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Laboratory assessment of the molluscicidal activity of B-2, a new chemical against Oncomelania nosophora.

Laboratory trials of sodium 2.5 dichloro-4-bromophenol named B-2 for the molluscicidal effect against Oncomelania nasophora were carried out by Komiya's immersion technique. The values of LC50 of B-2 varied from 0.38 ppm to 0.54 ppm depending on the collection time of the snail. They were almost equal to those of NaPCP, but lower than those of Niclosamide. In the tests of toxicity to carp, rainbow trout and killifish, B-2 showed lower toxicity than NaPCP. Some aspects of mollusciciding application of the chemical were discussed.

Animals

Field assessment of B-2 as a new molluscicide for the control of Oncomelania nosophora.

Sodium 2,5-dichloro-4-bromophenol named B-2 was evaluated for application in the field as a molluscicde against Oncomelania nosophora. A dosage of 10 g/m2 as 25% liquid form or 25 g/m2 as 10% granular form of B-2 was suggested as a standard dose for the control of O. nosophora. The residual concentration of B-2 in the soil after application was observed to decrease more rapidly than did that of NaPCP. The residual level of B-2 in the rice grains harvested from the paddy field in which the chemical was applied at most 4 times during the planting season did not exceed 0.03 ppm.

Animals

Snail immunity to schistosomes: insights from omics studies.

Schistosomiasis is a serious public health concern, with transmission facilitated by a small number of freshwater snail intermediate host species. Infection outcomes vary greatly across the primary vector genera, Biomphalaria (for Schistosoma mansoni), Bulinus (for S. haematobium), and Oncomelania (for S. japonicum), even within species, ranging from full resistance to high compatibility. Omics methods have altered this field by correlating host genotype, baseline immunological status, and time-resolved responses to whether invading miracidia are eliminated or develop sporocysts. Evidence from genomes, transcriptomics, proteomics, and epigenomics suggests that resistance is frequently primed prior to exposure. However, the clearest divergence between resistant and susceptible trajectories occurs during a small early window (<12-48&#x202f;h) after penetration. During this time, recognition, hemocyte recruitment, and soluble effector deployment either come together quickly or are delayed and guided by parasite-derived modulators. Established infections cause the host to adapt to chronic conditions through immune regulation, metabolic reprogramming, tissue and neuroendocrine remodeling, microbiome modification, and parasite castration. Comparative genomics reveals that each vector genus has evolved its own immunogenomic profile, which includes lineage-specific expansions of recognition and effector gene families. Together, these findings can help with field surveillance and intervention by providing molecular compatibility markers, functional tools for testing candidate genes, and tactics that target parasite-derived immune modulators. Integrated multi-omics approaches are a top priority, yet they are still limited in snail vectors compared to other disease vector systems.

Animals

Laboratory and field assessment of the molluscicidal activity of gogo (Entada phaseoloides) against the amphibious snail intermediate host of Schistosoma japonicum.

A molluscicidal fraction occurs naturally in the bark of a vine (gogo in Tagalog), Entada phaseoloides, which grows indigeneously and abundantly in the Philippines. Butanol fraction of the methanol extracts of the bark was most toxic against Oncomelania quadrasi with the LC50 of 3.6-5.8 ppm. Analytical work on the butanol fraction by thin layer chromatography indicated that the active molluscicidal agents contained at least two kinds of saponins. The potency of E. phaseoloides remained rather stable over a wide range of pH values, in the presence of minerals and yeast cells and after ultraviolet irradiation of solutions. Our preliminary field trials, however, showed that doses as higher than 40 g per square meter would be needed to produce a satisfactory molluscicidal effect under field conditions.

Animals

Studies on the fresh water cercariae in Leyte Island, Philippines. 5. Cercariae from Planorbidae.

In the previous papers of this series, the cercariae from Oncomelania quadrasi (Part 2), from Thiaridae (Part 3), and from Viviparidae and Pilidae (Part 4) were reported continuously. The present paper deals with the cercariae from Planorbidae. These studies were all carried on during the period of 1975 and 1976 in Leyte Island, Philippines. The number of snails examined were, 2,214 Segmentina hemisphaerula, 837 Gyraulus convexiusculus, and 279 Indoplanorbis exustus. From the former two species of snails, eight species of cercariae were detected, but no cercaria was found from Indoplanorbis exustus. The eight species of cercariae comprise 3 furcocercous cercariae, 2 amphistome cercariae, one echinostome cercaria and 2 xiphidiocercariae. These are described and illustrated with a tentative name from Cercaria leyteensis no. 29 to Cercaria leyteensis no. 36, in addition with some remarks on their presumptive life histories.

Animals

Studies on the fresh water cercariae in Leyte Island, Philippines. 6. Cercariae from Lymnaeidae and Bulinidae.

In the previous paper of this series, the cercariae from Oncomelania quadrasi (Part 2), from the snails of Thiaridae (Part 3), from the snails of Viviparidae and Pilidae (Part 4), and from Planorbidae (Part 5) were reported continuously. In this paper the crecariae from Lymnaeidae and Bulinidae were dealt with. These studies were all carried on during the period of 1975 and 1976 in Leyte Island, Philippines. From the lymnaeid snails seven species of cercariae, comprising two echinostome cercariae, one fasciolid cercaria, and four xiphidiocercariae were detected. From the bulinid snails, only two xiphidiocercariae were found, both of which were identifiable with those from the lymnaeid snails. These seven species of cercariae are described and illustrated with a tentative name from Cercaria leyteensis no. 37 to Cercaria leyteensis no. 43, in addition with some remarks on their presumptive life histories.

Animals