Table of Content

28 February 1989, Volume 7 Issue 1

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EPIDEMIOLOGICAL SURVEILLANCE OF FILARIASIS AFTER ITS BEING BASICALLY ERADICATED IN SHANDONG PROVINCE

1989, 7(1):  4-7. 

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This paper reports the results of epidemiological surveillance in areas where filariasis has been basically eradicated and control measures no longer adopted in Shandong Province. A 3-year longitudinal surveillance in 18 villages in 5 counties and a cross-sectional survey in 13 villages of 4 counties were carried out. The results showed that the average microfilaria rate was further reduced from 0.28% and 0.15% in 1980 to 0.19% and 0.05% in 1986, decreased by 32.1% and 66.7% respectively. 34.2% of the microfila-remic cases were found to be negative during the two-year follow-up. The positive rate of IFA and skin test was 34.2% and 38.6% respectively. In longitudinal surveillance. of the 240 992 Culex pipiens pallens dissected, 152(0.06%) were found to harbour di-fferent stages of larvae, among them, 5 were infective larvae from 4 vector mosquitoes. In cross-sectional survey, of the 3875 Culex pipiens pallens dissected only l which had bitten immigrant from Zhejiang was found to contain one larve at stage 1. No positive mosquito was found in the household of native villagers. No new infection was disco-vered at longitudinal and cross-sectional survey. The transmission of filariasis in these areas was interrupted. The results showed that in areas where filariasis has been basically eradicated, further control measures may not be instituted, but the management popula-tion movement and surveillance should be strengthened.

OBSERVATIONS ON THE GROWTH DYNAMICS OF 4 STRAINS OF TOXOPLASMA GONDII IN HELA CELLS

1989, 7(1):  8-11. 

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Growth dynamics of PP, CN and ZS2 strains of Toxoplasma gondii isolated in China was studied and compared with that of RH strain. HeLa cells were used in this work. It took only 2 min for the organisms of RH strain to infect the HeLa cells when con-tacting with the cells. By contrast, the CN strain requires 5 min, the ZS2 and PP strains, 10 min.Tcxoplasma began its multiplication after a lag time of about 6 h in the HeLa cells. The mean generation time of the 4 strains was assessed by calculating the number of the parasites in the parasitophorous vacuoles at different incubation times and by the linear regression equation. The results showed that the mean generation time was 5.2 h for RH strain, 5.98 h for CN strain, 6.78 h for ZS2 strain and 7.69 h for PP strain.Among the 3 strains of Toxoplasma gondii isolated in China, CN strain was similar to RH strain in their infectivity and proliferation.

REPORT ON A FUNGUS PARASITIZING ENTAMOEBA HISTOLYTICA

1989, 7(1):  12-14. 

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Infection of Entamoeba histolytica with chytridiaceous fungus Sphaerlta was observed in some specimens obtained from a farmer and stained with iron-haematoxylin. The fungi were found in 78% of tne cysts, mostly immature ones. Within the amoebae this parasite occurred singly, in groups, or in the form of a sporangium. It was located in the cytoplasm, the glycogen mass or the chromatoidal bars.In the same specimen, the parasitic fungus was also found in 18% of E. coli cysts; in 11% of E. nana cysts; while only one of 16 E. hartmanni cysts was parasitized.It is an interesting case of superimposed parasitism so far reported in China as well as a rare rase of several species of amoebae being heavily involved with the same in the scientific literarure.

DERMAL RESPONSES OF VARIOUS HOSTS TO INFECTION WITH SCHISTOSOMA JAPONICUM CERCARIAE

1989, 7(1):  15-18. 

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The present investigation concerns with tne dermal reactions produced in various host species by the invading schistosomula in primary infection. Eight animal species including mouse, rat, hamster, jird, guinea pig, rabbit, rhesus monkey and pigeon were used. A small area of shaven abdominal skin exposed to 300 Schistosoma japonicum ceicariae was taken at different time intervals from each animal species. The dermal responses of various hosts to schistosomula varied with their suscepti-bility. In the case of pigeon, an unsusceptible host, the skin reaction was very severe. Cutaneous lesions were observed as early as 0.5-2 h post-infection and cellulat infiltration increased markedly with time. Thereafter the schistosomula were surrounded by many leucocytes with eosinophilic granules, and finally became disimegrated. In various mammalian hosts the skin reaction to the primary infection was slight, consisting of hyperemia, edema and cellular infiltration mainly by neutrophils with the exception of guinea pig in which the cellular infiltration was eosinophilic in nature (Figs. 1-9).

THERAPEUTIC EFFECT OF PYRONARIDINE IN PLAIN TABLETS AND ENTERIC-COATED TABLETS IN FALCIPARUM MALARIA PATIENTS

1989, 7(1):  19-21. 

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A new oral dosage regimen and formulation of pyronaridine basing on tne pharma-cokinetic studies and a theoretical dosage regimen reported pnviously, was clinically evaluated for its therapeutic and undesirable effects on falciparum malaria patients in west Hainan Province, where chloroqine-resistant falciparum malaria was prevalent. 32 cases were treated with pyronaridine by tne new dosage regimen of 0.5g in d1 and 0.3g in d2 in plain tablets(groupA), while additional 32 patients received enteric-coated tablets of pyronaridine by the current dosage regimen as a control(groupB), which was 0.4g×2 on dn and 0.4g on d2. The average fever clearance time for A and B groups was 27.0 ± 14.1 and 30.2±13.8h respectively(P0.05),and the clearance time for asex-ual parasites was 57.2±10.2 and 57.9±8.7h. Upon 28d following-up examination, the cure rates were found to be 100% in group A and 93.8% in group B. The undesirable responses were recorded in 18.8% of group A patients(6/32), and 28.1% of group B (9/32)respectively, and they were light and tolerable and short in time duration. It was shown that the new dosage regimen of pyronaridine could retain the same therapeutic effect as that currently used, although the total dose was reduced by one third. Hence, an important basis was provided for more rational use and further study of pyronaridine in malaria therapy.

AN EPIDEMIOLOGICAL STUDY OF THE RESIDUAL VIVAX MALARIA CASES IN HUANGHUAI PLAIN

1989, 7(1):  22-27. 

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In order to get more knowledge of the epidemiological characteristics of the residual cases of vivax malaria in Huanghuai Plain at the present time, a case-control study was carried out from March to May, 1986 in Zhoukou Prefecture, Henan Province and in Xuzhou City, Jiangsu Province. In both areas, the incidence of vivax malaria in 1985 was lower than 1‰, The data were analyzed with the conditional logistic multi-regression model and calculated by using Apple II microcomputer. All the malaria cases selected were within an interval less than 20 days(N.B. The incubation interval of vivax malaria is 20 days) during the transmission season because the cases should be independent of each other and fit with logistic multi-regression model. Three controls were matched for each case at random, including a neighbourer person in the same village and a person outside the village. The questionnaire contained a total of 31 relevant items of the subjects, families and villages. Six risk factors (personal history of malaria, family member's history of malaria, number of cases in the village in 1984, direction of breeding place, using mosquito-net and number of livestock) related to malaria transmission were obtained through the analysis of the model. The results were in accord with actual epidemiological characteristics in the region, indicating that the conditional logistic multi-regression model can be applied to epidemiological analysis (study) under controlled conditions and provided quantitative method for analysis of socio-economic eflects on malaria. The distribution of the cases and their affecting factors were discussed.

STUDIES ON THE VARIABILITY OF INCUBATION PERIOD OF VIVAX MALARIA FOLLOWING MOSQUITO BITING

1989, 7(1):  28-31. 

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From September 1985 to May 1987, 30 peoplc were experimentally infected by Ano-pheles sinensis infected with Plasmodium vivax isolated from northwestern part of Hunan Province. The findings displayed in graphs demonstrate that the incubation period was variably depended on the number of infective mosquitoes used in the experiment. The short incubation period of 15.8±1.9d was frequently observed in 6 persons bitten by 10 infected mosquitoes. However, when one mosquito was allowed to fecd on each of 24 volunteers, the incubation period was either short (17.3±1.2d) or prolonged (284.7± 37.7d) in the ratio of l to 1.Based on these data it is suggested that tertian malaria of long incubation period must exist everywhere in China. In addition, the rational classification of vivax malaria and the ratio between long and short incubation periods in nature are also discussed in detail.

SCANNING ELECTRON MICROSCOPIC OBSERVATIONS ON ADULTS OF ANGIOSTRONGYLUS CANTONENSIS

1989, 7(1):  32-34. 

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Scanning electron microscopic observations were made on adult Angiostrongylus can-tonensis, The apex of the head has a round mouth with two rows of 6 sensory papillae each around it. The papillae of the outer row are more rudimentary and inconspicuous. A pair of amphidial pores are visible on the external side of lateral papillae of the inner row. The surface of the body is covered with a circular striated cuticle and short lon-gitudinal ridges lying between two circular cuticles. The two copulatory spicules at the posterior end of male worms are obviously different in morphology. According to their morphological characteristics, we named them "tube-like" copulatory spicule and"grooves-like" copulatory spicule. The former, when enclosed in the latter, appeared as a single one. The copulatory bursa of the males and the structures of the tail part of the female are also described (Figs.l-18).

COMPARATIVE STUDIES ON DIAPAUSE RESPONSES BETWEEN CULEX TRITAENIORHYNCHUS AND CULEX PIPIENS PALLENS

1989, 7(1):  35-39. 

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By comparing the diapause responses between locally hibernating species, C. piptens pallens, and C. tritaeniorhynchus the overwintering way of which is yet unknown, we found the relative identities of these 2 species in their ovarian diapause criteria, change of the mid-gut and the behaviour of refusing blood feeding. The increases in body weight and fatty contents in the diapaused tritaeniorhynchus were much less than those in diapaused pipiens species. Moreover, their ability to resist low temperature was also found significantly weaker. In Shanghai area, the date of the critical photoperiod for C. tritaeniorhynchus was found around the 25th of September with a daylight exposur-length (including twilight) of about 13 hours and 43 minutes, being 20 days earlier than that of the locally hibernating species C. pipiens pallens. The gonotrophic dissocia-tion during critical photoperiod occurred more frequently in tritaeniorhynchus than in pipiens mosquitoes. In contrast to pipiens species, it is extremely difficult to obtain diapaused tritaeniorhynchus in nature post critical photoperiod. The possibility of a seasonal migrative behaviour of C. tritaeniorhynchus was discussed.

HISTOCHEMICAL STUDIES ON SOME ENZYMES IN CLONORCHIS SINENSIS

1989, 7(1):  40-42. 

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The localization of some enzyme in adult worms of Clonorchis sinensis was studied by histochemical method in this paper. Acid phosphatase was detectcd mainly in digestive duct, subtegument and tne walls of testis, uterus and ovary; acetylcholinestcrase was found in oral sucker, ventral sucker, pharynx; and ATPase was found to exist in oral sucker, ventral sucker, pharynx and musclxe layer in the subtegument. The eggs of C. sinensis possessed the above three enzymes (Figs.l-5).

MEBENDAZOLE-MEDICATED-SALT IN THE CONTROL OF HOOKWORM INFECTION

1989, 7(1):  43-46. 

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From 1984-1987, mass application of mebendazole-medicated salt was studied for the control of hookworm infection in 5 pilot areas (Wuming, Shanlin, Bobai, Guilin and Rongxian Counties) in Guangxi Zhuang Autonomous Region. The dosages of me-bendazole (mixed with salt) administered were 15mg, 25mg, 30mg, 40mg, 50mg, 60mg, 70mg, 80mg, l00mg or 200mg per person per day for 15, 20 or 30 days. The results showed that 40mg/day for 15-20 days could result in stool egg negative conversion rates of 92.3 to 94.4%, while 50mg/day for 30 days resulted in 96.9 to 100%. Con-currently, the hookworm infection rate in pilot areas dropped by 57.9-71.7% in a short time; whereas the stool egg negative conversion rate of Ascaris lumbricoides was as high as 99.1% to 100% at the same dosage, when the dosage of 100mg/day for 30 days was given, the egg negative reversion rate for Trichuris trichiura was 97.6%. Promising result was also recordcd concerning the tolerance of the medicated salt, as the side effects in the inhabitants were mild.In conclusion, the authors considered that the application of mebendazole-medicated salt was a simple and effective measure in controlling hookworm infection, especially in the light of solving the problem of incomplete mass detection and selected mass treat-ment. Furthermore, it is much more economic from the cost-effect point of view.

THE DISCOVERY OF MELANOIDES TVBERCULATA AS THE FIRST INTERMEDIATE HOST OF ECHINOCH ASMUS JAPONICUS

1989, 7(1):  47-48. 

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This paper reports on the discovery of cercariae which are similar to those of Echino-tomatidae in Melanoides tuberculata in Yunxiao and Zhaoan Counties of Fujian. Encysted metacercariae were found in the gills of fresh-water fish after experimental infection with the cercariae for 3 to 4 hours. Adult worms identified as Echinochasmus japonicus were obtained front Mesocricetus auratus and dove after infection with the metacercariae. Melanoides tuberculata was recorded for the first time as the first intermediate host of E. japonicus and its natural infection rate was found to be 1.1%. The morphological characteristics of the cercaria are described.

INHIBITORY EFFECT OF CHEMICALLY AND ENZYMATICALLY TREATED ERYTHROCYTIC MEMBRANE ON THE INVASION OF PLASMODIUM FALCIPARUM MEROZOITES

1989, 7(1):  49-52. 

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By treating chemically and enzymatically erythrocytic membrane to change its structure and properties, the recognition of merozoite to erythrocyte and the effect of erythrocyte skeleton protein on the invasion of P. falciparum (Fcc-l/HN) were studied. It was found that the invasion of merozoite into erythrocyte digested with trypsin was greatly decreased; merozoite invasion into the erythrocyte treated with neuraminidase or wheat germ agglutinin (WGA) was partially inhibited; erythrocytes treated with cross-linker diamide and depolymerizer colchicine, N-ethyl maleinimide (NEM) of skeleton protein had evident resistance to invasion; the invasion of merozoite into erythrocyte treated with 2.0mM of NEM was completely blocked.

SCANNING ELECTRON MICROSCOPIC OBSERVATIONS OF OOKINETE FORMATION OF PLASMODIUM YOELII YOELII IN VITRO

1989, 7(1):  53-56. 

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The ookinete formation and mature ookinete of Plasmodium yoelii yoelii were described. During the development from zygote to ookinete, at first a finger-shaped or a stick-shaped projection protruded from one side of zygote (Fig. l).The anterior end of the projection assumed a truncated cone shape (Figs. 1-5). Following enlargement of the projection, the body of zygote gradually wrinkled and shrank and became smaller (Figs. 2-5). An annular structure developed between the newly formed ookinete and the remaining body of zygote (Figs. 5-6), which ultimately separated from the ookinete.Tile ookinete was banana-shaped. The surface of mature ookinetes was smooth (Fig. 13). On the tip there was an apical complex showing truncated cone shape. Behind the apical end there were a few pellicular folds (Figs. 9-11).Through the course of development of the ookinete the parasite constantly showed obvious movement. As the parasites protruding forward, longitudinal and spiral wrinkles appeared on their body surface (Figs. 2-4, 10-12).

CRYOPRESERVATION OF MICROFILARIAE AND THIRD-STAGE LARVAE OF BRUGIA MALAYI AND SUBSEQUENT DEVELOPMENT IN THE HOSTS

1989, 7(1):  57-60. 

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Methods are studied for the cryopreservation of microfilariae (mf) and third-stage larvae (L3) of periodic Brugia malayi. RPMI-1640 tissue culture medium containing 6% dimcthyl sulfoxide (DMSO) and 15% newborn calf serum were used as cryoprotectant.The larvae survived best when specimens were frozen at the rate of -0.5℃ to -1.0℃ per minute using the vapor phase of liquid nitrogen, when the temperature rea-ched - 70℃ to - 90℃ the specimens were placed directly into the liquid nitrogen (-196℃).After the thawing of the mf which had been stored for 6212 and 375 days in cryogen, 26.2% of the mf were shown to be viable and developed in Aedes togoi. It was also shown that the survival rate of L3 cryopreserved for 28-321 days was also S6.2% and that, wben 107 L3 frozen for 321 days were inoculated after being thawed into one jird, one live female adult was recovered at awopsy 71 days after inoculation, its morphology being the same as the unfrozen specimens.There was no correlation between the time of cryopreservation and the survival rate of the larvae.