The OU brought samples of canned sardines to a parasitologist at the American Museum of Natural History to determine through DNA testing if worms found in those cans come from worms located in the intestinal tracts of the fish or if they come from worms located in the bodies of the fish – a difference with halakhic import, because worms located in fish flesh are kosher, while those located in the intestinal tract are not.
Worms are commonly found in fish.
Dr. Mark Siddall found the worms originated in the flesh of the fish, and the OU now considers canned sardines (with kosher supervision, of course) to be kosher.
Besides relying on DNA to determine a kashrut question, what is most interesting to me is the NY Times' understanding of the issue:
Talmudic debates can turn on fine distinctions, but this was relatively straightforward. The presence of worms could have been a sign that, during the preparation of the canned sardines, muscle from the fish had been improperly handled and allowed to mix with intestinal contents of the sardines, rendering them unkosher.
No, sorry, NY Times. That is not correct.
What makes the sardines not kosher are the worms. If no worms are found, or if finding worms is very rare – which was, apparently, the case for some time – then the fish is kosher no matter how the intestines are handled.
There isn't a processing issue with the sardines – there's an infestation issue with the sardines, and there is no special processing protocol for kosher supervised canned sardines.
A minor point, perhaps, but it does illustrate how difficult it is for reporters to correctly cover issues related to Orthodoxy and Jewish law.
As for the worms, their very common in many types of fish, including otherwise kosher types of fish, and have been pretty much forever. They're perfectly safe to eat as long as they've been cooked or frozen first.
But like bugs on fresh produce, rabbis have been using modern technology (light boxes, magnification, etc.) to find them, something Jewish law never imagined.
That hyper scrutiny has created a whole new range of foods Orthodox Jews cannot eat or can eat, but only by paying very inflated prices for special kosher brands – like Bodek vegetables, for example.
Here's a link to a paper written by Dr. Mark Siddall, a curator and professor in the invertebrate department of the American Museum of Natural History, who conducted the testing for the OU: