Cat Suddenly Peeing Outside Litter Box

[The Snark]

I have been checking for signs of that since day one, so this must be some sort of delayed hatching of eggs or something.

My data may be old but you will have 21 days of worms. The de-wormer won't affect the eggs so 3 weeks of hatching out. Now if they have the cat equivalent of Ivermectin it's no big deal as it stays active in the gut for three weeks.

 

[TheraMygale]

This is going to be the hardest part. Because if the worms are out, there will be eggs here and there . I know you are good on the cleaning. Just make sure you vaccum extra places: where it goes to sleep and sit. The eggs can drop when there is contact with anus/licking. Thats how they spread so quickly.

i dont want to scare you, just help/inform. Although you probably know this, but maybe not someone reading this:

the worms can be transfered to humans. Extra handwashing will be important. Until the issue is resolved. I would avoid kissing the cat.

a cat collar could assist in reducing the licking of infectious zones. That does stress cats though.

im sorry for the cat. And im sorry for you to have to go through this. Sending you positive thoughts.

as a kid, i got worms. I was always petting outdoor cats and dogs. It was a horrible physical and psycological feeling. One i still feel disgust about. But i it puts me in a place where i know what i am talking about. My parents had to clean the bed sheets often, the bathroom. The shame that was put on me, just a child, was terrible. I now live with an obsession of cleaning my hands. I am always washing my hands after i touch anything, and dont pet animals i dont know.

even animals i do know, who are treated, i barely pet. I wash my hands asap after.

a few years ago, a person i knew, got them while traveling. She was a grown women. It happens.

 

[The Snark]

. Because if the worms are out, there will be eggs here and there

A very common method of transmission is animals sniffing feces or each other's butts. Or their licking themselves back there. The eggs can even go airborne. This is why vets assume worm infestations in all their patients that aren't strictly kept isolated indoors.
At stables we always dose Ivermectin every 2 to 3 months. Speaking of which, always administter Ivermectin on a completely empty stomach. Otherwise it will get carried out with the feed and not remain active in the gut. Same applies to humans. Dose 2 to 3 hours before or after eating.