Song Yu 宋　宇, Xiao Shuhua 肖树华, Wu Wei 吴　伟, Zhang Shaoji 张绍基, Xie Huiqun 谢慧群
Xu Xueping 许雪萍, Hu Xinyong 胡新勇, Cui Qing 崔　庆, Chen Minggang 陈名刚 and Zheng Jiang 郑　江

　　Objective　To study the preventive effect of artemether (Art) in protecting the people from schistosome infection during flood fighting in schistosomiasis endemic area of Poyang Lake, Jiangxi Province.
　　Methods　From mid July to mid August in 1996, the water level in Poyang Lake rose due to torrential rains and 2 embankments, Zhedi and Jiangtongdi, which appeared in dangerous situation and were selected as the pilot spots. After those who went to fight against flood arrived at the pilots their sera were collected within 48 hours and were examined with indirect hemagglutination test (IHA), enzyme-linked immunosorbent assay (ELISA) and McAb-ELISA. Individuals with negative outcome in the 3 tests were then selected as the study subjects and were allocated randomly to the Art or the control group. The first dose of Art given to the individuals contacted with the infested water within 11-15 days was 6 mg/kg. If the individual continually contacted the infested water, the same dose of Art was given once every 15 days. After the individuals withdrew from the pilot, one more dose of Art was administered 7-15 days later. Placebo (starch) was given to individuals in the control group at the same period as in artemether group. Stool examinations were made in both groups 40-50 days after the last medication for evaluation of the preventive effect of artemether. Double blind method was used in the administration of both artemether and placebo.
　　Results　In Zhedi pilot, the individuals fought against flood for about 1 month. In Art group, 99 individuals receiving 3 doses of the drug completed the stool examination with egg-positive rate of 4% and no acute schistosomiasis was seen. In the control group, among 110 people who completed the observation, 44 were egg-positive with an infection rate of 40%, and 29 were identified as having acute schistosomiasis. In Jiangtondi, the studied individuals contacted the infested water for only about 4 hours. But in the control group 4 out of 102 individuals were egg-positive, while none of the 103 individuals in Art group receiving 2 doses of the drug showed schistosome infection. No apparent side effect was seen in the people treated with artemether.
　　Conclusion　After oral Art was given to the people fighting against flood in schistosomiasis endemic area of Poyang Lake, it was shown that the oral Art has a promising effect on controlling acute schistosomiasis and reducing the infection rate.
　　

Chin Med J 1998; 111(2):123-127


　　Although remarkable achievements have been attained in the control of schistosomiasis in China, the disease is still endemic in 122 counties (cities). Among them more serious endemic areas are distributed along the Yantze River from the middle to lower reaches, and the lakes leading to the river. In these areas the intermediate hosts, Oncomelania snails breed extensively, the water level is difficult to control and domestic animals (cattle and pigs) are herded in the marshlands. Thus, the marshlands are usually contaminated by the feces of the domestic animals with schistosomiasis. Furthermore, the water level of the Yantze river rises during the rainy season each year, which results in frequent flooding and needs a great amount of manpower to fight against flood. For this reason, individuals, who attend to fight against flood, are not only easy to be infected with schistosomes but also easy to acquire schistosomiasis. Therefore, it is necessary to adopt an effective measure to protect them from schistosome infection. In recent years, artemether (Art), an antimalaria drug, has been developed for prevention of schistosome infection after a series of experimental studies.1　The preliminary field trials indicated that oral Art was effective not only in reducing infection rate and intensity of infection but also in controlling acute schistosomiasis.2,3　In 1996, oral Art was used in those fighting against flood in schistosomiasis endemic areas of Poyang Lake for protecting them from the infection.

METHODS

Selection of pilot
　　According to the information provided by Jiangxi Provincial Headquarters for Flood Control we knew the frequency and areas where the dangerous flood situation usually emerged every year during the flood season around the embankment of Poyang Lake. According to the knowledge of prevalence of schistosomiasis and the Oncomelania snail situation, some areas were selected in advance to serve as the pilot spots when dangerous flood situation appeared.

Subjects
　　In contact with the related health division of the provincial government, about 2000 individuals with an age range of 18-40 and a majority from non-endemic areas were selected as the subjects for the study immediately when they went to fight against flood in the selected pilots.

Drug
　　Each Art capsule contained 100 mg of the drug, while the capsule with the same size and color was used as the placebo containing starch. Both Art capsule and placebo were provided by Kunming Pharmaceutical Corporation.

Administration regimen and laboratory examination
　　During the flood period we kept close contact with the Provincial Headquarters for Flood Control and the related health division of the provincial government. After the reserve pilot fell into dangerous situation and the reserve individuals arrived in the pilot we came to the spot immediately. Within 48 hours after the individuals contacted the infested water, the sera from them were examined by indirect hemagglutination test (IHA),4　enzyme-linked immunosorbent assay 4　(ELISA) and McAb-ELISA.5　The individuals who showed negative result in the 3 tests were then selected as the study objects and allocated randomly to the Art or the control group. In the Art group, the first dose of Art was given to the individuals within 11-15 days after contact with the infested water. If the people continually contacted the infested water, the same dose of Art was given once every 15 days. After withdrawal of the individuals from the pilots, one more dose of the drug was given within 7-15 days later. Placebo (starch) was given to the individuals in the control group at the same period as in Art group. Double blind method was used in administration of both Art and placebo.

Epidemiological investigation in the pilots
　　After the flood control was over, the prevalence data of schistosomiasis along the inside of embankment of the pilots were collected. The snail situation revealed in the marshlands outside the embankment of the pilots was also examined after withdrawal of the flood.6

Evaluation of preventive effect
Infection rate and intensity
　　40-50 days after the end of fighting against flood and withdrawal of the individuals from the pilots, stool examination was made in both the Art group and the control gorup by hatching test after nylon bag concentration for schistosome eggs. In each case a large sample of feces were collected and divided into 3 portions for examination. The egg-positive sample was further examined by Kato-Katz method for determination of the egg number per gram of feces (EPG).7

Acute schistosomiasis
　　Cases of acute schistosomiasis appearing in both the Art group and the control group during the observation period were diagnosed definitely and recorded.

　　The preventive effect of Art was evaluated according to the above-mentioned 3 parameters.

Statistical assay
　　All data collected were analysed by X2 test and student t test.

RESULTS

General characteristics and snail situation of the pilots
Zhedi pilot
　　The embankment is located in the south-west end of the Poyang Lake in a fan-form water network of Ganjiang River lower reach. The embankment outside the lake is 12 km in length and arc-shaped close to the north of the Poyand Lake. The outside of the embankment is an area of muds and stones of about 300 m, whereas a middle river flows over the further 300-800 m. Beyond the outer lateral side marshlands of different size are distributed occuping a total area of 4.5×106 m2. Weeds are overgrown in the marshland which are suitable for snail breeding. Furthermore, because of herding of the cattles, the marshlands are contaminated seriously by the feces of cattle with schistosmiasis. According to the monitoring result of the local health division, no snail was found inside the embankment since 1990. In summer the outside of the embankment is immersed in the water, but it protrudes as a continent in winter. So the local residents frequently went to the outside of the embankment for living or productive activities and thus might be infected with schistosomes. From the last ten days of June to the first ten days of July, 1995, dangerous situation happened in Zhedi due to flood and about 2000 residents went to fight against flood. After withdrawal of the flood, 216 cases of acute schistosomiasis in a short period were recorded.

　　In October 1996, snail survey was carried out in marshlands outside the Zhedi by collecting snails randomly in 114 frames (0.11 m2/frame) of surface earth with a frame distance of 50×10 m. The snails were detected in 104 out of 114 frames and the infected snails in 14 frames. The number of living snails and infected snails were 4376 and 26 respectively, with mean densities of 38.4/0.11 m2 and 0.2281/0.11 m2 respectively.

Jiangtondi pilot
　　The embankment is located in the western side of the lake mouth. In 1996, fecal examinations were made in the residents of 3-60 living close to the embankment. The results showed that the schistosome infection rate of the residents was 9.2%, whereas the mean infected snail density was 0.0162/0.11 m2.

Situation of contact with the infested water
Zhedi pilot
　　On July 12 to August 13, 1996, the water level of Zhedi rose over 2.1 m of the warningline due to the torrential rain in upper reach of the Yangtze River. On July 13-15, more than 400 people arrived at the embankment for fighting against flood. The sera from 312 people were examined by three serological tests (IHA, ELISA and CAg) within 48 hours and 48 people with positive result in one of the 3 tests were excluded from the study. The other 264 individuals with negative in 3 serological tests were equally and randomly allocated to the Art group and the control group. In the first 15 days and August 4-13, the main modes of contact with the infested water by the individuals fighting against flood were inspection of the embankment, stack of the stone and bath. But from July 28 to August 13, the No. 9 typhoon attacked the embankment and the waves were lifted from the north eastern side of the lake. Thus, the main modes of contact were replenishment of the slippery slope and stack of the stone. Time spend on fighting against flood was 33 days. The modes of contact were similar in the Art group and the control group and the mean duration of contact the infested water by each individual was also similar in the two groups (28.6±7.6 days and 28.7±9 days, respectively).

Jiangtongdi pilot
　　At the same period as the above-mentioned, the flood also attacked the Jiangtondi and 235 individuals went to fight against flood. After serum examination 205 individuals with negative in the above-mentioned 3 serological tests were allocated randomly to Art group (103) and the control group (102). The two groups contacted the infested water for only 1 day and the mean duration of contacting were about 3.5 hours.

Administration regimen and side effect
　　In Zhedi pilot, the first oral dose of 6 mg/kg Art was given to the Art group after the contact of the infested water for 15 days. 15 days later, i.e., 30 days after the contact the second dose of Art was given. One more dose of Art was taken another 15 days after withdrawal from the pilot. In the control group, 6 mg/kg placebo (starch) was given to the individuals in the same period as in Art group. In Jiangtongdi pilot, the Art group and the control group were treated orally with a dose of either Art or placebo of 6 mg/kg 11 days after contact with the infested water. Another dose of either drug was given 7 days after the first one.

　　No apparent side effect of oral Art was seen, except that one case complained transient fever after each administration. Therefore, the compliance rate of Art administration was very good.

Preventive effect
Zhedi pilot
　　Since some individuals were out or in vacation, 99 individuals in Art group completed the 3 administrations of Art and stool examination, and only 4 of them presented schistosome egg in the feces with a positive rate of 4%. In the control group, the corresponding data were 110%, 44% and 40% respectively. The difference in egg-positive rates between the two groups was statistically significant. Furthermore, the EPG of the Art group was also significantly lower than that of the control gorup (Table).

Jiangtongdi pilot
　　In Art group, stool examination was made in 103 individuals and none of them showed schistosome egg, whereas in the control group, 102 individuals had their stool examined and 4 of them showed schistosome egg with a positive rate of 3.9% (Table).

Acute schistosomiasis
　　During the observation period, no case of acute schistosomiasis was seen in the Art group, whereas in the control

Table. Protection of individuals from infection with Schistosoma japonicum after preventive therapy with artemether (Art)

Pilot site Group No. of cases No. of cases

followed

 No. of cases
with egg positive		 Infection
rate (%)		 EPG No. of acute
schistosomiasis
Zhedi Control 132 110 44 　　　40.0 　80±107 (40) 29
　 Art 132 　99 　4 4.0** 18±12** (4) 　0
Jiangtongdi Control 102 102 　4 3.9* 48±35 　0
　 Art 103 103 　0 0 　 　0
　　* P<0.05 vs the contorl; ** P<0.01 vs the control; Parenthesis represents the number of cases.

group 29 cases suffered from acute schistosomiasis. Among them, 6 cases had high fever sustaining over 39℃-40℃, hepatomegaly and splenomegaly, bloody diarrhoea and positive in egg hatching test with a large number of miracidia. The lowest and highest titre of serum with positive reaction in IHA assay were 1∶320 and 1∶1280, respectively. The highest percentage of eosinophils was over 50%, whereas the lowest, 30%. The temperature of the other 23 individuals fluctuated around 38℃ accompanied by diarrhea and feces with blood and mucous, and 16 out of 23 presented apparent hepatomegaly in the left lobe. The serum titres with positive reaction in IHA assay were 1∶20 to 1∶640. Eosinophils in the peripheral blood smear were 20%-35% and the schistosome eggs were seen in the feces. All these cases were diagnosed definitly as acute schistosomiasis.

DISCUSSION

　　Since the fighting against flood is an urgent affair, it is difficult to perform stool examination in the studied individuals within a short period in order to exclude the previous schistosome infection. However, in this study most of the individuals were from non-endemic areas and had no chance to contact the infested water. Therefore, 2 highly sensitive and specific methods (IHA and ELISA) used to determine the specific antibody titres and a CAg assay used to measure the active infection as well as to reflect the worm burden were adopted to examine the sera from the individuals arriving in the pilot within a short period. In the meantime, any case with positive reaction in one of the three serological assays was excluded in this study. Thus, the objects selected by the above-mentioned methods should be considered free from schistosome infection, and were suitable for the study of prophylactic drug.

　　In schistosomiasis endemic areas of marshlands type, the residents usually contacted the infested water by way of daily activities and productive activities, which usually led to schistosome infection. Particularly, swimming and playing in water were the major causes of the acute schistosomiasis.8,9　In fighting against flood, the individuals contacted the infested water with not only larger body surface but also longer duration. Thus, they were vulnerable to the acute infection. In Zhedi pilot the individuals under study contacted the infested water for about one month, 7 hours per day. Therefore, the rates of infection and the cases of acute schistosomiasis were rather high. Even in Jiangtongdi, several individuals in the control group who only contacted the infested water for several hours were also infected with schistosomes. The results indicated that adoption of effective measure to protect the individuals in fighting against flood was an urgent need. In the pilots, Art given orally resulted in a promising preventive effect. The protection rate of the individuals was 90%-100% and no case of acute schistosomiasis was seen, showing that Art could be used either as an intervention approach for controlling schistosomiasis10-12　or in those who are anticipated of intense water contact for a period of time in heavily endemic areas. Such people include individuals involved in the occupations of flood control, water transportation, water conservation and construction. Since oral Art exhibits its killing effect on schistosomules harboring in the host, it serves as a systematic drug for prevention of schistosomiasis. With the dosage we used, Art displays no apparent side effect but has a good compliance rate.

　　The project was supported by the 9th Five-year Key Research Program of China; in part by Joint Research Management Committee (JRMC) from a World Bank for China Schistosomiasis Control.
　　Correspondence to: Prof. Xiao Shuhua, Jiangxi Institute of Parasitic diseases， Nanchang 330046, China (Song Y, Wu W, Zhang SJ, Xie HQ and Xu XP)
　　Institute of Parasitic Diseases, Chinese Academy of Preventive Medicine， Shanghai 200025, China (Xiao SH, Chen MG and Zheng J)
　　Jiangxi Provincial Headquarters for Fighting against Flood, Nanchang 330008, China (Hu XY)
　　Health Department of Army force in Jiangxi Province, Nanchang 330006, China (Cui Q)

REFERENCES

　　1. Xiao SH, You JQ, Yang YQ, et al. Experimental studies on early treatment of schistosomal infection with artemether. Southeast Asian J Trop Med Public Health 1995; 26:306.
　　2. Xiao SH, Shi ZG, Zhou SJ, et al. Field studies on the preventive effect of oral artemether against schistosomal infection. Chin Med J 1996; 109:272.
　　3. Xiao SH, Wang JL, Wang CZ, et al. Protection of the residents from schistosome infection using oral artemether in mountainous area. Chin J Parasitol Parasitic Dis 1996; 14:11.
　　4. Department of Endemic Disease Control, MOPH. Hand book for schistosomiasis control. 1st ed. Shanghai: Shanghai Scientific Technique Press, 1990: 120-36.
　　5. Yang ZZ, Lu ZY, Wang W, et al. Detection of schistosome ova antigen by dot-ELISA with monoclonal antibody. Shanghai Immunol J 1990; 10:113.
　　6. Department of Endemic Disease Control, MOPH. Hand book for schistosomiasis control. 1st ed. Shanghai: Shanghai Scientific Technique Press, 1990: 37-45.
　　7. Department of Endemic Disease Control, MOPH. Hand book for schistosomiasis control. 1st ed. Shanghai: Shanghai Scientific Technique Press, 1990: 109-19.
　　8. Qin ZH. Investigation and analysis of acute schistosomiasis in Westeast lake area. Chin J Schistosomiasis Cont 1992; 4:116.
　　9. Yang HR, Wang Y. Epidemiological investigation and analysis of 461 cases of acute schistosomiasis. Chin J Schistosomiasis Cont 1992; 4:117.
　　10. Tian ZY, Xiao SH, Xiao JW, et al. Observation on reducing schistosomal infection rate in an islet with embankment type endemic area after prophylaxis with oral artemether given to the population throughout the whole transmission season. Chin J Parasitol Parasitic Dis 1997; 15:212.
　　11. Wang JL, Xiao SH, Yang Z, et al. Observation on the effect of oral artemether on controlling schistosomiasis in Yunnan mountainous endemic area. Chin J Parasitol Parasitic Dis 1997; 15:138.
　　12. Xu MS, Xiao SH, song Q, et al. Observation on the effect of artemether on controlling schistosomiasis japonica in an endemic area of marshlands. Chin J Parasitol Parasitic Dis 1997; 15:208.

(Received May 29, 1997)