Parasite is an organism that lives on beyond the organ or the organ in another organism (different species), which are harmful. Parasitic organisms consists of protozoa, fungi, insect low level, worms and others. Parasites can cause sick fish. Based dwelling parasites are grouped into 2 groups;
1) Ecto-parasites (external parasites); ie parasites that live on organs outside of its host.
2) Endo-parasites (internal parasites); ie parasites that live in the inner organs of its host.
Based on the life cycle of the parasite divided into several groups, namely:
1) intermittent parasites are parasitic life cycle periodically at a certain time to be stuck outside or inside the host body, while at other times having to leave the host body, when this cycle is not experienced then the parasites will die.
2) facultative parasites are parasites that period of his life can be free without a host organism. This parasite is only occasional need to host, such as feeding or breeding.
3) Obigatery parasites, namely parasites throughout their life cycle attached outside or inside the host body, this parasite will die if there is no host.
Host in this case is fish or shrimp can be classified based on the nature of the parasite menumpanginya.
1) Intermediate host (host temporary) that is host to be carrying the parasite at certain stages (larvae). On the other stadia exist in an alternate host.
2) Ultimate host (host last) is the host to be carrying parasites adults only.
3) Definitive host (host fixed) host that can only be boarded by certain parasites alone, without a host this parasite can not live.
4) Indefinitive host (host not fixed) host not only can be boarded only certain parasir. Host but more can still be alive when carrying these parasites
Three levels of disease that may occur are:
1) acute; Infection occurs so quickly that fish die without showing any obvious symptoms.
2) chronic; Infection occurs slowly and systematically and showed various symptoms are swelling of the body cavity, which may be accompanied by ulcers or exophthalmia.
3) Latent; Infection occurs so weak that the fish seemed not show symptoms of the disease, but potentially as a (carrier).
The nature of the host can be said as a vector when it can bring a certain parasite, therefore distinguished by a disease;
1) Disease Primer
At certain fish that are immune to the disease can be regarded as a vector (such as adult fish). The fish even in the presence of pathogens (agents that cause disease), but does not cause significant disease in the fish. The pathogen will spread and cause symptoms of pain on other weaker fish (small fish).
2) secondary disease
Pathogens (agents that cause disease) will cause illness when their stress factors on fish;
a) Lack of nutrients
b) Changes in water quality fish beyond endurance.
c) Handling the fish harvest, removal of fish from one place to another that causes stress to the fish.