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A common technique used to diagnose diseases in marine shrimp is the microscopic examination of wet-mount preparation of tissue for specific abnormalities associated with the disease. For example larval mycosis is easily diagnosed in wet-mount preparations of whole shrimp larvae.
Required Materials: Clean microscope slides, cover slips, pipette, tweezers, light microscope.
Procedure: Place a drop of clean saltwater on a slide. Put the whole larvae or tissue (ie gill filament) in the water. Place the edge of a coverslip on the slide so that it touches the edge of the water. Slowly lower the coverslip to prevent forming and trapping air bubbles. Place the slide under the microscope and proceed from the lowest-power to the highest-power objectives making minor corrections in focus and light as necessary.
Post Larvae Visual Examination and Fitness
The purpose is to assess the behavioural and physical condition of post larvae.
Required Materials: Clean microscope slides and cover slips. Glass beaker 500ml. Pipette. Compound microscope with 10x eyepiece and 4x, 10x,40x and 100x objectives. Ocular micrometer.
Procedure: Collect a sample of 20 to 100 post-larvae in a 500ml glass beaker. Observe and grade the swimming behaviour of the shrimp. Record observations and comment if dead shrimp are present in sample. For microscopic evaluation, examine a minimum of 10 animals. Collect each larvae with a pipette and wet-mount them. Place slide on stage of compund microscope. Study each larvae for the following features and record in data sheet.
Features: Fullness of gut. level of hepatopancreatic lipid vacuolation. Grade of bacterial infestation on the appendages, eyes, gills, body and abdomen. grade of infestation of attached protozoa. Grade of melanized cuticle lesions. Grade of dark, grainy muscle lesions. Presence of internal melanized nodules. grade of BP polyhedra in the hepatopancreas. Condition of the chromatophores along the ventral abdomen or other microscopic physical abnormalities. Muscle to gut ratio: Measure the diameter of the mid-gut and the vertical height of the muscle in the 6th abdominal (tail) segment. Divide the muscle height by the mid-gut diameter to determine the Muscle:Gut (M:G) ratio. Healthy postlarvae have a M:G of > 4:1 while weaker postlarvae have a ratio < 4:1
HEALTH MANAGEMENT & DISEASE CONTROL INDEX
Hepatopancreatic parvo-like virus (HPV) . Reo-like virus (REO) . Lymphoid organ vacuolization virus (LOVV) . Taura Syndrome Virus (TSV) . Rhabdovirus of Penaeid Shrimp (RPS) . White Spot Syndrome Virus (WSSV) . Infectious hypodermal and hematopoietic virus (IHHNV) . Baculovirus penaei (BP)
Vibriosis . Epicommensal fouling disease (filementous bacteria) . Necrotizing Hepatopancreatitis (NHP) . Black spot disease (BSD) . Mycobacteriosis
Larval mycosis . Fusariosis
Haplosporidia . Gregarines . Cotton Disease
Black Gill Disease (BGD) Dissolved Oxygen Crisis Nitrogen Gas Bubble Disease