A series of experiments were carried out to obtain some informations on host resistance in mice infected with Toxocara canis. Approximately 210 male BLAB/c mice were used and given various doses of infective eggs. For the purpose. the mean percentages of eosinophils were counted. and recovery rates of larvae from the liver, lung, brain, carcass and other tissues were examined separately at various intervals according to the experimental schedules.

Experiment I: Mice in groups I-1 and I-2 were given a single dose of 30 eggs and 100 eggs, respectively. Eosinophils and larvae were examined daily for 6 days and weekly for 21 weeks. Experiment II : Mice in groups II-1 and II-2 were given 100 eggs weekly for 2 weeks and 50 eggs for 4 weeks from 1 week after an initial administration of 30 eggs. Eosinophils were counted weekly and larvae were examined at 3 weeks after the final administration, respectively. Experiment III : Mice in 6 groups from III-1 to III-6 were given a challenge dose of 100 eggs at 1. 2. 3. 5. 7, and 9 weeks after an initial administration of 30 eggs. Eosinophils were counted weekly for 3 weeks and larvae were examined at the 3rd week after the challenge infection, respectively.

The means of eosinophils in groups I-1 nd I-2 respectively were 6.4% and 8.2% at 6 hr. and reached a maximum peak of 16.8% and 21.6% at 2 weeks, and the means decreased rapidly for the next 6 weeks. then fell gradually. The superinfection and the challenge infection in Experments II and III caused quicker and more intense rises of the eosinophils.

The recovery rates of larvae in groups I-1 and I-2 respectively showed 3 peaks at 48 hr. 1 week and 3 weeks, then decreased gradually. At 48 hr. 88.2% and 93.5% of the larvae recovered and 38.0% and 40.8% of the total larvae given were found in the liver, then decreased gradually until none was found at the end of the experiment. On the contrary. in the brain and carcass, the larvae accuulated repidly through the 1st week and the rates persisted up to the 8th week without remarkable variation. The recovery rates of larvae in total, and from the brain and carcass in groups of Experiments II and III decreased remarkably, whereas those from the liver increased significantly compared with groups I-1 and I-2 at the corresponding weeks of examination.

Transition patterns of the means of eosinophils in groups of Experiments I and II and those of total recovery rates of larvae in groups of Experiment I were essentially similar each other in rise and fall throughout the experiments.

From the overall results, it is strongly suggested that eosinophils do affect the development of resistance to invading Toxocara larvae, and the higher recovery rates of larvae in the liver indicates that the liver is the organ which may play a role of protection against infection with T. canis larvae by means of immunomechanism in mice.

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.

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

Citations to this article as recorded by  

• 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

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.