[The experimental studies on Capillaria hepatica]

Abstract

Capillaria hepatica is an extremely common parasite of rats. Several human cases have also been reported from various parts of the world and recently these aroused the clinical interests. The present study was undertaken to investigate the biological observations of C. hepatica and the changes occurring in blood picture and serum protein in the experimentally infected hosts. The source of C. hepatica obtained from the deposit of non-embryonated eggs encapsulated in the liver of house rats(Rattus norvegicus) in Seoul. The eggs isolated from the infected liver tissues by the freshly prepared artificial gastric juice at 37 C and embryonated in the incubator 27 degrees to 30 degrees C for four to five weeks. For the observation of migratory pathway to the liver, ten mice were infected orally with 1,000 embryonated eggs of C. hepatica, and another ten mice were infected intraperitoneally. No larvae were found in the washings of peritoneal cavity after oral infection, but after the third day of infection, the larvae were isolated from liver tissues. These indicated that the majority of larvae are transported to the liver by the hepatic portal system. On the other hand, 1,000 embryonated eggs of C. hepatica were inoculated into the peritoneal cavity of mice by mantoux syringe containing antibiotics. One third of inoculated eggs hatched out in the peritoneum during two days after inoculation, hatched in the peritoneal cavity invade directly to the surface of liver. Twenty white rats were infected orally with 1,000 to 2,000 embryonated eggs for the study of the development of C. hepatica in the liver and histopathological changes of the infected liver in the course of infection. C. hepatica in the liver of white rats developed rather slowly at the first tenth day after infection, but at the 13th day developed rapidly in its size. The worms were sexually differentiated at the l7th day after infection. At the 20th fully formed eggs appeared in the white or yellowish lesions on the surface of rat liver and they are also found in uterine tubule of the female worm. After the 33rd day, male worm disappeared and only female worms packed with eggs were detected in the liver tissues. However the long hair-like tightly coiled worms were also usually found in the hepatic cysts, and the degenerated or dead worms were observed in the small cysts on the surface of the liver at the 59 th day after infection. Microscopical examination on the first week after infection revealed inflammatory reactions with the dilatation of central vein, Kupffer cell mobilization, focal necrosis and perivascular infiltration. After two weeks of infection granulomatous inflammation were observed around or adjacent to the worms in the lobules. The worms are surrounded by macrophages, multinucleated giant cells, a dense infiltration of lymphocytes, monocytes, neutrophils and, especially, eosinophils. After the third and fourth week, the microscopical findings of infected rat livers have shown proliferation of connective tissues and regeneration of liver cells. During the fifth to sixth week after infection, rat liver showed marked proliferation of fibrous connective tissues encapsulated the worms and massive deposition of the eggs. At the later time the liver reveals many pseudolobules which are caused by postnecrotic cirrhosis. These are irregularly subdivided into lobule by a fibrous septum. The worms were fragmented by the phagocytes and encapsulated by connective tissues. And then finally they appeared to be replaced by the calcium-like material. The liver shows typical cirrhosis after the eighth week after infection. In order to investigate the changes of blood picture and serum protein components of rabbits infected with C. hepatica, twenty rabbits were divided into four groups by the doses of eggs. Group A was given doses of 1,000 embryonated eggs, group B 5,000 eggs, group C 10,000 eggs and group D 30,000 eggs. The pictures of blood especially leukocyte and eosinophil counts and of serum protein were checked every week for ten weeks in the course of infections. The marked elevation of the leukcocyte, eosinophil counts and percentage of eosinophils was observed at the sixth to the seventh week in the course of infection in all groups of rabbits. At the tenth week after infection a decrease was shown in their counts. However in the heavily infected groups (Group C & D) these values persisted relatively in high levels even thereafter. In the white rats given doses of 1,000 to 2,000 eggs, eosinophil counts increased to the peak at the fourth week and decreased at the seventh week after infection. The changes in serum protein components of infected rabbits were investigated by paper electrophoresis. Blood collections were done by the cardiac puncture in the early morning. Serum total protein was determined by Biurets method, serum protein fractionating and A/G ratio by paper electrophoresis using Whatman No.l filter paper and barbital buffer (pH 8.6, ionic strength 0.06). Total protein increased at the sixth and seventh week after infection and the albumin and A/G ratio had decreased significantly in the heavily infected groups at the fifth and sixth week. The alpha-globulin and beta-globulin were not significant in the lightly infected groups(Group A & B), but they decreased after seventh week in the heavily infected groups. The gamma-globulin and &ggr;/A ratio of the heavily infected groups were significantly increased at fifth to seventh week. Statistically the calculation of entropy was applied to the data obtained in all groups. In the lightly infected groups, the entropy was included almost in the normal ranges, however in the heavily infected groups it was excluded from the normal range during the first to eighth week after infection.