A Halachik Treatise about Worms in Fish and Animals

Before I discuss the "halachik" problems and solutions pertaining to worms in kosher fish, I will first introduce you to some of the pertinent facts related to this topic.

This report is based on my telephone conversations 12/17/96, 12/18/96 and 1/27/97 with Dr. Terry Dick of the department of Zoology at the University of Manitoba in Winnipeg, and on 01/14/97 and 01/20/96 with Professor Ron Rosen chairman of the department of Biology at Berea College in Berea Kentucky, and on my own insights and understanding of the subject.

This report primarily discusses the life cycle of the tapeworm called Triaenophorus crassus which has been closely observed, and comparisons are made to other fish and animal parasites.

Water is full of fertilized eggs of parasitic tapeworms ready to be hatched, and other such parasitic worms. Various vertebrates (i.e. birds, etc.) eat fish infested with worms, and following the development of a larval worm into an adult in the vertebrate host, eggs of worms are deposited in the water with the host's droppings. Worms whose vertebrate hosts live near the water deposit their eggs in this environment. For example, mammals, such as otters and bears, which are associated with water, excrete eggs of worms into these waters.

Larval tapeworms of "Triaenophorus crassus" mature only in the northern pike. They are not infective and they do not cause health problems in the human. During the spawning of the pike, the female fish lays its own eggs in the water, and the male pike issues its sperm into the water near the eggs. While in the water the sperm that is near an egg, is somehow attracted to the female pike's egg and moves in to fertilize this egg. I base this on the on the percentage of eggs fertilized and the probability of fertilization by chance, in these waters, calculating water current and direction and space between the eggs and the sperm, etc. During this same period, the tapeworm that is now attached by its scolex (its "head" with its accompanying hooks) to the lining of the pike's intestine, fertilizes its own eggs and releases them into the pike's intestine where they are excreted by the pike through its anus into the water. During this process the tapeworm looses its grip on the pike's intestinal lining, and the pike is then able to expel it into the water the same way it did to the tapeworm's eggs. Then the cycle starts over again.

I have suggested several reasons why the tapeworm is expelled from the pike at the time of the pike's spawning. (a) When a tapeworm fertilizes and expels its eggs, there may be chemical changes in its body that could weaken it temporarily at the time it releases the eggs. This may be a cause why it cannot hold onto the wall of the pike's intestines. (b) At the time of the pike's spawning, it may release hormones that may be harmful to or weaken the tapeworm so that it looses it hold on the wall of the pike's intestine. (c) We must also take into consideration the weakening of that part of the wall because of prolong abuse by the tapeworm scolex.

The pike during spawning, is in shallow water, where microscopic water animals called zooplankton are numerous. If a zooplankton ingests a fertilized tapeworm egg within the first two days from when it has entered the water, it will be infective to its host. If the fertilized egg is not ingested by its host within the first two days, it will die in the water. The life span of the zooplankton is about one month.

The tapeworm eggs embryonate in fresh water in several hours, depending on water temperature. The hatched ciliated embryo (coracidium) must be ingested (eaten) within hours by the zooplankton or it will die. A similar pattern is true for the other types of fertilized eggs that are eaten by clams, snails, shrimp, mollusks, etc.

The maximum width of a hatched embryo while in the water is about one tenth of a millimeter or the width of a thin hair. It is however, invisible to the naked eye because it is opaque as water and does not transmit light. It is in this way comparable to microorganisms that are found in almost everything we eat. It does have cilia (hairlike processes) that enable it to move about in the water but not on a hard surface. However, while in the zooplankton it transforms and changes shape, and loses it's cilia and other features which give it mobility. It lies there in the zooplankton as a growing mass.

In the zooplankton, the hatched embryo can reach one third of a millimeter in width. At this stage of about two weeks following ingestion by the zooplankton, the mature procercoid larva first appears and may be ingested by the whitefish or cisco; it is still colorless like water and cannot be seen with the naked eye.

A similar pattern is true for the other type of animals such as clam's, shrimp, snails, mollusks, etc. which ingest these hatched embryos and that are ingested by other fish.

The infected zooplankton must be ingested by the whitefish and the cisco fish for the larval tapeworm to differentiate into a plerocercoid in the flesh of the whitefish and cisco. (Pike generally do not eat zooplankton, but they do eat whitefish and cisco. Very young pike will eat zooplankton.)

The method of ingestion for the whitefish and cisco is through the fish's mouth which grab the zooplankton, but cannot chew it because these fish species lack teeth. (The pike have teeth to chew.) From the mouth, food passes past the gills into the stomach and intestine. The gills are lined with blood vessels and are composed of various arrangements of thin, highly vascularized membranes over which water passes, thus permitting exchange of oxygen, carbon dioxide and other solutes by diffusion. Kinetic energy is responsible for this process. The oxygen diffuses into the blood within the gill's capillaries thus oxygenating the blood. The operculum or gill cover moves forwards and backwards, thus adding force to the water flowing through the gills and helping to push the food into the stomach through its pharynx.

Upon ingestion in the whitefish, the zooplankton itself becomes food absorbed by the stomach's chemicals (i.e. HCL, pepsin, etc.) The hatched embryo of the tapeworm is not a stomach worm and cannot survive there. It escapes and bores through the stomach wall and enters the meat of the fish within the first five days, and lives there but does not mature to produce eggs. Only in the adult pike does it mature to produce eggs. The food cannot enter the fish's body through the nose because there is no opening in the body from the nose. To be more exact, these fish do not have a nose but they do have openings called "nares". In many species the external nares open into internal nares within the mouth, and any parasite entering through the nares would from the mouth enter the stomach by passing the gills. There are several ancient groups of fish that have scales and functional lungs. They surface and gulp in air through their mouths. These fish are found primarily in the Amazons of South America and not in the Mediterranean.

Plerocercoid larvae bore through the fish flesh by dissolving tissue. This is accomplished by its microscopic size and by secreting enzymes into the tissues of the flesh. During migration in the flesh, the worm is growing all the time by absorbing molecules such as amino acids and glucose through its tegument (natural body covering). When it ceases migration at approximately two months (at 150C), the host then encapsulates the parasite in a host "cyst", and after 90 days it is then infective to the pike if they ingest infected whitefish. It will then be able to grow into an adult in the intestine of the pike.

Once it penetrates the flesh of the whitefish it does not leave unless it is digested by another fish. By then it is too mature to penetrate the flesh of the new host and moves to the intestines, as will be explained.

Only the procercoid larva and other similar larva at the initial stage of ingestion by the whitefish and cisco, can penetrate into fish flesh. They are colorless and cannot be seen with the naked eye. Other type of larva such as Proteocephalus larvae, mature in the intestine by attaching to the wall of the intestine.

The pike ingest mature larvae (plerocercoids) found in the whitefish and cisco. Since they cannot penetrate the flesh at this stage, they escape from the stomach into the intestine and attach their scolex first to the wall of the intestine, slightly penetrating the surface of the wall, in order to avoid being expelled. They then live off the food digested by the pike. There are other fish that are eaten by the pike that are infected with parasitic larvae unable to be seen by the naked eye. Some of these parasites penetrate into the pike's flesh while others attach themselves onto the flesh or organs or onto the gut wall of the intestines, and still others just lie there in the intestines living off the host's food. Some develop living off their host more than others.

Not all parasitic larvae found in invertebrates such as clams, shrimp, snails, mollusks etc., that are ingested by the whitefish and cisco will penetrate the host's flesh or organs, even in the initial stage when they are colorless. (Color does not determine its capacity to penetrate tissue.) Some will attach themselves to the walls of the intestine and from there will grow into adult parasites. Some are able to survive by attaching themselves to the walls of the stomach or intestine and maturing there, living off food digested by the host but never reaching adulthood. Some species of flukes penetrate the liver, heart, gills, and brain, and some will just attach themselves on these organs.

If a large fish ingests a smaller whitefish, the mature larvae from the smaller fish cannot penetrate the flesh, so they attach themselves to the wall of the intestine. The result will be that we have mature tapeworm larvae in the flesh because they penetrated during the early stage, and mature tapeworm larvae in the intestine because they were ingested as mature larva.

Plerocercoid larvae can survive from five to six years in the whitefish. Only if the larva is eaten by the pike can the larva mature. It will then grow into an adult in about 8 to 10 months and attain maturity in about one year, at the time the pike spawns in the spring and releases its own eggs together with the mature tapeworm with its eggs. When it dies in the whitefish, the tapeworm's remains become absorbed into the flesh, and the flesh cyst which contained the larva is healed and forms scar tissue. The end of the mature adult in the pike is marked by the expulsion of the tapeworm with its fertilized egg through the anus of the pike.

Parasitic worms called flukes, can penetrate the flesh of the fish from outside and inside when they are at their initial stage of development (larvae) and are not visible to the naked eye even though they may be slightly pigmented.

The same general rules of parasitic penetration apply to parasites in animals but with different species. For example, hookworms penetrate the animal flesh early in development when it cannot be seen by the naked eye.

In conclusion, when parasites penetrate into the flesh of vertebrates (fish or mammal or other types of animal) and succeed in remaining there in a parasitic cyst, they penetrate when they are in their very early stage of development, and at this stage they are not visible to the naked eye. An exception to this rule is very rare. When they develop in the parasitic cyst, they are often visible to the naked eye. Parasites that attach themselves to the flesh or organs of fish, mammals or other animals can do so either during the earlier stages of development or later stages when they are visible.

The Torah forbids us to eat worms or larva that have been exposed to the earth's environment. If, however, these worms were born in a fish bowel, or in a well, whose waters are not flowing but are stationary, or in a fruit or vegetable, that has been detached from the ground, or in the body of a fish, or out of the earth's gravitational pull, they are not prohibited until they exit and are exposed to the earth's environment. There is a Rabbinical prohibition against eating these worms unless they are eaten with some food.

If the egg was exposed to the earth's environment but was hatched when it entered the fruit or fish, it is not considered that it was exposed to the earth's environment. Even if it did hatch in the earth's environment but at this stage it was microscopic and colorless and invisible to the naked eye when it penetrated the host, and it grew there, it is not prohibited until it leaves its host.

If it penetrated the flesh of a living animal that is prohibited to eat of its flesh if cut out when alive (אבר מן החי), then this parasitic worm that is now part of the animal's flesh is also prohibited as the flesh, and even after ritual slaughtering, because the worm is still alive. Rashi is of the opinion that only parasitic worms that enter into the animals flesh become part of it and are prohibited, he excludes those that attach themselves on the outside of the flesh within the animal, that are permitted because they do not become part of the animal. Tosefos disagrees with Rashi and is of the opinion that both are considered part of the animal, and are prohibited.

Cooks are cautioned, either not to taste raw ground fish, nor the broth of fish before it is fully cooked, or to taste the broth before the fish is put into the pot, even if the pot contains only the flesh of the fish that was washed well. The reason is tapeworm illness. Grinding the raw fish destroys the cysts of the parasites and is the cause for them now roaming about on the ground fish. Whole fish meat that is cooked, at the start of the cooking the warm water may cause the larvae in the flesh to exit and enter into the broth. Upon tasting the ground fish or the fish broth, these parasites will relocate into his intestine. There the larvae grow and cause a health problem that can be treated. This is less of a problem with animal or chicken meat due to the stringent regulations governing the packing houses controlled by the Board of Health. Nevertheless, it is advisable not to taste the broth at the start of the cooking. If however, there are visible larvae in a broth of cattle or poultry meat, these larvae are forbidden even after they have been killed through the cooking if they are still visible. If these larvae were not seen until after the start of the cooking, the cooking may proceed until fully cooked. The broth is then permitted providing that the parasites have disintegrated and they are no longer visible. If they are visible, then the broth is only permitted after removing all the parasites.

If the fish is first frozen for four days, then the parasites have been killed and we no longer have a problem.

There are many species of fish that harbor parasites in their flesh. One would have good reason to suspect that these live larvae, some visible and others not visible to the naked eye, will exit into the broth during the onset of the cooking. Those parasites that are not visible but that can cause serious health problems are forbidden to ingest due to health reasons. If they are visible, then they are forbidden by the Torah to eat, because we suspect that they exited the broth in the spoon and thereafter returned to the broth in the spoon. If the broth was tasted after cooking when the parasites have been killed, they no longer present a health problem and are permitted to eat, as will be explained in the following paragraph.

The Chochmas Adam brings the Ramo, who differentiates between worms found in vegetables and fruits, which grow from the ground, and fish or cheese which do not grow from the ground. With the latter, even if the larvae left their cysts due to the grinding and are now roaming on the ground fish meat, or, if the host was in a dish and the worms left the host but not the dish, these worms have not yet been exposed to the earth's environment until they leave the dish, and are presently permitted. When they are killed in the dish after cooking, they are permitted even if the dead parasites are exposed to the earth's environment. If there is soup in the dish, he is permitted to eat the soup with a spoon assuming that the larvae are dead either due to exposure to the soup or due to the cooking, assuming that the larvae disintegrated. Even in a situation where the dead worms are visible, he may eat the soup with the spoon, this way he is eating some food with the dead larvae. It is therefore preferable to prepare ground fish in a dish.

Spice factories receive shipments of natural spices and grind them for consumer consumption. These factories are subjected to government tolerance specifications for insect infestation. These regulations are of no concern to the halacha. Even if there are no apparent insects on the outside of the batch, nevertheless, the owner is responsible to spot check the batch by taking samples from different parts inside the batch. If insects are found on these samples, this batch must be commercially washed and spot checked again. If the second spot check does not show insects then the natural spices may be ground even if there were some unseen insects in the batch because they will be nullified by more than sixty parts of permitted food.

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