Since Senoo and Lincicome (1951) first have brought up for attention to the existence of malayan filariasis in Korea, several reports on the epidemiological investigations of the disease had already been made by many workers. However it is little known what kind of mosquitoes are involved as the major vectors in main endemic areas. In Cheju-Do, known as one of main endemic areas in Korea, Aedes togoi is most likely suspected as an important vector because of their abundant collections and vigorous biting attack to human. As a part of studies on filariasis in Korea, an essential preliminary is to determiine whether this mosquito, Aedes togoi collected in the above areas is receptive to the microfilariae of B. malayi. Therefore, the present paper is concerned chiefly with the development of B. malayi in A. togoi. It is also hoped that the studies on the larval morphology in the mosquito host and the structure of microfilariae will provide the base line data required for later investigation of the different vector hosts. The studies were summarized as follows: The measurements of the fixed points in percentage of the body length of microfilariae from the Giemsa stained thick films were made, and they showed that cephalic space was 8 percent,cephalic space length to width, 1.3:1, nerve ring, 21.2 percent, excretory pore, 30.8 percent, excretory cell, 36.5 percent, R1 cell, 66. 5 percent, anus 80.4 percent and body length 202 micrometer(l81-228 micrometer) maximun width 7.6 micrometer. A study on the development of microfilaria malayi in the mosquito, Aedes togoi was carried out at room temperature (24-30 C). Mosquitoes used in this experiment were reared from larvae collected from the tide water rock pool in the coastal areas of Cheju-Do and they were fed with a blood meal of carrier donors whose microfilaria densities were in the range from 0.5 to 0.7 per cmm of blood. All of the microfilariae ingested by mosquito exsheathed in stomach, penetrated into the body cavity and then migrated into the thoracic muscles of the mosquitoes within 10 hours, after two moults in the mosquito host, the length of the developing 3rd stage larvae reached in size of 1.3-1.7 mm x 23-32 microns with anal ratio, 2.6 to 3.6. The first appearance of 3rd stage larvae in the mosquito host in this experiment was in 8th day after infection. The larvae were observed in the various cavities of mosquito, such as head, thoracic cavity, abdomen, halters, eye and legs. During the larval development in larval development in the host, the shortening of body length was first observed and then elnongation was followed until becoming 3rd stage larvae. Aedes togoi was proved to be the most suitable host for this species of microfilaria malayi in the above endemic areas.

The occurrence of Sarles' phenomenon (Cerkarien Hullen Reaktion) are proved in the excysted metacercariae of Clonorchis sinensis which were incubated in the sera from rabbits given a varying number of metacercariae of C. sinensis per orally. The precipitates were formed around the oral sucker and excretory bladder of the excysted larvae. Sarles' phenomenon began to be positive from the 2nd to 3rd week after infection. In the excysted larvae of C. sinensis precipitates were not produced in the sera of rabbits infected with Metagonimus yokogawai and Capillaria hepatica. The number of eggs in the feces (E.P.G.), intradermal reaction, the course of infection and Sarles' phenomenon was studied in 6 clonorchiasis patients. Sarles' phenomenon appeared in the sera of some clonorchiasis patients. However, it assumed that this phenomenon correlated with the degree and the course of infection of clonorchiasis.

The eggs and rhabditoid larvae of canine hookworm were irradiated with ultraviolet rays for one hour at a distance of 10, 20, 30, and 40 cm. The infective stage larvae of the same parasites were irradiated for l, 3, 5 and 14 hours from the same distances. The infective larvae were also exposed under direct sunlight for l, 2, 3 and 4 hours. Parasites: Ancylostoma caninum was used. Eggs were collected in vitro from female adult worms. The worms were kept at 37 C in petri-dish filled with Kreb's Ringer solution. There was an average of two cell stages, and they were used as early as possible before the morula stage. Rhabditoid larvae were obtained by culture of the above eggs for twenty-four hours in 25 C incubator. The larvae reached the infective stage in seven days culture at the same condition. Irradiation of Ultraviolet Ray: Kingston ultraviolet light (100 volt, 10 watt, 50 cycles, 0.230 ampere) was used. The potential U.V.R. power was 1.8 watts. The distances between the material and the light were 10, 20, 30 and 40 cm at a temperature of 25 C in each case. The samples were smeared on the tile in order to keep them in saturated moisture. Fully wetted ten ply gauze was laid underneath the tile. The tile was surrounded by 2x5 cm rectangular piece of glass in order to prevent the spread of the larvae to the outside. All of the samples received irradiation for one hour and were cultured for a period of seven days. The hatching of the egg and the development of the larvae were observed. For the purpose of the study, the infectivity and pathogenicity of the irradiated samples, were inoculated into mice orally. The lungs, livers and carcass were examined three days after the infection. A routine pathological examination of the organs was also carried out. In order to study the eggs productivity, the larvae were given to the proper host, dog. The eggs in the feces were examined from three to 6 weeks after infection, both quantitatively and qualitatively. As a supplementary experiment, the infective larvae of canine hookworm were exposed four hours under direct sunlight (September 25), and the infectivity and pathogenicity of the host were examined. Hatching, development and infectivity of irradiated eggs: Hatchability of the irradiated group for one hour according to the distance from the light to the sample were 48.0 percent at 10 cm, 60.3 percent at 20 cm, 85.2 percent at 30 cm and 88. 2 percent at 40 cm respectively. None of them developed to the infective stage. They remained rhabitoid for several days and were destroyed. None was found alive in the host. 93.0 percent of the control group hatched and developed to the infective stage. Development and infectivity of irradiated rhabditoid larvae: None of the irradiated group reached the infective stage. Under irradiation they coiled and died soon after straightening out again. Only the group irradiated at the distance of 40cm survived for six days. They finally granulated. There was no manifestion of irradiated larvae alive in the host tissue. Life span, infectivity, pathogenicity and egg-productivity of the irradiated infectve stage larvae: All were destroyed in the group of fourteen hours irradiation at 40 cm distance. Thirteen precent survived in the five hours irradiation group at the same distance. The survivability of larvae was reduced by the period of irradiation and at the shortest distance. The infectivity to mice was only 0.8 percent at 30 cm, and 8.2 percent at 40 cm in the three hour irradiation group. The recovery of the infected larvae from the host tissues was reduced as the irradiation period was increased and the distance shortened. The pathogenicity was paralleled with the vitality of the irradiated larvae. From the groups of one hour irradiation and ten cm distance, three hour irradiation and ten to thirty cm distance, the egg-productivity was all negative. But as the irradiation period decreased and the distance lengthened the egg-productivity tended closer to normal. The infective stage larvae which were exposed to direct sunlight were destroyed within three hours, but survived 81 percent in the one hour exposure group and 20 percent in the two hour exposure group. The summary of the results is as follows: The hatching of eggs was reduced to half for one hour irradiation at the ten cm distance. Even hatched larvae did not develop to infective stage. Infectivity was inhibited by the irradiation to at the ten cm distance for one hour. About ten percent of the irradiated infective stage larvae were recovered from the infected animal among the group of 40 cm distance for one hour. The egg-productivity became lower in the group of one hour irradiation at 40 cm distance. The pathogenicity of the irradiated group was mild compared to the control group. The direct sunlight destroyed the infective stage larvae within three hours. In general, the ultraviolet ray showed the inhibitory action in the hatching, development, pathogenicity and egg-productivity of the hookworm. The grade was paralleled with the period of irradiation and reversed to the distance between the light and samples.

In order to confirm whether the migrating larvae of parasites could carry pathogenic organisms into liver and cause hepatitis, a series of experiments has been carried out. Clonorchis sinensis: Recovery rate of larvae in the abdominal cavity of rabbits: One to seven days after the administration adolescariae were recovered from the abdominal cavity in less than l percent of the total number of metacercariae given. Generally, 1-6 larvae were found from each animal which was given 900-1,000 metacercariae, though many larvae were already found in the common bile ducts or remained still in intestine. Fate of Clonorchis sinensis in abdominal cavity: The young or mature worms which were introduced directly into the abdominal cavity were examined l5, 32, 40 and 42 days after the inoculation. Several larvae were found on the surface of liver in four animals. All the worms on the surface of the liver were dead and the biopsied liver tissues on the area where the worms were attached showed no pathological changes. Two of them were between bile duct and liver tissue but pus cell infiltration surrounding them was observed. In every case, pus cell infiltration was found in the peripheral portion of the liver and pus nodules on the surface of intestine and mesentery. The nodule in the intestinal wall contained the eggs of Clonorchis sinensis. Two worms in the abdominal cavity were still alive. From the above results it is suggested that the larvae of Clonorchis sinensis were capable of penetrating the intestinal wall and reaching the organs in the abdominal cavity and surviving for l5-42 days, but they were unable to penetrate the organs. No bacterial flora appeared from the lesion by culture method. Fate of Clonorchis sinensis which was inoculated into the peripheral region of liver: Small abscess was observed at the same area. Microscopically, the area became edematous and the vessels in the peripheral region were dilated. The parasites became necrotic and amorphous. Pathologically the lesions appeared as eosinophilic masses and neutrophile leukocytes were infiltrated surrounding the masses. In some cases, the dead worms were found apart from the original place of inoculation but no leukocyte infiltration was found. There was linear infiltration between the original site and the portion where the dead worm was found. The distance from the capsule varied from 0 to 4 mm. Sometimes, the eggs of Clonorchis sinensis were also found. In all cases, there were no living worms in liver tissues and hepatic ducts. In all case,. the bacteriological examination was negative. Do clonorchis sinensis transfer the microorganism? Five adult worms of clonorchis sinensis were incubated in the saline solution containing Staphylococcus aureus. The intestinal contents of these worms were cultured in the Nutient-agar plate and examined by Methylene Blue and Gram's stain. The area of liver tissue where the Clonorchis sinensis were inoculated showed no inflammatory changes after the 3 days of inoculation but no living Staphylococcus aureus was found in the culture media with which the pieces of liver tissues were smeared. Hookworm: Cutaneous infection: Four to eight days after the cutaneous infection of Ancylostoma caninum, the mice were sacrificed. Grossly, there was no abnormal finding in liver. The pieces of liver tissues were smeared on the Nutrient-agar plate, and cocci were found in four out of six examined. The microorganism were confirmed as the same species of Diplococcus pneumoniae which were grown in the hookworm culture media. Oral infection: 1,000 filariform larvae of Ancylostoma caninum were given orally. 24 hours later, the mice were sacrificed and the pieces of liver tissue were smeared on the Nutrient-agar plate. After 50 hours at 36 C, the bacterial colonies were examined bacteriologically. Staphylococcus albus was found from two out of four samples. Grossly there was no abnormality on the surface of liver, but microscopically there were spots like microabscesses which were infiltrated by leukocytes. The larvae were also found from other portions of liver tissues and they were surrounded by yellow colored material. In another experiment, a combination of Ancylostoma duodenale and Staphylococcus aureus was fed to mice. The mice sacrificed five days after the oral administration of Ancylostoma duodenale cultivated in the media containing Staphylococcus aureus. The liver pieces were examined routinely. The larvae cultivated in normal tap water which contained no Staphylococcus aureus was used as control. In the experimental mouse, the cocci appeared in the liver. Pathologically, microabscesses infiltrated with neutrophile leukocytes were found, but there was no manifestation of inflammatory change due to Staphylococcus aureus. There was only mechanical trauma due to the larvae penetration. Haemorrhage appeared only where the larvae were found.