If wormwood is dangerous, then I am dead. I grew up in a country where everyone uses it for stomach upsets. As a matter of fact, the vermouth taste in the Italian Vermouth Wine is wormwood, and you drink a bit of it when your stomach is upset. About 35 years ago, I found out by fluke that wormwood tea or the herb chewed is a great first aid for respiratory problems, and I have been using it daily since then without any problems. The bitter taste also takes away the craving for chocolate.
What is dangerous is the absinth which is made from wormwood. It is a wormwood-flavored liqueur with almost twice the potency of alcohol of any other liqueur. It may well be the alcohol which does damage, not the wormwood, or maybe it depends on the variety of wormwood used. I am only guessing here. Absinthe was banned in some European countries for years, but it is again available in those countries, including in Britain.
All wormwoods are artimisias like the herbs which the aboriginal people call "sage" which is used for smudging and which has the same healing properties as wormwood.
I doubt, though, that you will be able to get your dog to drink anything as bitter as wormwood. I don't know about tapeworm, but any other kind of worm and pest such as fleas can be gotten rid of by adding nutritional yeast to the diet of humans or of pets. If a person is allergic to yeast, then use B vitamins instead. I have never heard of a pet being allergic to yeast. A yeast allergy is caused by a history of overeating on bread and it is quite common among North Americans.
Examples of naturally occurring anthelmintics include:
* Tobacco (Nicotiana tabacum & Nicotiana rustica)
* Moringa oleifera (Moringaceae)
* Neem (Azadirachta indica)
* Black walnut (Juglans nigra)
* wormwood (Artemisia absynthium)
* clove (Syzygium aromaticum)
* Hagenia (Hagenia abyssinica)
* Diatomaceous Earth (DE)
* Pineapple (Ananas comosus)
* kalonji (Nigella sativa) seeds
* male fern (Dryopteris filix-mas)
* Monarda fistulosa (Wild Bergamot)
* Honey mixed with water and vinegar was also used as a vermifuge.
* Plumeria (P. acutifolia or P. rubra) in Brazilian folk medicine.
* Peganum harmala
* Banisteriopsis caapi
* genistein (from soy and other legumes)