월남의 flea index와 살충제에 대한 벼룩의 저항력에 관한 조사 연구

Abstract

[한글]

Flea Index and Resistance Test of Adult Fleas to Insecticides in Vietnam

Choong-Hyun Hwang, M.D.

Department of Medical Science The Graduate School, Yonsei University

(Director: Professor Chin-Thaok Soh, M.D.)

The author was engaged in the plague control campaign as a leader of the Korean

Preventive Medicine Team dispatched to Region Ⅱ in Republic of Vietnam from 1968

to 1969,In the study, the author attempted to assess the current plague situation

by a flea-index survey and to determine the effectiveness of insecticides available

in the areas. A summary of this study is as follows:

Seven villages of five provinces in the region were selected for the study where

the plague was endemic. All the fleas on the trapped rodents were counted and

identified. The fleas: Xenopsylla cheopis kept in containers were identified by

host, locality and the phase of DDT dusting.

Each flea-strain was exposed to DDT and malathion testing paper for one hour,

then left under normal conditions for 24 hours. Additionally, exposure to DDT was

done for 24 hours. The foregoing procedures were repeated two or four times again.

The applied method was the standard test and techniques recommended by World Health

Organization.

The collection of the fleas on rodents in the Nha-Trang city was made for five

days every third week from January until December in 1968 for the flea index.

The rodents trapped from the Nah-Trang city throughout the year totalled 332 with

1,185 fleas. The total flea-index was 3.6 ranged from 7.9 in February to 0.9 in

November. The average flea-index in the dry season (February through August) was

5.2 which was higher than 2.0 in the rainy season. The specific flea-indices were

as fellows; the average flea-index on the Rattus norvegicus was 4.3 ranging from

12.0 in February to 1.1 in December. Sunus murinus was 2.6 ranged 6.0 in August to

0.2 in December, and R. exulans was 1.8 ranging 7.0 in July to none in both month

of October or December.

The fleas infestated on rodents in Nha-Trang were predominantly species of X.

cheopis.

The flea colonies established by Cheopis fleas collected from the trapped rodents

totalled ten. The four were from fleas collected before dusting, and the remainders

were from those collected after dusting. The Bangkok flea strain showed partial

resistance to DDT (control colony).

The fleas collected before dusting:

The flea strains of Binh-Dinh, Tuyen-Duc and Pleiku had no death in each

concentration, except Pleiku strain, 7% death at 4% DDT in three or four replicate

test in the one hour exposure. The Bangkok strain showed only 13% mortality rate at

4% 007 in three replicates in one hour teat.

In 24-hour exposure test, only the Pleiku strain showed 60% of the death rate at

4% concentration and the LC^^50 was 3.0% based on the data in above. The other two

strains showed less than 21% death rate at th? highest DDT concentration.

The Bangkok strain flea showed 33%, 70%, 87% and 87% at 0.5%, 1.0%, 2.0% and 4.0%

DDT, respectively in three replicates. The test exposing for one hour with 12.8%

malathion revealed 100% death rate in all the strains, except Pleiku strain 90%,

but none in the control group.

The fleas collected after ducting:

The flea-strains of seven colonies originated in the province of Binh-Dinh,

Khanh-Hoa, Pleiku and Phu-Yen survived in all the test cases and control group,

except one death from the Khanh-Hoa's at 2.0% DDT, and one (5%) death at 4.0%

concentration in Pleiku and Phu-Yen's.

In the 24-hour exposure, five strains of Binh-Dinh, Khanh-Hoa, and Phu-Yen skewed

less than65% of death rate at 4% concentration. Two of Pleiku strains which

originated in the rodent R.exuians and S. murinus showed 55% and 65% of mortality

at 4% DDT, respectively. Based on these data, the LC^^50 resulting is 3.2% and

3.8%, respectively.

Among the malathion exposed group for one hour, two strains of Khanh-Hoa revealed

100% death rate in 12.8%, but no death was observed in the control group of two

replicates, the LC^^50 of malathion was 6.0∼6.2% in one hour exposure group.

The results of the study are summarized as follows;

1. The total flea-index in the sampled area of Nha-Trang was 3.6, fluctuating by

month and season. The flea-index in dry season was appeared higher than that of the

rainy season.

2. All of the fleas in the selected areas were resistant to DDT, regardless the

horst and locality. The highest mortality at 4% DDT concentration was 65% in a

24-hour exposure in the Pleiku strain originated from S. murinus. The others were

less than 50% of mortality.

All of fleas in the tested areas were susceptible against malathion. The death

rate was 90∼100% at the highest concentration of 12.8% by one hour exposure.

[영문]

The author was engaged in the plague control campaign as a leader of the Korean Preventive Medicine Team dispatched to Region Ⅱ in Republic of Vietnam from 1968 to 1969,In the study, the author attempted to assess the current plague situation by a flea-index survey and to determine the effectiveness of insecticides available in the areas. A summary of this study is as follows:

Seven villages of five provinces in the region were selected for the study where the plague was endemic. All the fleas on the trapped rodents were counted and identified. The fleas: Xenopsylla cheopis kept in containers were identified by host, locality and the phase of DDT dusting.

Each flea-strain was exposed to DDT and malathion testing paper for one hour, then left under normal conditions for 24 hours. Additionally, exposure to DDT was done for 24 hours. The foregoing procedures were repeated two or four times again.

The applied method was the standard test and techniques recommended by World Health Organization.

The collection of the fleas on rodents in the Nha-Trang city was made for five days every third week from January until December in 1968 for the flea index.

The rodents trapped from the Nah-Trang city throughout the year totalled 332 with 1,185 fleas. The total flea-index was 3.6 ranged from 7.9 in February to 0.9 in November. The average flea-index in the dry season (February through August) was 5.2 which was higher than 2.0 in the rainy season. The specific flea-indices were as fellows; the average flea-index on the Rattus norvegicus was 4.3 ranging from 12.0 in February to 1.1 in December. Sunus murinus was 2.6 ranged 6.0 in August to 0.2 in December, and R. exulans was 1.8 ranging 7.0 in July to none in both month of October or December.

The fleas infestated on rodents in Nha-Trang were predominantly species of X. cheopis.

The flea colonies established by Cheopis fleas collected from the trapped rodents totalled ten. The four were from fleas collected before dusting, and the remainders were from those collected after dusting. The Bangkok flea strain showed partial

resistance to DDT (control colony).

The fleas collected before dusting:

The flea strains of Binh-Dinh, Tuyen-Duc and Pleiku had no death in each concentration, except Pleiku strain, 7% death at 4% DDT in three or four replicate test in the one hour exposure. The Bangkok strain showed only 13% mortality rate at 4% 007 in three replicates in one hour teat.

In 24-hour exposure test, only the Pleiku strain showed 60% of the death rate at 4% concentration and the LC^^50 was 3.0% based on the data in above. The other two strains showed less than 21% death rate at th? highest DDT concentration.

The Bangkok strain flea showed 33%, 70%, 87% and 87% at 0.5%, 1.0%, 2.0% and 4.0% DDT, respectively in three replicates. The test exposing for one hour with 12.8% malathion revealed 100% death rate in all the strains, except Pleiku strain 90%, but none in the control group.

The fleas collected after ducting:

The flea-strains of seven colonies originated in the province of Binh-Dinh, Khanh-Hoa, Pleiku and Phu-Yen survived in all the test cases and control group, except one death from the Khanh-Hoa's at 2.0% DDT, and one (5%) death at 4.0% concentration in Pleiku and Phu-Yen's.

In the 24-hour exposure, five strains of Binh-Dinh, Khanh-Hoa, and Phu-Yen skewed less than65% of death rate at 4% concentration. Two of Pleiku strains which originated in the rodent R.exuians and S. murinus showed 55% and 65% of mortality

at 4% DDT, respectively. Based on these data, the LC^^50 resulting is 3.2% and 3.8%, respectively.

Among the malathion exposed group for one hour, two strains of Khanh-Hoa revealed 100% death rate in 12.8%, but no death was observed in the control group of two replicates, the LC^^50 of malathion was 6.0∼6.2% in one hour exposure group.

The results of the study are summarized as follows;

1. The total flea-index in the sampled area of Nha-Trang was 3.6, fluctuating by month and season. The flea-index in dry season was appeared higher than that of the rainy season.

2. All of the fleas in the selected areas were resistant to DDT, regardless the horst and locality. The highest mortality at 4% DDT concentration was 65% in a 24-hour exposure in the Pleiku strain originated from S. murinus. The others were less than 50% of mortality.

All of fleas in the tested areas were susceptible against malathion. The death rate was 90∼100% at the highest concentration of 12.8% by one hour exposure.