What’s Going on with the “Bugs” in the Fish?

By the time you see this article, you may have heard that there is serious discussion currently going on in the Torah world regarding “bugs” in many of your favorite fish. You may have heard snippets of the back and forth, seen a list of which rabbis permit and which rabbis forbid. I hope this article gives you a better understanding of the issues at hand, and provides a better understanding of where each side is coming from.

Question: What are these “bugs”?

Answer: Almost all species of fish, to a greater or lesser extent, suffer from attack by parasites (which are the “bugs” currently under discussion). What are parasites, and how do they differ from bugs? Parasites are small organisms that live at the expense of the host, off of whom they directly feed. While “bugs” eat various plants or decaying matter, parasites eat their host (talk about hakaras hatov!) There are two main types of parasites. Ectoparasites are those found on the external surfaces of a fish (i.e. the skin, fins and gills), while endoparasites are found in the flesh and organs. The issue under discussion is the infestation of endoparasites in several species of freshwater and salt water fishes.

Question: Is there a difference between parasites and bugs in halacha?

Answer: From a halachic perspective there is little or no appreciable difference between the two and both are referred to collectively as “tolayim”. One who consumes a visible parasite that has been separated from its fish host would likely violate the similar prohibitions to those found on consuming a similarly positioned “bug”.

Question: How big are these parasites?

Answer: At some times, they are as large as several millimeters in size. This is a size which is generally considered by poskim to be “nireh laynayim” (visible to the naked eye). Many fish have parasites which are not visible to the naked eye, and these parasites are halachically permitted, as are most things in halacha which cannot be detected with normal human senses.

Question: How often does parasite infestation occur in the effected species?

Answer: Many parasites are found in large enough frequency as to be considered at least a “miyut hamatzui” (frequent enough in occurrence as to be considered halachically significant and thus require our attention). In the case of insects in vegetables, for example, a vegetable which is found to be infested to this extent needs to be washed in a way that removes the concern. Should the parasites be considered forbidden, one would be required to look for them (even if they were not immediately visible) and remove them (washing would not remove them from fish). Kashrus agencies would either have to stop certifying products made with these species of fish or advise consumers that they would need to check for and remove these parasites themselves.

Question: So far this doesn’t sound good. If a vegetable was similarly affected, all authorities would agree that one would be prohibited to eat the vegetable without removing the insects (though to what degree might be a matter of discussion). Why shouldn’t it be clear that the fish similarly infested should be forbidden until the parasites affecting them are removed?

Answer: The tolayim affecting fish may be mutar! The Shulchan Aruch in Yoreh Deah 84:16 states that worms found in the viscera of fish are forbidden, but those found in the flesh or between the skin and flesh are permissible.

Question: If so, what is the disagreement about?

Answer: Some have suggested that there are reasons why some of the parasites affecting our fish supply might not be the same as those permitted in the Gemara Chulin 67B and in Shulchan Aruch.

Here are some of the potential concerns:

  • The Gemara may be discussing tolayim that spontaneously appear in the flesh, while modern day parasites migrate from the viscera.
  • The Gemara may be discussing tolayim which enter the fish (i.e. the fish ate a smaller creature which was infected by a parasite) at a time when the tolayim are not visible to the naked eye, while these parasites may enter the fish at a time when they are visible.
  • The Gemara may be discussing tolayim which migrated from the viscera to the flesh at a point when they were not visible, while these parasites may be visible at the time when they migrate from the viscera to the flesh.
  • The Gemara may be discussing tolayim which migrated from the viscera to the flesh while it was alive, while these parasites may migrate after the death of the fish.

Question: Specifically with regards to the one parasite everyone seems to be focused on, is it true that this is a new parasite which did not exist in the time of Chazal?

Answer: There is no indication that any parasite exists today that has not existed from the time of Matan Torah, even less possibility that something has “evolved” since the time of the Beis Yosef and that therefore new halachos would apply to it. For example, some have suggested that the nematode Anisakis is a new creature which poskim could not have discussed before and of which the the rabbanim of the last generation were unaware. This does not seem likely, as various mentions of Anisakis infestation have been documented by scientists since the early 1800s. It is true that the diagnosis of anisakiasis (the name of the condition when a human is infected with a live anisakis parasite) only came around in the 1950s, but that has to do with changes in medical technology used in diagnosis and not in the origin of the species.

Question: So in the end, is it mutar or assur?

Answer: Some rabbonim are recommending their mispallelim refrain from eating any species of fish which might be infected with any of the visible species of parasites. For the most part, this recommendation comes as a caution while the rabbonim wait for more thorough research to be done on the size of the parasite at both the stage when it enters the fish originally and again when it leaves the viscera for the flesh. Some rabbonim feel that if it were visible at either of these two stages, it might be cosidered a forbidden species of tolaas. It is worth noting that all rabbonim agree that tolayim found in the stomach are forbidden (as stated in the aforementioned citing of Shulchan Aruch). Some argue that if this parasite is in fact found in the stomach and the reason we find it in the flesh is because the primary processor did not eviscerate the fish quickly enough, one should ignore the fact that the parasite was found in the flesh and focus on the fact that it came from the stomach.

Other rabbonim (including Rav Yisroel Belsky, with whom I was granted generous audience to understand both the issues, and in more complete detail his opinion) feel strongly that the parasites currently affecting various species of freshwater and salt water fish are not appreciably different from those that existed in the time of Chazal, and the parasites found in the flesh of fish are still permitted. Rabbi Belsky understands that Chazal told us that the tolayim found in the flesh are mutar because of the severah of “minah gavli” (see Rashi’s understanding of the Gemara Chulin 67B, where the term is explained to mean that the parasite grows in the fish and becomes permitted as part of the fish regardless of its original size when entering the fish or migrating from the viscera), and that we are not commanded to become experts in the field of parasitology in order to know how a parasite got into the flesh in order to know which types are permitted. The rabbonim permitting the parasites also point out that Chazal did not differentiate between the permitted types of parasite in the flesh from the forbidden types, which might also lead one to believe there is no halachic distinction in how one found the parasite in the flesh.

Question: Practically speaking, do I have to be machmir on this issue or not?

Answer: As with all issues of halacha, one is advised to seek the educated council of a qualified halachic authority to advise on a practical mitzvah observance.

OU Kosher Staff