Table of Content

30 November 1995, Volume 13 Issue 4

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EXPERIMENTAL STUDIES ON THE PREVENTIVE EFFECT OF ARTEMETHER AGAINST SCHISTOSOMAL INFECTION

1995, 13(4):  241-248. 

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In order to study the preventive effect of artemether (Art) against schistosomal infection, mice, rabbits and dogs infected with Schistosoma japonicum cercariae were treated intragastrically (ig) with Art on various days after infection. The preventive effect was assessed by total and female worm reduction rate, the number of the animals without female worm, measurement of some parameters relevant to the acute schistosomiasis, and histopathological observation on the liver. The results showed that in mice a promising effect was obtained when an initial dose of Art 300 mg/kg was given ig on d 7 after infection with cercariae, followed by repeated dosing every wk for 4 times. In rabbits and dogs treated ig with Art according to above mentioned appropriate regimen on d 7 after infection at a dosage of 10 or 15 mg/kg given every 1 or 2 wk for 2-4 times, the total and female worm reduction rates were 96.8%-100%, and part of the animals were free from female worm. After preventive treatment of the rabbits with Art, the body temperature and eosinophil count were normal and no schistosome egg was found in the feces. When rabbits infected with 48-52 schistosome cercariae once every other day for 5 times were initially treated ig with Art 15 mg/kg on d 7 after the first infection, and the same dosing was given repeatedly every 1 or 2 wk for 2-4 times, the total and female worm reduction rates were 97.6%-98.4%. Histopathological observation showed that the above mentioned infected dogs and rabbits received preventive treatment with Art exhibited a promising protective effect on their livers. The protective effect of Art given every 1 wk on the liver was similar to that of the drug given every 2 wk. The results indicate that Art possesses an effect for prevention of schistosomiasis which could be helpful for reducing infection rate and intensity of infection, and controlling acute schistosomiasis.

A STUDY ON BEHAVIOURAL CHARACTERISTICS OF STAYING ON THE MOUNTAIN AND ITS RELATIONSHIP WITH MALARIA INFECTION IN LI AND MIAO MINORITIES IN HAINAN PROVINCE 

1995, 13(4):  255-259. 

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A study of sociology combined with epidemiology was conducted in Li Minoritys two villages and Miao Minoritys two villages nearby the foot of mountain in a historically malaria hyperendemic area, Nanqiao Township of Wanning County in August, 1993. The results showed that malaria infection was closely correlated to the behaviour of staying overnight on the mountain of Li and Miao Minorities during farming seasons. Most of Li people stayed overnight on the mountain for planting areca were adults, accounting for 21.6% of the whole population, the duration of stay was about half a year; Miao people stayed overnight on the mountain planting and harvesting upland rice, always with their family member, so the percentage of people who had stayed on the mountain was as high as 82.1%, the duration of stay was about one and half a month. Blood smear examination showed that the malaria parasite rates in both Li and Miao villages were 11.1% and 24.1 %, respectively, the positive rate of P. falciparum was 1.0% and 9.1%, respectively, the positive rate of IFA (titer≥1∶40)was 31.2% and 46.5%, respectively. It is indicated that both the rate of parasitaemia and the P. falciparum infection were much higher in Miao Minority than those in Li Minority( P 0.001). A cohort analysis showed that the malaria parasite rate of population who having not stayed, having ever stayed and being stayed on the mountain was 6.5%, 27.4% and 42.1%, respectively, of them the rate of P. falciparum infection was 0.5%, 8.8% and 18.4%, respectively. The results suggest that malaria acquired from mountainous forest referring to “up mountain infection” is a major source of malaria infection and a significant risk factor in determining the prevalence of malaria (especially falciparum malaria) in Hainan Province. This behavioural risk factor has become the main obstacle for malaria control in Hainan Province. Therefore, controlling “up mountain infection” and adopting appropriate anti malaria measures to protect the risk population who have to work and stay on the mountain should be strengthened in the malaria control program.

ERYTHROCYTE IMMUNITY AND REGULATING FACTORS IN MICE INFECTED WITH PLASMODIUM BERGHEI ANKA STRAIN

1995, 13(4):  260-263. 

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After seventy two ICR mice were inoculated with Plasmodium berghei ANKA strain, parasitaemia was revealed in all animals inoculated in two to seven days. During the course the number of malaria parasites increased rapidly from 2.3±1.3×10 3 on d 2 to 93.7±1.8×10 3 on d 7, the number of erythrocytes increased from 8.2±0.9×10 12 /L on d 0 to 11.1±1.0×10 12 /L on d 2 and then decreased gradually, reaching 1.9±0.4×10 12 /L on d 7, and the number of white blood cells appeared to be fluctuated. Additionally, the rosette rate of erythrocyte C 3b receptor and the rosette rate of erythrocyte immunocomplex increased on d 2 and then decreased gradually to a very low level, suggesting that the erythrocyte immune function reduced in malaria. It is assumed that the reduction in erythrocyte immune function in malaria is attributed to the damage of the erythrocyte membrane in addition to the changes in the function of the erythrocyte immunoregulating factors.

STATUS AND STRATEGY OF PARASITOSIS CONTROL IN PREVENTIVE HEALTH CARE IN CHINA

1995, 13(4):  264-268. 

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According to the result of nationwide human parasitic disease distribution survey, the public significance of parasitosis control was set forth in terms of preventive health care and economic impact as well as parasitosis control and primary health care. A suggestion was made on the control strategy aiming at the parasitosis of priorities listed in the above survey.

STUDIES ON THE BIONOMICS OF PHLEBOTOMUS CHINENSIS IN MOUNTAIN CAVE AND ITS RELATION TO CONTROL IN NORTHERN SICHUAN 

1995, 13(4):  273-276. 

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After a survey of the gonotrophic cycle of 5 147 female Phlebotomus chinensis collected from the caves in the mountain area 1 500 m above sea level in Nanping County, Sichuan Province where this sandfly was proved to be the typical predominant wild species living mostly in the wild cave at a very high density, a large cave was sprayed with alphamethrin at a dosage of 50 mg/m 2 in July, 1993. As a result, the sandfly density dropped to zero spanning over a period of two peak seasons. The authors consider that the residual effect of alphamethrin is long enough to suppress sandfly density in the cave for at least two years, and stress that the spray is a favourable measure in all the year round in reducing the sandfly population density and preventing visceral leishmaniasis.

EFFECT OF MONOCLONAL ANTIBODIES ON THE ENTRY AND DEVELOPMENT OF PLASMODIUM VIVAX SPOROZOITE IN CULTURED CELLS

1995, 13(4):  288-292. 

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We have observed the effect of monoclonal antibodies against sporozoites(2F2, NVS3,2E10) and blood stages (4B2,8E3) of P. vivax on entry and subsequent development of P. vivax sporozoites in HepG2 A16 cells in vitro . The results demonstrated that inhibitory effects of monoclonal antibodies on the attachment and entry were found to be related to the antibody concentration. At 25 μg/ml, the percentages of inhibition of sporozoite invasion were 100%(2F2), 76%(NVS3) and 10.5% (2E10). Even if the invasion was not totally inhibited, the presence of abnormal exoerythrocytic schizonts suggested that continued effect of antibodies after sporozoite penetration still existed. No significant effects of 4B2 (4.5%) and 8E3 (3.4%) were recorded as compared with normal mouse serum. These findings indicate that inhibition of sporozoite invasion assay may be useful for determining the protective effect of anti sporozoite antibodies in vitro .

SCANNING ELECTRON MICROSCOPE OBSERVATION ON THE EGGS OF MUSCA DOMESTICA VICINA

1995, 13(4):  294-295. 

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The surface structures of the eggs of house fly( M. domestica vicina) were examined by SEM. A layer of membranaous structure with small holes in clusters covering the whole egg was seen. The membranous structure is supported by large amount of tissue masses of different sizes. The submembranous tissue is dotted with numerous concave holes. A hatching crack with a layer of very thin and vulnerable membrane runs lengthwise across the concave surface of the egg.

COMPARATIVE STUDY ON HEPATIC AND INTESTINAL PATHOLOGICAL CHANGES IN DIFFERENT ANIMALS WITH SCHISTOSOMIASIS JAPONICA

1995, 13(4):  296-298. 

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The pathological changes of livers and intestines were compared among cats, dogs and rabbits infected with Schistosoma japonicum cercariae for three months. The results showed that the most serious lesions were seen in rabbits while the slightest were in cats. The granulomatous response was more distinct in livers than in intestines in all of the three animals. The increment ratio of egg granuloma in livers was 3.52,2.64 and 1.81 in rabbits, dogs and cats,respectively. The eggs were deposited singly or in strings, few granuloma formation was observed in the intestines. In addition to inflammatory infiltration, swelling and/or dropping of mucosa the gland destruction and ulcer were also observed in the mucosa. The investigation demonstrated that pathological lesions varied in different animal species.