[Automatic microscopic scanning system in etiological diagnosis of schistosomiasis].

OBJECTIVE: To apply the automatically microscopic scanning system in the etiological diagnosis of schistosomiasis, as an alternative to the traditional manual microscopy detection, and improve the detection rates and efficiency of examinations of fecal slides. METHODS: A single-blind method was used throughout the process of both the automatic microscopic scanning system and traditional manual microscopy reading. Each of five professionals read 20 Kato-Katz manure piece samples. The detection results and time for each sample were recorded. The two methods were compared by the film reading speed, sensitivity, specificity, and accuracy. RESULTS: The overall accuracy of the diagnosis of schistosomiasis of the automatically microscopic scanning image system was 99.00%, higher than that of the traditional manual microscopy detection (91.00%) (P < 0.05); the sensitivity and specificity of the image system were 98.57% and 100%, respectively, and also higher than those of the traditional manual microscopy method (90.00% and 93.33%) (all P < 0.05). CONCLUSIONS: The automatically microscopic scanning system is powerful, the scanning speed is fast, and the operation is easy. Its speed, accuracy, sensitivity and specificity are superior to those of the conventional manual microscopy; therefore, it is suitable for the etiological diagnosis of schistosomiasis at the grassroots' level.

[Experimental study on compatibility of three species of freshwater snails with Angiostrongylus cantonensis].

OBJECTIVE: To compare the compatibility of three species of freshwater snails, Pomacea canaliculata, Cipangopaludina chinensis, Bellamy a aeruginosa, with Angiostrongylus cantonensis. METHODS: The snails were infected by the first-stage larvae of A. cantonensis under the same conditions. Twenty snails of each species were randomly sampled after exposed to the larvae for 1, 3, 6, 12, 24 hours, respectively. Each group was placed into an aquarium. Each species with same number was established as control. All the aquaria were equipped with a filter, the water temperature was kept at (24 +/- 1) degrees C. In the first two weeks, the number of death was recorded. Later, the snails were successively examined to record the weight and worm burden of each snail. RESULTS: Some snails were dead which mainly happened in the first week postinfection. The death rate and infection rate were not associated with exposure time and snail species. Worm burden of P. canaliculata was significantly higher than the other two species, however, the worm density of P. canaliculata and B. aeruginosa was not significantly different but higher than that of C. chinensis. The worm burden and worm density of P. canaliculata and B. aeruginosa, respectively, were significantly different among five exposure-time groups, but that of C. chinensis was not. CONCLUSION: All the three snail species show a high compatibility with A. cantoneasis. In general, the compatibility of P. canaliculata is superior to the other two species.

The effect of temperature on the development of Angiostrongylus cantonensis (Chen 1935) in Pomacea canaliculata (Lamarck 1822).

Angiostrongyliasis cantonensis, clinically presented as eosinophilic meningitis, is a snail-borne parasitic disease. We studied the effects of different temperatures on the larval development of Angiostrongylus cantonensis in the freshwater snail Pomacea canaliculata. Six groups of snails were infected and each group was cultured under different temperature conditions. At predefined intervals, four snails from each group were dissected to examine the larval development. The development-time curve of each group was drawn according to the fraction of third-stage larvae present. The developmental time was defined as the time needed until 50% of the first-stage larvae developed into third-stage larvae. A linear regression model was established based on the time (D; in days) and the corresponding temperature (T; in degrees Celsius): DT = 15.04 x D + 262.53. The threshold temperature for larval development was 15.04 degrees C and the thermal constant was 262.53 degree-days. These parameters could be helpful in estimating the number of parasite generations in a year and the impact of climate change on the distribution of A. cantonensis.

[Studies on susceptibility of Pomacea canaliculata of different developmental stages to infection with Angiostrongylus cantonensis].

UNLABELLED: OBJECTIVE To study the susceptibility of Pomacea canaliculata of different developmental stages to Angiostrongylus cantonensis infection. METHODS: P. canaliculata snails breeding at laboratory were divided into four rank (I-IV) according to the weight, and infected with the first stage larvae of A. cantonensis from Fujian Province. Their mortality, infection rate, worm burden, and the size, development and distribution of larvae in snails were examined. RESULTS: Snails at different developmental stages were readily infected with A. cantonensis. The infection rate was between 76% and 100%, with no significant difference among the groups (P>0.05). Snails at earlier developmental stage showed higher mortality. The heaviest worm burden and the largest number of snails harboring more than 100 larvae were found in snails of rank III. In general the larvae in snails showed a synchronous development in the groups. Sizes of the third stage larvae in snails of various ranks were homogeneous. The period before the third stage larva emergence and the time for a peak percentage of the larvae exhibited no significant difference among the four ranks. The larvae widely distributed in various parts of snails, with more in the lung and foot, and larvae from snails of different ranks could all infect rats successfully. CONCLUSION: P. canaliculata of the four ranks can all be infected by the first stage larvae of A. cantonensis. Rank III snails may be better for studying the relationship between P. canaliculata and A. cantonensis. The potential role of young snails in angiostrongyliasis transmission should be recognized.