Study on the effects of several pesticides to the life cycle of paragonimus westermani
[영문]The lung fluke infestation(Paragonimiasis) is one of the most important endemic diseases in the mountainous areas of Korea. In the last several decades, a lot of surveys have been carried out concerned with paragonimiasis from on epidemiological viewpoint(Kobayashi 1926, Hunter et al. 1949, Walton and Chu 1959, Seo 1960, Kang et al. 1964 a, b, Kim and Yang 1964, Yun 1965, Soh 1966, Ahn et al. 1966, Chang 1967, Kim et al. 1967). Semisulcospira libertina the first intermediate host of Paragonimus westermani, is widely distributed in mountain streams of Korea(Mianaga, 1938), and the second intermediate host Cambaroides similis inhabits almost the same region. Eriocheir sinensis and Sesarma dehaani are also popularly known the second intermediate hosts, and are widely distributed eve in plain areas(Soh 1962, Kang et al. 1964 c, Yun 1965, Chu and Lee 1966). Recently Soh et al.(1964) added one more second intermdiate host: Palaemon nipponensis from Koheung -Goon, Chollanam-Do.
The main means of Paragonimus infestation have been known by of ingestion of crayfish juice in a raw condition and by unproperly cooked crabs. However, there has been no report concerning the biological control of Paragonimus infestation in Korea. Only Lee and Kim(1963), and Kim(1965) tried laboratory experiments for the
destruction of Parafossarulus manchouricus, the 1st intermediate host of Clonorchis sinensis, and cercariae of C. sinensis with several pesticides. the most reasonable control measure for Paragonimus infestation is considered to the life cycle of
Paragonimus westermani by eliminating the eggs, metacercariae and the 1st 2nd intermediate hosts. However, only several informations concerning the resistance of metacercariae of P. westermani in several physico-chemical agents have been
reported up to date(Tsu-Da 1959, Lee et al. 1965, Kim 1967). since 1967, the author has been carried out an epidemiological study of Paragonimus infestation in the northeastern coastal regions(Yangyang and Sokcho).
The purpose of this study is to evaluate the effective use of some pesticides for the control and prevention of Paragonimus infestation by interrupting the life cycle of the parasites.
Materials and Methods
A. Epidemiological survey.
ⅰ) Intradermal test for Paragonimus infestation was done among residents and school children at Yang-yang -Goon and Sokcho city, Kangwon-Do, Korea utilizing paragonimus antigen(Fig.1). The antigen was prepared with vernonal buffered saline solution at N.I.H., Korea.
ⅱ) Crayfish(Cambaroides similis) were caught from three streams in the areas where the highest positive rates by paragonimus skin test were observed. All crayfish were dissected and carefully examined under dissecting microscope to detect the metacercaris.
B. Experiment with several pesticides.
ⅰ) Pesticides: Sodium pentachlorophenate(NaPCP), Formalin, Copper sulfate(CuSO^^4 ), Malathion and Calcium cyanate(CaCN^^2 ). The Concentration of each test solution will be described in the chapter of respective results.
ⅱ) Eggs of Paragonimus were collected from the feces of paragonimus infected dogs in the laboratory. They were put in experimental solutions of pesticides for 6, 12, 24, 36, 48 and 72 hours respectively, according to the designed plan. The eggs in the test solution were washed with distilled water 5 to 12 times and were placed in the incubator(temp. at 27±2℃) for 3 week to observed the development and viability of the miracidia inside the eggs.
ⅲ) Metacercariae of Paragonimus were collected from infected crayfish. Ten metacerariae were used in each experimental group. They were put in a test solution for 1, 3 and 5 hours respectively and washed with 0.85% saline solution 5 times,
then examined the morphology and mibility.
ⅳ) Snails(Semisulcospira libertina) were collected from streams of Beopwon-Ri, Chunhyen-Myeon, Pajoo-Goon. The experiment was carried out at the same place keeping natural conditions. Ten snails were put in each test solution. Three, 6, 12, 24, 48, and 72 hours later the snails were transferred from the petri-dishes to stream water for several hours and observed the survivability.
ⅴ) Crayfish were caught from the same place where the snails were collected. Three crayfish were used in each experimental group. They were put into test solution for 3, 6, 12, 24 and 48 hours respectively and transferred from the dishes to stream for several minutes to check the viability.
1. Positive rate of intradermal test.
A total of 3,617 people and school children both(male 1,756, female 1,861) were tested in Yangyang-Goon and Sokcho city by using V.B.S. antigen. Positive rates of the intradermal reaction were 22.4%(810), of which 26.9% were in male and 12.6% in female. The school children showed higher positive rate(25.4%) than
residents(14.4%). A difference of the positive rate was appeared according to the age group, and the highest positive rate was observed in the age group of 21-30(31.6%). Geographically, the highest positive rate was seen at Hyenbuk-Myeon(58.9%) and the lowest was at Yongyong-Myeon(11.6%, Table 1-3).
2. Metacercaria in crayfish.
A total of 2,270 crayfish were caught from three streams; Hyenbuk-Eoseong, Kanghyen-Kangseon and Hyennam-Haesong. The metacercariae were found only from Hyenbuk-Eoseong Stream in 506(54.6%) crayfish out of 929(Table 4).
3. Experiments with several pesticides.
ⅰ) Ovicidal effects: The effective concentrations of pesticides were; 0.1 to 0.001 mg/ml with NaPCP, 0.5 to 0.005 mg/ml with formalin, 50.0 to 10.0 mg/ml with copper sulfate, 10.0 to 0.5 mg/ml with malathion and 20.0 to 1.0 mg/ml calcium cyanate.
All eggs were destroyed within 12 to 48 hours in 0.1 and in 0.01 mg/ml of NaPCP solutions. In formalin solution all the eggs were destroyed within 12 hours at 0.5 mg/ml, and within 36 hours at 0.1 mg/ml concentration. The effective ovicidal action of malathion was observed at the concentration of 10.1 mg/ml for 6 hours and of 2.5 mg/ml for 36 hours. The action of the calcium cyanate solution was observed 20.0 mg/ml for 6 hours and 5.0 mg/ml for 72 hours, respectively. However, less ovicidal effect was appeared in 50 mg/ml solution of copper sulfate even after 72
hours. The most effective pesticide for destruction of the eggs was NaPCP(Table 5 and Fig. 2).
ⅱ) Resistance of metacercaria: The effective concentrations of pesticides were; 1.0 to 0.5 mg/ml with NaPCP, 2.5 to 0.1 mg/ml with formalin, and copper sulfate in the same concentration as formalin, 10.0 to 0.5 mg/ml with malathion and 10.0 to 0.05 mg/ml with calcium cyanate.
In Na-PCP solution all the metacercariae were killed within 3 hours at the concentration of 0.25 mg/ml, and were killed within one to 5 hours at the concentrations of 2.5 and at 1.0 mg/ml of formalin solution respectively. In copper sulfate solution all the metacercariae were killed within one hour at the concentration of 2.5 mg/ml. In malathion solution, most of the metacercariae were killed within 1 to 5 hours at the concentrations of 10.0 and at 2.5 mg/ml, and in calcium cyanate solution, all metacercariae were killed within 1 to 5 hours at the concentrations of 10.0 and 1.0 mg/ml respectively. The most effective mortality of metacercariae was observed in the solution of NaPCP(Table 6 and Fig. 3).
ⅲ) Molluscidal effect: The effective concentrations of pesticides were; 1.0 to 0.01 mg/ml with NaPCP, 10.0 to 0.1 mg/ml with formalin, 10.0 to 0.05 mg/ml with copper sulfate, 10.0 to 0.5 mg/ml with malathion and 50.0 to 1.0 mg/ml with calcium cyanate.
The effective molluscidal action of NaPCP solution was observed at the concentrations of 1.0 mg/ml in 24 hours and of 0.1 mg/ml in 72 hours, and the action of the copper sulfate was observed 10.0 mg/ml in 3 hours and of 0.1 mg/ml in 48 hours respectively. In formalin solution all the snails(Semisulcospira libertina) were killed within 3 hours and 72 hours at the concentrations of 10.0 and at 1.0 mg/ml, within 24 hours and 72 hours at the concentrations of 10.0 and at 2.5 mg/ml of malathion solution ,and in calcium cyanate solution they were killed completely within 12 hours and 72 hours at 50.0 and at 5.0 mg/ml respectively. The potent agents in low concentration for molluscidal action were copper sulfate and NaPCP. The order of the other agents for molluscidal effect were formalin, malathion and calcium cyanate(Table 7 a, b and Fig. 4).
ⅳ) The destructive action to crayfish(Cambaroides similis): The effective concentration of pesticides were; 1.0 to 0.05 mg/ml with NaPCP, 10.0 to 1.25 mg/ml with formalin, 10.0 to 0.5 mg/ml with copper sulfate, 1.0 to 0.125 mg/ml with malathion and 10.0 to 1.25 mg/ml with calcium cyanate.
Al the crayfish were killed within 3 hours and 48 hours in 0.5 and in 0.05 mg/ml of NaPCP solutions respectively. In formalin solution they were killed within 3 hours and 48 hours at the concentrations of 5.0 and 2.5 mg/ml. respectively. The effective action of copper sulfate solution was observed at the concentration of 10.0 mg/ml for 6 hours and 1.25 mg/ml for 48 hors, and the action of malathion was observed at the concentrations of 0.5 mg/ml for 12 hours and at 0.125 mg/ml for 24 hours. In the calcium cyanate solution all crayfish were killed within 6 hours and 12 hours at the concentrations of 10.0 mg/ml and 2.5 mg/ml respectively. The killing power of the pesticides to crayfish were NaPCP, formalin, calcium cyanate,
copper sulfate and malathion in the decreasing order(Table 8 and Fig. 5).
Epidemiological and experimental studies on the Paragonimus westermani infestation were done at the northeastern coastal regions of Korea from 1967 to 1969. The results are summarized at follows:
1. The positive rate of skin test on P. westermani infestation among the residents and school children in Yangyang-Goon Sokcho city was 22.4%(810 out of 3,617).
2. Crayfish caught from the highest endemic area showed the highest positive rate of metacercarial infestation.
3. NaPCP shoed the strongest ovicidal action and killing effect to metacercaria and crayfish.
4. Both copper sulfate and NaPCP shoed better molluscidal effects than the other compounds tested. The above results suggest that the pesticides used for agricultural purposes may contribute to the control of Paragonimus westermani infestation by breaking the regular life cycle.