There are many different species of tapeworm that affect poultry although they are not often found and thankfully, most of them are completely harmless. Large numbers can cause weight loss and a reduction in laying. Tapeworms or Cestodes vary in length, some are 4 to 5 mm long and others are up to 25cm long! Tapeworm infect birds indirectly via intermediate hosts such as flies, earthworms and snails. The adult tapeworm lives in the intestines of the bird, it buries its head in the lining of the intestines. Tapeworm is quite rare to find in chickens but none the less can still be found on occassions.
Diarrhoea (sometimes bloody diarrhoea such as with Raillietina tapeworms, that use beetles as an intermediate host) weight loss, reduced egg production. Tapeworm segments or worms in droppings. Death can occur with very large infestations. The photo to the right, courtesy of chickenvet shows (white) tapeworm segments in a chicken's dropping.
There is conflicting advice on what kills tapeworm. Flubenvet at the standard dose will not usually kill these worms. Vets will sometimes prescribe Flubenvet at a stronger dose under their clinical judgement but above the standard dose, although a withdrawal period for eggs as well as meat will then be necessary (your vet will advise you on a suitable withdrawal period which by law has to be a minimum of 7 days).
Controlling the number of intermediate hosts, such as the number of flies can be a useful solution. Red Top Fly Traps for example catch thousands of flies, reducing their numbers.
Worming Chickens provides some ideas for worming poultry but the advice of your vet will be required to have Flubenvet prescribed at the higher dose or another product that will kill Tapeworms.
Tapeworm and Fluke in Backyard Fowl written by Poultry Vet Richard Jackson provides further information on these worms that is well worth reading too.