Page 182 - The Veterinary Laboratory and Field Manual 3rd Edition

Parasitology 151

Figure 3.27 Life cycle of Taenia solium and T. saginata. (A) T. saginata, the beef tapeworm, forms cysts in the
tissues of the bovine (cattle) intermediate host. (B) T. solium, the pork tapeworm, forms cysts in the tissues
of the porcine (pig) intermediate host. (C) Humans are the definitive host for the beef and pork tapeworms.
Infection occurs in humans following ingestion of undercooked beef or pork meat. (D) Adult tapeworms
develop in the human small intestine. In some cases humans may also act as the intermediate host for
T. solium and develop cysts in the body, occasionally these cysts occur in the brain.

such as lungs, liver, kidney or brain. This type of dIaGnoSIS
cysticercus is technically called cysticercus cellulo- In the definitive host tapeworm segments are
sae. The cystic stages and hosts of other Taenia often passed in chains but individual eggs can also
sp. tapeworms and the hydatid tapeworm are be observed in faeces. Diagnosis in the interme-
outlined in Table 3.5. diate host depends primarily on the inspection
of carcasses for cysticerci in the heart, liver,
cLInIcaL SIGnS and dISEaSE ProcESS lungs, masticator muscles and tongue. Cysts
There are often no clear clinical signs of the can range in size from 5 mm to 6 cm long. The
disease in the intermediate host unless the preferred sites for cysticerci of different Taenia
cyst becomes very large or, due to its location, sp. are variable but meat inspection procedures
it starts to compress surrounding tissue result- are usually based on the compromise between
ing in clinical signs related to local dysfunction. detection of cysticerci and the preservation of
If cysts rupture there may be a generalized economic value of the carcasses. Ante-mortem
allergic reaction to released tapeworm larvae diagnosis of cysticercosis in the intermedi-
and fluids. Adult tapeworms may cause diar- ate host is difficult. In humans, it is presently
rhoea and abdominal discomfort in the final carried out by laboratory detection of cysti-
host. cerci by CAT (computerized axial tomography)

Vet Lab.indb 151 26/03/2019 10:25