Internal Factors That Can Affect Fish Disease
Description: After understanding the external factor that can affect fish disease, it is also useful to know about the internal factors contributing to fish disease.
In the previous article, we have discussed the external factors that can affect fish disease. Contrary to those factors that encompass elements such as fish environment, treatment, and other living organisms accompanying the cultured fish, internal factors that can affect fish disease are mostly sourced from within the fish.
The understanding of such internal factors can provide insights on how to mitigate the adverse effect on the cultured fish. Some of the notable internal factors that can affect fish disease are genetic disorders, endocrine disorders, and immune deficiency.
Genetic disorders in fish are typically caused by inbreeding. Spawn as a result of inbreeding may incur the following abnormalities:
• Slow fish growth and varying fish sizes such as stunted fish
• More susceptible to pathogen infection
• Defective development of fish organs, such as crooked body and defective fish larvae and defective operculum
Therefore, to prevent the occurrence of genetic disorders, a strict selection of the mother when breeding is essential.
Endocrine disorders in fish usually manifest in the hyperplasia of thyroid in the gland or more commonly known as goitre. This condition is characterized by the appearance of a visible tumor on the fish tongue, mouth, or pharynx. Though it may look and sound horrific, it is generally benign in nature.
Fish suffering from goitre are usually weak, inactive, and more susceptible to disease. It is caused by rapid cell reproduction rate, but mostly because of iodide deficiency. In fish, often the iodide intake from sources is hindered by nitrites.
Also, goitrogenic substances such as that found in cassava, cabbage family, and canola meal can damage iodide substance. Therefore, goitrogenic substances should be avoided in the fish meal. The treatment of iodide deficiency can be done via iodide replacement therapy or the administration of thyroxine.
As with the immune systems in human, immune system in fish protect them from harmful threats such as viruses, bacteria, other micro-organisms, and toxins. Deficiency or failure in immunity poses a major risk for the aquaculture industry.
Research shows that the administration of immunostimulants and prebiotics such as β-glucan, mannan oligosaccharide, and nucleotides has a positive impact on fish weight gain and overall growth performance. Moreover, such immunostimulants and prebiotics are proven to increase survival upon bacterial challenge as well as to increase fish’ endurance on stressors.
Those are the internal factors that can affect fish disease. Understanding all these factors, both external and internal, can help us better prepare for the health and well-being of the cultured fish.