Align-ju STUDENT
the fluid-filled cysts , numerous scolices are budded off , which form the infective stages [ 6 ] . The IH can be asymptomatic for years until the hydatid cysts grow to a size that causes clinical signs [ 5 ] . Therefore , clinical risk is usually higher in longer-lived animals , such as horses , that can remain ‘ partnered ’ with their parasite for life ( Figure 4 [ 7 ] ). The adult tapeworm itself is very small compared with most tapeworms and is of little clinical concern to the EH . The eggs can be identified through microscopic examination of faeces ; however , the typical taeniid egg cannot be definitively identified as either Taenia or Echinococcus species [ 6 ] .
Figure 3 . Hydatid cyst in an equine liver .
Cestodes in cats and dogs
Dipylidium caninum ( the flea tapeworm ) is considered the most common cestode in dogs and cats in the UK and is occasionally zoonotic [ 5 ] . Diagnosis is generally through the identification of motile segments found around the host ' s anus or in faeces . If dried out and no longer motile , these may look like grains of rice . The tapeworm can be identified by opening the segment and noting the egg packets . The IHs are fleas , for example , Ctenocephalides felis , or lice , such as Trichodectes canis . Ingestion of the flea or louse by the EH is required to complete the life cycle . Control is dependent on treating the flea or louse infestation to prevent re-infection , as well as treating the tapeworm [ 1 ] . Praziquantel or niclosamide are effective against adult tapeworms [ 5 ] .
Figure 4a . Hydatid cyst with budding scolices [ 7 ] .
Taeniid tapeworms can infect dogs , cats and humans . Table 2 shows examples of different taeniids and their EHs . Note that the IHs are often less specific , resulting in a wider risk group . For example , in dogs T . hydatigena can infect the EH when it ingests raw meat containing larval cysts , and in cats T . taeniaeformis can infect the EH when it ingests prey containing larval cysts [ 1 ] . Treatment is with praziquantel or niclosamide .
Echinoccosus granulosus can use either sheep or humans as IHs and can cause the disease hydatidosis . Hydatid cysts form usually in the liver ( Figure 3 ) or lungs . Within
Figure 4b . E . granulosus scolex with rostellum visible [ 7 ] .
Figure 4c . A taeniid egg [ 7 ] .
Table 2 . Taeniid ( Taenia and Echinococcus ) species of tapeworm , their end hosts and their intermediate hosts . |
Species |
End hosts |
Intermediate hosts |
Taenia hydatigena |
Dogs |
Sheep , pigs , cattle , horses |
Taenia pisiformis |
Dogs |
Rabbits |
Taenia taeniaeformis |
Cats |
Mice , rats |
Taenia saginata |
Humans |
Cattle |
Echinococcus granulosus |
Dogs |
Ruminants , humans |
Echinococcus multilocularis |
Dogs |
Rodents , humans |
Volume 39 ( 2 ) • April 2024
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