Hi there! Dr. Hurst here.
It starts to work right away (as soon as the body absorbs it from the GI tract). It may take a few days to kill the tapeworm. You may see segment shedding for a few days, but none after that. If you do I would suspect that it did not work. At 13 pounds her dose is actually 1 1/2 tablets, but the 1 tablet may be enough.
Bear in mind you will not see the dead worm come out (usually). The medication causes the tapeworm not to be able to withstand digestion. So it dies and is broken down and absorbed by the intestines. In rare instances (usually when the worm is very large) it can come out in the stool.
If she still has fleas you may see more segments down the road. That is likely a new tapeworm. Flea control is important because ingesting a flea is how they get the tapeworm.
If I can be of further assistance please let me know! Best wishes!
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Hi again! The "Already tried" section of your question did not show up for some reason. Let me address this portion.
The symptoms you describe concerning Cosmo are not really consistent with a tapeworm infection. Ordinarily the only symptoms we see are maybe some diarrhea and weight loss. They rarely cause other problems. I hate to say it but I think something else is going on with your sweet boy.
Since he is not feeling well I would hold off putting on the Zodiac on him as this can make them feel bad as well and that may confuse the issue. Go ahead and use it on the other cats.
By the way, the tapeworm segments themselves are not infective, even if ingested. Part of the life cycle of the tapeworm occurs in the body of a flea, so eating a flea is required. (Some pets can get a different type of tapeworm from eating mice and other small creatures, but since you have seen the segments on more than one cat it is the fleas that are the cause here, I'm sure.)
Cosmo's symptoms are very vague and could be caused by a number of issues. I think he needs to have an exam and some bloodwork performed to try to determine the cause of his not feeling well. Don't wait on this as cats who don't eat can get in trouble very quickly!! They can get a disease called fatty liver syndrome from not taking in enough calories and it can happen within several days of not eating. So I would highly recommend you have him seen today if possible.
If I can be of further assistance please let me know. Best wishes!