BALB/c mice were used and divided into 2 experimental groups ; group 1, infected with a single dose of 50 Clonorchis matacercariae and group 2, challenged with 50 metacercariae at the 4th week after primary infection with the same dose of metacercariae. Normal mice were served as control. Three mice in each group were examined weekly for 10 weeks. Mice in groups 1 and 2 were sacrifficed. Liver including gall bladder and common bile duct was group were intraperitoneally injected with ethanol and fixed. The liver including common bile and sectioned serially and stained with toluidine blue for examination of appearance degree of mast cells. The medenterium was used for examination of appearance degree of mast cells and percentage of degranulating cells.

The results obtained in this study are summarised as following:

1) Average number of worm recovered was 13.1 in group 1 and 15.7 in group 2, respectively, throughout the examination. Mean number by week after reinvection in group 2 revealed a slight increase, ranging from 3.0 to 9.0, comparing with those in group 1.

2) In control mast cells were found in the mesenterium, but not in the bile duct, small intestine and lymphnodes. No mast cells were found in the small intestine in groups 1 and 2. In group 1 nast cells showed a moderate appearance degree at the 3rd week and persisted for 2-4 weeks in the bile dust, mesenterium and lymphnodes. Group 2 shoeed a moderate or marked degree ehich persisted for longer period after reinfection in the tissues.

3) Average percentage of degranulating cells in the mesenterium was 9.1% in control and 26.3% in froup 1, respectivley, throughout the examination and 51.7% during 6 weeks after reinfection in group 2. The peak was 36.7% at the 3rd week after primary infection in groups 1 and 2. In group 2, the percentage of degranulating cells increased promptly and markedly to 77.3% at the 1st week after reinfection.

4) Chronological of appearance degree of mast cells and percentage of degranulating cells in the tissues, particularly in the bile duct showed an obvious tendency to parallel to chronological change of number of worm recovered in the liver.

From the adove results, it is strongly suggested that mast cells in mice infected with Clonorchis sinensis are deeply implicated in expulsion of worms in bile dust.

Wistar rats were used and divided into 3 groups ; group I treated with 0.03% 3'MeDAB alone far 12 weeks, group II given 50 Clonorchis metacercariae alone and group III given 50 metacercariae at the beginning of the treatment with 0.03% 3'MeDAB for 12 weeks. Three rats from each group were examined at 4 week interval up to 40 weeks. For histopathological examination hematoxylin-eosin stain was applied and for ultrastructoral examination electron microscope was used.

In light microscopic examination, nuclear enlargement and hyperchromasia, and nucleolar enlargement were noted in all groups. In group II cell cord disarray, focal necrosis and inflammatory cell infiltration were observed in the later stage. Beside those findings, in group III pseudolobular formation, and cirrhotic changes were demonstrated, and findings of well differentiated hepatocellular carcinoma composed of hyperchromatic and dendritic hepatocytes were evidenced in a case for the first time at the 36th week, then appeared in 2 cases at the 40th week.

In electron microscopic examination nuclear and nucleolar enlargement together with proliferation of rough endoplasmic reticulum and mitochondria were common findings, mild in group I, moderate in group II and marked in group III, in general. With the lapse of time, groupI demonstrated some additional pictures such as clumps of nucleolar chromatin, double nuclei,multiple nucleoli, electron dense granules and nucleolar margination, and group III revealed much more outstanding features such as prominent nucleolar modification, cytoplasmic pseudoinclusion in nucleus, increased free ribosomes and seperation or focal interruption of outer nuclear membrane.

A study on white blood cells(WBC) in BALB/c mice infected with Toxocara canis larvae was carried out. Mice were divided into 4 groups ; group I and group II was given a single dose of 30 and 100 infective eggs, respectively,and group III and group IV was given 100 eggs weekly for 2 weeks and 50 egg for 4 weeks from I week after an inital administration of 30 eggs. respectively. Total WBC and differential count of WBC were examined at 2 week intervals up to the 20th week.

An immediate leucocytosis took place; slight in group I, mild in group II, moderate in group III and marked in group IV.

In differential count, neutrophils in group I and group II reached the lowest level in the 2nd week, then returned to within normal limits, while in group III and gruop IV showed a rise, respectively. Eosinophils in group I and group II respectively reached a maximum peak in the 2nd week and in group III and group IV respectively showed a quiker and more intense rise in the earlier stage, and decreased rapidly for the next several weeks, then fell gradually. Lymphocytes in group I decreased gradually up to the 6th week, then returned to within normal limits, but in groups II, III and IV showed a more or less rapid decrease in the earlier stage and persisted up to the end of observation without remarkable variation, Monocytes in groups I and II were within normal limits, and in groups III and IV showed some monocytoses. No alterations were noted in the basophile count.

The present study was performed to reveal out infection rate. worm recovery rate and individual worm burden in mice rats, rabbits and goats experimentally infected with metacercariae of Fasciola hepatica for establishment of animal model as experimental host of the fluke. Metacercariae were obtained from experimentally infected snails. Lymmaea Pervia.

The results obtained are summarised as follows ;

1) Infection rate was 100% in mice, rabbits and goats. respectively, and 73.3% in rats.

2) Days(mean) that eggs were found in the faeces for the first time after infection were 37~46 days(4l days) in mice. 39~49 days(44 days) in rats. 49~63 days(56 days) in rabbits and 68~88 days(78 days) in goats. respectively. The flukes mature more quickly in smaller hosts.

3) Worm recovery rate and mean of individual worm burden were 27.7% and 1.7 in mice. 10.7% and 1.1 in rats. 36.0% and 10.8 in rabbits and 42.7% and 21.3 in goats. respectively. Goats are regarded as favorable experimental hosts of the fluke.

The present study was carried out to obtain more information clarification of the susceptibility of the snails, Lymnaea pervia and L. auricularia to the common liver flukes, Fasciola hepatica and F. gigantica. The snails were collected from paddy field and irrigation route in a rural area located along the Han-gang riverside. Cercariae naturally shed from the snails were examined for identification for Fasciola spp. On the other hand, L. pervia and L. auricularia were artificially bred and the offsprings were divided into 3 groups according to day of age; baby snail group(5-7 days of age), young group(15-17) and adult group(more than 60), respectively, and used for infection of miracidia of F. hepatica and F. gigantica. The liver flukes were collected from Korea cattle and morphologically classified for the experiment. Eggs of F. hepatica and F. gigantica were cultured in the laboratory. After hatching, miracidia were used to infect the snails.

The results obtained in the present study were summarised as follows ;

1) Cercariae were naturally shed from both species of snails and cercariae of Fasciola spp. were found from 3(1.2%) among 250 individuals of L. pervia, but not from 200 individuals of L. auricularia.

2) Among 376 worms of Fasciola spp., 23(6.1%) were F. hepatica, 144(38.3%) were F. gigantica and 209(55.6%) were intermediate form, respectively.

3) Infection rates in the baby, young and adult snail group of L. pervia treated with F. hepatica miracidia were revealed as 57.6%, 53.1% and 47.9%, respectively, and with F. gigantica were 100.0%, 95.6% and 86.4%, respectively. The differences of infection rates between the corresponding groups of the former and the latter were highly significant(p<0.005). However. infection rates in the baby and young groups of F. hepatica- or F. gigantica-treated L. auricularia were very low, and no infection was established in the adult groups.

From the results. it is evidenced that L. pervia is the most suitable intermediate host for F. gigantica and F. hepatica in Korea.

The effects of carcinogens, 3'-methyl-4-dimethylaminoazobenzene(3'-MeDAB) and aflatoxin B₁ on ultrastructural changes of biliary epithelial cells in the rats experimentally infected with Clonorchis sinensis were investigated using male rats of the Sprague-Dowley strain. The animals were divided into 5 groups : group I, given 50 Clonorchis metacercariae alone ; group II-a, treated with 0.03% 3'-MeDAB alone for 12 weeks; group II-b, treated with 1.0ppm aflatoxin B₁ alone for 12weeks : group III-a, given 50 metacercariae at the beginning of the 12 weeks treatment with 3'-MeDAB and group III-b, treated with 50 metacercariae plus 1.0ppm aflatoxin B₁. Since the 4th week of experiment, ultrastructures of epithelial cells were observed, using transmission electron microscope. In group I, some elaborate interwoven folds of lateral cytoplasm forming labyrinths of interconnected intercellular space, variety in nuclear shape and marked proliferation and swelling of rough endoplasmic reticulum were characteristic. In groups II-a and II-b, remarkable enlargement of nuclear size, increase of chromatin granules along the inner membrane of nucleus and nucleolar margination were prominent. On the other hand, group III-a or group III-b revealed mostly combined findings of those shown in Clonorchis-infected rats and carcinogen-treated ones. Furthermore, the presence of liver fluke and carcinogen led to neoplastic change. In general, treatment with 1.0ppm aflatoxin B₁ alone(group II-b) or 1.0ppm aflatoxin B₁ plus Clonorchis metacercariae(group III-b) resulted in much earlier onset of alterations than that with 0.03% 3'-MeDAB alone(group II-a) or plus metacercariae(group III-a) throughout the observation. Despite differences in time of onset of alterations, they appeared to be essentially of the same order in cases of groups II-a and II-b, or groups III-a and III-b, respectively. In conclusion, it was clearly evidenced that Clonorchis infection plays an important role as a promotor in cholangiocarcinogenesis in the rats treated with 3'-MeDAB or aflatoxin B₁.

Recently, the present authors obtained 6 worms (4 females and 2 males) from both eyes of a farmer aged 23. Worms were fixed in 10% formalin, examined, and measured. All of worms were identified as Thelazia callipaeda Railliet and Henry, 1910. The findings of parasitological studies on 21 specimens (12 females and 9 males) removed from 12 cases of human thelaziasis already described in Korea were reviewed together with our findings. And percentages of lengths of main structures to the body length of each worm were also calculated for comparison. Female and male specimeus measured 14.31 and 10.93mm in length, 0.42(2.9%) and 0.34mm(2.8%) in diameter, 0.03(0.2%) in length of buccal cavity, 0.70(5.1%) and 0.56mm(5.2%) in distance from anterior end to esophago-intestinal junction, and 0.08(0.5%) and 0.05mm(0.5%) in length from posterior end to anus or cloaca in average, respectively. Vaginal openings in all of female were located about 0.2mm anteriorly to esophago-intestinal junctions. Minimum and maximum in male worms, respectively. In our 4 female specimens only a pair of processes at terminal of the tail were demonstrated, while in 2 males 8 pairs of precloacal and 3 pairs of postcloacal papillae were noted. Some wrinkle-like structures were observed on ventral and dorsal surfaces in posterior portion of a male specimen.

In Korea, paragonimiasis is one of the most important endemic parasitic diseases with significant clinical relvance. Since 1917 when Kobayashi has reported a high infection rate(88.0%) of paragonimus metacercariae among crayfish, an important intermediate host, Kanghwa-gun has been known to be a hyperendemic region of paragonimiasis. The present authors carried out an epidemiologic studies to obtain some current informations on the change in epidemiologic aspects of paragonimiasis in Giljeong-ri, Yangdo-myun, Kanghwa-gun, the most hyperendemic region. The infection status of Paragonimus metacercariae in crayfish have been examined. And a total of 392 students of Kangnam Middle School was examined by the intradermal test with Paragonimus antigen. In order to detect Paragonumus egg from the positive reactors, the fecal and sputum examinations were performed. As shown in Tables 1 and 2, there are marked reducing tendencies in the infection rate in crayfish and in the average number of metacercariae per crayfixh examined; 66.2% and 17.2 in 1981, 59.6% and 8.4 in 1984 and 20.0% and 0.6% in 1987, respectively. According to Table 3, 7.1% of the students showed positive reaction to Paragonimus autigeu with the sexual distribution of 8.0% in male and 6.0% in female. However, no Paragonimus eggs were found from the positive reactors by the fecal and sputum examinations.

Citations

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• Recent Incidence of Paragonimus westermani Metacercariae in Freshwater Crayfish, Cambaroides similis, from Two Enzootic Sites in Jeollanam-do, Korea
  Jin-Ho Song, Fuhong Dai, Xuelian Bai, Tae-Im Kim, Hyun-Jong Yang, Tong-Soo Kim, Shin-Hyung Cho, Sung-Jong Hong
  The Korean Journal of Parasitology.2017; 55(3): 347.     CrossRef
• Paragonimus and paragonimiasis in Korea
  D W Choi
  The Korean Journal of Parasitology.1990; 28(Suppl): 79.     CrossRef

Eleven percent of 128 soil samples examined in Seoul area for Toxocara canis eggs were positive. In experimental observation, 34 larvae were collected from 10 mice which have been infected with total 110 infective stage eggs obtained from soil samples and cultured in the laboratory room. Another group of mice was infected with larvae from mice and examined for reinfectivity test, and some larvae were detected in the liver tissue on the 2nd day after infection. By hisotological examination, an eosinophilic abscess was observed in the center of a typical granuloma in the liver on the 21st day after infection. It suggests that the larvae transmitted from another paratenic host is more pathogenic

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• Tests on the centrifugal flotation technique and its use in estimating the prevalence ofToxocarain soil samples from urban and suburban areas of Malaysia
  A.G. Loh, D.A. Israf
  Journal of Helminthology.1998; 72(1): 39.     CrossRef