Most infections are asymptomatic. Manifestations may include abdominal discomfort, diarrhoea, vomiting, and weight loss. Vitamin B12 deficiency with pernicious anaemia may occur. Massive infections may result in intestinal obstruction. The allergic response can be due to ingestion of live or more rarely, dead roundworms of this species.
It is not a common cause of allergy although under-diagnosis cannot be ruled out. Fish parasites are killed by freezing and heating treatments. For fish parasites other than flatworms or flukes trematodes , freezing treatments must be at a temperature of o C for not less than 24 hours or o C for at least 15 hours in all parts of the fish. Flatworm or fluke larvae of Opisthorchis spp.
They must not place fishery products that are obviously contaminated with parasites on the market for human consumption. This is a general requirement requiring FBOs to conduct a risk assessment. Therefore fresh water fish at risk of flatworm or fluke trematode infection would need to receive a more severe freezing treatment than listed in Regulation EC No. Food business operators placing on the market the following fishery products derived from finfish or cephalopod molluscs: a fishery products intended to be consumed raw; or b marinated, salted and any other treated fishery products, if the treatment is insufficient to kill the viable parasite; must ensure that the raw material or finished product undergo a freezing treatment in order to kill viable parasites that may be a risk to the health of the consumer.
Yes there are exemptions to the above requirement to treat for viable parasites. The European Commission have indicated that in the case of wild catches, the food business operator FBO must demonstrate that there are epidemiological data available indicating that the fishing grounds of origin do not present a health hazard with regard to the presence of parasites.
Furthermore, the absence of freezing treatment of those products must be authorised by the competent authority. EFSA in its Scientific Opinion on risk assessment of parasites in fishery products, mentioned above, concluded that "all wild caught seawater and freshwater fish must be considered at risk of containing any viable parasites of human health concern if these products are to be eaten raw or almost raw. For wild-catch fish, no sea fishing grounds can be considered free of Anisakis simplex ".
So, to date, requirements are not met to allow the FBO to avoid the freezing treatment required as regards wild caught fish. However, the situation of fishery products derived from fish farming is different. It is important to note that to be included in this category the fishery products must originate from cultured embryos and have been fed exclusively on a diet that cannot contain viable parasites that present a health hazard.
In this case the freezing treatment can be avoided if one of the following conditions is applied:. In condition 1 , the food business operator harvesting the farmed fish must ensure that documentation accompanies physically or electronically each batch of farmed fish, assuring that the correct information as regard the exemption from the freezing treatment is available before the fishery products are placed on the market. This information can be included in the commercial documents or in any other information accompanying the fishery products.
In condition 2 , the documentation, always under the responsibility of the food business operator harvesting the farmed fish, must accompany each batch of farmed fish, as described before, demonstrating in addition that the verification procedures received the approval of the Competent Authority. Also, in that case the correct information as regard the exemption from the freezing treatment must be available before the fishery products are placed on the market. Currently, a freezing exemption automatically applies to farmed Atlantic Salmon reared in Ireland in floating cages or onshore tanks, that have been cultured from embryos fed exclusively on a diet that cannot contain viable parasites that present a health hazard; and, exclusively reared in an environment that is free from viable parasites Condition 1 above.
If such fish are subsequently frozen and thawed, this fact must be included on any labelling i. This assurance is provided in a document issued by the supplier. If the FBO is sourcing product that is exempt from the freezing treatment then a record of the exemption declaration must accompany the batch.. For example, tapeworms are more susceptible to freezing than are roundworms.
Flukes appear to be more resistant than roundworms. Trimming away the belly flaps of fish or candling and physically removing parasites are methods for reducing the numbers of parasites. However, they do not completely eliminate the hazard, nor do they minimize it to an acceptable level. The health risk from parasites is far less than the risk from bacterial pathogens and mishandling of seafood. Sakanari, et al. An in-depth discussion of the candling method with finfish and molluscs is described.
The U. Sometimes, parts of the worm may also be passed in the stool. The tapeworm absorbs the nutrition from food that the infected person eats. This may lead to vitamin B12 deficiency and anemia.
People who are infected sometimes pass segments of worm in their stools. These segments can be seen in the stool. You will receive medicines to fight the parasites. You take these medicines by mouth, usually in a single dose.
The drug of choice for tapeworm infections is praziquantel. Niclosamide can also be used. If needed, your health care provider will prescribe vitamin B12 injections or supplements to treat vitamin B12 deficiency and anemia.
Tapeworm infections. Hunter's Tropical Medicine and Infectious Disease. Philadelphia, PA: Elsevier; chap Tapeworms cestodes.
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