Thanks for the questionCustomer
In direct answer to your question : I have never come across any natural product which would be effective in treating tapeworms, sorry. When you are dealing with worms it is important for your cat's sake to get rid of them all, that having been said you can sort this problem out with over the counter drugs which would be very safe for your cat.
1. It is more than likely what you are seeing is tapeworms, you can usually see live ones round your cat's rectal area if you have a look a few times, they are about the size of a grain of rice and you can sometimes see them move.
If you see a live one check this link so we can make sure what we are dealing with, link to a picture of tapeworm segments : IMAGE
2. If this is what we are dealing with there is no cause for concern, this can be treated with simple oral medication which your vet can supply or over the counter medication from a good pet store. Try something like Tradewinds which is now an over the counter product and is the same as Droncit which before you could only get from the vet, it contains Praziquantel. I have prescribed loads of droncit over the last twenty eight years and found it to be safe and effective.
3. Make sure your cat is always free from fleas as they can be part of the tape worm life cycle. It would also be good practice to regularly worm your cat against both round and tape worms, again effective round worm tablets would be available from your vet or better pet stores.
4. Tapeworms are very rarely a risk to people, here is a link which covers the subject : LINK
If I have not answered your question fully enough or if you would like to ask more I will be on line for the next hour or so and I will be delighted to discuss your question further.
Scott Nimmo BVMS MRCVS