Experimental studies indicated that the killing process of schistosomes induced by praziquantel comprises two aspects, i.e. the direct effect of praziquantel on schistosomes and the host immune reaction. The former one appears in stimulation of worm activity, spasmodic contraction of worm musculatures and severe damage to the tegument, which results in hepatic shift of schistosomes, influence on the nutrition absorption, excretion/secretion and defense function of the tegument, followed by the secondary interference with the worm metabolism. While the latter one involves the destruction of the host concomitant immune mechanism after tegumental damage and peeling, which is unfavorable for worm survival. Particularly, the exposure of the worm surface antigen provides a target which can be attacked by specific antibodies. Therefore, the antischistosomal activity of praziquantel is immune-dependent. In this paper some host factors involved in the killing process of schistosomes induced by praziquantel were summarized.

This paper reports the histologic changes in the proliferation and growth of two echinococcus types in 25 patients, 15 with liver or lung cystic echinococcosis and 10 with liver alveolar echinococcosis. The results indicated that these two echinococcus types shared two modes of proliferation including exogenous and endogenous budding. In cystic echinococcus type, endogenous budding showed localized hyperplasia of the germinal membrane, the formation of the brood capsule, and the development of the protoscolices. Exogenous budding appeared chiefly in the migratory process of the protoscolices from the germinal membrane to the outside of the exocyst passing through the laminated layer and the fibro-exocystic wall (Figs. 1-4). In alveolar echinococcus type, endogenous budding was characterized by the propagation of the alveolar wall towards the intra-alveolar cavity with the formation of septum. Exogenous budding showed the alveolar wall propagated towards the exterior to produce daughter and grand-daughter alveoli (Figs. 5-7).

Large numbers of Plasmodium chabaudi gametocytes can be produced in the splene-ctomized Wistar rats 3-4 days after the intravenous inoculation of high parasitaemia mouse blood. On the 8-9th day, the number of gametocytes reduced greatly. The level of gametocytaemia was related to the time of splenectomy and the amount of the infected blood inoculated. The gametocytes in the rat were normal in their ability of exflagellation and their infectivity to anophelines.

Surface topography of the Anisakis type I 3rd stage larva (L3), the main pathogen of anisakiasis, was observed by scanning electron microscope under magnifications of 400 to 14000X. The head bears a trapezoid undivided lip mass, with 2 mammillary elevations at the middle of the two lateral sides and a cuticular boring tooth on its ventral side. The mouth leading into the esophagus is situated in the centre of the centrally located cuticular elevation of the lip mass. The excretory pore opens ventrally just behind the boring tooth. The surface of the lip mass shows fine striations, but looks smooth elsewhere. Neither flat papillae nor minute "teeth" or "hairs" described hither to have been observed. The cuticle of the body surface shows shallow and irregular annular grooves and folds and numerous fine longitudinal micro-furrows and cristae. These surface markings appear uniformly from head to tail and to the utmost end of the pagoda like mucrones at the tip of the tail. The ventrally located crescent anus is situated about 90?m from the base of the mucron.

The dynamic process of the bone marrow and spleen CFU-E from the mice infected with Plasmodium berghei was observed and the growing curve of CFU-E of infected mice was compared with that of normal mice. Results revealed no significant suppressive effect on CFU-E by P. berghei infection. It is indicated that the maturity and differen-tiation of erythrocytes were the foundation of invasion and parasitism by merozoites.

Fecal specimens of 35 parasitologically confirmed cases of giardiasis, 41 acute, gastroenteritis, 23 acute baciUary dysentery, 40 normal persons and 15 jirds experimentally infected with G. lamblia were tested with conterimmunoelectrophoresis (CIE). It was found that 33(94%) out of the 35 giardiasis patients and 14(93%) out of 15 infected jirds showed positive reaction, while fecal specimens of other cases, normal persons, or normal jirds all showed negative reaction. Besides, CIE was performed in 4 giardiasis patients before and after metronidazole treatment. Prior to metronidazole, they were all CIE positive, one day post metronidazole, 3 of them were still CIE positive, and Giardia cysts or trophozoites were also present in their stools. However, from the second day onwards, all of them became CIE negative, while cysts or trophozoites also disappeared from their stools. Apparently, detecting Giardia antigen in fecal specimens with CIE of feces is not only a sensitive tool for detecting current infection, but also a, useful tool for evaluating therapeutic effects in giardiasis.

Indirect fluorescent antibody test (IFAT) using frozen sections of Brugia malayi adult worms as antigen was employed in the diagnosis and epidemiological investigation of human filariasis. Sera were collected from 704 cases with bancroftian or malayan microfilaremia. the positive rate was 92.8-99.1%. Of 150 healthy people from non-endemic areas, only one showed a positive reaction (false positive rate 0.7%) (Table 1). This technique proved to be highly sensitive and specific for the diagnosis of filariasis and the antigen is easy to prepare. It might be used in sero-epidemiological investigation for the assessment of filariasis control.

The present report is concerned with the surface structure of the metacercaria of Pa-ragonimus iloktsuenensis as visualized with the scanning electron microscopy. The meta-cercariae were obtained from the liver of tne Sesarma dehaani collected in Yingkou county, Liaoning Province.The tegumental spines of the metacercaria are single-pointed and densely distributed over the entire body and are slightly different in size and shape in different parts of the body. On the forebody of the ventral surface, a vertical ridgeline can be seen in the middle of the spines.In addition to the short spines, there are two circles of non-ciliated papillae on both lips of the oral and the ventral suckers. Around the oral sucker, there are 12 papillae on the outer circle and 6 on the inner circle; around the ventral sucker, there are 6 papillae on both the outer and inner circles. No sensory papillae were found around the ventral sucker. On each side of the anterior part of the ventral side, 8 to 10 pairs of papillae are arranged in two rows.

Microfilariae (mff) obtained from the peritoneal cavities of infected jirds (Meriones unguiculatus) were injected intravenously into 6 mouse strains: SMMC/B, BALB/cCR, LACA, ICR/JCL, 615 and Kunming strain. The mff in the peripheral blood of the 6 mouse strains in the above sequence were detectable within 1-150, 24-80, 30-60, 3-96, 12-45 and 45-60 days after inoculation of 2 ? 105 mff per mouse. The survival period of mff was longer in SMMC/B mice than in mice of the other strains, and the density of mff in blood was also higher in the former than in the latter. Out of 18 SMMC/B mice 13 remained microfilaria-positive on the 60th day after inoculation. The duration and level of microfilaraemia were proportional to the dose of parasites injected Microfilariae disappeared from the peripheral blood of all mice 3 days after injection of 1 ?104 mff, but were still detectable 60 days after injection of 2 ? 105 mff. In addition, mff disappeared much faster from the peripheral blood of SMMC/B mice after the second inoculation than after the first one. Although the mff had already disappeared from the peripheral blood of the infected and reinfected mice for about 1 to 2 months, they could still be found in the internal organs, mostly in the small blood vessels of the lungs (about 90%). The mff maintained a nocturnal sub-periodicity in the recipient mice, similar to those observed in the donor jirds, with a peak density hour between 2:28 and 5: 48 a.m.The results show that this mouse model might be a simple and useful system in which various factors controlling the fate of mff can be studied independently.

The mosquito vector of filariasis malayi and its vectorial capacity was investigated In 5 endemic villages in Leshan Prefecture, Sichuan Province. The results showed that the man-biting rate, numan blood index and vectorial capacity of An. lesteri anthropophagus were 0.7, 5.1 and 10.63 times higher than those of An. sinensis. Besides, the natural infection by microfilaria in An, lesteri anthropophagus was also higher than that in An. sinensis by 5 times.From the above result, the authors concluded that An. lesteri anthropophagus was the main vector for transmitting filariasis malayi in the area under study.