Mathematical models such as the negative binomial, Poisson and Polya-Eggenberger distributions were applied to the observed data of the number of metacercariae of Paragonimus iloktsuenensis in crab hosts, Sesarma dehaani which were collected in Hadong, South Kyong-sang Do, Korea. From the above analysis, it was found that the pattern of density of metacercariae of this lungfluke among the crab hosts was well fitted to the negative binomial distribution, rather than to the Poisson or Polya-Eggenberger distribution.
parasitology-helminth-trematode ; Paragonimus iloktsuenensis ; epidemiology ; mathematics ; metacercaria ; crab ; Sesarma dehaani

A study on the infection status of intermediate hosts of Paragonimus, snail and crab, was conducted on Che Ju Island for four years to understand ecology of Paragonimus in the area and to evalute the control program by mass chemotherapy The infection rate of the first intermediate host of Paragonimus, snail, showed higher rate in the area where human association was more frequent and had higher human infection rate compared with the area with lower human infection and less contact by people. Larger snails were infected more frequently than smaller ones. After the mass treatment on human population, the infection rate of snail dropped markedly in four years. The infection rate and the intensity of infection of crabs were influenced by many factors:by frequency of human association, by prevalence of paragonimiasis in the population and volume of water flow, dilution effect. The distribution of metacercariae in infected crabs varied by body sites; the most frequently in gill, next in legs, internal organs and thoracic muscle in order. If crabs were examined for existence of metacercariae only gills, about 6% of infected crabs of may be missed as negative. The infection status of the crabs was not different by distance from the actual site of pollution. Also seasonal fluctuation of crab infection was not remakable. The crab infection by size showed time sequence of exposure; smaller crabs had lower infection rate and metacercaria density reaching to the maximum by 3 cm of size. As shown in the snail infection, the crab infection remarkably decreased after the control measure of human paragonimiasis, mass chemotherapy, in four years.
parasitology-helminth-trematoda ; paragonimiasis ; Paragonimus westermani ; metacercaria ; epidemiology ; snail ; crab ; host ; chemotherapy

Metacercariae of a kind of Levinseniella species were found from a brackish water crabs, Macrophthalmus japonicus de Haan, in the brackish area of Hyungsan river of Kyungpook province. Habitats were the epigastric and progastric regions of Macrophthalmus japonicus. One hundred and seventy five crabs out of 178 examined (98.3 per cent) were infested with metacercariae of Levinseniella species. The infested number of metacercariae in each crabs was average 100 ea. The excystation of metacercaria has not developed in vitro (both saline and tyrode's solution). Many eggs were observed in the metacercariae maintained for 24 or 48 hours in the water-bath. No differences were observed between semi-adult fluke from rat host and those maintained for 24 or 48 hours in vitro.
parasitology-helminth-trematode ; Levinseniella ; Macrophthalmus japonicus ; crab ; epidemiology ; tyrode's solution ; saline

An ecologic study on Paragonimus in Malaysia was attempted from May to September 1967. Seven streams located in various directions and distances from Kuala Lumpur were surveyed for the study of intermediate hosts, snail and crab. One Malayan village and one aborigine village where infected crabs were found, and two tuberculosis hospitals in K.L. were surveyed for the study of human population. Intradermal tests along with sputum or stool examination to detect human infection by Paragonimus were employed. Wild animals, only a few, were shot in the vicinity of the aborigine village and several domestic cats from the Malayan village were bought. These animals were autopsied and examined for adult Paragonimus. Among five species of crab collected from the study areas, only two species, Potamon jahorenes and Parathelphusa maculata were found to be infected with Paragonimus. P. maculata seemed to be better crab host for the Paragonimus because this species had higher infection rate and metacercarial density than the other in the very same area. Three out of seven streams had infected crabs and the infection rate as well as the infection intensity varied from one stream to another. Only avilable snail in the streams was identified as Brotia costula. The infection rate of the snail was very low, six snails out of 11,898, which is about the same rate reported from other countries. Infected snail, however, had thousands of rediae uncountable containing about twelve microcercocercariae in each redia, sufficient enough to maintain the life cycle of the parasite even with only a few infected snail, the amplifier. This is the first confirmed report on the snail host of Paragonimus from Malaysia where the existence of Paragonimus had been reported in 1923. The first trial to study human population by means of intradermal test, sputum and/or stool examinations in Malaysia showed no evidence of human infection of Paragonimus. The number of animals, wild and domestic, examined for natural infection was too small to draw any statement. These examined animals were all negative for adult Paragonimus. Even though more extensive studies on wild animals and human population may be necessary for the definite conclusion, the facts that infected crabs from jungle stream where human contacts are extreamely rare, and also highly infected crabs from the area where none of humans or domestic animals were infected, strongly suggest the life cycle of Paragonimus in this area may be maintained by wild animal hosts rather than by human host. The morphology of all stages of the parasite, the pattern of penetrating glands, flame cells and excretroy bladder of cercaria, lancet shaped single cuticular spines and 6 branched ovary of adult worm obtained from experimentally infected cat, and the shape of egg including all measurements agree well with the characteristics of Paragonimus westermani.
parasitology-helminth-trematoda ; Paragonimus westermani ; epidemiology-paragonimiasis ; crab ; Potamon jahorenes ; Parathelphusa maculata ; cat