The histopathology of Fasciola hepatica infections in sheep

Abstract

Experimental infections of lambs with Fasciola hepatica are described. The growth rate of the parasite, time of entry to the bile ducts, and time of patency are recorded and a preferential migration of the parasite in the liver parenchyma noted. The gross and histological lesions produced in the liver from 1 to 40 weeks after infection are described and compared with previous observations in cattle.The parenchymal migration of the parasite is shown to consist of two phases, a free migrating phase up to the 6th week, and a localized phase after the 6th week prior to entry into the bile ducts. Hepatic cell regeneration is observed and hepatic fibrosis is minimal. The localized phase of migration is associated with a unique peripheral palisade of giant cells in the fluke tracts and with the formation of pseudofollicular aggregation of lymphocytes. The presence of flukes in the bile ducts produces fibrosis of the duct walls. The walls, however, remain pliable and expanded to accommodate the parasites and calcification was never observed.

Subacute and acute fasciolosis in sheep in southern Brazil

“…At approximately 5 weeks post-infection, the lesions are similar to those of acute fascioliasis; however, the functional reserves of the liver are sufficient to avoid death (Sewell 1966;Rushton and Murray 1977). In cases of acute fasciolosis, sheep do not usually succumb to their disease before week 7 or 8 of infection; at this stage, approximately 60 % of flukes are migrating in the left liver lobe (Brunsdon 1967;Dow et al 1968). …”

“…Extensive liver damage, hemorrhagic dark red tracts of necrotic liver parenchyma, and the presence of immature flukes are a characteristic of acute fasciolosis between the fourth and sixth weeks post-infection (Dow et al 1968). The presence of macrophages, Langhans-type giant cells, and fibrous tissue indicates subacute disease, which occurs between 6 and 10 weeks after (Boray 1967;Dow et al 1968).…”

The Pathogenesis of Primary and Secondary Infection with Fasciola hepatica in Mice

“…The chronic phase begins 30 to 40 days after exposure as the parasites enter the bile ducts . The lesions during these periods have been described for cattle [8] and sheep [9] and resemble those in mice during the incubation and acute phases of the disease . During the chronic phase rather extensive fibrosis occurs in the livers of cattle, but not sheep [18].…”

“…A m o n g th ese, the sea rc h fo r a su ita b le labo rato ry h ost h a s received much a ttention and in fec tio ns in m ice , ra ts, [4][5][6]13], catt le [8] a n d sh ee p [9]. The p athoge n esis o f second a ry in fec tio ns h a s rece ived le ss a tt e n tio n , pa rt icularly in mice , a n d co m pari sons of the lesions p roduced in suc h infecti o n s in m ice a n d ruminants h a ve not been m a d e .…”

Evaluation of Bilirubin, Phosphorus, Calcium and Cholesterol Levels in Bile of Livers Consistent with Hepatic Fascioliasis

“…Biliary stage or establishment, in which the worms are mature and begin to ovulation. These steps increase the diameter of the bile ducts, damage the liver tissue, and finally cause impairment in the production of liver enzymes, hemorrhage, anemia, fibrosis, jaundice, and a decrease in the function of the gallbladder in the production of different chemicals and even death (6). In the meantime, biliary fluid is one of the most important substances that is altered by invasion and replacement of the parasite, and it seems that biliary fluid can be used to determine the progression of the disease and the degree of damage to the liver cells (7), and to examine the changes in the production of bile duct material.…”