Like in terrestrial animals, the ultimate success of disease control relies primarily on the proper laboratory diagnosis which is a function of the proper choice of samples with the highest likelihood of detecting the pathogen. The integrity of samples upon receipt by the laboratory is of paramount importance to the fidelity of laboratory results. The recommended protocols in this section represent the universal standards accepted by most laboratories and regulatory agencies and should be followed verbatim unless there are other policies or regulations that require omission or addition of other steps at the sampling process. Before you start sampling there are a number of questions that you need to be guided by their answers. These are:

Why do we need to sample farmed or wild fish?

1.     To determine cause of morbidity or mortality

2.     To determine prevalence and incidence of a disease

3.     To determine freedom of disease in a farm, compartment, or a zone

4.     For farm inspection or certification purposes

5.     To prevent transboundary transmission of pathogen along with live shipments

6.     To better understand disease ecology

7.     To determine level of Disease impact

8.     To determine the epidemiology status of a disease

9.     For surveillance purposes:

10. Following an exposure event to sewage or untreated water.

11. To determine the disease status of fry collected from the wild before stocking them with other farmed fish.

What are the general guidelines for sampling?

The following should be considered:

 -  Representation of all age groups,

 -  Include all strains of the same species present at the facility,

 -  In case of testing for freedom of disease, the sample should consist of a

statistically valid number of a specific lot of a susceptible species          

- Moribund fish should be included when present.

- If more than one water source is used for fish production, fish from all water sources should be included in the sample.

- Sample collection should be performed under aseptic precautions paying attention not to mix or mislabel samples.

- If the investigation requires RNA isolation, an RNA-stabilizing buffer should be added to the sample (e.g., RNAlater)

- If histopathological examination is ordered, tissues must be placed in a fixative, such as 10% neutral buffered formalin or Davidson’s fixative. Use 10:1 volume of fixative to sample.