Abstract:
The liver tapeworm, Slilesia hepatica, Wolflbugel, 1903, a liver tapeworm which belongs to
the family Anoplocephalidae, is widespread in Africa and inhabits the bile ducts of sheep,
cattle and wild ruminants. Livers infected with this parasite hold no health risk for the
consumer, but are condemned at South African abattoirs for aesthetic reasons. Large scale
infections amongst live-stock can cause considerable economic losses.
The meat provision area of Bloemfontein is a semi-arid region with a summer rainfall. In this
area livers contaminated with S. hepatica were found a common occurrence under sheep.
Based on percentage infection, the region can clearly be divided in three parts (light, medium
and heavy). Infection was prevalent in a high percentage of sheep especially in the southern,
western and eastern parts of the area. For the region as a whole, and also for the various
parts, the seasonal prevalence of S. hepatica under sheep varied notably during the 12
months of study. The highest occurrence was found in autumn and early winter months and
the lowest during spring. From the results it can be concluded that an increase in average
daily temperature and rainfall promoted the spreading of this parasite. Daily temperature
was the predominant factor.
The degree ofliver infection with S. hepatica under sheep, was notably higher amongst older
animals compared to younger animals. Despite the above-mentioned fact, it seemed that the
parasite showed no preference for sheep of a specific age.
The parasite showed a preference for attaching to the distal end of the left liver-lobe from
where continuous movement of the parasite in the bile-ducts caused fibrosis, cystic
dilatation, plasma cells and lymphocyte forming in the surrounding liver tissue. Infection
with this parasite had no effect on the nutritional state of the animal.
Prasikwantel (Cestocur, Bayer) effectively removed the parasite from the liver within
twenty-four hours after dosing. Recovering lightly infected livers with the aid of a vacuum
pump can result in considerable cost and time saving for abattoirs and retail. This method of
recovering infected sheep livers at abattoirs, in contrast with hand recovering (physically
removing infected bile-ducts or unthreading the tapeworms from the bile ducts), had no
notable liver weight loss. Hand-removal of parasites from bile-ducts took considerably more
time in contrast with vacuuming with a pump.
