These embryos perforate the tissue of the liver, become fixed in it, and derive from it the nourishment necessary for their conversion into cystic bladders of varying size, either sterile or fertile.
The number of vesicles is rarely large, and when only one or two are present they seldom produce sufficient disturbance to attract attention. On the other hand, when numerous they deform the liver, produce glandular atrophy, increase the total size of the organ, and lead to the appearance of clearly marked symptoms.
Fig. 127.—A racemose echinococcus, natural size. (After Leuckart, 1880.)
The cystic vesicles contain a clear, limpid, transparent fluid, in which float secondary, daughter, or granddaughter vesicles.
Fig. 128.—Section through a multilocular echinococcus, × 30. (After Leuckart, 1880.)
Symptoms. Echinococcosis of the liver has no well-marked symptoms, and is therefore difficult to diagnose in animals whose liver is deeply seated, and therefore beyond palpation. The signs which may characterise the period of penetration of the embryos through the intestine and into the depths of the liver, and which are probably represented by slight colic, vague pain and diarrhœa, usually pass unnoticed. But later, when the liver is extensively invaded appetite becomes irregular without apparent cause, animals show intractable diarrhœa, general feebleness, dulness, and wasting.
Fig. 129.—A multilocular echinococcus from the liver of a steer, natural size.—(After Ostertag, 1895.)