For the past year or so there is a persistent flu-like disease in the area where I am. It tends to kill a lot of cats. One of my cats had 6 kittens and another had 7. That was last summer. Now 13/13 kittens are dead, of which 11 from disease.

In the smaller cat-mom, the 6 kittens were too much for her to feed, so they started showing symptoms early. In the larger cat-mom, breastfeeding kept for quite a while and they were absolutely healthy. Once they grew up somewhat, naturally the cat couldn't handle them either, so when I started feeding them processed cat food (dry + canned), they started dropping like flies. That's when I made the connection. I don't think it's the food per se, as it is the lack of proper nutrients which then make their body vulnerable to flu-like diseases. It's the same with humans, for example proper vitamin D + selenium intake can prevent a lot of viral infections. So I was like, ok, let's buy more fish-food, which has more selenium and vitamin D - in case this disease is some kind of virus, so they can more properly defend against it. And then I found out that fish/meat content are around 4-5% in these cans (trace amount - most of the food was not ...food).