Table of Content

31 August 1995, Volume 13 Issue 3

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EFFECT OF ENVIRONMENTAL TEMPERATURE, CRYOPRESERVATION AND AGING ON PLASMODIUM VIVAX SPOROZOITES DEVELOPING INTO EXOERYTHROCYTIC STAGES

1995, 13(3):  165-169. 

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After Anopheles stephensi mosquitoes with salivary infection of Plasmodium vivax were put in environments with temperatures of 30±1℃, 26±1 ℃ or 13±1 ℃ for 5 d, their glands were aseptically dissected and sporozoites were collected and inoculated into HepG2A16 cell monolayers. Seven days post-inoculation the cultured materials were harvested and the exoerythrocytic schizonts and hypnozoites were observed under the microscope by using immunoperoxidase staining technique. The results showed that the sporozoite developing rate of 30±1℃ group and 13 ± 1℃ group was significantly lower than that of 26 ± 1℃group (0. 33‰, 0.35‰, and 0. 75‰, respectively). The proportion of hypnozoites in the total number of EE forms was the highest in the low temperature group (62. 5%) compared with 26±1 ℃ and 30±1℃ group (40.1 % and 42. 7% respectively). Suggesting that the low environmental temperature first affected the viability of tachysporozoites or the phenotype of sporozoites and thus resulted in heightened hypnozoite rate. This is parallel to the epidemiological data that in the regions of high latitute vivax malaria with long incubation period was more frequently observed. When the sporozoites within the body of mosquito were cryopreserved at -70℃ or in liquid nitrogen for 24 h or 5 d respectively, the proportion of hypnozoite increased 87. 4% and 82. 4%, respectively. However, cryopreservation did not inactivate all of the tachysporozoites, indicating that the resistance to ultralow temperature in bradysporozoite was much greater than that in tachysporozoites. Aging of sporozoites decreased their developing rate and the exoerythrocytic (EE) schizonts were found to grow sluggishly and asynchronously, indicating that the size of EE schizont and the age of sporozoites are in negative correlation. Meantime, proportion of the hypnozoite decreased significantly.

FIELD STUDIES ON PREVENTIVE EFFECT OF ARTEMETHER AGAINST INFECTION WITH SCHISTOSOMA JAPONICUM

1995, 13(3):  170-173. 

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From August to October 1994, a field trial of preventive treatment with artemether (Art) was carried out in Minglang District of Yiyang City, Hunan Province, an islet with embankment type endemic area nearby southern Donting Lake region. The residents who frequently contacted with the infested water were selected for study and allocated to the Art group and the control group in reference to paired methods of randomization table. About one month before administration of Art, all residents under study were examined by stool hatching technique after nylon-bag concentration to determine the infection rate of each group, and then treated with praziquante1 at a single dose of 40 mg/kg in stool egg-negative residents and 50 mg/kg in stool egg-positive ones. In Art group, the first dose of 6 mg/kg was given in late August, followed by repeated dosing every 15 days for 3 times. Placebo (starch) was given to the study residents in the control group at the same time as in Art group. The efficacy was evaluated by stool examination 25 - 32 days after the last medication. The results showed that after the preventive administration of Art, 2O out of 365 study residents in Art group revealed stool positive with an infection rate of 5. 5%, while in the control group 51 out of 376 study residents showed stool positive with an infection rate of 13. 6%. The difference between the two groups was statistically significant. Meantime, two cases of acute schistosomiasis were seen in the control group, but none was observed in Art group. The egg per gram of feces (EPG) determined with the Kato-Katz method was 122±79 (range 12-192) in Art group and 681 ± 909 (range 12-2 760) in the control group. No apparent adverse side effect was seen during the treatment with Art, and no abnormal change in liver and renal function was detected after the last medication. The preliminary study indicates that application of the preventive administration of Art in the endemic area during the transmission season may effectively reduce both the infection rate and intensity of schistosomiasis.

STUDIES ON DIAGNOSIS OF FALCIPARUM MALARIA BASED ON AMPLIFYING SPECIFIC SSUrDNA FRAGMENT WITH NESTED PCR

1995, 13(3):  174-177. 

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Two pairs of primers specific to small subunit ribosomal DNA of Plasmodium falciparum were designed and the expected SSUrDNA fragment was amplified for detecting P.falciparum infection with double-ternperature-nested polymerase chain reaction using DNA prepared by boiling method. The results showed that the nested PCR could amplify a constant size of desired SSUrDNA fragment of P. falciparum which was further confirmed by digestion of restrlction endonuclease and could detect parasitemia level of 0. 8 × 10-6. It has great potentials for identifying Plasmodium species in ring form of erythrocytic stage and detecting mixed Plasmodium infections. Therefore, it is suggested that this method is sensitive, accurate, simple and rapid in detecting Plasmodium falciparum in blood samples for malaria diagnosis.

STUDIES ON THE DELTAMETHRIN-MEDICATED BATH OF DOMESTIC DOGS FOR INTERRUPTING VISCERAL LEISHMANIASIS TRANSMISSION

1995, 13(3):  178-181. 

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In a previous paper, it was reported that deltamethrin-medicated bath of domestic dogs had a strong killing effect against Ph. chinensis, and could also inhibit its blood sucking ability or cause its death shortly after blood sucking. The effect could last for 3O days to 114days, and mostly for 2 months in the local area.Based on our previous study, three villages (Yongle, Yongfeng, Anle ) and a town (Chengguan) were selected from the mountainous region with high incidence of visceral leishmaniasis in Nanping County, northern Sichuan for carrying out an extensive experiment of medicated bathing of domestic dogs, where there were 13 new infected cases in the year of 1991 before the experiment. During the sandfly season in 1992, two rounds of rnedicated bathing of dogs were conducted, the drug concentration used was 50 ppm. From September 1992 to August 1993, the number of new infected cases was 11 in the above mentioned three villages and a town. Another two rounds of medicated bathing of dogs had been conducted during the sandfly season in 1993.The results show that there was no new infection from September 1993 to October 1994 in the three villages and a town, indicating that through two years' consecutive extensive medicated bathing of dogs in the endemic areas, canine visceral leishmaniasis transmission had been signlficantly interrupted.The authors consider that in the mountainous region of southern Gansu and northern Sichuan where it has been difficult to treat dogs, it might be more practical to use deltamethrin bathing of dogs for interrupting the transmission of canine visceral leishmania sis.

STUDIES ON THE ENZYME CYTOCHEMISTRY OF TOXOPLASMA GONDII AND THE INFLUENCE OF ARTEMETHER

1995, 13(3):  182-184. 

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Male mice of Kunmlng strain were infected with 10 000 tachyzoites intraperitoneally. 2 hours after infection the mice were divided into 2 groups and administered 5 % of amylurn and 200 mg/kg of artemether by gavage for 8 consecutive days. The ultrastructural enzyme cytochemical studles on cytidine monophosphatase (CMP ase) and glucose-6-phosphatase (G-6-P-ase) of the parasites were carried out. CMP-ase was found scattered in the lysosomes of the parasites as well as in the macrophages. No differences were observed in the localization and intensity of CMP-ase activity between the nontreated and treated with drug parasites. G6-P-ase was found surrounding the parasite membrane and scattered in the parasitophorous vacuole in the nontreated parasites. After treatment with artemether, the intensity of G-6-P-ase activity was decreased compared with nontreated control parasites. It is suggested that artemether may exert some action on the G-6-Patase of T. gondii and thus influence the energy metabolism of the parasite.

OBSERVATION ON HYPNOZOITE OF DIFFERENT ISOLATES OF PLASMODIUM VIVAX IN CULTURED MATERIALS

1995, 13(3):  185-188. 

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The hypnozoites of different isolates of P. vivax from Shenzhen and Shixin, Guangdong Province, Changsha, Hunan Province and Yincheng, Hubei Province of China in cultured materials were observed employing immunoperoxidase staining method. The percentages of hypnozoites among exoerythrocytic stages were 40.1, 43. 5, 50. 6 and 57. 1 %, respectively,indicating that the percentage of hypnozoites and the latitude are in positive correlation. The equation is y= - 6. 68+ 2. 05x. When the dlfference in latitude of Plasmodium vivax isolate source was more than 5°, a significant difference in the percentage of hypnozoites in various geographic isolates was found. However, the average diameters of hypnozoites and schizonts among various geographic isolates showed no significant difference. The results showed that ln the regions north to the Yangtze Rlver, the proportion of hypnozoite in the liver stage of P.vivax was larger than those in the southern China, being consistent with the clinical manifestations.

EFFECT OF PRAZIQUANTEL TREATMENT ON SERUM CIRCULATING SOLUBLE EGG ANTIGEN-ANTIBODY COMPLEX (SEAIC) LEVEL IN MICE INFECTED WITH SCHISTOSOMA JAPONICUM

1995, 13(3):  189-192. 

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Employing Capture ELISA, we determined the level of the circulating soluble egg antigen-antibody complex (SEAIC) in sera from mice infected with Schistosoma japonicum for 7 weeks and then treated the infected mice with praziquantel (100 mg/kg body weight). It was noted that the serum SEAIC level in treated mice dropped gradually after treatment. There was a significant decrease in 13 out of 15 mice in serum SEAIC levels at five weeks after treatment, OD value dropped from O. 358±0. 074 to 0.165±0. 049 (P0. 01). The serum SEAIC level in 10 mice declined to disappear (OD0.097) by the 7th week after treatment.By contrast, no significant changes in serum SEAIC levels were found in the non-treated mice, the serum SEAIC level in the control group maintained moderately high (OD=0. 266±0. 076) till the end of the observation.

COST-BENEFIT ANALYSIS ON MALAYAN FILARIASIS CONTROL IN MIAOXI TOWNSHIP, HUZHOU CITY, ZHEJIANG PROVINCE DURING 1964-1987

1995, 13(3):  193-196. 

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The methods adopted in this paper were as follows: (1) The cost of the filariasis control was estimated to be direct cost and indirect cost; (2) Using the reduction rate of acute inflarrlmatory attack as the measurable indicator of control effectiveness; (3) Estimating the case number of acute inflammatory attack occurred after control year by year basing on the goodness by fitting in the reduction trend of acute inflammatory attack with hyperbola formula; (4) Assuming that the case number of acute inflammatory attack would be relatively stable at the same level of pre-control if filariasis control measures were not implemented;(5) The benefit from the filariasis control was estimated by transforming the increasing manworking day and sav1ng the mediclne expenses of patients due to the reduction of acute inflammatory attack. By allowing seven percent discount on cost and benefit, the total cost was 21 182 Yuan, the total benefit was 119 859 Yuan, the ratio of cost-benefit was 1: 5. 7,implying that putting in one Yuan to filariasis control in this township may gain benefit 5. 7Yuan.

STUDIES ON MODE OF HUMAN INFECTION WITH ECHINOCHASMUS LILIPUTANUS

1995, 13(3):  197-199. 

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Epidemiological survey and experimental studies on the mode of human infection with Echinochasmus liliputanus were carried out in Chenqiaozhou Village 9 Hexian County, Anhui Province in 1992. The results showed that humans could be infected through drinking unboiled water containing E. liliputanus cercaria or eating raw fish containing the metacercaria.The infection rates of E. liliputanus were 1. 5% in the inhabitants who did not drink raw water,and 20. 1% in those who used to drink raw water. It was only the cercaria, not the metacercaria that was detected in the water from ponds of this village. None of the investigated inhabitants ate uncooked fish. The results indicated that drinking raw water containing E. liliputanus cercaria was a major way through which a humans were infected and eating food containing the metacercaria was a minor mode of human infection.

ACRIDINE MUTAGEN ICR-170 INDUCED DEVELOPMENTAL SUPPRESSION OF OVARY AND VITELLINE GLAND IN FEMALE SCHISTOSOMA JAPONICUM

1995, 13(3):  200-202. 

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Mice of Kunming strain were infected with Schistosoma japonicum cercariae previously incubated with various concentrations of acridine mutagen ICR-170 for different time durations. At 6 weeks after infection, the mice were autopsied. The results showed that 24 out of 28(85. 7%) adult female worms had deformed or lacked ovaries and vitelline glands when the cercariae were treated with the agent at a concentration of 10μg/ml and incubated at 30. 5℃ for 30min. No apparnet changes were observed in the male worms inhabiting the mesenteric and portal veins with the females worms in their gynecophoral canals. The mutagenized female schistosomes obtained from the present experiment might be served as another form of attenuated worms for the induction of protective immunity.

SEQUENCE ANALYSIS OF APICAL MEMBRANE ANTIGEN Ⅰ FROM A PLASMODIUM FALCIPARUM ISOLATE COLLECTED FROM MENGPENG TOWNSHIP, YUNNAN PROVINCE

1995, 13(3):  203-208. 

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Genomic DNA from a Plasmodium falciparum isolate (CMP-1) collected from a falciparum malaria patient at Mengpeng Township, Mengla County, Yunnan Province was used as the template for PCR amplification primered with oligonucleotides from the conserved regions of the apical membrane antigen I (AMA-1) as reported. PCR products recovered from the low melting-point agarose gel electrophoresis were digested with BamHI and EcoRI to generate fragments approximately 420, 445 and 900 bp which were used as the inserts to insert into the M13 mp8 and M13 mp9 vectors for sequencing using 373 sequencer. 1773 bases were read out, among which 17 point mutations were found to result in substitutions of 15 codens which were non-synonymous mutations except for one as compared with that of the consensus. In particular, a relatively hot region of variation was apparent between amino acids 160 and 210.

THE INHIBITORY EFFECTS OF IMMUNE SERA AGAINST TWO RECOMBINANT HYBRID ANTIGENS ON THE GROWTH OF PLASMODIUM FALCIPARUM IN VITRO

1995, 13(3):  209-213. 

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The inhibitory effects of rabbit immune sera against two recombinant hybrid antigens(C and CAC) of Plasmodium falciparam to the multiplication and development of in vitro cultured P.falciparum parasites were tested. Although both of anit-C and anti-CAC immune sera had inhibitory effect on parasites, the anti-CAC serum showed much greater effect than that of anti-C serum(P0. 05). The inhibitory capacities in the sera to parasites were enhanced with the increase in the serum concentration as well as with the prolongation of the incubation time of the sera with the parasites. It was shown that after 72 h incubation of the anti-CAC serum with the parasites at the concentration of 1 %, 10% and 20%, the inhibition rates were 15%, 54% and 82%, respectively. The immune sera caused the dispersion of parasite cytoplasm, atrophy of parasites, agglutination of free merozoites and degeneration of schizonts, suggesting that the hybrid antigen could produce multi-functional protective antibodies against antigens of Plesmodium falciparum.

CHARACTERISTICS AND RECENT TRENDS IN ENDEMICITY OF HUMAN PARASITIC DISEASES IN CHINA

1995, 13(3):  214-217. 

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An analysis of the nationwide survey of the distribution of human parasites in the light of the literature previously published, two major trends in the endemicity of parasitic diseases in China was observed. For one trend, the infection rate of E. histolytica, Fasciolopsis buski and soil-transmitted helminthasis etc. declined markedly. The second trend was that the prevalence of food-transmitted parasitic diseases (Trichinella spiralis, Clonorchis sinensis,Paragonimiasis, cysticercosis) and hydatidosis was increasing. The relationship between the social economic factors and the .two trends were discussed.

STUDIES ON ELEMENTS IN ANOPHELES SINENSIS INFECTED WITH BRUGIA MALAYI MICROFILARIAE

1995, 13(3):  218-221. 

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Amounts of Certain elements in Anopheles sinensis, both normal ones (emerged mosquitoes, d0, d5, d8, d12 and d18 after taking blood meal) and those infected with Brugla malayi microfilaria (d5, d 8, d12 and d18 after infection), were determined using IL-551 and PE-603 atomic absorption spectrometer(AAS). The results showed that 9 kinds of trace elements including Fe, Zn, Cu, Cd, Al, Pb, Mn. Ni and Cr and 4 kinds of macro elements as K, Na, Ca, Mg were present in both the noninfected and infected mosquitoes. Comparing the contents of the elements between the noninfected and infected mosquitoes, the amounts of many kinds of elements reduced obviously in mosquitoes infected with microfilaria. The quantity and kinds of elements reduced in mosquitoes with the days of infection, for instance, 10 kinds of elements on the 5th day, 11 on the 8th day, 9 on the 12th day and 7 on the 18th day after infection(Tables 1, 2).

OBSERVATION ON DYNAMICS OF CIRCULATING ANTIGEN FROM PATIENTS WITH CYSTICERCOSIS BEFORE AND AFTER TREATMENT

1995, 13(3):  222-224. 

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The dynamics of circulating antigen (CAg)level in sera from pat1ents with cysticercosis before and after albendazole treatment were detected by using monoclonal antibody-based double antibody sandwich EL1SA (McAb-ELISA). The results indicate that after the patients with cysticercosis had been treated for one, two and three treatment courses, the levels of CAg in sera decreased with the increase in the number of treatment courses, their average OD value dropped from 0. 499 before treatment to 0. 291, 0. 073 and 0. 051 after treatment, respectively, and the corresponding negative conversion rates of CAg detection were 20. 0%, 57. 9% and 87. 5%, respectively. Sera from eight patients who had received three courses of albendazole treatment were detected for CAg and CAb before and after treat ment. The results indicate that the CAb level dropped rather slowly after three courses of treatment as compared to CAg level. It is concluded that detecting circulating ant1gen might be used as a promising method for evaluating the drug efficacy.

THE COURSE OF MALARIA CONTROL AND PRESENT STATUS IN ZHEJIANG PROVINCE

1995, 13(3):  225-228. 

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Through forty years' sustained efforts in the prevention and treatment of malaria in Zhejiang Province, the malaria incidence dropped from 76. 65k in the Fifties to 0. 91 in the Eighties. Three malaria epidemics emerged in 1954 ,1962 and 1973, respectively, among them the epidemic in 1962 was the most serious one with 0. 88 million cases reported and an incidence of 330. The annual incidence of the overall counties/cities was below 1 after 1988. Only 172 malaria cases were found in 1992, the incidence being 0. 04. No indigenous malaria case was found in 38 counties in 1992, accounting to 43. 7% of the total malaria endemic counties. The number of imported malara cases was 3 829, amounting to 89. 2 % of the total number of cases. Through the spot-check of the Ministry of Public Health in 1993, it was confirmed that the criteria of basic elimination of malaria in the province was attained.