Z2substageof larval penaeid

shrimp

syndrome: a group of signs that occur together

and characterize a particular abnormality

first characterized in a paper by Lorenzo Juarezof

Grupo Granjas Marinas (Florida)


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Zoea II Syndrome

Because different larval diseases can share

common clinical signs, it is difficult to

characterize as distinct pathological agent could be associated with water quality, nutrition

and/or pathology

it is felt to be a distinct syndrome, per se, because

of its life-stage specificity, remarkable similitude

of clinical signsreported throughout the Americas,

not noticedprior to 1993


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Zoea II Syndrome

Species affected:P. vannameiandP. stylirostris,

although primarily the former

Clinical signs: nauplii appear normal and healthy,metamorphose to Z1and start eating normally,

long fecal strands are exhibited

36-48 hrs after achieving Z1, first signs appear:

anorexia, evacuation of guts, lethargy, erratic

swimming, loss of normal pigmentation

deathdue to starvation in Z1-2molt


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lecture 9a shrimp bacterial diseases

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