I am thinking of a Dollop episode that discussed pigs in early New York City. They were the trash clean up before there were people dedicated to the job. They were allowed to just run free and scrounge whatever offal they could find. It could have been less that pigs were unclean, rather pigs kept things clean. If people ate all the pigs, there would be corpses and fecal matter lying around for extended periods of time which would cause disease.

isnt mostly pork tapeworm they worry about.

Salmonella can be obtained just by touching chickens it doesn't require eating them. Trichinella is obtained by eating pork, raccoons, foxes, etc

Conjecture: it may have simply been trichinella

There was also the result of drawing a sharp line between the in-group and everyone else. If we have strict dietary laws but the people on the other side of the hill don’t share them, then it follows that they’re unspeakable barbarians, and that we should not trade or cooperate with them, let alone intermarry, and indeed, it’s acceptable to kill them and take their stuff, as surely such a barbarous people would do the same to us.

i have a specific unusual food allergy. I always presumed abraham or ishmael or jacob or moses or one of them mythical folk had a food allergy against pigs and said "you know what, if i started a religion about not eating pigs maybe i wouldn't get the runs every time i went out to eat"

Poultry eats carrion as well. Matter of fact, I'd wager pigs are more hygenic than poultry.

Maybe they just thought pigs are too cute to eat.

I thought it was due to the parasites, worms?, that pork gets in hot arid countries which is why both the Jews and Muslims don't eat it

Could also just be an exaggerated case of "ew, poor people food", since pigs will eat damn near anything.

I guess chickens are similarly omnivorous and take up less space though (plus, eggs). And are arguably easier to transport and defend (a rooster can fuck you up)