Metacercariae Of Fasciola Gigantica Research Articles

Assessment of the attenuation produced by irradiation of Fasciola gigantica metacercariae in hamsters

Severe pathological changes were seen in hamsters given metacercariae of Fasciola gigantica irradiated at doses below 4 krads. No adult flukes were recovered from hamsters given metacercariae irradiated at doses above 4 krads and little hepatic damage was caused. It was not ascertained whether resistance resulted following these latter infections.

Antibody response of calves to a single infection of Fasciola gigantica determined by an indirect fluorescent antibody technique

The antibody response of six calves infected with 500 metacercariae of Fasciola gigantica each was monitored throughout 30 weeks of infection using an indirect fluorescent antibody technique (IFA). In vitro excysted F gigantica were employed as the test antigen. All animals showed high antibody titres from two to six weeks post-infection. Thereafter the antibody titres diminished gradually. Although all the experimentally infected animals harboured fluke burdens at autopsy, most gave negative IFA tests from 22 weeks post infection onwards. Specific immunofluorescent staining occurred on the surface glycocalyx of the newly excysted flukes. It is likely that this glycocalyx provides one of the earliest antigenic stimuli for the host's immune reactions to fascioliasis.

An in vitro study of the relative importance of bile and carbon dioxide in the activation of Fasciola gigantica metacercariae

The relative importance of bile and atmospheric stimuli in activating metacercariae of Fasciola gigantica prior to excystment has been studied by omitting each in turn from the in vitro excystment medium, and by separating each from the period of incubation at 37 degrees C. The results indicate that bile is less important than carbon dioxide in triggering excystment, and may serve only to increase the permeability of the cyst wall to carbon dioxide. It is speculated that activation involves initiation of carbon dioxide fixation and anaerobic metabolism due to the high concentration of carbon dioxide and low redox potential prevalent in the gut.

The Pathogenic Effect of Experimental Infections with Fasciola Gigantica in Cattle

SUMMARY Sixteen young cattle, 7–13 months of age, which had not previously been exposed to Fasciola infection, were each infected with 500, 1000 or 2000 metacercariae of Fasciola gigantica. The experimental infections were followed for periods of 12 to 18 weeks. These animals were grazed on good pasture in the Kenya highlands under conditions which were similar to commercial farm practice. None of the animals which had received 500 or 1000 metacercariae showed any signs which could be attributed to fascioliasis and all remained in good condition, although they did not gain weight so quickly from 11 weeks after infection as the uninfected control animals over the same period. However, both the cattle which were infected with 2000 metacercariae showed clinical symptoms and lost weight from about 10 weeks after infection. One of these animals was slaughtered 12 weeks after infection ; the other, which had eperythrozoa in a blood smear taken at 14 weeks after infection, became progressively weaker and was slaughtered in extremis 15 weeks after infection. This animal was the only one which developed anaemia. By comparing these results with those of previous authors, attention is drawn to the wide range in pathogenicity of F. gigantica that has been recorded in previously uninfected cattle. Factors which may influence the course of the infection are reviewed and in particular it is concluded that the plane of nutrition has a greater effect than has hitherto been appreciated.

Experimental chronicFasciola gigantica infection in sheep

Ten sheep14–15 months of age were each infected with a single dose of60 metacercariae ofFasciola gigantica and studied over a period of seven months. No clinical symptoms were observed and the anaemia which developed was slight and transient.

経口, 非経口的な肝蛭実験感染家兎における肝蛭の脊髄内迷入例について

A dose of 50 metacercariae of Fasciola gigantica, from which had been removed outer cysts, was injected to rabbits in the longissimus muscle and in the subcutaneous tissue of the back and thigh. Two rabbits receiving subcutaneous injection at the thigh passed without manifesting clinical symptoms. Eight of nine animals receiving subcutaneous or intramuscular injection at the back exhibited aralysis in the fore and hind quarters and ischuria 28 to 65 days after injection and succumbed or were moribund 1 to 11 days later.These symptoms were observed on 4 rabbits of 54 given 20 to 50 metacercariae each per os 12 to 71 days before.Gross changes in rabbits suffering from paralysis in the fore and hind quarters consisted of remarkable hemorrhage, cell infiltration, and degenerative changes in the muscle and subcutaneous tissue in which metacercariae had been injected. Hemorrhage in the spinal cavity and hemorrhage and cavitation in the parenchyma were also seen.In the rabbits infected by the parenteral route, young larvae with inhibited growth were found in lesions of the muscle and the subdural portion of the spinal cord. They were detected also from the liver of such animals as autopsied 46 or more days after infection.One to three young larvae were found in each spinal cord in 7 of 12 rabbits exhibiting paralysis in the hind quarters. It has been made clear that hind-quarters paralysis and ischuria were caused by aberration of liver flukes in the spinal cord.