Worms in Fish
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Loading ...WORMS IN FISH
By Rabbi Mordechai Kuber
Introduction – Shulchan Aruch (YD 84:16) prohibits intestinal worms, because they might originate outside the fish, but permits flesh worms, because they form in the permitted fish flesh. Scientific research has long discredited SG (spontaneous generation), thereby casting the permissibility of flesh worms in doubt. Many Poskim resolve this conflict by saying that worms appear to originate in the flesh, but that they actually begin in microscopic size outside the fish, but develop to visible, halachically relevant form only within the flesh. Other Poskim, mainly in Eretz Yisrael, are not at all perturbed by this scientific rejection of SG, preferring instead Chazal’s literal word.
Those who reinterpret SG confront numerous difficulties, as the microscopic-to-visible theory must clear numerous scientific and halachic hurdles. Those who accept SG do not face any of these difficulties, but they nevertheless cannot permit worms that have been demonstrated to arrive in the flesh not through SG, but through invasion. There are those who claim that the ubiquitous anisakis is such a worm, and is therefore prohibited.
In this article, we present and discuss the difficulties confronting those who both reject SG and permit anisakis, and discuss the evidence presented that anisakis is invasive.
This author publicly acknowledges that he is not a Poseik for Klal Yisrael. His intention is only to acquaint readers with the issues, and to foster mature discussion. In the final analysis, we follow the rulings of our Gedolim and Poskim.
Difficulties with Applying Microscopic-to-Visible Theory – Applied to fish worms, this theory adopts the scientifically documented life cycle of internal fish parasites: microscopic larvae are ingested by crustaceans, which are subsequently ingested by the host fish; the larvae then migrate from the stomach to the flesh, where they develop and appear to have spontaneously generated.
We presume the details to be roughly similar for all flesh worms, and therefore we discuss only the one most thoroughly researched. Anisakis, when it hatches on the ocean floor, is 14-20 microns wide. Some claim that the nascent worm is indiscernible by the human eye because of its narrowness. Others note that it is as wide as angora hair and retinal stitches, which are both visible. If anisakis is visible at this stage, and such external worms are confirmed as the source of fish-flesh infestation, then flesh worms must be prohibited. Some counter that we may disregard the borderline visibility of hatched anisakis, and all the other difficulties we are about to present, because all this occurs in submarine secrecy, out of range of our detection. Since we first discover the worms only within the flesh, we may presume that they originated there, regardless of how they actually arrived. This approach is flawed, as the Gemara states that intestinal worms are prohibited because they are really outside trans-nostril invaders. Thus, we are concerned about worms’ origins, even if their development and travels are shielded from view. Therefore, if anisakis are visually discernible from the time of their hatching, they are certainly prohibited.
Even if hatched anisakis are invisible, this theory must address the growth of the larvae to visible stage within the prohibited crustacean. There is no explicit ruling concerning this, and the law seems to be disputed. In addition, we would need to say that the transfer of the larva from the crustacean to the host fish is not considered as if the worm left its growth environment, for then it would be prohibited, even if it were permitted up to that point. We would need to distinguish between these worms and a worm that develops within post-harvest fruit and crawls out, directly into another picked fruit. In the latter case, we rule stringently, even though the worm never was exposed to the outside. In this case, we would have to say that the host fish is also considered a growing environment, for the larva continues to develop there.
We have still not cleared all the hurdles, even if the larvae have survived the triple challenge of their initial visibility, their development within prohibited crustaceans, and their transfer out of their growth environment to the host fish. We still need to allow for their migration from the intestines to the flesh, while simultaneously claiming that other, prohibited larvae that could reside in the stomach cannot likewise pierce the intestinal wall. This is obviously an untenable argument.
Finally, a Gadol Hador has reputedly absolutely rejected the microscopic-to-visible theory. He rules that even if larva is microscopic at the time of migration or initial ingestion, its visible, grown form is prohibited, since it developed from a migratory source.
In summary, proponents of outside origin of permissible fish-flesh worms face significant challenges to their theory.
The Migratory Evidence – As we mentioned in the introduction, worms that originate outside the fish are prohibited, even if we have not rejected SG. Some have presented four proofs that flesh anisakis are migratory, and do not originate in the flesh. First, identical anisakis are found in proximate abundance in the fishes’ stomachs. Second, tunnels connect the worm-sites to the stomachs. Third, worms seem less predominant in farmed fish, suggesting that worm-infested ocean waters are the external cause of flesh infestation. Fourth, and finally, worms are more prevalent in the belly flaps and abdominal walls of fish, suggesting that this disparity of distribution results from the proximate source of the intestinal worms.
Before we discuss these proofs, we mention that the current round of questioning the halachic status of flesh-worms was sparked by noticing migration from the peritoneum (abdominal-wall membrane) to the flesh underneath. This membrane adheres to the muscle, and is not attached to the digestive tract. There is no physical reason to classify it as part of the intestines. In addition, there is no precedent in Halachah to prohibit the worms in this membrane; the worms there should be as permitted as are those in the flesh. Hence, the worms observed to migrate are permitted worms, and there was never any cause for alarm!
We now refute all four proofs. First, proximity of intestinal anisakis does not compromise the ability of flesh to develop anisakis on its own, and therefore does not at all imply that the flesh worms are invaders. Intestinal worms also developed within a fish or crustacean, and moved to their new, visceral home after the demise or ingestion of their former host. Thus, there is no reason for the presence of intestinal worms to cast aspersion on the internally developing nature of their flesh-resident neighbors. As an analogy, consider a farmer who purchases a few bushels of wheat at a roadside stand, and then dumps them between the rows of his wheat field. Would it make any sense to suggest that the dumped wheat has not grown in a field, and then to continue along this faulty line of reasoning and conclude that the waves of grain have been transplanted? Certainly not! Likewise, the presence of ingested intestinal anisakis should not generate any suspicion at all about the native origins of the identical flesh worms.
In addition, Pri Chadash (84:45) prohibits fish-liver worms because they invade through the nostrils, but does not seem concerned that abutting, intestinal worms might have infected the liver. It seems that Pri Chadash is convinced that intestinal worms pose no migratory threat. We also note that Pri Megadim (Sif’sei Daas 84:43) and others comment that intestinal worms are not certainly prohibited, but only out of doubt that they might have arrived from the outside. It is likewise possible that they developed internally, as is the case with flesh worms. So why should we be concerned about the presence of stomach worms, which might well have developed internally and be permitted? We cannot permit them, because we are not certain, but that doubt should not foster speculation about possible migration of these unverified invaders.
Regarding the second proof, we question the authenticity of the study that discovered these connecting tunnels. How many worms were identified, and how many of them had tunnels connecting their location to the stomachs? Apparently, not all worms, and not all fish, had connecting tunnels. This author has observed worms without connecting tunnels. The study seems inconclusive. But even presuming that its observations are sound, we question its directional conclusions. How do we know that these tunnels are evidence of migration from the stomach to the flesh? Perhaps they are evidence of the opposite – of worms migrating from the flesh to the stomach!
Rav Yisrael Isserlin (Hagahos Shaarei Dura §47) says exactly this. He permits white shwibrin worms that we observe burrowing from the surface deep into the flesh of fish, for we are certain that they originate within the fish flesh. Rav Isserlin understands that even when we witness penetration of these worms, we may presume that they were originally internal, since we often find them in the flesh, and are therefore aware that they develop within the flesh. Rav Isserlin is not concerned that these burrowing worms are originally external, and hence prohibited. We presume that flesh worms developed internally, even when the possibility of external penetration is present!
The third proof of migration seems more credible, for what else could account for the noticeably lesser incidence of infestation in farmed fish than in wild fish? We could propose, with some lack of conviction, that controlled farm conditions are less conducive to worm generation than are the wild, polluted waters of the oceans. Instead, we note with greater conviction that this proof is predicated on inconclusive and paltry evidence. There seems to be no more than one publicly available scientific study, from 1989, that makes the case for the lack of incidence of anisakis in farmed fish relative to the abundance of its incidence in wild fish. It discusses only salmon, comparing the zero incidence of anisakis in penned salmon, which are harvested at the age of only a year, to the abundance of infection found in wild salmon, which are caught as they return to spawn. Thus, the study compares young, pampered fish to fish that have traveled thousands of miles and are hours away from death. There is no question that the flesh of the older, more weary fish is much more susceptible to decay and worm generation than is that of the sprightly juniors.
Finally, the fourth proof is the easiest to brand as presumptuous, because it could well be that the belly flaps and abdominal walls are more accommodating to worm generation than are other locations. In a vacuum, stomach proximity might cause us to postulate about migration, but it is far from compelling enough to begin to challenge the universality of the Shulchan Aruch’s ruling.
Arguments For and Against Permitting Flesh Anisakis
Shulchan Aruch does not confine his ruling to a specific type of worm. Therefore, if the possibility exists that other worms, possessing migratory capabilities, are prohibited, his blanket permissive ruling is unconscionably and irresponsibly misleading. Rather, his unqualified ruling proves that migration is impossible. Nevertheless, some Poskim claim that Shulchan Aruch discusses only worms known to him, all of which were not migratory, and not contemporary anisakis, whose migratory nature has been verified to their satisfaction.
Some argue that modern-day catching and delivery methods allow fish to remain ungutted for much longer than in centuries, or even in decades, gone by. Therefore, although Shulchan Aruch rules that we may presume that freshly caught fish could not have migratory worms in its flesh, we cannot safely presume the same for fish caught days ago. We note that in Talmudic days, fishermen brought their ungutted fish to the market, sometimes a day or two after the catch (see Beitzah 24b and Shulchan Aruch Orach Chayim 515). So if Chazal were not concerned about post-catch migration even if fish were left unrefrigerated and ungutted two days after the catch, why should we be concerned about it nowadays if fish is left ungutted for a few hours, and refrigerated throughout?
Some invoke the force of tradition: since the codifying of the Talmud, no one has discussed today’s state of infestation where both the stomach and flesh are infested. They posit that it is unreasonable to presume that such tandem infestation was never reached throughout the millennia. Rather, there were certainly many incidences of such infestation, yet none of our sages of years gone by felt that the presence of nearby stomach worms negatively affects the permissibility of the flesh worms.
Others suggest that we cannot escape the attestation of the scientists that anisakis originate outside the fish, and migrate to the flesh from the intestines after they are ingested. We reject this view, as scientists cannot be the arbiters of post-Talmudic change. They cannot be objective, since they do not believe that worms could form within fish flesh on their own. Consequently, they believe that anisakis must migrate to the flesh from the stomach, and they will perforce misconstrue and ignore all contrary evidence, or rush to their preconceived migratory conclusions without convincing evidence of such. Thus, the conclusions of the scientific papers presented should be judged as presumptuous at best, and fraudulent at worst.
We also note that even the scientists are quite unclear about the source of the flesh worms. The CDC (Center for Disease Control) states unequivocally that intestinal worms migrate to the flesh only after the host fish dies. They are not discussing migration after the catch, but migration when fish die in the open waters and wait a while before being ingested by larger fish. Thus, the scientists admit that contemporary worms cannot pierce the abdominal wall during a fish’s lifetime. Accordingly, they would be perplexed when asked to explain the presence of flesh worms that clearly did not migrate there in the short time between catch and gutting. Thus, even scientific theory points away from migration!
We also note that if intestine-piercing migration does occur, we would expect to find intestinal ulcers, and we do not.
We conclude with one halachic argument. Rav Yitzchak of Dura (Shaarei Dura §47 and §52) rules that we must prohibit all flesh worms, since trans-nostril invasion is possible. Although they may well have internally generated, these natives would not be distinguishable from immigrants, and thus we must prohibit all worms. Shulchan Aruch rejects Rav Dura’s minority ruling, but we remain with an important lesson. If concern about the possibility of invasion trumps the universality of internal sourcing, then we must prohibit every flesh worm, without exception. There is no acceptable middle ground. Hence, claiming that we must be mindful of possible invasion is tantamount to completely rejecting Shulchan Aruch!
May all our actions, including eating fish and pondering the halachic status of its worms, bring glory to the sacred name of HaShem.
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Due to publication constraints, this is an abridged and modified version of the original article. For the complete version, which includes a comprehensive analysis of the Gemara and relevant Rishonim, please contact the author at JerusalemKosher@gmail.com.
Rabbi Mordechai Kuber, Rav of Beis Medrash Nachlas Tzvi Ohel Avraham in Telzstone, Israel, is a world renowned kashrus expert and educator. He can be reached at JerusalemKosher@gmail.com.
