Tapeworm and Tapeworm Larvae that Infect Sheep
Summary written by Peter Bates PhD, MSB, CBiol, FRES
Taken from Moredun Foundation Newsheet Volume 5 No. 13 (2012)
- Tapeworms are flat, segmented, parasitic worms. A mature tapeworm can be several meters in length, consisting of a head, neck and a chain of segments. The mature, terminal segments (containing large numbers of eggs) are cast-off regularly and are passed out in the host faeces.
- Tapeworms have complex, indirect, life-cycles including an intermediate host infected with immature stages and a final definitive host infected with the adult tapeworms. Historically, the larval stage was thought to be a separate, independent organism and not thought to be part of a tapeworm lifecycle. Consequently, the larval stage can have a different name to the adult tapeworm.
- Sheep are the final host of one species tapeworm (Monezia expansa), the adult tapeworm attaching to the intestine of the sheep. The intermediate host is a soil mite.
- M.expansais considered to be non-pathogenic to sheep and is more of a worry to flock owners through the obvious presence of expelled tapeworm segments in sheep faeces.
- Sheep are also the intermediate host to four species of tapeworm (Taenia hydatigena - the thin necked bladder worm, Taenia ovis - the sheep bladder worm,, Taenia multiceps - the tapeworm that causes gid and Echinococcus granulosus - the tapeworm that causes hydatidosis), all of which have the domestic dog as the final host.
- Sheep infected with the larvae of T. hydatigena, T. ovis, T. multiceps and E. granulosus can show clinical disease, and the larvae can also affect the growth rates of growing lambs. There can also be significant losses due to carcase and offal condemnations in slaughterhouses and cutting plants.
- Most tapeworms and tapeworm larvae found in sheep pose no health risk to humans. Humans can however become infected with E. granulosus larvae (hydatidosis), through contact with infected dogs or dog faeces. This can result in serious disease in humans, particularly children.
- Effective control of dog tapeworms and their larvae depends on an integrated control programme involving both dog owners (such as regular administration of a wormer effective against adult tapeworms and not feeding raw meat and bones) and sheep farmers (as for dog owners plus the prompt disposal of all sheep, goat and cattle carcases)
- This newsheet will cover the disease caused in sheep due to infection with the sheep tapeworm (M. expansa) and the larvae of the dog tapeworms (T. hydatigena, T. ovis, T. multiceps and E. granulosus)
More information on disease prevention can be found on the DVD 'Managing Your Flock for Peak Health' - programme 2 in the series 'Sheep on Your Smallholding'.
The full news sheet for any of the disease summaries can be ordered from the Moredun Foundation by using the following request form. The first news sheet title requested is free*, further news sheet titles are charged at £5.00 per copy (including postage).
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