Environmental studies regarding Paragonimiasis have been done in Sulak-Myun, Kapyung-Goon (I district) and Yongmoon-Myun, Yangpyung-Goon (II district), both of which are considered "active" endemic areas, and in Byukje-Myun, Koyang-Goon (III district) an "arrested" area.
1. Paragonimiasis is still active in the Uhmos River, Sulak-Myun, Kapyung-Goon, where 49% of crayfish contained Paragonimus metacecaria. Snails which are the first intermediate host of Paragonimus westermani were moderately present. In the Oonke River, Yongmoon-Myun, Yangpyung-Goon, crayfish which are the second intermediate host of Paragonimus westermani, were found in every area of the river, but snails were not found in any area of either branch of the river. They were caught in areas which are located below the junction. In the Daeja river, Bykje-Myun, Koyang-Goon, crayfish were found only in the upper stream of the river and snails were not caught in any area of the river.
2. The results described above are attributed to the fact that snails, which have minimal mobility and vitality, were complete1y obliterated by the long, unprecedented drought in 1965. In contrust, crayfish with great mobility and vitality survived. Thus without the snail, the life cycle of Paragonimus western1ani become incomplete, and the clinical disease disappeared.
3. Rainfall is very important in maintaining water flow in the river, a necessary factor for the life cycle of Paragonimus westermani. Therefore we have charted tile amount of rainfall in the Seoul and Choonchun areas in 1965, compared with the average of the past 30 years, in order to ascertain the degree of drought which influnced the Paragonimus westermani hosts and cohabitants.
4. Geographic conditions which are also very important in maintaining water flow in small rivers was investigated. The conclusion was drawn, that a long river has an advantage over a short during drought; a tortuous river provides a better opportunity for miracidia of Paragonimus westermani eggs to migrate to snails, and for Pargonimus cercaria to invade crayfish than a straight rapidly flowing river.
5. We must conclude that man may ingest Paragonimus metacercaria by drinking water from shallow wells and streams in areas endemic to paragonimiasis, when we note that one crayfish of four caught in shallow wells in Kapyung-Goon contained many Paragonimus metacercaria.
6. Other factors are the increase in traffic due to the expanding population in Korean farm areas, and the increase in the use of farm chemicals, which seep into the rivers and reduce the number of snails, crayfish and crabs available as potential hosts.
7. In recent years, the wild fauna in the mountains, one of the important terminal hosts of Paragonimus westermani, have been markedly reduced in number. This may have contributed to decreasing paragonimiasis as directly infective to man.
8. Health education on paragonimiasis, informing the people of the dangers of eating raw or inadequately cooked crayfish and crabs, or those soaked less than 10 days in soysauce, and drinking the water from shallow wells and streams, is demonstrated to have decreased the incidence of this disease.
9. Because of the preceding facts, paragonimiasis in Kyunggi-Prvince is being decreased.
|